O Chem II
Acid-catalyzed hydration of 2-methyl-1-butene would yield which of the following?
A) (CH3)2C(OH)CH2CH3
128) All of the hydrogen atoms in a molecule of cyclohexane are homotopic.
Answer: True
Which reaction would yield a racemic product?
C) Cyclopentene + Br2/H2O --->
Markovnikov addition of HI to 2-methyl-2-butene involves:
D) formation of a carbocation at C-2.
Consider the addition of HCl to 3-methyl-1-butene. The major product of the reaction would be:
2-Chloro-2-methylbutane
What is the chief product of the reaction of IBr with 2-methyl-2-pentene?
2-bromo-3-iodo-2-methylpentane
Addition of excess HCl to 2-methyl-3-heptyne would produce:
2-methyl-3,3-dichloroheptane and 2-methyl-4,4-dichloroheptane
A compound C4H9Br gave the following 1H NMR spectrum: triplet, 1.0 (3H); doublet, 1.7; multiplet, 1.8; multiplet, 4.1 (1H) Which is a reasonable structure for the compound?
A) CH3CH2CHBrCH3
Which of the following reactions would yield the final product as a racemic form?
A) Cyclohexene + Br2, H2O
Which reagent(s) given below could be used to synthesize cis-1,2-cycloheptanediol from cycloheptene?
A) KMnO4, OH, 5oC
The most resistant compound to the action of hot alkaline KMnO4 is:
A) Pentane
Cyclohexene reacts with bromine to yield 1,2-dibromocyclohexane. Molecules of the product would:
A) be a racemic form and, in their most stable conformation, they would have both bromine atoms equatorial.
Cyclohexene is treated with cold dilute alkaline KMnO4. Assuming syn addition, the spatial arrangement of the two hydroxyl groups in the product would be:
A) equatorial-axial
Even when one or more stereogenic centers are produced as the result of an addition reaction to an alkene, the product is always formed as a racemic mixture. Why is that?
Answer: Because alkenes are planar, and the reagent can add from either face.
130) The predicted ratio of the relative peak sizes in a quintet signal would be about 1:3:5:3:1.
Answer: False
An acceptable solvent to use for a deuterium exchange experiment with an alcohol would be CDCl3.
Answer: False
Due to the formation of a mercurinium ion in hydration of an alkene using oxymercuration- demercuration, we see overall anti-product form making this reaction stereospecific.
Answer: False
In halohydrin formation the reason why the halohydrin is the major product is because the solvent is more reactive that the bromide nucleophile.
Answer: False
Potassium permanganate is usually a preferred reagent for oxidative cleavage to form aldehyde, as it is a much milder and less toxic reagent than osmium tetroxide.
Answer: False
143) The rule that correctly predicts the regiochemistry of most ionic additions to alkenes is called ___.
Answer: Markovnikov's Rule
129) Hydrogen that are diastereotopic will show different chemical signals in the proton NMR.
Answer: True
Compounds that contain a benzylic carbon will often show a peak with a m/z of 91 in a mass spectrometry experiment.
Answer: True
The reason why anti-Markovnikov addition is seen in the hydration of alkenes using hydroboration-oxidation conditions is due to steric interactions with the boron group attaching to the less substituted carbon more easily.
Answer: True
The yields for an acid catalyzed hydration of an alkene can be increased by using dilute acid as this will help drive the equilibrium to products.
Answer: True
The introduction of a small amount of a peroxide to a hydrogen halide addition of an alkene will result in a(n) ___ addition where the hydrogen in the addition appears adds to the carbon with the ___ number of hydrogens.
Answer: anti-Markovnikov, fewest
pi bonds are quite susceptible to reaction with electron-seeking reagents, also referred to as ___.
Answer: electrophiles
133"NMR" stands for ___.
Answer: nuclear magnetic resonance
When a reaction that could potentially yield two or more constitutional isomers instead produces only one as the major product, the reaction is said to be ___.
Answer: regioselective
A reaction in which the reactant is not necessarily chiral but still produces primarily one stereoisomeric form of the product (or a specific subset of the possible stereoisomers) is referred to as a ___ reaction.
Answer: stereoselective
When a particular stereoisomer reacts in such a way that it gives a particular stereoisomer as a product, even if more than one stereoisomer is theoretically possible, the reaction is said to be ___.
Answer: stereospecific
Hydroboration-oxidation is a reaction with ___ stereochemistry and ___ regiochemistry.
Answer: syn, anti-Markovnikov
The conversion of ethylene to vinyl bromide can be accomplished by use of these reagents in the order indicated.
