Exam Problem Set 3

Select an answer for each of the 54 multiple-choice questions below, then press Check Answers. The answer key unlocks after a genuine attempt.

Alkyl Halides, Alcohols, Ethers and Epoxides

1. What is the IUPAC name for CH₃CHClCH(CH₃)CH₂CH₂CH₂CH₂Br?
A) 1-bromo-6-chloro-5-methylheptane
B) 7-bromo-2-chloro-3-methylheptane
C) 1-bromo-6-chloro-5,6-dimethylhexane
D) 6-bromo-1-chloro-1,2-dimethylhexane

2. What is the IUPAC name for (CH₃)₃CCH(OH)CH₂CH(OH)CH₂CH(CH₃)₂?
A) 1,1,1,6-tetramethyl-2,4-heptanediol
B) 2,2,7-trimethyl-3,5-octanediol
C) 2,2,6,6-tetramethyl-3,5-heptanediol
D) 2,7,7-trimethyl-4,6-octanediol

3 What is a correct name for the following compound?
 
A) 1,1-dimethyl-2-cyclohexenol
B) 3,3-dimethyl-1-cyclohexen-6-ol
C) 6,6-dimethyl-1-cyclohexen-3-ol
D) 4,4-dimethyl-2-cyclohexenol

4 Which of the following is a chiral C₅H₁₂O 1°-alcohol?
A) 3-methyl-2-butanol
B) 2-methyl-2-butanol
C) 3-methyl-1-butanol
D) 2-methyl-1-butanol

5 Which of the following reagents would you expect to react with bromocyclopentane by an S_N2 mechanism?
A) C₂H₅OH
B) C₂H₅O^(-) K⁽⁺⁾
C) NaCN
D) (CH₃)₃N

6 Chloroethane, C₂H₅Cl, does not react with methanol under mild conditions.
What reagent could be added to the reaction mixture to increase the rate of substitution.?
A) HCl (conc.)
B) NaOH
C) NH₄OH
D) AgNO₃

7 Which of the following compounds is unlikely to react with sodium metal?
A) C₂H₅OC₂H₅
B) C₂H₅OH
C) C₂H₅Br
D) C₂H₅NH₂

8 The reaction of sodium ethoxide with iodoethane to form diethyl ether is classified as ...
A) an electrophilic substitution
B) a nucleophilic substitution
C) a radical substitution
D) an electrophilic addition

9 Compound X reacts with HI. The product of this reaction, when treated with KOH in ethanol, gives Y ( an isomer of X ).
Ozonolysis of Y (H₂O₂ workup) produces two compounds: a two carbon carboxylic acid, and a four carbon ketone.
What is X?
A) 2-methyl-2-pentene
B) 4-methyl-1-pentene
C) 2,3-dimethyl-2-butene
D) 3-methyl-1-pentene

10 The S_N2 reaction of 1-chloro-3-methylbutane with sodium methoxide is relatively slow, but can be accelerated by the addition of a small amount of NaI.
How is this catalysis best explained?
A) The sodium cation helps pull off the chloride anion
B) The iodide anion activates the methoxide nucleophile
C) S_N2 reaction of iodide ion converts the alkyl chloride to the more reactive alkyl iodide
D) The NaI changes the mechanism to S_N1

11 Which one of the following alcohols will be oxidized by Jones' reagent (CrO₃ in 50% sulphuric acid) to a ketone having the same number of carbon atoms ?
A) 1-methylcyclohexanol
B) 3,3-dimethylcyclopentanol
C) 3-methyl-1-hexanol
D) 3-ethyl-3-hexanol

12 What reagent would be suitable for distiguishing 1-methoxy-3-methyl-2-butene from its isomer 4-methyl-3-penten-1-ol?
A) bromine in methylene chloride
B) KMnO₄ in aqueous base
C) AgNO₃ in dilute NH₄OH
D) sodium metal suspended in hexane

13 Synthesis of hexane-3,4-diol from trans-3-hexene may be accomplished in two ways:
  (i) OsO₄ hydroxylation   &   (ii) C₆H₅CO₃H epoxidation followed by NaOH opening of the epoxide ring.
Which of the following statements about the products from these reactions is correct?
A) the two methods giive the same product
B) (i) gives a chiral isomer, (ii) gives an achiral isomer
C) (i) gives an achiral isomer, (ii) gives a chiral isomer
D) two different isomers are formed, but both are chiral

