Unit 7 Alkyl Halides

Correct Answer Blank 1: sp2 or sp^2 Blank 2: p or 2p Blank 3: hyperconjugation

A carbocation has a positively charged C atom that is hybridized and has a vacant orbital. Overlap of this empty orbital with an adjacent C-H σ bond is called . This overlap delocalizes the positive charge, leading to increased stability.

Correct Answer Blank 1: 3 or three Blank 2: sp2 or sp^2 Blank 3: planar

A carbocation has groups bonded to the positively charged C atom, which is hybridized and therefore has a trigonal geometry. A nucleophile can attack a carbocation from either face due to its structure.

Reactants

A nucleophilic substitution reaction takes place where nucleophile A replaces leaving group B. The pKa's of H-A and H-B are 6.2 and 18.0 respectively. The _____ are favored at equilibrium. Multiple choice question. products reactants

Blank 1: hydrogen or H Blank 2: aprotic Blank 3: cations Blank 4: anions

A polar organic solvent that contains no OH or NH bonds cannot donate bonds and is known as a polar solvent. This type of solvent solvates well but interacts much less strongly with , although it does dissolve both types of ions.

Correct Answer Blank 1: protic Blank 2: cations Blank 3: anions

A polar organic solvent that is capable of forming intermolecular hydrogen bonds is called a polar solvent. This type of solvent forms ion-dipole interactions with , and solvates by hydrogen bonding.

hydrogen, more, stronger Reason: If the anion is shielded from the reaction it will be a less effective nucleophile. covalent, more, weaker Reason: A polar protic solvent solvates anions by means of hydrogen bonds. Correct Answer hydrogen, less, weaker

A polar protic solvent solvates anions very well by the formation of _____ bonds. This shields the anion from reaction and causes it to become a _____ effective nucleophile. The stronger the base the more strongly it is solvated and the _____ a nucleophile it becomes. Multiple choice question. hydrogen, more, stronger hydrogen, less, weaker covalent, more, weaker covalent, less, stronger

Correct Answer Blank 1: one or 1 Blank 2: no, zero, or 0

A reaction coordinate diagram for the SN2 reaction shown would have transition state(s) and reactive intermediates.

Correct Answer donating, greater, more

Alkyl groups are electron-_____ by induction, which allows the stabilization of an adjacent positive charge. The greater the number of alkyl groups attached to the positively charged C of a carbocation, the _____ the inductive effect and the _____ stable the carbocation.

Correct Answer Blank 1: inductive Blank 2: more

Alkyl groups donate electron density via inductiveBlank 1Blank 1 inductive , Correct Unavailable effects. Because of this donation, R3C+ is moreBlank 2Blank 2 more , Correct Unavailable stable than H3C+.

deficient, deficient deficient, rich rich, rich Correct Answer rich, deficient

Alkyl halides react readily with electron-_____ reagents such as nucleophiles and bases because the carbon atom of the carbon-halogen bond is electron ______.

addition, substitution Reason: A base will facilitate elimination of HX while a nucleophile will attack the carbon bearing the halogen, resulting in substitution. substitution, elimination Reason: A base will facilitate elimination of HX while a nucleophile will attack the carbon bearing the halogen, resulting in substitution. elimination, substitution Reason: A base will facilitate elimination of HX while a nucleophile will attack the carbon bearing the halogen, resulting in substitution. elimination, addition Reason: A base will facilitate elimination of HX while a nucleophile will attack the carbon bearing the halogen, resulting in substitution.

Alkyl halides typically undergo ______ -type reactions with Bronsted-Lowry bases and ______ -type reactions with nucleophiles. Multiple choice question.

A leaving group A nucleophile A C=C double bond Reason: A C=C double bond is a product of elimination, nor a reactant in a substitution. An sp3 hybridized C bonded to the leaving group A strong base Reason: A strong base would tend to promote elimination rather than substitution.

Alkyl halides undergo nucleophilic substitution reactions. Select all components that are required for a nucleophilic substitution reaction to take place.

Correct Answer weak; strong; low Reason: A good leaving group is one that readily accepts and stabilizes an extra pair of electrons. Good leaving groups are weak bases with relatively strong conjugate acids.

All good leaving groups are _____ bases with relatively _____ conjugate acids that have _____ pKa values. strong; weak; high weak; strong; high weak; strong; low strong; weak; low

Correct Answer two, two, one

An SN1 reaction is a _____-step process whose energy diagram contains _____ transition state(s) and _____ reactive intermediate(s). Multiple choice question.

Correct Answer Blank 1: inversion Blank 2: back, opposite, backside, opposite side, or rear

An SN2 reaction always results in of stereochemistry if the leaving group is bonded to a stereogenic center. This indicates that the nucleophile always attacks from the with respect to the leaving group.

Correct Answer Structure B Structure C Structure A

Arrange the following compounds in order of decreasing reactivity in an SN2 reaction (from most reactive at the top of the list to least reactive at the bottom). Instructions Choice 1 of 3. Structure B toggle button Structure B Choice 2 of 3. Structure A toggle button Structure A Choice 3 of 3. Structure C toggle button Structure C

Correct Answer Structure C Structure B Structure A

Arrange the following compounds in order of increasing reactivity in an SN2 reaction (from least reactive at the top of the list to most reactive at the bottom). Instructions Choice 1 of 3. Structure A toggle button Structure A Choice 2 of 3. Structure C toggle button Structure C Choice 3 of 3. Structure B toggle button Structure B

Correct Answer 3° alkyl halide 2° alkyl halide 1° alkyl halide methyl halide

Arrange the following in order of increasing reaction rate for an SN2 reaction. Place the least reactive species at the top of the list. Position 1 of 4 3° alkyl halide correct toggle button unavailable 3° alkyl halide Position 2 of 4 2° alkyl halide correct toggle button unavailable 2° alkyl halide Position 3 of 4 1° alkyl halide correct toggle button unavailable 1° alkyl halide Position 4 of 4 methyl halide correct toggle button unavailable methyl halide

Correct Answer decrease, faster

As the degree of substitution of an alkyl halide increases, the rate of the SN2 reaction it undergoes will _____. A 1° alkyl halide will therefore have a _____ rate of reaction than a 2° alkyl halide. Multiple choice question. decrease, slower increase, faster decrease, faster increase, slower

Correct Answer Blank 1: increases Blank 2: less

As the substitution of the C bearing the leaving group increases, the rate of the SN1 reaction for the substrate . A secondary alkyl halide will therefore react readily than a tertiary alkyl halide in this type of reaction.

Correct Answer stronger, stronger F- is a small anion compared to Br-

Bromide (Br-) is a ______ nucleophile than fluoride (F-) in water because fluoride will make ______ hydrogen bonds to the solvent. Multiple choice question. weaker, weaker stronger, weaker weaker, stronger stronger, stronger

Correct Answer Doubling the concentration of CH3CH2I will result in a doubling of the reaction rate. This reaction exhibits second-order kinetics.

Consider the SN2 reaction shown in the figure. Which of the following correctly describe the kinetics of this reaction? (Select all that apply.) Multiple select question. Doubling the concentration of CH3CH2I will result in a doubling of the reaction rate. Rate = [CH3CH2SH][I−][CH3CH2I][HS−] This reaction exhibits second-order kinetics. Halving the concentration of HS- will not affect the reaction rate.

Correct Answer achiral; enantiomeric; racemic

Consider the compound shown. In an SN1 reaction of this substrate, loss of the leaving group generates a carbocation that is _____. A nucleophile can attack this carbocation from either face, leading to _____ products in equal amounts, i.e., a(n) _____ mixture. Multiple choice question. chiral; enantiomeric; racemic achiral; diasteriomeric; racemic achiral; enantiomeric; optically active achiral; enantiomeric; racemic chiral; diasteromeric; optically active

A two-step mechanism is possible that proceeds through a carbanion intermediate. Reason: A two-step mechanism is possible that proceeds through a carbocation intermediate. A two-step mechanism is possible that has a second-order rate equation. Reason: A two-step mechanism is possible that has a first-order rate equation. Correct Answer Bond breaking and bond formation may be simultaneous. A two-step mechanism is possible where bond breaking occurs before bond making.

Consider the following nucleophilic substitution reaction: Nu:- + R-X → R-Nu + X:- Which of the following statements correctly describes the possible mechanisms of this reaction? (Select all that apply.) Multiple select question. Bond breaking and bond formation may be simultaneous. A two-step mechanism is possible where bond breaking occurs before bond making. A two-step mechanism is possible that proceeds through a carbanion intermediate. A two-step mechanism is possible that has a second-order rate equation.