B) (1) Br2; (2) NaOC2H5
Which set of reagents might be used to convert bromocyclohexane into cis-1,2- cyclohexanediol?
B) 1) Potassium tert-butoxide, 2) OsO4, pyridine then NaHSO4(aq)
What reagents might be used to convert cis-2-butene into trans-2-butene?
B) 1)HBr; 2)NaOEt, EtOH
A compound C5H11Cl which exhibits only two singlets in the 1H NMR spectrum must be:
B) 1-Chloro-2,2-dimethylpropane
For the compound adamantine, how many different signals would you see in the proton NMR? (Assume that you can see them all.)
B) 2
How many signals would you expect to find in the 1H NMR spectrum of CH3OCH2CH2OCH3?
B) 2
What is the chief product of the acid-catalyzed hydration of 2,5-dimethyl-2-hexene?
B) 2,5-dimethyl-2-hexanol
A prominent (M -18) peak suggests that the compound might be a(n):
B) Alcohol
Which reaction sequence would convert cis-2-butene to trans-2-butene?
B) Br2/CCl4; then 2 NaNH2; then Li/liq. NH3
Which reaction of an alkene proceeds with anti addition?
B) Bromination
What is the molecular formula of this compound? m/z intensity 84 M 10.00 85 0.56 86 0.04
B) C5H8O
Addition of 2 mol of HCl to 1-butyne would yield:
B) CH3CH2CCl2CH3
Which reaction would give a meso compound as the product?
B) Cyclopentene + OsO4, then NaHSO3
The interaction of the pi bond of an alkene with an electrophile can initially result in the formation of a species termed a pi complex. Which of these cannot combine with an alkene to form a pi complex?
B) NH3
Predict the splitting pattern you would observe for the proton at C1 of 2,3-dimethyl-2- phenylbutane.
B) Singlet
How many compounds are possible from the addition of bromine to CH2=CHCH2CH3 (counting stereoisomers separately)?
B) Two
R)-3-Chloro-1-butene reacts with HCl by Markovnikov addition, and the products are separated by gas chromatography. How many total fractions would be obtained and how many would be optically active?
B) one optically active fraction and one optically inactive
A pair of enantiomers results from which of these reactions?
C) 1-pentene + HCl ---->
How many 1H NMR signals would cis-1,2-dichlorocyclopropane give?
C) 3
How many 1H NMR signals would trans-1,2-dichlorocyclopropane give?
C) 3
Consider the expected 1H NMR spectrum of 1,1,3,3-tetramethylcyclopentane. Which of the following is likely to be observed?
C) 3 signals: all singlets
What is the theoretical multiplicity of the C-2 proton signal in the 1H NMR spectrum of 2- hydroxymethyl-1,3-propanediol, shown below?
C) 7
An optically active compound, Y, with the molecular formula C7H12 gives a positive test with cold dilute KMnO4 and shows IR absorption at about 3300 cm-1. On catalytic hydrogenation, Y yields Z(C7H16) and Z is also optically active. Which is a possible structure for Y?
C) CH3CH2CH(CH3)CH2CCH
When either cis- or trans-2-butene is treated with hydrogen chloride in ethanol, the product mixture that results includes:
C) CH3CH2CH(CH3)OCH2CH3
Which of these compounds belongs to the class of substances commonly known as "halohydrins"?
C) ICH2CH2OH
Which of these compounds will not be represented by a singlet only in the 1H NMR spectrum?
C) Isobutane
2-Pentyne will not react with:
C) NH3
The thermodynamic parameters at 298 K for the following reaction are given below. CH2=CH2 + HCl --gas phase--> CH3CH2Cl Ho = -64.9 kJ mol-1 So = -131 J K-1 mol-1 Go = -25.8 kJ mol-1 Which of the following statements is true of the reaction?
C) The entropy term is unfavorable but the formation of ethyl chloride is favored.
3,3-dimethylcyclohexene is subjected to reaction with cold, dilute KMnO4, to give 3,3- dimethyl-1,2-cyclohexanediol. In the most stable conformation of the product, the hydroxyl groups would be:
C) axial-equatorial
A compound that would show two triplets and a septet in the 1H NMR spectrum could be:
C) chlorocyclopropane
123) Select the structure of a compound C6H14 with a base peak at m/z 43.
D) (CH3)2CHCH(CH3)2
Which alkene would yield only CH3CH2COOH on oxidation with hot alkaline potassium permanganate (followed by acid work-up)?
D) (E)-3-hexene
Which of the following compounds would not be represented by a lone singlet in the proton NMR?
