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Organic Chemistry, 9e (Wade)
Chapter 3 Structure and Stereochemistry of Alkanes
1) Which of the statements below accurately describe(s) alkanes?
A) Alkanes are hydrocarbons which contain only single bonds.
B) Alkanes belong to the class of unsaturated hydrocarbons.
C) Alkanes are the simplest and least reactive class of organic compounds.
D) both A and B
E) both A and C
Answer: E
Diff: 1
Section: 3.1
LO: 2.6
2) Which of the following types of hydrocarbons is(are) saturated?
A) alkanes
B) alkenes
C) alkynes
D) aromatics
E) All of the above are saturated.
Answer: A
Diff: 1
Section: 3.1
3) If a hydrocarbon has no double or triple bonds, it is said to be ______.
Answer: saturated
Diff: 1
Section: 3.1
4) Straight-chain alkanes are also called ______.
Answer: n-alkanes
Diff: 2
Section: 3.2
LO: 3.1
5) The structure below is a potent analgesic agent (pain reliever) (J. Med. Chem., 2009, 5685). How many secondary carbons are in this structure?
A) 2
B) 4
C) 6
D) 12
Answer: A
Diff: 2
Section: 3.3
GO: G5
6) If an acyclic alkane hydrocarbon contains n carbon atoms, how many hydrogen atoms must it also contain?
A) n
B) 2n
C) n + 2
D) 2n + 2
E) n - 2
Answer: D
Diff: 2
Section: 3.2
LO: 3.1
GO: G2
7) A series of compounds, like the n-alkanes, that differ only by the number of groups, is called a(n) ______series.
Answer: homologous
Diff: 2
Section: 3.2
LO: 3.1
8) A bicyclic alkane contains 12 carbon atoms. How many hydrogen atoms does it contain?
A) 20
B) 22
C) 24
D) 26
E) 28
Answer: B
Diff: 2
Section: 3.10
LO: 3.1
9) How many methylene groups are present in 2,4-dimethylhexane?
A) 0
B) 1
C) 2
D) 6
E) 8
Answer: C
Diff: 2
Section: 3.2
LO: 3.1
GO: G7
10) Triacontane is an unbranched alkane that contains 30 carbon atoms in each molecule. How many hydrogen atoms are present in each molecule of triacontane?
A) 30
B) 32
C) 58
D) 60
E) 62
Answer: E
Diff: 3
Section: 3.2
LO: 3.1
11) How many secondary (2°) carbons are found in 5-ethyl-3,3,4-trimethylheptane?
A) 1
B) 4
C) 2
D) 3
E) 6
Answer: D
Diff: 1
Section: 3.3
GO: G7
12) Provide an acceptable name for (CH3CH2CH2)3CH.
Answer: 4-propylheptane
Diff: 1
Section: 3.3
LO: 3.2
MCAT LO: MCAT3.1
13) Provide the name of the compound below.
Answer: 3-fluoro-2,2-dimethylhexane
Diff: 1
Section: 3.3
LO: 6.1
MCAT LO: MCAT6.1
14) Provide the name of the compound below.
Answer: 2,3,6,7-tetramethylnonane
Diff: 1
Section: 3.3
LO: 3.2
MCAT LO: MCAT3.1
15) Provide an acceptable name for the alkane shown below.
CH3CH2CH2CH2CH2CH3
Answer: hexane orn-hexane
Diff: 1
Section: 3.3
LO: 3.2
MCAT LO: MCAT3.1
16) Provide an acceptable name for the alkane shown below.
Answer: 2,5-dimethylheptane
Diff: 1
Section: 3.3
LO: 3.2
MCAT LO: MCAT3.1
17) Draw an acceptable structure for 4-tert-butyloctane.
Answer:
Diff: 1
Section: 3.3
LO: 3.1
MCAT LO: MCAT3.1
18) Draw an acceptable structure for 3-ethyl-3-methylhexane.
