Open ending questions ONLYCombo of Homework/Review assignments: Organic Chemistry I - Final Exam Study Guide"

structure?

(2R,3R)-2,3-dichlorobutane

Which of the following is a polar aprotic solvent?

(CH3) 2S=O (for certain) CH3CN, but is on cusp

Which of the following bromides will react faster with CH3OH in an SN1 reaction?

(CH3)2CBrCH2CH3

structure?

(R)-3-methyl-1-pentyn-3-ol

Write the name of five +I groups.

+I NH4+: Ammonium group H3O+: Hydronium group C2H3+: Vinyl group CH3+: Methyl group C3H5+: Allyl group

Write the name of five -I groups.

-I NH2-: Amino group OH-: Hydroxyl group CHO-: Carbonyl group NO2-: Nitro group HSO3-: Sulfonic group

1-Butanol is heated with HBr. Write the detailed mechanism of the reaction.

1-Butanol is heated with HBr. Write the detailed mechanism of the reaction. 1-Butanol is heated with HBr. Write the detailed mechanism of the reaction.

When 1-bromobutane is reacted with the bulky base, potassium t-butoxide, in t-butyl alcohol, the major elimination product is:

1-butene

Write the postulates of Baeyer's Strain Theory.

1. All cycloalkanes are Co-planar because the atoms present in any cycloalkane molecule lie in the same plane. C-C angle is 109°28' 2. The deviation of bond angle from the normal tetrahedral angle is called angle strain 3. The greater the angle strain, the greater the instability of ring 4. The higher the stability of the ring the greater would be its ease of formation

Write and explain the Cahn-Ingold-Prelog rules of priority determination.

1. Assign priority # to each group attached to the chiral C. 2. Atom w/ highest atomic # is assigned highest priority, #1. 3. ties, look at the next atoms along the chain. 4. Double & triple bonds are treated like bonds to duplicate atoms.

Arrange and justify the order of acidic strength of the following compounds: Chloroacetic acid, Fluoroacetic acid, Dichloroacetic acid, and Trichloroacetic acid.

1. Chloroacetic acid 2. Fluoroacetic acid 3. Dichloroacetic acid 4. Trichloroacetic acid - The stronger electron withdrawing group the more stable the conjugate base so the stronger the acid will be. Fl is more electronegative and a stronger WG (withdrawing group) than Cl. Multiple EWG increases the acidity more than a single group.

Write the broader classification of organic chemical reactions. Give examples in each case

1. Classification by Structural Change 2. Classification by Reaction Type 3. Classification by Functional Group

3 reasons atoms bond?

1. each atom wants a full outermost energy level 2. gain, lose, & share valence electrons to achieve the duet or octet rule "being happy" 3. Gives each atom an electron configuration similar to that of a noble gas

Arrange the following five compounds with the increasing order of acidity:

2 1 5 3 4

What do you mean by "condensation reaction"? Give an example.

2 molecules combine to form a larger molecule. For example, an alcohol reacts with a carboxylic acid and forms an ester

How many different types of strains are possible in a molecule?

3, angle, torsional, steric

Which of the following structures is (E)-2,3-dichloro-2-pentene?

5

What do you mean by conjugate acid and conjugate base? Explain with suitable example (equation is to be given).

A conjugate acid, within the Brønsted-Lowry acid-base theory, is a species formed by the reception of a proton (H+) by a base—in other words, it is a base with a hydrogen ion added to it. On the other hand, a conjugate base is merely what is left after an acid has donated a proton in a chemical reaction. Hence, a conjugate base is a species formed by the removal of a proton from an acid.

Define and explain with appropriate examples: Lactonization and Lactamization.

A lactone is a cyclic ester, lactam is a cyclic amide

What is electronegativity?

A measure of how strongly the atoms attract electrons in a bond. The bigger the elctronegativity difference the more polar the bond

Al(OH)3 is a Brønsted base but Lewis acid —Explain.

According to the Brønsted-Lowry theory: an acid only exists as such in relation to a base, and vice versa. Al(OH)3 + OH− ⇌ Al(OH)−4 acting as an acid: loses H+ to become OH−. 3H+ + Al(OH)3 ⇌ 3H2O + Al3+(aq) acting as a base: gains H+ to become 3H2O+

What do you mean by pro-R and pro-S?