14 Reaction of 1,4-dibromobutane with Mg turnings in ether gives the bis-Grignard reagent, BrMgCH₂CH₂CH₂CH₂MgBr.
What is the product from the reaction of meso-2,3-dibromobutane with Mg under the same conditions?
A) trans-2-butene
B) cis-2-butene
C) meso-CH₃CH(MgBr)CH(MgBr)CH₃
D) racemic-CH₃CH(MgBr)CH(MgBr)CH₃

15 Which reagent(s) would best accomplish the following transformation?

A) H₃O⁺ & heat
B) (i) HgSO₄ in H₂O   (ii) NaBH₄
C) (i) B₂H₆ in ether   (ii) H₂O₂ and base
D) (i) HOBr   (ii) Mg in ether

16 Which of the following reagents would not effect the following transformation?

A) KCl (5 molar solution)
B) HCl & ZnCl₂
C) SOCl₂
D) PCl₃

17 What will be the chief product from the following reaction sequence?

18
          I OH^(-)   II CH₃CO₂^(-)   III HO₂^(-)   IV H₂O
The above molecules and ions are all nucleophiles. What is the relative order of their reactivity in an S_N2 reaction with ethyl bromide?
A) I > II > III > IV
B) IV> III > II > I
C) III > I > II > IV
D) II > III > IV > I

19 In the S_N2 reaction of cyanide ion with (CH₃)₂CHCH₂CH₂X what is the relative order of reactivity for the following X substituents?
          I X = F   II X = Cl   III X = Br   IV X = I
A) I > II > III > IV
B) IV> III > II > I
C) III > I > II > IV
D) II > III > IV > I

20 Which of the following does not convert a 1°-hydroxyl group into a good leaving group for a S_N2 reaction?
A) SOCl₂
B) CH₃SO₂Cl
C) PBr₃
D) NaI

21 How is the following reaction best classified?
  (CH₃)₃CBr + (CH₃CH₂)₃N -----> (CH₃)₂C=CH₂ + (CH₃CH₂)₃NH⁽⁺⁾ Br^(-)
A) S_N2 substitution
B) E2 elimination
C) electrophilic addition
D) cationic rearrangement

22 Which of the following isomeric chlorides will undergo S_N2 substitution most resdily?
A) 4-chloro-1-butene
B) 1-chloro-1-butene (cis or trans)
C) 1-chloro-2-butene (cis or trans)
D) 2-chloro-1-butene

23 Which reagent would be best for achieving an E2 elimination of 3-chloropentane?
A) C₂H₅ONa
B) CH₃CO₂Na
C) NaHCO₃
D) NaI

24 Which reaction conditions would be best for the synthesis of isobutyl sec-butyl ether
  CH₃CH₂CH(CH₃)-O-CH₂CH(CH₃)₂ ?
A) (CH₃)₂CHCH₂OH + H₂SO₄ + heat
B) CH₃CH₂CH(CH₃)OH + H₂SO₄ + heat
C) CH₃CH₂CH(CH₃)ONa + (CH₃)₂CHCH₂Br
D) (CH₃)₂CHCH₂ONa + CH₃CH₂CH(CH₃)Br

25 A chiral C₅H₁₀O ether reacts with hot HI to give a C₅H₁₀I ₂ product
Theatment of this with hot KOH in ethanol produces 1,3-pentadiene. What is the structure of the original ether?

26 A C₇H₁₃Br compound reacts with KOH in ethanol to form 3-methylcyclohexene as the major product.
What is a likely structure for the starting alkyl bromide?
A) cis-4-methylcyclohexyl bromide
B) trans-3-methylcyclohexyl bromide
C) cis-2-methylcyclohexyl bromide
D) trans-2-methylcyclohexyl bromide

27 A synthesis of 2,5-dimethyl-2-hexanol from 2-methylpropene requires the formation of two four-carbon intermediates, X and Y.
These intermediates combine to give the desired product after the usual hydrolysis work-up.
Select appropriate methods of preparing X and Y from 2-methylpropene
A) X add HBr, then react with Mg in ether   Y add water, acid-catalysis
B) X add HBr (peroxides), then react with Mg in ether   Y react with C₆H₅CO₃H in CH₂Cl₂
C) X add HOBr   Y add B₂H₆in ether, then NaOH
D) X add HOBr   Y add HBr (peroxides) ,then react with Mg in ether