Answer:
Diff: 1
Section: 3.3
LO: 3.1
MCAT LO: MCAT3.1
19) A student named the following molecule "4-isobutylheptane." Why is this incorrect? What is the correct name?
Answer: 2-methyl-4-propylheptane is the correct name. The name was incorrect because although heptane is the longest chain in both names, the substituent isobutyl is branched, while methyl and propyl are not.
Diff: 1
Section: 3.3
LO: 3.1
GO: G2
MCAT LO: MCAT3.1
20) Name the haloalkane shown.
Answer: 3,4-dibromoheptane
Diff: 1
Section: 3.3
LO: 6.1
MCAT LO: MCAT6.1
21) Provide an acceptable name for the following compound.
Answer: 4,4-dichloro-6-isopropyl-3-methylnonane
Diff: 2
Section: 3.3
LO: 3.2
MCAT LO: MCAT3.1
22) Provide an acceptable name for [(CH3)3C]2CHCH3.
Answer: 2,2,3,4,4-pentamethylpentane
Diff: 2
Section: 3.3
LO: 3.2
MCAT LO: MCAT3.1
23) Provide the IUPAC name of (CH3CH2)3CH.
Answer: 3-ethylpentane
Diff: 2
Section: 3.3
LO: 3.2
MCAT LO: MCAT3.1
24) Provide the IUPAC name of (CH3)2CHCH2CH2C(CH3)3.
Answer: 2,2,5-trimethylhexane
Diff: 2
Section: 3.3
LO: 3.2
MCAT LO: MCAT3.1
25) Predict the molecular formula of 4-ethyl-5,5-dimethyldodecane.
Answer: C16H34
Diff: 2
Section: 3.3
LO: 3.1
26) Provide an acceptable name for the alkane shown below.
Answer: 5-sec-butyl-2,2-dimethylnonane or 2,2-dimethyl-5-(1-methylpropyl)nonane
Diff: 2
Section: 3.3
LO: 3.2
MCAT LO: MCAT3.1
27) Provide an acceptable name for the alkane shown below.
Answer: 4-isopropyldecane or 4-(1-methylethyl)decane
Diff: 2
Section: 3.3
LO: 3.2
MCAT LO: MCAT3.1
28) Provide an acceptable name for the alkane shown below.
Answer: 3-ethyl-4,4-dimethylheptane
Diff: 2
Section: 3.3
LO: 3.2
MCAT LO: MCAT3.1
29) Draw an acceptable structure for 6-ethyl-2,6,7-trimethyl-5-propylnonane.
Answer:
Diff: 2
Section: 3.3
LO: 3.1
MCAT LO: MCAT3.1
30) Provide an acceptable name for the alkane shown below.
Answer: 2,2,3,6-tetramethylheptane
Diff: 2
Section: 3.3
LO: 3.2
MCAT LO: MCAT3.1
31) Provide an acceptable name for the alkane shown below.
Answer: 6-ethyl-2-methyl-5-propyldecane
Diff: 2
Section: 3.3
LO: 3.2
MCAT LO: MCAT3.1
32) Provide an acceptable name for the alkane shown below.
Answer: 2-fluoro-7-methyl-5-propyldecane
Diff: 2
Section: 3.3
LO: 6.1
MCAT LO: MCAT6.1
33) Identify the correct IUPAC name for the following structures.
A) 4-(2-iodo-1-methylethyl)-3-methylheptane
B) 3-s-butyl-1-iodo-2-methylhexane
C) 1-iodo-2,4-dimethyl-3-propylhexane
D) 2,4-dimethyl-1-iodo-3-propylhexane
Answer: A
Diff: 2
Section: 3.3
LO: 6.1
GO: G2
MCAT LO: MCAT6.1
34) Name the haloalkane shown.
CH3CH2C(CH3)2CH2CH2I
Answer: 1-iodo-3,3-dimethylpentane
Diff: 2
Section: 3.3
LO: 6.1
MCAT LO: MCAT6.1
35) Name the alkane shown.