Correct Answer A matches Choice, Reactants Reactants B matches Choice, Transition state Transition state C matches Choice, Products Products D matches Choice, Ea Ea E matches Choice, ΔH° ΔH°

Consider the following reaction coordinate vs. energy diagram. Match the position on the diagram (A-E) with the appropriate description.

Correct Answer Br- is a weaker base than -NH2. Br- is a better leaving group than -NH2. The reaction will favor the reactants.

Consider the nucleophilic substitution reaction shown, and select all the statements that correctly interpret the data provided. Multiple select question. Br- is a weaker base than -NH2. Br- is a better leaving group than -NH2. The reaction will favor the products. -NH2 is more stable than Br-. The reaction will favor the reactants.

SN2; vinyl Reason: A vinyl halide will not undergo an SN2 reaction, but not because of an unstable carbocation intermediate. Correct Answer SN1; vinyl Reason: A vinyl halide will not undergo an SN2 reaction, but not because of an unstable carbocation intermediate.

Consider the structure shown in the diagram. This type of compound does not undergo _____ reactions because heterolysis of the C-X bond would form a highly unstable _____ carbocation. Multiple choice question. SN1; vinyl SN2; vinyl SN2; aryl SN1; aryl

Correct Answer Blank 1: products, product, or product(s)

Equilibrium favors the __________ of nucleophilic substitution when the leaving group is a weaker base than the nucleophile.

Correct Answer Blank 1: activation Blank 2: product or products Blank 3: greater, faster, or higher

For any reaction, the energy of the transition state determines the activiationBlank 1Blank 1 activiation , Incorrect Unavailable energy of the reaction and therefore the reaction rate. In an endothermic reaction, the energy of the transition state is closer to the energy of the productsBlank 2Blank 2 products , Correct Unavailable of the reaction. A more stable product will therefore form at a fasterBlank 3Blank 3 faster , Correct Unavailable rate since anything that stabilizes the product also stabilizes the transition state.

Correct Answer Blank 1: stronger Blank 2: weaker, worse, or poorer

For two nucleophiles with the same nucleophilic atom, the __________base is the stronger nucleophile. For this reason, the acetate anion CH3COO- __________is a nucleophile than the ethoxide anion CH3CH2O-.

Correct Answer A weak nucleophile decreases the rate of competing SN2 reactions, thus favoring the SN1 mechanism.

How does a weak nucleophile influence the mechanism of nucleophilic substitution that occurs? Multiple choice question. A weak nucleophile decreases the rate of competing SN2 reactions, thus favoring the SN1 mechanism. A weak nucleophile favors the SN1 mechanism as it lowers the energy of the transition state. A weak nucleophile favors the SN2 mechanism as it requires two steps to react. A weak nucleophile increases the rate of SN1 reactions, thus favoring the SN1 mechanism.

Correct Answer Blank 1: p or 2p Blank 2: greater or higher

Hyperconjugation describes the overlap of the empty ____________ , orbital on the positively charged C atom of a carbocation with an adjacent σ bond. A more substituted carbocation has more adjacent σ bonds with more possibility for hyperconjugation. The greater the substitution of a carbocation, ____________ its stability.

Correct Answer aprotic, protic

In a nucleophilic substitution reaction the nature of the solvent plays an important role, particularly for 2° substrates, which can react via either mechanism. The rate of any SN2 reaction is increased by the use of a polar _____ solvent, whereas a polar _____ solvent promotes the SN1 mechanism. Multiple choice question. protic, aprotic aprotic, protic protic, protic aprotic, aprotic

Correct Answer Blank 1: two or 2 Blank 2: carbocation

In a nucleophilic substitution reaction, a -step mechanism involves first bond breakage to form a intermediate, followed by bond formation.

weaker, increases, decreases Reason: A polar aprotic solvent does not solvate the nucleophile well. The stronger the base, the stronger the nucleophile in this type of solvent. Nucleophilicity shows the same trend as basicity and therefore decreases down a group. stronger, increases, decreases Reason: Nucleophilicity shows the same trend as basicity and therefore decreases down a group. weaker, decreases, decreases Reason: A polar aprotic solvent does not solvate the nucleophile well. The stronger the base, the stronger the nucleophile in this type of solvent. Correct Answer stronger, decreases, decreases

In a polar aprotic solvent such as acetone, the _____ the base the stronger the nucleophile. In this type of solvent, nucleophilicity _____ down a group on the periodic table as basicity _____.

decreases, decreases, increases Reason: In a polar protic solvent, nucleophilicity follows the opposite trend to basicity. The stronger the base, the stronger its interaction with the protic solvent and the less nucleophilic it will be. decreases, increases, increases Reason: The ability to stabilize an extra pair of electrons increases as size increases down a group. The more stable the base the weaker it will be; basicity therefore decreases down a group. Nucleophilicity follows the opposite trend in a polar ptoic solvent. increases, increases, increases Reason: Basicity decreases down a group in the periodic table. increases, increases, decreases Correct Answer increases, increases, decreases

In a polar protic solvent, nucleophilicity _____ down a group of the periodic table as the size of the anion _____ and basicity _____.

lower, weaker Reason: A bond involving an sp2 orbital will have a higher % s character than a bond involving an sp3 orbital. lower, stronger Reason: A bond involving an sp2 orbital will have a higher % s character than a bond involving an sp3 orbital. The bond will therefore be shorter and stronger. higher, weaker Reason: An orbital with more s character is closer to the nucleus. A bond formed using such an orbital will be shorter and stronger than a bond involving an orbital with less s character. Correct Answer higher, stronger Reason: An orbital with more s character is closer to the nucleus. A bond formed using such an orbital will be shorter and stronger than a bond involving an orbital with less s character.

In a vinyl or aryl halide, the carbon involved in the C-X bond is sp2 hybridized and has a ______% s character than the carbon atom of an alkyl halide C-X bond. Vinyl or aryl C-X bonds are therefore shorter and ______ than alkyl C-X bonds, therefore requiring more energy to break. lower, weaker higher, stronger lower, stronger higher, weaker

Correct Answer products, decreases, increases

In an endothermic reaction,anything that stabilizes the ______ also stabilizes the transition state. Lowering the energy of the transition state ______ the energy of activation, which ______ the rate of reaction. Multiple choice question.

Blank 1: nucleo Blank 2: sp^3 or sp3 Blank 3: leaving

In any nucleophilic substitution reaction, a(n) _________-phile attacks a(n) _______hybridized C atom and displaces a(n) ________group.

nucleophiles Reason: Since resonance-stabilized phosphate anions are weakly basic, they are poor nucleophiles and good leaving groups. leaving groups Reason: Since resonance-stabilized phosphate anions are weakly basic, they are poor nucleophiles and good leaving groups. Correct Answer leaving groups

In biological substitution reactions, phosphorus-derived groups such as phosphate, diphosphate, or triphosphate typically act as ______. Multiple choice question. nucleophiles leaving groups

Correct Answer Blank 1: nucleophile Blank 2: leaving Blank 3: back Blank 4: inversion or inversion of configuration

In the SN2 reaction a(n) attacks an electrophilic carbon center at the same time as the bond to the group breaks. This attack is described as a -side attack, which results in complete of stereochemistry at a stereogenic center.

Correct Answer Blank 1: strong or good Blank 2: aprotic Blank 3: SN2

In the reaction shown, a secondary alkyl halide is reacted with a strongBlank 1Blank 1 strong , Correct Unavailable nucleophile in a polar aproticBlank 2Blank 2 aprotic , Correct Unavailable solvent. The mechanism for the substitution reaction that occurs is therefore sn2Blank 3Blank 3 sn2 , Correct Unavailable.

Correct Answer Blank 1: 180

In the transition state of an SN2 reaction, the incoming nucleophile and outgoing nucleophile are degrees apart.

σ, withdraw Reason: Alkyl groups donate electron density by induction. Withdrawal of electron density would not stabilize a positive charge. Correct Answer σ, donate

Induction refers to the withdrawal or donation (release) of electron density that operates through _____ bonds. Alkyl groups _____ electron density by induction and are therefore able to stabilize a positive charge. Multiple choice question. σ, donate σ, withdraw π, withdraw π, donate

Correct Answer Blank 1: strong, good, or powerful

It is generally true that a strong base is a _____________, nucleophile, although steric factors and solvent effects can alter this relationship.

Correct Answer Blank 1: increases Blank 2: decreases

Leaving group ability___________ from left to right across a row of the periodic table as basicity _____________.