A. An sp3 carbon with two groups the same is also a prochiral center B. The two identical groups are distinguished by considering either and seeing if it was increased in priority in comparison with the other * If the center becomes R the group is pro-R and pro-S if the center becomes S

What is the difference between absolute configuration and relative configuration?

Absolute configuration: the precise 3-dimensional arrangement of atoms in space Relative configuration: compares the 3-dimensional arrangement of atoms in space of 1 compound with those of another compound.

Draw and explain the Eclipsed and Staggered conformation(s) of Ethane.

An eclipsed conformation is the highest energy, least stable conformer where all 6 C-H bonds are as close as possible to each other. A staggered conformer is the lowest energy, most stable conformer and all C-H bonds are as far away as possible.

Describe with suitable diagram the hybridization of carbon in methane

As seen in methane (CH4), carbon can form 4 bonds. The rationale behind this phenomenon is hybridization. Supporting evidence shows that 1 s and 3 p orbitals are being combined to form hybrid orbitals, allowing polyatomic molecule to have 25% s character and 75% p character. Thus, we call methane a sp3-hybridized molecule.

Except proton, Brønsted acids are not Lewis acids — Justify.

Bronsted acids are not Lewis acids because they cannot accept an electron pair directly (only a proton would be a Lewis acid)

How can you classify the major reactive intermediates in organic chemistry? Give examples.

Charged and Uncharged

(R)-2-chlorobutane is correctly represented by which of the following:

I

Calculate the formal charge (FC) on nitrogen and boron atoms in H3N - BH3.

B: 5-(0+4) = + 1 N: 3-(0+4) = - 1

Why was Baeyer's theory incorrect?

Baeyer assumed that all cycloalkanes are flat (most adopt a puckered 3-D conformation), he also did not consider the contribution of torsional strain to the overall strain energy of a molecule

Aluminum hydroxide (Al(OH)3) is amphoteric in nature — Justify (equations need to be given).

Because Aluminum hydroxide can be both an H+ donor and receiver it is amphoteric

NH3 is a polar molecule but BF3 is non-polar—justify.

Because F is evenly distributed around B but H is not evenly distributed around N

Benzoic acid is stronger acid than acetic acid— Explain:

Because the benzoate ion resulted from Dissociation of Benzoic acid is stabilized by resonance whereas the Acetate ion resulted from Dissociation of Acetic acid IS NOT stabilized.

Why is chloroform (CHCl3) polar whereas carbon tetrachloride (CCl4) is non-polar?

Carbon tetrachloride doesnt have a dipole moment but chloroform has a H and so the electrons will be focused on the Cl, not the H.

2,4,4-trimethylheptane

C10H22

4-ethyl-3,4-dimethyloctane

C12H26

3,3-diethyl-2,5-dimethylnonane

C15H32

Trans-1,2-diethyl cyclopropane

C7H14

What makes resonance structure have decreased stability?

Electron delocalization, an increased amount of potential energy or resonance

What do you mean by dipole moment? Explain, considering water molecule as an example.

Dipole moment a measure of polarity of a molecule due to the difference of charge on either end of the molecule. Example> H2O has a permanent dipole moment due to H being much less electronegative than O creating a partial negative charge on the O's and a partial + on H's.

Antiperiplanar geometry is usually preferred for _____ reaction.

E2

Explain torsional strain in a molecule.

Eclipsing of bonds on neighboring atoms

Electromeric effect is seen in ________ π system whereas resonance effect predominates in __________ π system.

Electromeric effect is a temporary effect and takes place between two atoms joined by a multiple bond, i.e., a double or triple bond. It occurs at the requirements of the attacking reagent, and involves instantaneous transfer of a shared pair of electrons of the multiple bonds to one of the linked atoms. It is denoted as E effect. Resonance is a hypothetical concept in which molecule is represented by more than one form called canonical form or resonating structure and the property of the molecule is represented by combination of all canonical forms called resonance hybrid.

Explain the terms with appropriate examples: "electrophile" and "Nucleophile".

Electrophile: An electron deficient atom, ion or molecule that has an affinity for an electron pair, and will bond to a base or nucleophile. Nucleophile: An atom, ion or molecule that has an electron pair that may be donated in bonding to an electrophile (or Lewis acid).

What do you mean by Eutomer & Distomer?

Eutomer (bioactive enantiomer): The enantiomer of a chiral drug possessing therapeutic activity of interest Distomer (inactive enantiomer): that with lower affinity or less activity or non-activity

Explain angular strain in a molecule.