[(CH3)2CH]2CHCH3
Answer: 2,3,4-trimethylpentane
Diff: 2
Section: 3.3
LO: 3.1
MCAT LO: MCAT3.1
36) Name the alkane shown.
Answer: 5-ethyl-2,2-dimethyloctane
Diff: 2
Section: 3.3
LO: 3.2
MCAT LO: MCAT3.1
37) How many methyl groups are present in 2,4-dimethylhexane?
A) 0
B) 2
C) 4
D) 6
E) 8
Answer: C
Diff: 2
Section: 3.3
LO: 3.1
GO: G2
MCAT LO: MCAT3.1
38) Identify the correct IUPAC name for the following structure.
A) 6-bromo-1-cyclopentyl-3,6-dimethylhexane
B) 1-bromo-5-cyclopentyl-1,4-dimethylpentane
C) 2-bromo-6-cyclopentyl-5-methylhexane
D) 5-bromo-1-cyclopentyl-2-methylhexane
E) none of the above
Answer: D
Diff: 3
Section: 3.10
LO: 6.1
GO: G2
MCAT LO: MCAT6.1
39) Identify the correct IUPAC name for each compound shown below.
A) 2-bromo-3-sec-butyl-4-ethylhexane
B) 2-bromo-4-ethyl-3-sec-butylhexane
C) 3-(1-bromoethyl)-2,4-diethylhexane
D) 4-(1-bromoethyl)-3-ethyl-5-methylheptane
E) 4-(1-bromoethyl)-5-ethyl-3-methylheptane
Answer: D
Diff: 3
Section: 3.3
LO: 6.1
GO: G2
MCAT LO: MCAT6.1
40) Provide the name of the compound shown.
Answer: 2,2,7-trichloro-4-ethyl-6-isobutyl-7,10-dimethyldodecane
Diff: 3
Section: 3.3
LO: 6.1
MCAT LO: MCAT6.1
41) Give structures for the three isomers with molecular formula C5H12 and provide the common name of each.
Answer:
Diff: 3
Section: 3.3
LO: 3.2
GO: G7
MCAT LO: MCAT3.2
42) Provide an acceptable name for the alkane shown below.
Answer: 3-ethyl-7-methyl-5-propylnonane
Diff: 3
Section: 3.3
LO: 3.2
MCAT LO: MCAT3.1
43) Draw an acceptable structure for 4-ethyl-6-(1,2-dimethylpropyl)decane.
Answer:
Diff: 3
Section: 3.3
LO: 3.1
MCAT LO: MCAT3.1
44) Draw an acceptable structure for 1-ethyl-2-(2,2-dimethylpentyl)cyclopentane.
Answer:
Diff: 3
Section: 3.10
LO: 3.1
MCAT LO: MCAT3.1
45) When one compares the densities of n-hexane and water, one finds ______.
A) that n-hexane is less dense than water
B) that n-hexane is more dense than water
C) that these two compounds have the same density
D) that the relative densities of two immiscible compounds cannot be measured
Answer: A
Diff: 1
Section: 3.4
LO: 3.3
MCAT LO: MCAT3.3
46) A branched alkane has ______boiling point relative to the isomeric linear alkane. There are ______London force interactions in the branched alkane.
A) a higher; stronger
B) a higher; weaker
C) a lower, stronger
D) a lower; weaker
E) the same; similar
Answer: D
Diff: 1
Section: 3.4
LO: 3.3
MCAT LO: MCAT3.3
47) Consider the three isomeric alkanes n-hexane, 2,3-dimethylbutane, and 2-methylpentane. Which of the following correctly lists these compounds in order of increasing boiling point?