The nucleophile matches Choice, donates an electron pair. donates an electron pair. The carbon atom at which substitution occurs matches Choice, accepts an electron pair from the nucleophile. accepts an electron pair from the nucleophile. The Lewis base in this reaction is the matches Choice, nucleophile. nucleophile. The Lewis acid in this reaction is the matches Choice, carbon atom at which substitution occurs. carbon atom at which substitution occurs.

Match each species with the role it plays in a nucleophilic substitution reaction.

A- benzylic halide B- vinyl halide C- aryl halide D-allylic halide

Match each type of organic halide with the correct general structure.

Correct Answer Polar aprotic solvents matches Choice, do not solvate nucleophiles well and nucleophiles are therefore more nucleophilic. do not solvate nucleophiles well and nucleophiles are therefore more nucleophilic. Polar protic solvents matches Choice, stabilize ionic intermediates by solvation. stabilize ionic intermediates by solvation.

Match the solvents described to the appropriate description. Instructions Polar aprotic solvents.... Polar protic solvents.... do not solvate nucleophiles well and nucleophiles are therefore more nucleophilic. stabilize ionic intermediates by solvation.

A matches Choice, 4-chloro-2-methylhexane 4-chloro-2-methylhexane B matches Choice, 2-chloro-2-methylpentane 2-chloro-2-methylpentane C matches Choice, 1-bromo-2-methylcyclohexane 1-bromo-2-methylcyclohexane D matches Choice, 2-bromo-3,4-dimethylheptane 2-bromo-3,4-dimethylheptane

Match the structure of each alkyl halide to its correct IUPAC name. 4-chloro-2-methylhexane 2-chloro-2-methylpentane 1-bromo-2-methylcyclohexane 2-bromo-3,4-dimethylheptane

Correct Answer SN1 reaction matches Choice, The rate is doubled when the concentration of the alkyl halide is doubled. The rate is doubled when the concentration of the alkyl halide is doubled. SN2 reaction matches Choice, The rate is quadrupled when the concentration of both the alkyl halide and nucleophile are doubled. The rate is quadrupled when the concentration of both the alkyl halide and nucleophile are doubled.

Match the type of substitution reaction to the appropriate description. Instructions SN1 reaction SN1 reaction drop zone empty. SN2 reaction SN2 reaction drop zone empty. The rate is doubled when the concentration of the alkyl halide is doubled. The rate is quadrupled when the concentration of both the alkyl halide and nucleophile are doubled.

Correct Answer Blank 1: weaker, poorer, or worse Blank 2: stronger or better

NH3 is a nucleophile than -NH2 because a negatively charged nucleophile is always a nucleophile than its conjugate acid.

Blank 1: lone, nonbonded, non-bonded, or unshared Blank 2: pi Blank 3: proton, H+, hydrogen, or H Blank 4: electro

Nucleophiles and bases are structurally similar since both have either a(n) __________pair of electrons or a _____________ bond. They differ in their site of reaction. A base attacks a _____________, whereas a nucleophile reacts at a(n)_____________ -philic center, often a carbon atom.

Correct Answer weak, resonance-stabilized bases

Phosphate, diphosphate, and triphosphate make good leaving groups in biological substitutions because they are ______. Multiple choice question. strong, resonance-stabilized bases weak, resonance-stabilized bases neutral, stabilized bases

Correct Answer 1. I- 2. Br- 3. HO- 4. H2N-

Place the following groups in order of decreasing leaving group ability. Place the best leaving group at the top of the list. Instructions HO- H2N- Br- I-

Correct Answer H3C- HO- HS- HSe-

Place the following groups in order of increasing leaving group ability. Place the worst leaving group at the top of the list. HS- H3C- HSe- HO-

Correct Answer CH3S- CH3O- CH3HN-

Place the following nucleophiles in order of increasing nucleophilic strength (weakest at the top to strongest at the bottom) for a nucleophilic substitution reaction carried out in acetone. Instructions Choice 1 of 3. CH3HN- toggle button CH3HN- Choice 2 of 3. CH3O- toggle button CH3O- Choice 3 of 3. CH3S- toggle button CH3S-

Correct Answer CH3S- CH3O- CH3HN-

Place the following nucleophiles in order of increasing nucleophilic strength (weakest at the top to strongest at the bottom) for a nucleophilic substitution reaction carried out in acetone. Position 1 of 3 CH3S- correct toggle button unavailable CH3S- Position 2 of 3 CH3O- correct toggle button unavailable CH3O- Position 3 of 3 CH3HN- correct toggle button unavailable CH3HN-

Correct Answer CH3CH2O- CH3CH2S- CH3CH2Se-

Place the following nucleophiles in order of increasing nucleophilic strength (weakest at the top to strongest at the bottom) for a nucleophilic substitution reaction carried out in ethanol (CH3CH2OH). Instructions Choice 1 of 3. CH3CH2O- toggle button CH3CH2O- Choice 2 of 3. CH3CH2Se- toggle button CH3CH2Se- Choice 3 of 3. CH3CH2S- toggle button CH3CH2S-

weak; weak; steric hinderance Reason: Potassium t-butoxide is sterically hindered around oxygen, which makes it a weak nucleophile but doesn't affect the basicity of the oxygen. strong; strong; inductive effects Reason: Potassium t-butoxide is sterically hindered around oxygen, which makes it a weak nucleophile but doesn't affect the basicity of the oxygen. Correct Answer strong; weak; steric hinderance

Potassium tert-butoxide [KOC(CH3)3] is a ______ base, but a ______ nucleophile due to ______. Multiple choice question. weak; weak; steric hinderance strong; strong; inductive effects strong; weak; steric hinderance

Correct Answer Blank 1: enantiomers or nonsuperimposable mirror image forms

Racemization is the formation of equal amounts of two products that are ____________________ of each other from a single chiral starting material.

Correct Answer C A B

Rank the alkyl halides shown by rate of SN2 reaction. The alkyl halide that will undergo an SN2 rate fastest will be on the top and slowest on the bottom. Instructions Choice 1 of 3. A toggle button A Choice 2 of 3. B toggle button B Choice 3 of 3. C toggle button C

Correct Answer CH3CH2CH2Cl CH3CH2CH2Br CH3CH2CH2I

Rank the following alkyl halides in order of increasing reactivity in an SN2 reaction. Place the least reactive compound at the top of the list. CH3CH2CH2Cl CH3CH2CH2Br CH3CH2CH2I

Correct Answer I- Cl- F- HO-

Rank the following nucleophiles in order of increasing nucleophilicity in a polar aprotic solvent. Place the least nucleophilic species at the top of the list. Position 1 of 4 I- correct toggle button unavailable I- Position 2 of 4 Cl- correct toggle button unavailable Cl- Position 3 of 4 HO- incorrect toggle button unavailable HO- Position 4 of 4 F- incorrect toggle button unavailable F-

Correct Answer I- Cl- F- HO-

Rank the following nucleophiles in order of increasing nucleophilicity in a polar aprotic solvent. Place the least nucleophilic species at the top of the list. Instructions Choice 1 of 4. HO- toggle button HO- Choice 2 of 4. F- toggle button F- Choice 3 of 4. Cl- toggle button Cl- Choice 4 of 4. I- toggle button I-

Correct Answer H2N— HO— F—

Rank the nucleophiles shown in order of their nucleophilicity in acetone. Order them with the strongest nucleophile on top and the weakest on the bottom. Position 1 of 3 H2N— correct toggle button unavailable H2N— Position 2 of 3 HO— correct toggle button unavailable HO— Position 3 of 3 F— correct toggle button unavailable F—

Correct Answer SN1, SN2

Reaction with a weak nucleophile will favor the _____ mechanism for nucleophilic substitution, whereas reaction with a strong nucleophile in high concentration will favor the _____ mechanism. Multiple choice question. SN1, SN2 SN2, SN1 SN1, SN1 SN2, SN2

Correct Answer Blank 1: methyl

S-Adenosylmethionine (SAM) is a sulfonium salt that can transfer a _____________ group to a nucleophile in the cell.

True Reason: Incorrect: SN1 reactions are favored by using polar protic solvents that stabilize ionic intermediates by solvation. Correct Answer False

SN2 reactions are favored by using polar protic solvents that stabilize ionic intermediates by solvation. True False

Correct Answer Blank 1: strong or stronger Blank 2: weak or weaker

SN2 reactions are favored with nucleophiles, while SN1 reactions are favored with nucleophiles.

CH3CH2OH Reason: HO- is a strong base and a poor leaving group. CH3CH2F Reason: F- is a poor leaving group (the C-F bond is very strong). Correct Answer CH3CH2I Reason: I- is a weak base and a good leaving group. CH3CH2O+O+H2 Reason: H2O is a weak base and a good leaving group.

