Exam Problem Set 2

Select an answer for each of the 58 multiple-choice questions below, then press Check Answers. The answer key unlocks after a genuine attempt.

Alkanes, Alkenes, Alkynes and their Alicyclic Couterparts

1. What is the IUPAC name for CH₃CH₂C(CH₃)₂CH₂CH(CH₃)₂?
A) 3,3,5-trimethylhexane
B) 2,2,5-trimethylhexane
C) 2,4,4-trimethylhexane
D) 1,1,3,3-tetramethylpentane

2. Which of the following conformational structures is 2-methylpentane ?

3 The alkane CH₃CH₂C(CH₃)₂CH₂CH(CH₃)₂ has how many 1°, 2°. 3° & 4° carbon atoms?

4 There are four constitutional isomers having the formula C₄H₉Cl
Which of the following would be a correct IUPAC name for one of these isomers?
A) 1-chloro-2-methylpropane
B) 3-chlorobutane
C) 2-chloro-2-methylbutane
D) 1-chloro-3-methylpropane

5 Which isomer of hexane has only two different sets of structurally equivalent hydrogen atoms.?
A) 2,2-dimethylbutane
B) 2-methylpentane
C) 3-methylpentane
D) 2,3-dimethylbutane

6 Limiting your answer to cycloalkanes and ignoring stereoisomers, how many C₆H₁₂ constitutional isomers are there?
A) 6
B) 9
C) 12
D) 13

7 The IUPAC name for (CH₃)₂CHCH(CH₃)CH₂CH=CH₂ is ...
A) 4,5-dimethyl-1-hexene
B) 4,5,5-trimethyl-1-pentene
C) 2,3-dimethyl-5-hexene
D) 4-methyl-4-isopropyl-1-butene

8 How many isomeric pentenes (C₅H₁₀) exist? (count stereoisomers as well)
A) 4
B) 5
C) 6
D) 7

9 The preferred conformation of cis-1,3-dimethylcyclohexane is ...
A) chair--diaxial
B) chair--diequatorial
C) chair--one axial / one equatorial
D) boat--mixed orientations

10 Which of the following represents the most stable conformation of all cis-1,2,4-trimethylcyclohexane?

11 A C₆H₁₂ compound reacts with ozone to yield a single C₃H₆O product. Gas phase free radical bromination of the hydrocarbon gives a single C₆H₁₁Br product. A likely identification of this compound is ..
A) cyclohexane
B) cyclohexene
C) 3-hexene
D) 2,3-dimethyl-2-butene

12 The terpene ocimene has the IUPAC name (3E)-3,7-dimethyl-1,3,6-octatriene, what is the structural formula of this compound?

13 The most typical reaction of simple alkenes is ...
A) electrophilic substitution
B) nucleophilic substitution
C) electrophilic addition
D) nucleophilic addition

14 Which of the following dimethylcyclobutanes is chiral ?
A) trans-1,2-dimethylcyclobutane
B) cis-1,2-dimethylcyclobutane
C) trans-1,3-dimethylcyclobutane
D) cis-1,3-dimethylcyclobutane

15 What is the structure of bicyclo[3.1.1]heptane?

16 Which of the following C₆H₁₂ isomers has the largest heat of combustion?
A) cyclohexane
B) methylcyclopentane
C) ethylcyclobutane
D) propylcyclopropane

17 The radical halogenation of 2-methylpropane gives two products: (CH₃)₂CHCH₂X (minor) and (CH₃)₃CX (major)
  Chlorination gives a larger amount of the minor product than does bromination, Why?
A) Bromine is more reactive than chlorine and is able to attack the less reactive 3° C-H.
B) Bromine atoms are less reactive (more selective) than chlorine, and preferentially attack the weaker 3° C-H bond.
C) The methyl groups are more hindered to attack by the larger bromine atom.
D) Bromination is reversible and the more stable 3°-alkyl bromide is formed exclusively.

18 A tertiary carbocation (carbonium ion) is more stable than either a secondary or primary carbocation because ...
A) it carries three positive charges
B) it has a pyramidal configuration
C) it has a trigonal planar configuration
D) it possesses three electron-donating substituent groups

19 Which of the following is not an electrophile?
A) C₂H₅OC₂H₅
B) BF₃
C) [CH₃]₃C⁽⁺⁾
D) HOCl

20 Which of the following olefins would you expect to react most rapidly with concentrated sulphuric acid ?
A) H₂C=CH₂
B) (CH₃)₂C=CH₂
C) Cl₂C=CCl₂
D) CF₃CH=CH₂

21 Which compound is a likely product from addition of Cl₂ to 1-butene?
A) CH₃CH₂CH₂CHCl₂
B) CH₃CH₂CHClCH₂Cl
C) ClCH₂CH₂CH₂CH₂Cl
D) CH₃CH₂CCl₂CH₃

22 The product from OsO₄ hydroxylation of trans-2-butene will be ...
A) achiral
B) optically active
C) racemic
D) a meso compound