A) 2,3-dimethylbutane < 2-methylpentane < n-hexane
B) 2-methylpentane < n-hexane < 2,3-dimethylbutane
C) 2-methylpentane < 2,3-dimethylbutane < n-hexane
D) n-hexane < 2-methylpentane < 2,3-dimethylbutane
E) n-hexane < 2,3-dimethylbutane < 2-methylpentane
Answer: A
Diff: 2
Section: 3.4
LO: 3.3
GO: G7
MCAT LO: MCAT3.3
48) Name the following compound and use the appropriate cis/trans designation.
Answer: trans - 1-bromo-3-(tert-butyl)cyclohexane
Diff: 2
Section: 3.15
LO: 6.1
MCAT LO: MCAT6.1
49) ______is the n-alkane of greatest molecular weight which is a gas at room temperature and pressure.
Answer: Butane
Diff: 2
Section: 3.4
LO: 3.3
MCAT LO: MCAT3.3
50) Place the following alkanes in order of increasing boiling point:
CH3(CH2)6CH3, CH3(CH2)5CH3, (CH3)3CCH2CH2CH3
Answer: (CH3)3CCH2CH2CH3 < CH3(CH2)5CH3 < CH3(CH2)6CH3
Diff: 2
Section: 3.4
LO: 3.3
MCAT LO: MCAT3.3
51) Why are alkanes described as hydrophobic?
Answer: Alkanes are nonpolar and as such they do not dissolve to any appreciable extent in water.
Diff: 2
Section: 3.4
LO: 3.3
MCAT LO: MCAT3.3
52) Which intermolecular force is primarily responsible for the interactions among alkane molecules?
Answer: van der Waals or London forces
Diff: 2
Section: 3.7
LO: 3.3
MCAT LO: MCAT3.3
53) What is the major constituent of natural gas?
A) octane
B) butane
C) propane
D) ethane
E) methane
Answer: E
Diff: 1
Section: 3.5
GO: G5
54) Within the context of commercial uses of alkanes, explain what "knocking" is.
Answer: "Knocking" is the potentially damaging, premature explosive combustion of certain gasoline mixtures in a car's engine.
Diff: 1
Section: 3.5
LO: 3.3
GO: G5
MCAT LO: MCAT3.3
55) Explain why the lowest energy conformation of decane is an extended, or zig-zag conformation.
Answer: The lowest-energy conformation for any straight-chain alkane is the one with all the internal carbon-carbon bonds in their anti conformations. These anti conformations give the chain a zigzag shape.
Diff: 1
Section: 3.9
LO: 3.4
GO: G8
MCAT LO: MCAT3.4
56) Which alkanes have largely replaced Freons as propellants in aerosol cans?
A) methane and ethane
B) propane and butane
C) pentane and hexane
D) nonane and decane
E) none of the above
Answer: B
Diff: 2
Section: 3.5
LO: 3.3
GO: G5
MCAT LO: MCAT3.3
57) How many carbons do the primary alkane constituents of gasoline contain?
A) C1—C2
B) C3—C4
C) C5—C8
D) C8—C12
E) C12—C16
Answer: C
Diff: 2
Section: 3.5
LO: 3.3
GO: G5
MCAT LO: MCAT3.3
58) ______is the reaction process through which long-chain alkanes are converted into a mixture of short-chain alkanes and alkenes.
Answer: Catalytic cracking
Diff: 2
Section: 3.5
GO: G5
59) List three commercial products which are composed primarily of alkanes.
Answer: natural gas, gasoline, kerosene, heating oil, lubricating oil, liquefied petroleum gas, jet fuel, diesel oil, petroleum jelly
Diff: 2
Section: 3.5
LO: 3.3
GO: G5
MCAT LO: MCAT3.3
60) Linear alkanes generally have higher phase transitions than their branched isomers. However, the melting point of cyclohexane is 6° C while the melting point of hexane is -95° C. Briefly suggest a reason why this is.
Answer: Cyclohexane is more symmetric molecule and doesn't have as many degrees of freedom or conformational flexibility as hexane. This allows it to pack in a more regular lattice and has stronger IMFs between the molecules and therefore a higher boiling point.