Expansion or compression of bond angles away from the preferred 109.5°28'

Why is CH3COOH stronger acid than HOH?

HOH (H2O) is a weaker conjugate acid, making it a stronger base and CH3COOH is a stronger conjugate acid making it a weaker base.

Explain the terms with appropriate examples: "Homolysis" and "heterolysis".

Homolysis: a covalent single bond is broken so that one electron of the shared pair remains with each fragment. Heterolysis: the bond breaks with both electrons of the shared pair remaining with one fragment

Write the differences between Inductive effect and Field effect

Inductive effect is defined as permanent displacement of shared electron pair in a carbon chain towards more electronegative atom or group. • Inductive effect is a polarization through σ-bond; drop off rapidly with number of σ-bonds. • Field effect is a polarization through space; drop off rapidly with the distance. • In most cases, inductive and field effects operate together and difficult to separate them.

Arrange the relative strength of the following factors on acidity (structural effects) of a molecule: Resonance, Atomic radius, Electronegativity, Inductive effect.

Inductive effect, Electronegativity, Atomic radius, Resonance

Hi is more acidic than HF — Explain.

Iodine is so much bigger than fluorine that the charge is more stable on this larger atom. Thus, the trends for acidity of the hydrohalic acids are as follows: HI is strongest, followed by HBr, HCl, and finally HF.

What do you mean by Cahn-Ingold-Prelog R-S notational system?

It is the R/S rotation system: clockwise = R (right, rectus) Counterclockwise = S (left or sinister) Assigning the Absolute Configuration 1. Use the Cahn-Ingold-Prelog priority rules to assign priority (one through four) to the four groups on the "chiral" atom. 2. Orient the molecule so that the lowest priority atom is in the back (away from you). Look at the remaining three groups of priority 1-3. If the remaining three groups are arranged so that the priorities 1>2>3 are in a clockwise fashion, then assign the chiral center as R ("rectus" or right). If the remaining three groups are arranged 1>2>3 in a counterclockwise manner, then assign the chiral center as S ("sinister" or left)

rrange the following molecules according to increasing acidic order: Hydrofluoric acid, Methane, Water and Ammonia— Explain your predicted order.

Methane < Ammonia < Water < Hydrofluoric acid

Draw the conformations of (i) Cis-decalin (ii) Trans-decalin and (iii) the most stable shape of decane.

Most stable is Trans-decalin

Discuss "unfamiliar chairality" with examples from biphenyl and allene (one each).

Nonmobile Conformers: If the conformer is sterically hindered, it may exist as enantiomers.

Arrange and justify the order of acid strength of the following molecules: O2NCH2COOH, FCH2COOH, CICH2COOH, BrCH2COOH, ICH2COOH, CH3COOH, (CH3)2CHCOOH.

O2NCH2COOH > FCH2COOH >CICH2COOH > BrCH2COOH> ICH2COOH > CH3COOH Reason : Acidic strength decreases as -I effect of the group or halogen decreases.

Define optical purity. The specific rotation of (S)-2-iodobutane is +15.90. Determine the % composition of a mixture of (R)- and (S)-2-iodobutane if the specific rotation of the mixture is -3.18.

Optical purity is a comparison of the optical rotation of a pure sample of unknown stereochemistry VS a sample of pure enantiomer.

(R)-2-chlorobutane

R, S, transition

Explain the terms "resonance contributor" and "resonance hybrid" considering benzene as an example.

RC: diff. structures of same molecule each representing a different form that a molecule can take RH: a dipiction of a molecule showing an intermediate form of all the RC in one model Benzene can have 2 different configurations of 3 double bonds and Benzenes res. hybrid would be drawn with 6 dotted lines representing possible double bonds.

Explain with appropriate equations (at least two) why water is called amphoteric?

Referring to the Bronsted Theory, an acid is an H+ donor and a base is the one that accepts the H+ . Because water can do both it is therefore amphoteric.

explain steric strain in a molecule.

Repulsive interactions between nonbonded atoms in close proximity. Repulsive interaction occurring between atoms that are forced closer together than their atomic radii allow. In other words, repulsive interactions when two atoms or groups bump into one another.

The structure of one of the enantiomers of carvone is shown below. Find the asymmetric carbon atom, and determine whether it has the (R) or the (S) configuration.

S configuration

Treatment of (S)-2-bromobutane with sodium hydroxide results in the production of a compound with an (R) configuration. The reaction has most likely taken place through...