Select all of the molecules that contain good leaving groups. Multiple select question. CH3CH2OH CH3CH2F CH3CH2I CH3CH2O+O+H2

The C-X bond is cleaved homolytically to form radicals. Reason: The C-X bond is cleaved heterolytically. The reaction takes place at an sp2 hybridized C atom. Reason: The reaction takes place at an sp3 hybridized C atom. Correct Answer A nucleophile donates an electron pair to an electrophilic C atom. As the C-X bond is cleaved, the electrons of the C-X σ bond are accepted by the leaving group.

Select all of the statements that correctly describe nucleophilic substitution of an alkyl halide. The C-X bond is cleaved homolytically to form radicals. The reaction takes place at an sp2 hybridized C atom. As the C-X bond is cleaved, the electrons of the C-X σ bond are accepted by the leaving group. A nucleophile donates an electron pair to an electrophilic C atom.

Correct Answer Na+ is solvated by ion-dipole interactions with dimethyl ether. CH3O- is solvated by ion-dipole interactions with dimethyl ether.

Select all of the statements that correctly describe the interactions between NaOCH3 (sodium methoxide) and dimethyl ether (CH3OCH3). Multiple select question. NaOCH3 is not solvated by dimethyl ether. Na+ is solvated by hydrogen bonding with dimethyl ether. Na+ is solvated by ion-dipole interactions with dimethyl ether. CH3O- is solvated by ion-dipole interactions with dimethyl ether. CH3O- is solvated by hydrogen bonding with dimethyl ether.

Correct Answer F- is solvated by hydrogen bonding with water. K+ is solvated by ion-dipole interactions with water.

Select all of the statements that correctly describe the interactions between the given species and water. Multiple select question. F- is solvated by hydrogen bonding with water. KF is neutral and is not solvated by water. K+ is solvated by ion-dipole interactions with water. K+ is solvated by hydrogen bonding with water.

Correct Answer F- is solvated by hydrogen bonding with water. K+ is solvated by ion-dipole interactions with water.

Select all of the statements that correctly describe the interactions between the given species and water. Multiple select question. K+ is solvated by hydrogen bonding with water. F- is solvated by hydrogen bonding with water. KF is neutral and is not solvated by water. K+ is solvated by ion-dipole interactions with water.

Correct Answer are bimolecular reactions follow second-order kinetics

Select all statements that complete the following sentence. SN2 reactions _____. Multiple select question. involve the formation of carbocations are bimolecular reactions follow second-order kinetics proceed by a two-step mechanism

When a neutral nucleophile is used, the initial substitution product is neutral. Reason: When a neutral nucleophile is used, the initial substitution product is positively charged. This product readily loses a proton to form a neutral product. Correct Answer For negatively charged nucleophiles, all atoms originally bound to the nucleophilic center stay bonded to it after substitution occurs. Negatively charged nucleophiles are used as salts with Li+, Na+, or K+ counterions to balance charge.

Select all statements that correctly describe nucleophiles that are used in substitution reactions. Multiple select question. For negatively charged nucleophiles, all atoms originally bound to the nucleophilic center stay bonded to it after substitution occurs. Negatively charged nucleophiles are used as salts with Li+, Na+, or K+ counterions to balance charge. When a neutral nucleophile is used, the initial substitution product is neutral.

Nucleophilicity increases up a column of the periodic table. Reason: Nucleophilicity increases down a column of the periodic table Correct Answer HS- is a more powerful nucleophile than HO-. Smaller anions are more strongly solvated than larger anions and are less nucleophilic.

Select all statements that correctly describe nucleophilic strength in a polar protic solvent. Multiple select question. HS- is a more powerful nucleophile than HO-. Smaller anions are more strongly solvated than larger anions and are less nucleophilic. Nucleophilicity increases up a column of the periodic table.

Correct Answer use of a polar aprotic solvent use of primary and methyl halides

Select all that apply Which of the following factors favor SN2 reactions? (Select all that apply.) Multiple select question. use of weak nucleophiles use of tertiary alkyl halides use of a polar aprotic solvent use of primary and methyl halides

Nucleophilicity increases up a column of the periodic table. Reason: Nucleophilicity increases down a column of the periodic table. Correct Answer Smaller anions are more strongly solvated than larger anions and are less nucleophilic. HS- is a more powerful nucleophile than HO-.

Select all statements that correctly describe nucleophilic strength in a polar protic solvent. Multiple select question. Smaller anions are more strongly solvated than larger anions and are less nucleophilic. HS- is a more powerful nucleophile than HO-. Nucleophilicity increases up a column of the periodic table.

In a substitution reaction the halogen X is replaced by a nucleophile. The C-X σ bond is broken and the C-Nu σ bond is formed in an elimination reaction. Reason: The C-X σ bond is broken and the C-Nu σ bond is formed in a substitution reaction. Elimination reactions lead to the formation of a new π bond. Alkyl halides undergo elimination reactions with Bronsted-Lowry bases.

Select all statements that correctly describe substitution and elimination reactions of alkyl halides. Multiple select question.

Correct Answer This species is a sulfonium salt. This species takes part in methylation reactions. This species is soluble in the aqueous environment in the cell.

Select all statements that correctly describe the structure shown. Multiple select question. This species is a sulfonium salt. This species takes part in methylation reactions. This species is known as adrenaline. This species is soluble in the aqueous environment in the cell.

Boiling points increase with the size of the halogen due to the increasing polarizability. Melting points of alkyl halides increase as the size of R increases. This is due to increasing polarity of the molecules. Reason: Melting points of alkyl halides increase as the size of R increases. The increasing surface area leads to stronger intermolecular forces between molecules. Alkyl halides are insoluble in water as they are weakly polar and the alkyl chain is hydrophobic.

Select all statements that correctly describe the trends in the physical properties of alkyl halides.

The number 1 in SN1 refers to the number of steps in the mechanism. Reason: The number 1 in SN1 refers to the kinetic order of the reaction. Only the nucleophile appears in the rate equation. Reason: Only the alkyl halide appears in the rate equation. Correct Answer The rate follows first-order kinetics. Only 1 reactant appears in the rate equation.

Select all statements that describe an SN1 reaction of an alkyl halide. The number 1 in SN1 refers to the number of steps in the mechanism. Only the nucleophile appears in the rate equation. The rate follows first-order kinetics. Only 1 reactant appears in the rate equation.

Correct Answer The reaction will occur as written because I- is a weaker base than -SCH3. The reaction will occur as written because I- is a better leaving group than -SCH3.

Select all that apply Consider the nucleophilic substitution reaction shown, and select the statements that correctly describe the outcome (the pKa values of CH3SH and HI are 10.4 and -10 respectively). Multiple select question. The reaction will occur as written because I- is a weaker base than -SCH3. The reaction will not occur as written because -SCH3 is a better leaving group than I-. The reaction will occur as written because I- is a better leaving group than -SCH3. The reaction will not occur as written because -SCH3 is a weaker base than I-.

Correct Answer Compound C will react most quickly because it will form the most stable carbocation. Compounds A and D will have very similar reaction rates.

Select all that apply Consider the structures of the alkyl halides shown, and select all the statements that correctly describe the relative reactivity of these compounds in an SN1 reaction. Multiple select question. Compound B will react slowly because the final substitution product will be sterically crowded. Compound C will react most quickly because it will form the most stable carbocation. Compound B will have the highest reaction rate because it forms an unstable 1° carbocation, which will quickly form a product. Compounds A and D will have very similar reaction rates.

LDA can easily attack a tetravalent carbon atom. Reason: LDA is a poor nucleophile and cannot attack a crowded tetravalent C due to steric hindrance. LDA is both a strong base and a good nucleophile. Reason: LDA is a strong base and a poor nucleophile. Correct Answer LDA is a nonnucleophilic base. LDA is a sterically hindered base.