Diff: 2
Section: 3.5
LO: 3.3
GO: G5
MCAT LO: MCAT3.3
61) In the complete combustion of heptane, how many moles of water are produced?
Answer: 8
Diff: 2
Section: 3.6
LO: 3.1
GO: G7
62) By using the appropriate molecular formulas, write a balanced equation which describes the complete combustion of cyclohexane.
Answer: C6H12 + 9 O2→ 6 CO2 + 6 H2O
Diff: 2
Section: 3.6
LO: 3.1
GO: G7
63) When a mole of decane undergoes complete combustion, how many moles of water are formed?
A) 1
B) 10
C) 11
D) 15.5
E) 22
Answer: C
Diff: 2
Section: 3.6
LO: 3.1
GO: G7
64) By using the appropriate molecular formulas, write a balanced equation which describes the complete combustion of nonane.
Answer: CH3(CH2)7CH3 + 14 O2 → 9 CO2 + 10 H2O
Diff: 3
Section: 3.6
LO: 3.1
GO: G7
65) The energy barrier for carbon-carbon bond rotation in propane is mainly due to ______.
A) angle strain
B) bond strain
C) muscle strain
D) steric strain
E) torsion strain
Answer: E
Diff: 1
Section: 3.7
LO: 3.4
66) The structures below are ______.
A) not isomers
B) conformational isomers
C) cis-trans isomers
D) structural isomers
E) both B and D
Answer: D
Diff: 2
Section: 3.7
LO: 2.4
GO: G5
MCAT LO: MCAT2.4
67) Which of the following best describes the molecules of a sample of ethane gas at room temperature?
A) Almost all of the molecules are frozen or locked in the eclipsed conformation.
B) Almost all of the molecules are frozen or locked in the staggered conformation.
C) The molecules are rapidly interconverting between the eclipsed and staggered conformations, but at any one time slightly more of them are present in the eclipsed conformation.
D) The molecules are rapidly interconverting between the eclipsed and staggered conformations, but at any one time slightly more of them are present in the staggered conformation.
Answer: D
Diff: 2
Section: 3.7
LO: 3.4
GO: G2
68) Draw a Newman projection of the most stable conformation of 2-methylpropane.
Answer:
Diff: 2
Section: 3.7
LO: 3.4
MCAT LO: MCAT3.4
69) Define the term conformation.
Answer: Conformations are different arrangements of the same molecule formed by rotations about single bonds.
Diff: 2
Section: 3.7
70) Use a sawhorse structure to depict the eclipsed conformer of ethane.
Answer:
Diff: 2
Section: 3.7
GO: G2
71) Draw the Newman projection of the highest energy conformation that results from rotation about the C2-C3 bond of 2,2-dimethylbutane.
Answer:
Diff: 1
Section: 3.8
LO: 3.4
MCAT LO: MCAT3.4
72) Which of the following statements concerning the conformers of butane is true?
A) Unlike ethane, all butane conformers are classified as eclipsed.
B) The lowest energy conformer of butane is the gauche conformer.
C) There is more torsional strain in the anti conformer than in the totally eclipsed conformer.
D) The eclipsed and totally eclipsed conformers have the same amount of nonbonded strain.
E) The gauche and anti conformers differ primarily in the amount of nonbonded strain present.
Answer: E
Diff: 2
Section: 3.8
LO: 3.4
GO: G7
MCAT LO: MCAT3.4
73) Convert the Newman structure below to the equivalent line-angle structure.
Answer:
Diff: 2
Section: 3.8
LO: 3.4
MCAT LO: MCAT3.4
74) Draw the Newman projection of the anti conformation of butane.
Answer:
Diff: 2
Section: 3.8
LO: 3.4
GO: G2
MCAT LO: MCAT3.4
75) Draw the Newman projection of the highest energy conformation that results from rotation about the C2-C3 bond of 2-methylbutane.