D) 1,2-ethanediol
An alkene with the molecular formula C8H16 undergoes ozonolysis to yield a mixture of (CH3)2C=O and (CH3)3CCHO. The alkene is:
D) 2,4,4-Trimethyl-2-pentene
The C7 compound which gives 3 signals in the broadband proton-decoupled 13C spectrum could be
D) 2,4-Dimethylpentane
29) Which alkene would you expect to be most reactive toward acid-catalyzed hydration?
D) 2-methyl-1-butene
Consider the expected splitting of the C2 proton signal in the 1H NMR spectrum of 1,1- dibromopentane. Presuming that the coupling constants for neighboring protons are sufficiently different, and that the instrument has sufficient resolving power, what is the theoretical multiplicity of the C2 proton signal?
D) 6
Which of the following reagents might serve as the basis for a simple chemical test that would distinguish between pure 1-pentene and pure pentane?
D) All of these choices.
A compound with the molecular formula C3H6Cl2 gave a 1H NMR spectrum consisting only of a triplet centered at 3.7 and a quintet centered at 2.2. The most likely structure for the compound is:
D) ClCH2CH2CH2Cl
Which of these compounds is not formed when gaseous ethene is bubbled into an aqueous solution of bromine, sodium chloride and sodium nitrate?
D) ClCH2CH2OH
The mass spectra of alkyl bromides and chlorides are characterized by an unusually intense ___.
D) M +2 peak
What compound would yield an equimolar mixture of CH3CH2CH2CHO and CH3CHO upon treatment with O3, followed by Zn/HOAc?
D) More than one of these choices.
A synthetic strategy for converting trans-2-butene into pure cis-2-butene would consist of which of the following?
D) Reaction with i) Br2, CCl4; ii) 2 NaNH2, NH3(l); iii) H2, Ni2B (P-2)
Predict the splitting pattern you would observe for the proton at C3 of 2,3-dimethyl-2- phenylbutane.
D) Septet
The data below from the molecular ion region of the mass spectrum of a halogen-containing compound are consistent with the presence of what halogen(s) in the original compound? intensity M 51.0 M +2 100.0 M +4 49.0
D) Two Br
121) Predict the base peak for 2-chloro-2-methylpropane,
D) m/z 57
Which of the following reactions of cyclobutene would yield a meso product?
D) reaction with D2, Pt
Consider the ozonolysis products obtained from all the unbranched and unsymmetrical isomers of heptene. The reaction product in each case would consist of:
D) two different aldehydes.
Consider the expected splitting of the C2 proton signal in the 1H NMR spectrum of 2-ethyl- 1,3-propanediol. Presuming that the coupling constants for neighboring protons are sufficiently different, and that the instrument has sufficient resolving power, what is the theoretical multiplicity of the C2 proton signal?
E) 15
The 1H NMR spectrum of which of these compounds would consist of a triplet, singlet and quartet only?
E) 3-chloro-3-methylpentane
One mole of an optically active compound, X, with the molecular formula C6H8 reacts with three moles of hydrogen in the presence of a catalyst to yield an optically inactive product that cannot be resolved. X also exhibits IR absorption at approximately 3300 cm-1. Which is a possible structure for X?
E) 3-methyl-1-penten-4-yne
Consider the expected 1H NMR spectrum of 2,4-dimethyl-1,4-pentadiene. Which of the following is likely to be observed?
E) 4 signals: two singlets, two doublets
How many 13C signals would you expect from anisole?
E) 5
Which of the following could be used as the basis for a simple test that would distinguish between 1-pentyne and pentane?
E) All of these choices.
Which of these compounds will react with cold concd. H2SO4, as well as Br2 in CCl4?
E) All of these choices.
Which reagent or test could be used to distinguish between 2-methyl-2-pentene and 2- methylpentane?
E) All of these choices.
What is the molecular formula of this compound? m/z intensity 78 M 10.00 79 1 80 3.3 81 0.3
E) C3H7Cl
Which of the following could be used to distinguish between 1-octyne and 3-octyne?
E) IR examination
A reagent or test that could be used to distinguish between 1-pentene and 1-pentyne would
IR examination
Which reagent or test could be used to distinguish between 3-pentyne and 1-pentyne?
IR examination
Carbenes are frequently produced by -elimination reactions. These are reactions in which the proton being lost and the leaving group are ___.
both attached to the same carbon
In general, when the addition of an unsymmetrical electrophilic reagent to an unsymmetrical alkene forms the product predicted by Markovnikov's rule, that occurs because:
it is formed via the more/most stable carbocation.