Select all that apply Lithium diisopropylamide (LDA) is shown in the diagram. Select all of the statements that correctly describe this species. Multiple select question. LDA can easily attack a tetravalent carbon atom. LDA is a nonnucleophilic base. LDA is a sterically hindered base. LDA is both a strong base and a good nucleophile.

use of acetone as the solvent Reason: Acetone is a polar aprotic solvent. 2° alkyl halides react by SN1 mechanisms in polar protic solvents. use of a strong nucleophile Reason: Strong nucleophiles favor the SN2 mechanism over the SN1 mechanism. Correct Answer use of polar protic solvents use of methanol as both the nucleophile and solvent

Select all that apply Secondary alkyl halides may react by SN1 or SN2 reaction mechanisms. Which of the following will favor an SN1 mechanism over an SN2 mechanism? (Select all that apply.) Multiple select question. use of polar protic solvents use of acetone as the solvent use of a strong nucleophile use of methanol as both the nucleophile and solvent

Correct Answer Structure B Structure D

Select all that apply Select all halides that will NOT undergo SN1 or SN2 nucleophilic substitution reactions. Multiple select question. Structure A Structure B Structure C Structure D

Correct Answer A and D D and F

Select all that apply Select all of the combinations that will produce the target compound by a substitution reaction. Multiple select question. A and D C and D D and F A and B C and E

More electronegative atoms release electron density by induction. Reason: More electronegative atoms withdraw electron density by induction. Inductive effects always refer to the withdrawal of electron density. Reason: Inductive effects may refer to the withdrawal or donation of electron density. Correct Answer Inductive effects operate through σ bonds only. Alkyl groups can stabilize a positive charge by induction.

Select all that apply Select all the statements that correctly describe inductive effects. Multiple select question. More electronegative atoms release electron density by induction. Inductive effects operate through σ bonds only. Alkyl groups can stabilize a positive charge by induction. Inductive effects always refer to the withdrawal of electron density.

Option A Option C

Select all that apply Select the starting material and nucleophile required to produce structure A.

Correct Answer Reaction B Reaction C

Select all that apply Which of the following reactions will proceed via an SN1 mechanism? Select all that apply. Multiple select question. Reaction A Reaction B Reaction C Reaction D

Bases usually attack carbon atoms. Reason: Nucleophiles usually attack carbon atoms. Nucleophiles and bases are structurally dissimilar. Reason: Nucleophiles and bases are structurally similar. Correct Answer A nucleophile is a Lewis base that attacks electrophiles other than protons. Nucleophiles and bases have a lone pair or π bond.

Select all that apply Which of the following statements correctly describe nucleophiles and bases? (Select all that apply.) Multiple select question. Bases usually attack carbon atoms. A nucleophile is a Lewis base that attacks electrophiles other than protons. Nucleophiles and bases are structurally dissimilar. Nucleophiles and bases have a lone pair or π bond.

Correct Answer The carbon atom of the C-X bond is sp2 hydbridized. The C-X bond is shorter and strong than the C-X bond of an alkyl halide.

Select all that apply Which of the following statements is/are correct about a vinyl halide? Multiple select question. The carbon atom of the C-X bond is sp2 hydbridized. The C-X bond is shorter and strong than the C-X bond of an alkyl halide. The rate of SN2 reaction with a vinyl halide is faster than for an alkyl halide. The carbon hybrid orbital of the C-X bond has 25% s-character.

Correct Answer ethanol, CH3CH2OH acetic acid, CH3COOH water, H2O

Select all the solvents from the following list that are both polar and protic. Multiple select question. DMSO, (CH3)2SO chloroform, CHCl3 ethanol, CH3CH2OH acetic acid, CH3COOH water, H2O

Polar protic solvents solvate anions by dipole-dipole interactions. Reason: Cations are solvated by ion-dipole interactions. Anions are solvated by hydrogen bonding. Correct Answer Polar protic solvents contain an OH or NH bond. Protic solvents form intermolecular hydrogen bonds. Polar protic solvents solvate both cations and anions well.

Select all the statements that correctly describe a polar protic solvent. Multiple select question. Polar protic solvents contain an OH or NH bond. DMSO is a common polar protic solvent. Protic solvents form intermolecular hydrogen bonds. Polar protic solvents solvate both cations and anions well. Polar protic solvents solvate anions by dipole-dipole interactions.

Good leaving groups have high pKa values. Reason: The conjugate acid of a good leaving group has a low pKa value. The leaving group itself would not have a low pKa value. Many leaving groups are not Bronsted-Lowry acids (e.g., Br-, I-, etc.). Good leaving groups have high pKa values. Reason: The conjugate acid of a good leaving group has a low pKa value. The leaving group itself would not have a low pKa value. Many leaving groups are not Bronsted-Lowry acids (e.g., Br-, I-, etc.). Correct Answer Good leaving groups accept an electron pair readily. Reason: A good leaving group must be able to stabilize an extra pair of electrons. Good leaving groups are therefore species that readily accept an electron pair. Good leaving groups are weak bases. Good leaving groups have strong conjugate acids.

Select all the statements that correctly describe the characteristics of a good leaving group. Multiple select question. Good leaving groups have low pKa values. Good leaving groups accept an electron pair readily. Good leaving groups are weak bases. Good leaving groups have high pKa values. Good leaving groups have strong conjugate acids.

Correct Answer There should be two products with opposite absolute stereochemistry. Reason: An SN1 reaction results in two products, one showing retention of configuration and the other showing inversion of configuration. In the first step, the arrow should end on the Br, not on the C at the reaction center.

Select all the statements that correctly describe the following SN1 reaction mechanism. Multiple select question. There should be two products with opposite absolute stereochemistry. The intermediate should not be a carbocation. In the first step, the arrow should end on the Br, not on the C at the reaction center. The second step should show the tail of the arrow beginning on the positive charge and ending on the oxygen atom.

Correct Answer A carbocation intermediate is formed in an SN1 reaction. The reaction rate is not affected by changing the concentration of the nucleophile. In an SN1 reaction both retention and inversion of stereochemistry are observed for reaction at a stereogenic center.

Select all the statements that correctly describe the mechanism of the SN1 reaction. Multiple select question. The SN1 reaction involves a single step. A carbocation intermediate is formed in an SN1 reaction. In an SN1 reaction a bond forms to the nucleophile before the bond is broken to the leaving group. The reaction rate is not affected by changing the concentration of the nucleophile. In an SN1 reaction both retention and inversion of stereochemistry are observed for reaction at a stereogenic center.

Correct Answer The energy of the first transition state is higher than the energy of the second transition state. The energy diagram shows two energy maxima corresponding to the two transition states. The first step of the reaction is endothermic.

Select all the statements that correctly describe the reaction coordinate vs. energy diagram for an SN1 reaction. Multiple select question. The energy of the carbocation intermediate is at an energy maximum. Reason: The energy of the transition states will be found at the energy maxima. The carbocation is an intermediate and although it is less stable than either starting materials or products its energy will not be at an energy maximum. The energy of the first transition state is higher than the energy of the second transition state. The energy diagram shows two energy maxima corresponding to the two transition states. The first step of the reaction is endothermic. The carbocation intermediate is more stable than the starting material.

A carbocation has a tetrahedral geometry at the positively charged C atom. Reason: A carbocation has a trigonal planar geometry at the positively charged C atom. Correct Answer The positively charged C atom of a carbocation has an empty p orbital available for bonding. The positively charged C atom of a carbocation is sp2 hybridized.

Select all the statements that correctly describe the structure of a carbocation. Multiple select question. The positively charged C atom of a carbocation has an empty p orbital available for bonding. The positively charged C atom of a carbocation is a stereogenic center. The positively charged C atom of a carbocation is sp2 hybridized. A carbocation has a tetrahedral geometry at the positively charged C atom.

Correct Answer More alkyl groups at the reaction site raise the energy of the transition state, slowing the reaction. More alkyl groups near the reaction site hinder the approach of the nucleophile, slowing the reaction.

Select all the statements that correctly describe why increasing the substitution of the alkyl halide decreases the rate of the SN2 reaction. Multiple select question. More alkyl groups at the reaction site raise the energy of the transition state, slowing the reaction. More alkyl groups at the reaction site lower the activation energy, slowing the reaction. Reason: More alkyl groups at the reaction site raise the activation energy, slowing the reaction. A more substituted alkyl halide interacts more strongly with the solvent, slowing the reaction. More alkyl groups near the reaction site hinder the approach of the nucleophile, slowing the reaction.

Correct Answer The Hammond postulate provides an estimate of the energy of the transition state for a reaction. The rate of a reaction depends on Ea, and the stability of a product depends on ΔG°.

Select all the statements that correctly reflect the Hammond postulate. Multiple select question. The Hammond postulate relates reaction rate to ΔH for the reaction. The Hammond postulate allows us to determine the structure of the transition state for a reaction. The rate of a reaction depends on Ea, and the stability of a product depends on ΔG°. The Hammond postulate provides an estimate of the energy of the transition state for a reaction.

A negatively charged nucleophile is always a weaker nucleophile than its conjugate acid. Reason: A negatively charged nucleophile is always a stronger nucleophile than its conjugate acid. Correct Answer For two nucleophiles with the same nucleophilic atom, the stronger base is the stronger nucleophile. Across a period (left to right) nucleophilicity decreases as base strength decreases.