SN-2

For primary alkyl halides _____ is favored with most nucleophiles, but _____ is favored with bulky bases like tbutoxide.

SN2, E2

Describe with suitable diagram the hybridization of carbon in ethylene

Sp2: Unlike methane, ethylene is shaped differently, despite the fact that the carbon in ethylene has the same electron configuration. What accounts for this difference? Supporting evidence shows that the carbon in an ethylene molecule is sp2 hybridized. This means that 1 s orbital is being mixed with 2 p orbitals.

Describe with suitable diagram the hybridization of carbon in acetylene.

Sp: Supporting evidence shows that acetylene is an sp molecule. This means that 1 s orbital is being mixed with 1 p orbital

The label of a chemical bottle says that the bottle contains 98% ee (S)-conformer— what does it mean?

That means the bottle contains 98% of an isomer{spatial isomer-> diastereomers->conformers}. S means the rotation of the bonds in the molecule.

Methanesulfonic acid (pKa = -1.2) is stronger acid than acetic acid (pKa = 4.74) — Explain.

The acetate ion shares the negative charge with 2 O atoms and the Methanesulfonic ion has a negative charge spread over 3 O atoms, this delocalization help stabilize the anion.

How can you explain the acid strength of Hypochlorous acid, Chlorous acid, Chloric acid and Perchloric acid?

The acid strength increases as the number of oxygen atoms increase. The number of oxidation will increase in Cl.

Arrange and justify the order of acidic strength of the following compounds: Butanoic acid, 2Chlorobutanoic acid, 3-Chlorobutanoic acid, 4-Chlorobutanoic acid.

The closer the Cl gets to the COOH, the stronger the acid. By adding an electron withdrawing group such as -Cl, this stabilizes the conjugate base resulting in a strong acid. The magnitude of the inductive effect depends on the number of bonds between the ewg and the size of the negative charge. 1. Butanoic acid 2. 4-Chlorobutanoic acid 3. 3-Chlorobutanoic acid 4. 2Chlorobutanoic acid

What do you mean by the flipping of a cyclohexane ring?

The exchange of axial and equatorial positions caused by an inter-converted chair conformation.

2-Bromobutane is heated with NaOH. Write the detailed mechanism of the reaction.

The mechanism of the reaction of 1-butanol with H bromide proceeds by displacement of water by bromide ion from the protonated form of the alcohol (the alkyloxonium ion). The slow step, displacement of water by bromide from the oxonium ion, is bimolecular. The reaction of 1-butanol with hydrogen bromide follows the Sn2 mechanism. The reacion of 2-butanol with hydrogen bromide involves a carboction intermediate.

Explain the terms with appropriate examples: "thermodynamic control" and "kinetic control".

Thermodynamically VS Kinetically Controlled Reaction: In a chemical reaction they can decide the composition in a reaction product mixture when competing pathways lead to different products and the reaction conditions influence the selectivity. The distinction is relevant when product A forms faster than product B because the activation energy for product A is lower than that for product B, yet product B is more stable. In such a case A is the kinetic product and is favored under kinetic control and B is the thermodynamic product and is favored under thermodynamic control.

Draw and explain the Sawhorse and Newman projection(s) considering Ethane as an example.

These conformations are the arrangement of atoms resulting from bond rotation. Sawhorse projects allow you to view C-C bonds from an oblique angle and indicate spatial orientations by showing all the C-H bonds *(you can see ALL C-H bonds). Newman projections only allow the visibility of ONE C bond.

Write the structures of maleic acid and fumaric acid. What is their relation to each other?

They are both cis-trans isomers with maleic is the cis and fumaric is the trans, unsaturated dicarboxylic acids Although these two acids have the same structural formula and differ only in the three-dimensional geometry of their molecules, their properties are very different. Maleic acid melts at 130 °C (266 °F) and fumaric acid at 286 °C (547 °F); at room temperature, maleic acid is about 100 times more soluble in water and about 15 times as strong an acid (although fumaric acid gives up its second proton more readily than maleic acid does). Only maleic acid forms an anhydride; fumaric acid does not. Fumaric acid occurs in nature and is a component of the tricarboxylic acid cycle, whereas maleic acid is not a natural product. Maleic anhydride, which is made industrially by oxidation of benzene (C6H6), is often used as a dienophile (isolated alkene component) in Diels-Alder reactions.