28 All of the following alkyl bromides react by S_N2 substitution when treated with sodium cyanide in methanol.
Which one does not undergo an inversion of configuration?
A) (R)-1-bromo-2-methylbutane
B) (S)-2-bromo-3-methylbutane
C) (R)-1-bromo-3,3-dimethylcyclohexane
D) cis-4-ethyl-1-bromocyclohexane

29 The structures of two 3°-bicyclic chlorides (I and II) are shown below.
 
Which of the following statements is correct?
A) on treatment with KOH in ethanol, both compounds undergo E2 elimination.
B) on treatment with KOH in ethanol, I undergoes substitution and II undergoes eleimination.
C) I is more reactive than II for both substitution and eleimination
D) II is more reactive than I for both substitution and eleimination

30 Reaction of (R)-2-chloro-4-methylpentane with excess NaI in acetone gives racemic 2-iodo-4-methylpentane
How can this be explained?
A) the reaction mechanism changes to S_N1
B) the reaction proceeds via a rapidly inverting radical intermediate
C) the substitution is S_N2, but repeated attack by iodide anion (with inversion) leads to racemization
D) iodide anion preferentially attacks chlorine, giving a rapidly inverting carbanion intermediate

31 Azide anion is a very good nucleophile. Predict the major product from the following reaction.

32 What is the chief product from the following reaction?

33 Consider the S_N1 solvolysis of the following 1°-alkyl chlorides in aqueous ethanol.
          I CH₃CH₂CH₂Cl   II CH₂=CHCH₂Cl   III CH₃OCH₂Cl   IV CF₃CF₂CH₂Cl
What is the order of decreasing reactivity?
A) III > II > I > IV
B) II > I > III > IV
C) IV > III > II > I
D) I > II > III > IV

34 In the S_N2 reaction of iodide ion with (CH₃)₂CHCH₂CH₂X what is the order of decreasing reactivity for the following X substituents?
          I X = -OH   II X = CH₃CO₂-   III X = CF₃SO₃-   IV X = CCl₃CO₂-
A) I > II > III > IV
B) IV > III > II > I
C) III > II > IV > I
D) III > IV > II > I

35 A C₆H₁₄O chiral alcohol is converted to a bromide by treatment with PBr₃.
Reaction of this bromide, first with Mg in ether, followed by quenching in 0.1 N HCl produces an achiral C₆H₁₄ hydrocarbon.
Which of the following is the original alcohol.?
A) 2-ethyl-1-butanol.
B) 4-methyl-1-pentanol.
C) 3-methyl-3-pentanol.
D) 3-methyl-1-pentanol.

36 Which of the following reaction sequences would best serve to convert 2-methyl-1-bromopropane to 4-methyl-1-iodopentane?
A) (i) Mg in ether; .(ii) ethylene oxide (C₂H₄O); (iii) HI & heat
B) (i) NaC≡CH in ether; .(ii) H₂ + Lindlar catalyst; (iii) HI
C) (i) KOH in alcohol; . (ii) C₆H₅CO₃H in CH₂Cl₂; (iii) NaC≡CH in ether ; (iv) 2 H₂ + Pt catalyst
D) (i) NaC≡CH in ether; .(ii) H₃O⁺ + HgSO₄; (iii) HI & heat

37 Which of the following organic halides will undergo an E2 elimination on heating with KOH in alcohol?
A) 2,2-dimethyl-1-bromopropane
B) 2,2-dimethyl-1-bromocyclohexane
C) benzyl chloride (C₆H₅CH₂Cl)
D) 2,5-dimethyl-1-bromobenzene

38 A chiral C₇H₁₆O₂ diol is oxidized by PCC in CH₂Cl₂ to an achiral C₇H₁₂O₂ compound.
Which of the following would satisfy these facts?