Select all the statements that correctly reflect the relationship between base strength and nucleophilicity. Multiple select question. A negatively charged nucleophile is always a weaker nucleophile than its conjugate acid. For two nucleophiles with the same nucleophilic atom, the stronger base is the stronger nucleophile. Across a period (left to right) nucleophilicity decreases as base strength decreases.

Correct Answer Complete inversion of stereochemistry is observed at the reacting center. The reaction follows second-order kinetics. The bond to the nucleophile is formed in the same step as the bond to the leaving group is broken.

Select all the statements that describe the mechanism of the SN2 reaction. Multiple select question. Complete inversion of stereochemistry is observed at the reacting center. The rate depends only on the concentration of the nucleophile. Reason: An SN2 reaction is a bimolecular single-step reaction. The rate depends on the concentrations of both the nucleophile and the electrophile. The reaction follows second-order kinetics. The reaction is not affected by the nature of the starting materials. Reason: The nature of the starting materials determines whether, and to what extent, an SN2 reaction will occur. The bond to the nucleophile is formed in the same step as the bond to the leaving group is broken.

The rate depends only on the concentration of the nucleophile. Reason: An SN2 reaction is a bimolecular single-step reaction. The rate depends on the concentrations of both the nucleophile and the electrophile. The reaction is not affected by the nature of the starting materials. Reason: The nature of the starting materials determines whether, and to what extent, an SN2 reaction will occur. Correct Answer The reaction follows second-order kinetics. Complete inversion of stereochemistry is observed at the reacting center. The bond to the nucleophile is formed in the same step as the bond to the leaving group is broken.

Select all the statements that describe the mechanism of the SN2 reaction. Multiple select question. The rate depends only on the concentration of the nucleophile. The reaction follows second-order kinetics. Complete inversion of stereochemistry is observed at the reacting center. The bond to the nucleophile is formed in the same step as the bond to the leaving group is broken. The reaction is not affected by the nature of the starting materials.

A Reason: Since this is an SN2 reaction there must be inversion of configuration. A shows retention of configuration and is not correct. B C Reason: A racemic product would be formed by an SN1reaction. D Reason: A substitution reaction is not shown by D. However, the absolute configuration at the stereogenic center is inverted. Correct Answer B

Select the correct structure for the product of the following SN2 reaction. Multiple choice question. A B C D

A Reason: The reaction will only affect the stereochemistry at the carbon bearing the leaving group. A shows both stereogenic centers undergoing inversion, which is not correct. B C Reason: An SN2 reaction results in inversion of stereochemistry at the carbon bearing the leaving group. C is not correct, since it shows retention of configuration at the carbon bearing the leaving group and inversion at the other stereogenic center. D Reason: An SN2 reaction causes inversion of stereochemistry at the carbon bearing the leaving group. D is not correct because it shows retention of configuration. Correct Answer B

Select the correct structure for the product of the following SN2 reaction. Multiple choice question. A B C D

Correct Answer C

Select the product of the nucleophilic substitution reaction shown. Multiple choice question. A B C D

Correct Answer B D

Select the starting material and nucleophile required to produce Structure A.

Correct Answer The formation of equal amounts of two enantiomeric products from a single chiral starting material

Select the statement that correctly describes racemization. Multiple choice question. The formation of a particular enantiomeric product from a single achiral starting material The formation of equal amounts of two enantiomeric products from a single chiral starting material The transformation of a pair of enantiomers into a pair of diastereomers The transformation of one enantiomer into another.

Correct Answer A good leaving group increases the rate of both SN1 and SN2 reactions.

Select the statement that correctly describes the effect of the leaving group on nucleophilic substitution reactions. Multiple choice question. A good leaving group favors the SN1 reaction since it promotes the formation of a carbocation. The role played by the leaving group depends on the solvent for the reaction. A good leaving group favors the SN2 reaction since it promotes attack by the nucleophile. A good leaving group increases the rate of both SN1 and SN2 reactions.

There is retention of stereochemistry, which implies backside attack by the nucleophile. Reason: An SN2 reaction does not exhibit retention of stereochemistry. There is inversion of stereochemistry, which implies frontside attack by the nucleophile. Reason: Inversion of stereochemistry can only occur if the nucleophile attacks from the backside. There is inversion of stereochemistry, which implies backside attack by the nucleophile. There is retention of stereochemistry, which implies frontside attack by the nucleophile. Reason: An SN2 reaction does not exhibit retention of stereochemistry. Correct Answer There is inversion of stereochemistry, which implies backside attack by the nucleophile.

Select the statement that correctly describes the stereochemical outcome of an SN2 reaction. Multiple choice question. There is retention of stereochemistry, which implies backside attack by the nucleophile. There is inversion of stereochemistry, which implies frontside attack by the nucleophile. There is inversion of stereochemistry, which implies backside attack by the nucleophile. There is retention of stereochemistry, which implies frontside attack by the nucleophile.

Correct Answer Backside attack minimizes repulsion between the nucleophile and the leaving group, which are both electron rich.

Select the statement that correctly explains why backside attack by the nucleophile is preferred in SN2 reactions. Multiple choice question. Backside attack prevents attraction between the electron-rich nucleophile and the electron-poor leaving group. Backside attack minimizes repulsion between the nucleophile and the leaving group, which are both electron rich. Backside attack allows the reacting carbon to retain its stereochemistry. Backside attack allows the reacting carbon to form more than 4 covalent bonds.

Correct Answer Acetone is a polar aprotic solvent because it cannot act as a hydrogen-bond donor. A polar aprotic solvent solvates cations by ion-dipole interactions.

Select the statements that correctly describe the characteristics of a polar aprotic solvent. Multiple select question. Acetone is a polar aprotic solvent because it cannot act as a hydrogen-bond donor. A polar aprotic solvent interacts strongly with anions as well as cations. A polar aprotic solvent solvates cations by ion-dipole interactions. A polar aprotic solvent cannot interact well with any type of ion.

A Reason: A is a weaker base than B. Right-to-left across a row of the periodic table, nucleophilicity increases as basicity increases. Corresct answer B Reason: A is a weaker base than B. Right-to-left across a row of the periodic table, nucleophilicity increases as basicity increases.

Select the stronger nucleophile from the following pair.

A Reason: A is a weaker base than B. Right-to-left across a row of the periodic table, nucleophilicity increases as basicity increases. Correct Answer B Reason: A is a weaker base than B. Right-to-left across a row of the periodic table, nucleophilicity increases as basicity increases.

Select the stronger nucleophile from the following pair. Multiple choice question. A B

CH3)3CF Reason: The SN1 leaving group in (CH3)3COH2+ is a neutral water molecule, which is an excellent leaving group. By comparison, F- is a poor leaving group. (CH3)3COH Reason: The SN1 leaving group in (CH3)3COH2+ is a neutral water molecule, which is an excellent leaving group. By comparison, OH- is a poor leaving group. Correct Answer (CH3)3COH2+

Select the substrate that reacts most rapidly in an SN1 reaction. Multiple choice question. (CH3)3CF (CH3)3COH (CH3)3COH2+

polar; more; electrophilic; nucleophiles

The C-X bond of an alkyl halide is _____ since the halogen (X) is _____ electronegative than carbon. The carbon atom of the C-X bond is _____ and as a result alkyl halides react readily with _____. Multiple choice question. polar; more; nucleophilic; electrophiles nonpolar; more; nucleophilic; electrophiles polar; more; electrophilic; electrophiles polar; less; electrophilic; nucleophiles polar; more; electrophilic; nucleophiles

Correct Answer transition state

The Hammond postulate provides an estimate of the energy of the ______ of a reaction. Multiple choice question. intermediate product starting material transition state

Correct Answer reactants, products

The Hammond postulate states that the transition state for a reaction most closely resembles the species to which it is closer in energy. In an exothermic reaction the transition state resembles the ______, whereas in an endothermic reaction the transition state more closely resembles the ______. reactants, products products, reactants,

Correct Answer Blank 1: carbocation, planar carbocation, or carbonium Blank 2: nucleophile Blank 3: enantiomers

The SN1 reaction involves loss of the leaving group to form a carbocationBlank 1Blank 1 carbocation , Correct Unavailable intermediate, which then reacts with a nucleophileBlank 2Blank 2 nucleophile , Correct Unavailable. Since the intermediate is planar, attack can occur from either face and the product will be an equal mixture of both enantiomersBlank 3Blank 3 enantiomers , Correct Unavailable if the reaction site is the only stereogenic center.