23 The product from bromine addition to trans-2-butene will be ...
A) optically active
B) racemic
C) a meso compound
D) chiral

24 Addition of 1 equivalent of bromine to 2,4-hexadiene at 0° C gives 4,5-dibromo-2-hexene plus an isomer.
Which of the following is that isomer?
A) 5,5-dibromo-2-hexene
B) 2,5-dibromo-3-hexene
C) 2,2-dibromo-3-hexene
D) 2,3-dibromo-4-hexene

25 How many sp hybridized carbon atoms are present in a molecule of 3-methyl-4-vinyl-1,2-heptadien-5-yne?
A) 2
B) 3
C) 4
D) 5

26 Treatment of 1-methylcyclohexene with an ether solution of diborane ( B₂H₆ ), followed by reaction with alkaline H₂O₂ produces what product?
A) 1-methylcyclohexanol
B) cis-1-methylcyclohexane-1,2-diol
C) cis-2-methylcyclohexanol
D) trans-2-methylcyclohexanol

27 Which of the following will be the kinetically favored product from the depicted reaction ?

28 Two C₄H₆ isomers give the same C₄H₈O product from HgSO₄ catalyzed hydration in aqueous acid.
 However, these isomers give different C₄H₆Br₄ products with excess bromine.
  What are these isomeric hydrocarbons?
A) cyclobutene and methylenecyclopropane
B) 1,2-butadiene and 1,3-butadiene
C) 1-butyne and 2-butyne
D) 2-butyne and cyclobutene

29 Which of the following structures would be considered an enol tautomer of cyclopentanone?

30 Two C₅H₈ isomers undergo catalytic (Pt) hydrogenation to form the same C₅H₁₀ product. On ozonolysis followed by oxidative workup (H₂O₂), one isomer gave a C₅H₈O₄ diacid, while the other isomer gave a C₅H₈O₃ ketoacid.
Which of the following isomeric pairs correspond to this evidence?
A) cyclopentene and 1-pentyne
B) cyclopentene and 1-methylcyclobutene
C) 1-methylcyclobutene and 3-methylcyclobutene
D) cyclopentene and 3-methylcyclobutene

31 Considering that the angles of a regular pentagon are 108°, why is cyclopentane not planar?
A) all the carbons are sp² hybridized, so there is considerable angle strain.
B) The C-C bonds are formed by overlap of p-orbitals, so the 90° angle results in large angle strain.
C) The cyclic overlap of bonding orbitals results in anti-aromaticity destabilization.
D) The five C-C bonds have eclipsing strain.

32 Which reaction conditions would best convert 3-hexyne to cis-3-hexene?
A) Pt catalyst and H₂.
B) Lindlar's Pd catalyst and H₂.
C) Na in liquid NH₃.
D) NaNH₂ in liquid NH₃.

33 Reaction of 1-hexene with NBS (N-bromosuccinimide) forms two isomeric bromohexenes, one of which is 3-bromo-1-hexene.
Which of the following is the other isomer?
A) 1-bromo-2-hexene.
B) 6-bromo-1-hexene.
C) 1-bromo-1-hexene.
D) 2-bromo-1-hexene.

34 A C₆H₁₀ hydrocarbon forms an insoluble silver salt when treated with silver nitrate in ethanolic ammonia.
Acid catalyzed hydration with a HgSO₄ catalyst generates a single C₆H₁₂O ketone, and pemanganate oxidation yields a C₅H₁₀O₂ carboxylic acid
This compound is most likely which of the following?
A) cyclohexene.
B) methylenecyclopentane.
C) 1-hexyne.
D) 3-hexyne.

35 Peroxide induced reaction of carbon tetrachloride with 1-butene produces which of the following?
A) 1,1,1,3-tetrachloropentane.
B) 1,1,1,2-tetrachloropentane.
C) 1-chloro-2-trichloromethylbutane.
D) 1,1-dichloro-2-ethylcyclopropane.

36 Which of the following isomeric hexenes will have the smallest heat of hydrogenation?
A) 4-methyl-1-pentene.
B) (E)-4-methyl-2-pentene.
C) (Z)-4-methyl-2-pentene.
D) 2-methyl-2-pentene.

37 A C₈H₁₄ hydrocarbon (X) is reduced by sodium in liquid ammonia to a single C₈H₁₆ product (Y).
Both of these compounds undergo hydrogenation (Pt catalyst) to give 2,5-dimethylhexane.
Ozonolysis of Y with an oxidative workup produces a single C₄H₈O₂ carboxylic acid.
Reaction of Y with perbenzoic acid (C₆H₅CO₃H) gives a chiral C₈H₁₄O product, but reaction with bromine gives an achiral C₈H₁₄Br₂ product
What are X and Y?
A) X is 2,5-dimethyl-3-hexyne ; Y is cis-2,5-dimethyl-3-hexene.
B) X is 2,5-dimethyl-3-hexyne ; Y is trans-2,5-dimethyl-3-hexene.
C) X is 2.5-dimethyl-1,5-hexadiene ; Y is 2,5-dimethyl-3-hexyne.
D) X is 2,5-dimethyl-2,4-hexadiene ; Y is cis-2,5-dimethyl-3-hexene.