Inductive effect

Transfer of charge (electron withdrawal or donation) through a chain of atoms in a molecule by electrostatic induction.

Comparing CF3SO3H (Trifluoromethanesulfonic acid) and CH3SO3H (Methanesulfonic acid), which has the higher pka? Why?

Trifluoromethanesulfonic acid is a stronger acid. When you compare the strengths of the conjugate bases, the weaker the base, the stronger the conjugate acid. In the case of the trifluoro derivative, the presence of the highly electronegative fluorine atoms serves to delocalize the negative charge to a greater extent. This additional delocalization makes trifluoromethanesulfonate a weaker base.

Briefly explain which of the two solvent mixtures, 40% 2-propanol in water or 60% 2-propanol in water, is more polar.

Water is more polar than propanol and so the mixture with 40% 2-propanol would be more polar.

Briefly explain what the Saytzeff's rule is. Outline a mechanism for the following compound using a strong acid.

When more than one alkene product is possible from the base induced elimination of an alkyl halide, the most highly substituted (most stable) alkene is usually the major product.

What do you mean by specific rotation? Explain.

[α]d - a standardized value for the optical rotation

A 1.00 gm sample is dissolved in 20.0 mL ethanol. 5.00 mL of this solution is placed in a 20.0-cm polarimeter tube at 20C. The observed rotation is 1.25 counterclockwise. Calculate specific rotation of the molecule.

a: observed rotation at 20°C = 1.25 ° l: the cell length in dm (1 dm = 10 cm)= 20 cm = 2.0dm c: concentration g/mL = 1.00g/20.0 mL

The SN2 mechanism for nucleophilic substitution reactions

involves one step and occurs with inversion of configuration.

Elimination reactions as in the SN-1 reaction, the slow step is the ________of the ________ to give a ________.

ionization; substrate; carbocation

What is the difference between lactone and lactam?

lactone is a cyclic intramolecular ester derived from a hydroxy acid while lactam is (organic chemistry) any of a class of cyclic amides, that are the nitrogen analogs of lactones, formed by heating amino acids; the tautomeric enol forms are known as lactims.

What is eudismic (eudysmic) ratio?

measures the pharmacological potency ratio of the eutomer to the distomer, (stereoselectivity of a chiral drug). *important to note that the eudismic designation refers to 1 biological action only, for a dual action drug, the eutomer for 1 activity may be the distomer for the other.

Which of the three molecules below is the enantiomer of the following molecule?

none

What do you mean by optical resolution and racemate?

optical resolution: In stereochemistry it is a process for the separation of racemic compounds into their enantomers (production of optically active drugs) racemate: A solution in which both enantiomers of a compound are present in equal amounts

What is rapid pyramidal inversion

rapid pyramidal inversion of the amine nitrogen prevents isolation of the enantiomers except where the nitrogen is part of a ring or has other geometrical constraint. switching between a pair enantiomers

What do you mean by (i) σ-bond and (ii) π-bond? Explain.

sigma bonds are two orbitals overlaping head on and pi bonds are the lobes overlapping

What is esterification? Give an example.

the general name for a chemical reaction in which two reactants (typically an alcohol and an acid) form an ester as the reaction product. Esters are common in organic chemistry and biological materials, and often have a characteristic pleasant, fruity odor. This leads to their extensive use in the fragrance and flavor industry. Ester bonds are also found in many polymers. The classic synthesis is the Fischer esterification, which involves treating a carboxylic acid with an alcohol in the presence of a dehydrating agent: RCO2H + R'OH is in equilibrium with RCO2R' + H2O

What is hybridization?

the idea that atomic orbitals fuse to form newly hybridized orbitals, which in turn, influences molecular geometry and bonding properties

SN-1 reactions show first-order kinetics because...

the rate-determining step involves only one molecule

What do you mean by 1,3-diaxial interactions? Explain with a suitable diagram.

the steric interaction between axial substituents bound to carbon atoms in a six-membered ring, resulting in a steric destabilization

Write the name of five +I and five -I groups

• Electron donating group (+I): O- COO- CR3 CHR2 CH2R, CH3 D • Electron withdrawing group (-I): NR3+ SR2+ NH3+ NO2 SO2R CN SO2Ar CO2H F Cl Br I OAr COOR OR COR SH SR, OH C≡CR Ar CH=CR2 [R = Alkyl, Ar = Aryl].