Correct Answer lower; more; lower

The SN1 reaction of t-Butylchloride [(CH3)3CCl] proceeds through a ______-energy of activation than isopropylchloride [(CH3)2CHCl]. This is because the t-butyl cation [(CH3)3C+] is ______ stable than the isopropyl cation [(CH3)2CH+], making it a ______-energy intermediate. Multiple choice question. lower; more; lower higher; more; lower higher; less; higher lower; less; higher

Correct Answer repulsion, rich, rich

The SN2 reaction proceeds through backside attack to minimize the ______ between the incoming electron-______ nucleophile and electron-______ leaving group. Multiple choice question. repulsion, rich, rich repulsion, rich, poor attraction, rich, rich attraction, rich, poor

Correct Answer Blank 1: determining or limiting Blank 2: endo Blank 3: higher, greater, faster, or quicker Blank 4: stability or energy

The energy diagram for an SN1 reaction is shown. The first step of the reaction is rate- because this step has the higher activation energy. This step is -thermic and the transition state resembles the carbocation intermediate rather than the reactant. The lower the energy of the intermediate, the the reaction rate. The rate of an SN1 reaction therefore depends on the relative of the carbocation intermediate formed.

Correct Answer 1. Find the sp3 hybridized carbon with the leaving group. 2. Identify the nucleophile, the species with a lone pair or π bond. 3. Substitute the nucleophile for the leaving group and assign charges (if necessary) to any atom involved in bond breaking/formation.

The following steps are needed to draw the product of any nucleophilic substitution reaction. Place the steps in the correct order with the first step at the top of the list. Choice 1 of 3. Substitute the nucleophile for the leaving group and assign charges (if necessary) to any atom involved in bond breaking/formation. Choice 2 of 3. Find the sp3 hybridized carbon with the leaving group. Choice 3 of 3. Identify the nucleophile, the species with a lone pair or π bond.

weaker, weaker Reason: The hydroxide anion is a stronger base than Cl-. In a polar aprotic solvent, a stronger base is also a stronger nucleophile. stronger, stronger stronger, weaker Reason: In a polar aprotic solvent, a stronger base is also a stronger nucleophile. weaker, stronger Reason: The hydroxide anion is a stronger base than Cl-. Correct Answer stronger, stronger

The hydroxide anion -OH is a _____ base than the chloride anion Cl- and therefore in a polar aprotic solvent -OH will be a _____ nucleophile.

Correct Answer SN1, SN2

The mechanism of a nucleophilic substitution reaction depends on the identity of the alkyl halide. The substitution mechanism for 3° alkyl halides is _____, whereas 1° and methyl halides react only by the _____ mechanism. For 2° alkyl halides other factors influence the mechanism of the reaction. Multiple choice question. SN2, SN1 SN1, SN2

Correct Answer products, decrease, higher

The rate of any reaction depends on the activation energy for the reaction, and hence the energy of the transition state. In an endothermic reaction, the transition state resembles the ______. In this type of reaction, if the stability of the reaction product decreases, the reaction rate will ______ because the value of Ea for a less stable product is ______. Multiple choice question. products, increase, lower reactants, increase, lower reactants, not change, the same products, decrease, higher

Correct Answer reactants, not change, the same

The rate of any reaction depends on the activation energy for the reaction, and hence the energy of the transition state. In an exothermic reaction, the transition state resembles the ______ most closely. In this type of reaction, if the stability of the reaction product increases, the reaction rate will ______ because the value of Ea for a more stable product is ______. Multiple choice question. reactants, decrease, higher products, increase, lower products, not change, the same reactants, not change, the same

Correct Answer Blank 1: decreases, lowers, reduces, hinders, inhibits, or lessens Blank 2: nonnucleophilic, non-nucleophilic, hindered, or non nucleophilic

The steric bulk of the tert-butoxide anion its reactivity as a nucleophile without affecting its ability to act as a base. A sterically hindered base that is a poor nucleophile is called a base.

Correct Answer Blank 1: vinyl, vinyl halides, or vinylic Blank 2: aryl or aromatic

The two organic halides shown do not undergo SN1 or SN2 nucleophilic substitution reactions. These halides are named and halides.

False Reason: Incorrect: Nucleophiles like -SH are often used as salts with Li+, Na+, or K+ counterions. Correct Answer True Reason: Correct: Nucleophiles like -SH are often used as salts with Li+, Na+, or K+ counterions.

True or false: Negatively charged nucleophiles are often used as salts. The identity of the counterion used to balance the charge is often inconsequential, and therefore it is omitted from the chemical equation.

True Reason: Incorrect: An SN1 reaction has two steps and is unimolecular, whereas an SN2 reaction has a single concerted step. The rate of both an SN1 and an SN2 reaction will double when the concentration of the alkyl halide electrophile is doubled. False Reason: Correct: An SN1 reaction has two steps and is unimolecular, whereas an SN2 reaction has a single concerted step. The rate of both an SN1 and an SN2 reaction will double when the concentration of the alkyl halide electrophile is doubled. Correct Answer False

True or false: A substitution reaction has two steps, and doubling the concentration of the alkyl halide is found to double the reaction rate. This is a bimolecular SN2 reaction. True false question.

False Reason: Alkyl, allylic, and benzylic halides have the halogen atom bonded directly to an sp3 hybridized C atom. True Reason: Alkyl, allylic, and benzylic halides have the halogen atom bonded directly to an sp3 hybridized C atom.

True or false: Aryl and vinyl halides have the halogen atom bonded directly to an sp2 hybridized C atom.

False Reason: Incorrect. A good leaving group increases the rate of both SN1 and SN2 reactions but does not cause one mechanism to be favored over the other. Correct Answer True

True or false: In a nucleophilic substitution reaction the identity of the leaving group affects the rate of reaction but does not determine its mechanism. True false question. True False

True Reason: SN2 reactions follow second-order kinetics. Rate = k[CH3Br][CH3O-] Correct Answer False Reason: SN2 reactions follow second-order kinetics. Rate = k[CH3Br][CH3O-]

True or false: In the SN2 reaction shown the rate equation is: Rate = k[CH3Br]

True Reason: Correct: Nucleophiles like -SH are often used as salts with Li+, Na+, or K+ counterions.

True or false: Negatively charged nucleophiles are often used as salts. The identity of the counterion used to balance the charge is often inconsequential, and therefore it is omitted from the chemical equation.

True Reason: The alkyl halide (methyl, 1°, 2°, or 3°), nucleophile (strong or weak), leaving group (good or poor), and solvent (protic or aprotic) must be examined in order to determine the mechanism of a substitution reaction. False Reason: The alkyl halide (methyl, 1°, 2°, or 3°), nucleophile (strong or weak), leaving group (good or poor), and solvent (protic or aprotic) must be examined in order to determine the mechanism of a substitution reaction. Correct Answer True

True or false: The nucleophile and solvent must be examined when attempting to determine the mechanism of a substitution reaction. True false question. True False

Correct Answer carbocation intermediate

Vinyl halides do not undergo SN1 reactions because of the instability of the ______. Multiple choice question. leaving group product carbocation intermediate

Correct Answer decreases; increases Reason: The ability to stabilize a negative charge increases as atomic size increases (charge is better stabilized as it spread over a larger volume). Atomic size increases down a group; hence basicity decreases and leaving group ability increases down a group.

When comparing atoms in the same group of the periodic table, basicity generally ______ and leaving group ability ______ down the group. Multiple choice question. decreases; increases increases; decreases decreases; decreases increases; increases

Correct Answer B and D A and C

Which of the following combinations of species may be reacted to form the target compound shown? (Select all that apply.) Multiple select question. E and F C and F B and E B and D A and C

Steric hindrance decreases both nucleophilicity and basicity. Reason: Steric hindrance decreases nucleophilicity without decreasing basicity. Correct Answer It is generally true that the stronger base is the stronger nucleophile. In polar protic solvents, nucleophilicity increases with increasing size of the nucleophile.

Which of the following correctly describe the general relationships between nucleophilicity and basicity? (Select all that apply.) Multiple select question. It is generally true that the stronger base is the stronger nucleophile. Steric hindrance decreases both nucleophilicity and basicity. In polar protic solvents, nucleophilicity increases with increasing size of the nucleophile.