39 What is the product from the acid catalyzed addition of methanol to 2,2-diethyloxirane?
A) 3,3-dimethoxypentane
B) 2-ethyl-1-methoxy-1-butanol
C) 2-ethyl-1-methoxy-2-butanol
D) 2-ethyl-2-methoxy-1-butanol

40 Which of the following is the product from ethanol addition to dihydropyran (shown on the left below)?

41 What product(s) are expected from the following reaction?
   
A) 2 CH₃CH₂I
B) 2 ICH₂CH₂OH
C) 2 ICH₂CH₂I
D) CH₃CH₂I + CH₃CH₂OH

42 Which of the following is the most likely product of this Diels-Alder reaction?

43 Reaction of 1,1-dibromopentane with three equivalents of NaNH₂ in ether is followed by treatment with 0.1M HCl at 0° C.
What is the product?
A) cyclopentene.
B) 1,2-pentadiene.
C) 2-pentyne.
D) 1-pentyne.

44 Which of the following reagents and conditions would best serve to convert 1-butyne to 1-bromo-1-butene?
A) 1 equivalent of HBr, no peroxides.
B) 1 equivalent of HBr, with peroxides.
C) 1 equivalent of Br₂, followed by 1 equivalent of KOH.
D) 2 equivalents of HBr, followed by 1 equivalent of KOH.

45 Which of the following reagents would be best for oxidizing a 1°-alcohol to an aldehyde?
A) H₃PO₄
B) PCC in CH₂Cl₂
C) Jones' reagent (H₂CrO₄)
D) OsO₄

46 If the rate of reaction of [0.1 M] sodium cyanide with [0.1M] 1-bromoethane is 1.4 x 10^-4,
what effect will an increase in NaCN concentration to [0.3] and alkyl bromide concentration to [0.2] have on the overall reaction rate?
A) increase by 2 times
B) increase by 3 times
C) iincrease by 6 times
D) increase by 1.5 times

47 A chiral C₅H₁₀O alcohol is reduced by catalytic hydrogenation to an achiral C₅H₁₂O alcohol.
The original alcohol is oxidized by activated MnO₂ to an achiral carbonyl compound (C₅H₈O)
Which of the following might be the chiral alcohol?
A) 1-penten-3-ol
B) 4-penten-2-ol
C) 3-methyl-2-buten-1-ol
D) 2-methyl-2-buten-1-ol

48 A water soluble C₆H₁₄O₂ compound is oxidized by lead tetraacetate (or periodic acid) to a single C₃H₆O carbonyl compound.
Which of the following would satisfy this fact?
A) meso-2,3-dimethoxybutane
B) 1,2-diethoxyethane
C) meso-2,5-hexanediol
D) meso-3,4-hexanediol

49 Which of the following is the most likely product from the reaction illustrated by the curved arrows in the formula on the left?

50 Which of the following ethers is unlikely to be cleaved by hot conc. HBr?

51 What reagents and conditions are used for the Simmons-Smith reaction?
A) CH₃I + Mg in ether
B) CH₂I₂ + Zn (Cu) in ether
C) BrCH₂CH₂Br + Zn in ether
D) CBr₄ + Zn (Cu) in ether

52 The Lucas test is used to distinguish small (7 or fewer carbons) 1°, 2° and 3° -alcohols.
The alcohol to be tested is added to a solution of anhydrous ZnCl₂ in conc. HCl at room temperature.
Which of the following statements is not correct?
A) 1°-alcohols dissolve, but do not react
B) 3°-alcohols react quickly to give an insoluble alkyl chloride
C) 3°-alcohols rapidly dehydrate, and the gaseous alkene bubbles out of the test solution
D) 2°-alcohols dissolve and react slowly to give an insoluble alkyl chloride

53 A C₆H₁₂O compound does not react with Br₂ in CCl₄, produces a flammable gas on treatment with LiAlH₄, and reacts with H₂CrO₄ changing the color from orange to green
  Which of the following compounds best agrees with these facts?
A) 1-methylcyclopentanol
B) methoxycyclopentane
C) 2-cyclopropyl-2-propanol
D) 2-cyclobutylethanol

54 Stereoisomers I and II undergo E2 elimination on treatment with sodium ethoxide in ethanol.
  One isomer reacts 500 times faster than the other. Also, one isomer gives X as the only product, whereas the other gives Y together with some X
  Which of the following statements provides the best assignment of I and II?

A) II reacts faster and gives both Y & X
B) II reacts faster and gives only X
C) I reacts faster and gives both Y & X
D) I reacts faster and gives only X