38 Which of the following compounds has two or more conjugated double bonds?

39 What reagent(s) would best achieve conversion of 3,3-dimethyl-1-butyne to the aldehyde (CH₃)₃CCH₂CHO?

40 Which of the following dienes would best serve as a diene in a Diels-Alder reaction?

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

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 1,1-dibromobutane?
A) 2 equivalents of HBr, no peroxides.
B) 2 equivalents of HBr, with peroxides.
C) 1 equivalent of Br₂.
D) 2 equivalents of Br₂ followed by i equivalent of KOH.

45 What is the relative rate of addition of HBr to I: 1,3-pentadiene;   II: 1,4-pentadiene;   and   III: 1-pentyne?
A) I > II > III.
B) III > II > I.
C) II > I > III.
D) III > I > II.

46 A chiral C₆H₁₂ hydrocarbon undergoes catalytic hydrogenation to yield an achiral C₆H₁₄ product. What is the starting compound?
A) cis-2-hexene
B) 3-methyl-2-pentene
C) 4-methyl-2-pentene
D) 3-methyl-1-pentene

47 Reaction of 3,3,6,6-tetramethyl-1,4-cyclohexadiene, first with excess aqueous mercuric acetate, then followed by sodium borohydride reduction, produces a mixture of isomeric C₁₀H₂₀O₂ alcohols.
Excluding enantiomers, how many isomeric products may be formed in this reaction?
A) 2
B) 4
C) 6
D) 8

48 A C₈H₁₂ chiral hydrocarbon, X, is reduced by catalytic hydrogenation to an achiral C₈H₁₄ compound.
Ozonolysis of X (H₂O₂ workup) gave a chiral C₈H₁₂O₄ dicarboxylic acid.
Which of the following could be X ?

49 Which of the following reactions of cyclohexene may be considered an oxidation?
A) addition of hydrogen (Pt catalyst) to give cyclohexane.
B) addition of HBr to give bromocyclohexane
C) epoxidation by perbenzoic acid to give cyclohexene oxide
D) mercuric acetate catalyzed hydration to give cyclohexanol

50 Addition of HBr to 2,3-dimethyl-1,3-cyclohexadiene may occur in the absence or presence of peroxides.
  In each case two isomeric C₈H₁₃Br products are obtained.
  Which of the following is a common product from both reactions?

51 What structural change takes place when an alkene undergoes a Simmons-Smith reaction?
A) addition of ethene gives a cyclobutane derivative.
B) the double bond is shifted to a more substituted location.
C) the double bond is converted to a triple bond.
D) a methylene group is added to give a cyclopropane derivative.

52 Cyclooctatetraene, C₈H₈, appears to be a conjugated annulene.
  In addition to the planar configuration, three non-planar structures may be considered, all of which are shown below.
  Which of these is most likely to be the favored conformation?   note that D is planar.

53 Which one of the following compounds contains the greatest number of sp² hybridized carbon atoms?
A) 1,4-Cycloheptadiene
B) 2,5-dimethyl-2,3,4-hexatriene
C) Phenylacetylene
D) 1,1-diallyl-3,3-divinylcyclobutane

54 Which one of the following compounds contains the greatest number of sp hybridized carbon atoms?
A) 1,4-Cyclooctadiene
B) 2,5-dimethyl-2,3,4-hexatriene
C) Phenylacetylene
D) 1,1-diallyl-3,3-divinylcyclobutane

55 Which one of the following compounds contains the greatest number of sp³ hybridized carbon atoms?
A) 1,4-Cyclooctadiene
B) 2,5-dimethyl-2,3,4-hexatriene
C) Phenylacetylene
D) 1,1-diallyl-3,3-divinylcyclobutane

56 Which of the following isomers has the lowest heat of combustion?
A) cis-1,2-dimethylcyclohexane
B) trans-1,2-dimethylcyclohexane
C) cis-1,3-dimethylcyclohexane
D) trans-1,3-dimethylcyclohexane

57   Compound Z, C₈H₁₄, reacts with excess hydrogen and a Pt catalyst to give 2,5-dimethylhexane as the only product.
  Z diplays three ¹³C nmr signals, all at higher field than 100 ppm, and does not absorb in the UV at wavelengths greater than 200 nm.
  Oxidation of Z by either ozone or potassium permanganate produces a single C₄H₈O₂ carboxylic acid. Deduce the structure of Z.
A) 2,5-dimethyl-3-hexyne
B) trans-2,5-dimethyl-3-hexene
C) cis-2,5-dimethyl-3-hexene
D) 2,5-dimethyl-2,4-hexadiene

58 Which of the following is the correct configurational prefix for the following diene?