The reaction temperature (hot or cold) Reason: Temperature affects the reaction rate, not the mechanism. Correct Answer The leaving group (good or poor) The nucleophile (strong or weak) The alkyl halide (methyl, 1°, 2°, or 3°) The solvent (protic or aprotic)

Which of the following factors need to be considered when attempting to determine the mechanism of a substitution reaction? (Select all that apply.) Multiple select question. The reaction temperature (hot or cold) The leaving group (good or poor) The nucleophile (strong or weak) The alkyl halide (methyl, 1°, 2°, or 3°) The solvent (protic or aprotic)

B Reason: B shows frontside attack by the nucleophile (CH3O-). Nucleophiles attack from the backside in SN2 reactions. C Reason: The electrophilic C should not have a δ+ in the transition state D Reason: D is the transition state for attack on the enantiomer of the alkyl iodide shown. Correct Answer A

Which of the following is the correct transition state for the SN2 reaction given in the figure? Multiple choice question. A B C D

B Reason: B is a weaker base since it is a resonance stabilized anion. For two nucleophiles with the same nucleophilic atom, the stronger base is the stronger nucleophile. Correct Answer A Reason: A is a stronger base since it is a localized anion.

Which of the following is the stronger nucleophile? Multiple choice question. B A

CH3CH2CH2Cl Reason: Cl- is a weak base and a good leaving group. Correct Answer CH3CH2OCH3 CH3CH2CH2CH3 CH3CH2CH2NH2

Which of the following molecules do not contain a good leaving group? (Select all that apply.) Multiple select question. CH3CH2OCH3 CH3CH2CH2CH3 CH3CH2CH2NH2 CH3CH2CH2Cl

CH3CH2OH Reason: Strong, negatively-charged nucleophiles favor the SN2 mechanism. H2O Reason: Strong, negatively-charged nucleophiles favor the SN2 mechanism. Correct Answer CH3O- -SH -CN

Which of the following nucleophiles favor the SN2 mechanism? Select all that apply. Multiple select question. CH3O- CH3CH2OH H2O -SH -CN

Identify the nucleophile, the species with a lone pair or σ bond. Reason: Identify the nucleophile, the species with a lone pair or π bond. Find the sp2 hybridized carbon that is connected to the leaving group. Correct Answer Substitute the nucleophile for the leaving group and assign charges (if necessary) to any atom that is involved in bond breaking/formation. Find the sp3 hybridized carbon that is connected to the leaving group.

Which of the following should be used to draw any nucleophilic substitution product? (Select all that apply.) Multiple select question. Find the sp2 hybridized carbon that is connected to the leaving group. Substitute the nucleophile for the leaving group and assign charges (if necessary) to any atom that is involved in bond breaking/formation. Identify the nucleophile, the species with a lone pair or σ bond. Find the sp3 hybridized carbon that is connected to the leaving group.

acetone Reason: Polar, aprotic solvents favor the SN2 mechanism, while protic solvents favor the SN1 mechanism. H2O Reason: Polar, aprotic solvents favor the SN2 mechanism, while protic solvents favor the SN1 mechanism. CH3CH2OH Reason: Polar, aprotic solvents favor the SN2 mechanism, while protic solvents favor the SN1 mechanism. DMSO Reason: Polar, aprotic solvents favor the SN2 mechanism, while protic solvents favor the SN1 mechanism. Correct Answer acetone DMSO

Which of the following solvents would favor an SN2 nucleophilic substitution mechanism? Select all that apply. acetone H2O CH3CH2OH DMSO

Correct Answer The starting material is a chiral alkyl halide. The reaction proceeds through a planar carbocation intermediate, which is achiral. The product of the reaction will be a mixture of two enantiomers.

Which of the following statements about the SN1 reaction of (R)-2-bromobutane with water are correct? Multiple select question. The starting material is a chiral alkyl halide. The product of the reaction will be a the (S) isomer. Reason: Because of the achiral intermediate, both (R)- and (S)-2-bromobutane will be formed. The reaction proceeds through a planar carbocation intermediate, which is achiral. The product of the reaction will be a mixture of two enantiomers. The product will contain no stereogenic center and will be achiral.

Halogen substituents are given a higher priority than alkyl substituents. Reason: Halogen substituents are of equal priority to alkyl substituents. To name a halogen substituent, change the -ine ending of the halogen to the suffix -o. The parent chain is the longest continuous chain of C atoms that is directly connected to the halogen.

Which of the following statements correctly describe the IUPAC method for naming alkyl halides? (Select all that apply.) Halogen substituents are given a higher priority than alkyl substituents. Reason: Halogen substituents are of equal priority to alkyl substituents. To name a halogen substituent, change the -ine ending of the halogen to the suffix -o. The parent chain is the longest continuous chain of C atoms that is directly connected to the halogen.

The donation of electron density from a C-H bond attached to the carbon of the carbocation into its empty p-orbital. The donation of electron density from the empty p-orbital of a carbocation to an adjacent C-H σ-bond. Reason: The carbocation is electron deficient and doesn't have electron density to donate. The empty p-orbital acts as an acceptor of electron density. The donation of electron density from an adjacent C-H σ-bond to the empty p-orbital of a carbocation. Correct Answer The donation of electron density from an adjacent C-H σ-bond to the empty p-orbital of a carbocation.

Which of the following statements correctly describes hyperconjugation? Multiple choice question. The donation of electron density from a C-H bond attached to the carbon of the carbocation into its empty p-orbital. The donation of electron density from the empty p-orbital of a carbocation to an adjacent C-H σ-bond. The donation of electron density from an adjacent C-H σ-bond to the empty p-orbital of a carbocation.

Nucleophilicity increases down a group of the periodic table as basicity increases. Reason: Basicity does not increase down a group. Nucleophilicity increases down a group in a polar protic solvent because the ability of the solvent to solvate the ion decreases with ionic size. Nucleophilicity is no longer related to basicity when a polar protic solvent is used. Reason: In a polar protic solvent, nucleophilicity generally increases as basicity decreases down a group of the periodic table. Correct Answer Nucleophilicity increases down a group of the periodic table as basicity decreases. Reason: A polar protic solvent solvates the nucleophile effectively. A weaker base will be less effectively solvated than a stronger base and will therefore be a stronger nucleophile. This is opposite of the trend observed in aprotic solvents.

Which of the following statements correctly describes the trend for nucleophilicity in a polar protic solvent? Multiple choice question. Nucleophilicity increases down a group of the periodic table as basicity increases. Nucleophilicity is no longer related to basicity when a polar protic solvent is used. Nucleophilicity increases down a group of the periodic table as basicity decreases.

Correct Answer The nucleophile should be attacking from the backside, not the frontside. There should be a δ- symbol on the Br in the transition state. There should not be a δ+ symbol on the C atom in the transition state.

Which of the following statements correctly identify the errors in the following mechanism for an SN2 reaction? Select all that apply. Multiple select question. The nucleophile should be attacking from the backside, not the frontside. The product has the wrong stereochemistry. The bond to the S in the transition state should be a full bond, not a partial bond. There should be a δ- symbol on the Br in the transition state. There should not be a δ+ symbol on the C atom in the transition state.

Scheme B Reason: B shows frontside attack by the Nu. SN2 reactions occur with backside attack. Scheme C Reason: C is an two-step (SN1) mechanism. Correct Answer Scheme A

Which reaction scheme gives the correct mechanism for the SN2 reaction shown? Multiple choice question. Scheme A Scheme B Scheme C

Hyperconjugation is another term for resonance. Hyperconjugation is the sideways overlap of adjacent p orbitals, which leads to delocalization of electrons. Reason: Hyperconjugation involves the overlap of an empty p orbital with the electrons of an adjacent σ bond, NOT the sideways overlap of adjacent p orbitals. It is a π bond that is formed by the sideways overlap of adjacent p orbitals. Hyperconjugation is the release of electron density from an alkyl group to a positively charged C atom. Reason: Alkyl groups donate electron density to a positively charged C atom by induction. Correct Answer Hyperconjugation is the overlap of an empty p orbital with the electrons of an adjacent σ bond.

Which statement correctly defines hyperconjugation? Multiple choice question. Hyperconjugation is another term for resonance. Hyperconjugation is the sideways overlap of adjacent p orbitals, which leads to delocalization of electrons. Hyperconjugation is the release of electron density from an alkyl group to a positively charged C atom. Hyperconjugation is the overlap of an empty p orbital with the electrons of an adjacent σ bond.

Angle strain Reason: Angle strain is a form of strain that is found in small rings (when the internal bond angles in a ring deviate from the ideal 109.5° tetrahedral bond angle). Torsional strain Reason: Torsional strain is a form of strain that is the result of eclipsing interactions in an eclipsed conformer. Correct Answer Steric hindrance

_____ results in a decrease in reactivity due to the presence of bulky groups at the site of a reaction. Multiple choice question. Angle strain Torsional strain Steric hindrance