Answer:
Diff: 2
Section: 3.8
LO: 3.4
GO: G2
MCAT LO: MCAT3.4
76) Consider rotation about the C3-C4 bond of hexane, and draw the Newman projection for the most stable conformation.
Answer:
Diff: 2
Section: 3.9
LO: 3.4
GO: G2
MCAT LO: MCAT3.4
77) Arrange the following conformers of butane in order of energy, lowest to highest: eclipsed, totally eclipsed, gauche, and anti.
Answer: anti < gauche < eclipsed < totally eclipsed
Diff: 2
Section: 3.8
LO: 3.4
GO: G2
MCAT LO: MCAT3.4
78) Among the butane conformers, which occur at energy minima on a graph of potential energy versus dihedral angle?
A) gauche only
B) eclipsed and totally eclipsed
C) gauche and anti
D) eclipsed only
E) anti only
Answer: C
Diff: 3
Section: 3.8
LO: 3.4
MCAT LO: MCAT3.4
79) Which line angle drawing best represents the Newman Projection shown below?
A)
B)
C)
D)
Answer: C
Diff: 3
Section: 3.8
LO: 3.4
MCAT LO: MCAT3.4
80) Without any change in conformation, translate the Newman projection shown below to a perspective structure.
Answer:
Diff: 3
Section: 3.9
LO: 3.4
MCAT LO: MCAT3.4
81) View a butane molecule along the C2—C3 bond and provide a Newman projection of the lowest energy conformer.
Answer:
Diff: 3
Section: 3.8
LO: 3.4
GO: G2
MCAT LO: MCAT3.4
82) Provide a Newman Projection of the gauche conformer of butane.
Answer:
Diff: 2
Section: 3.8
LO: 3.4
GO: G2
MCAT LO: MCAT3.4
83) From the perspective of viewing down the C2—C3 bond, draw the Newman projection of the most stable conformation of 2,3-dimethylbutane.
Answer:
Diff: 3
Section: 3.8
LO: 3.4
GO: G2
MCAT LO: MCAT3.4
84) From the perspective of viewing down the C2-C3 bond, draw the Newman projection of the least stable conformation of 2,3-dimethylbutane.
Answer:
Diff: 3
Section: 3.8
LO: 3.4
GO: G2
MCAT LO: MCAT3.4
85) In a Newman projection, siting down the C3-C4 bond, draw the structure below in its most stable conformation.
Answer:
Diff: 3
Section: 3.9
GO: G2
86) If a monocyclic alkane hydrocarbon contains n carbon atoms, how many hydrogen atoms must it also contain?
A) n
B) 2n
C) n + 2
D) 2n + 2
E) n - 2
Answer: B
Diff: 1
Section: 3.10
LO: 3.1
GO: G2
87) Give the IUPAC name for the cycloalkane shown below.
Answer: trans-1-ethyl-2-methylcyclopentane
Diff: 1
Section: 3.11
LO: 3.2
MCAT LO: MCAT3.1
88) Give the IUPAC name for the cycloalkane shown below.
Answer: cis-1-isopropyl-3-methylcycloheptane
Diff: 1
Section: 3.11
LO: 3.2
MCAT LO: MCAT3.1
89) What element of ring strain exists in cyclooctane but not in cyclopropane?
Answer: transannular strain
Diff: 1
Section: 3.10
LO: 3.5
GO: G2
90) Provide an acceptable name for the following compound.
Answer: isobutylcyclopentane or (2-methylpropyl)cyclopentane
Diff: 2
Section: 3.10
LO: 3.2
MCAT LO: MCAT3.1
91) Provide the name of the compound below.
Answer: sec-butylcycloheptane
Diff: 2
Section: 3.10
LO: 3.2
MCAT LO: MCAT3.1
92) Identify the correct IUPAC name for the structure shown below.
A) 1-tert-butyl-2-chloro-5-bromocycloheptane
B) 5-bromo-1-tert-butyl-2-chlorocycloheptane
C) 1-bromo-4-chloro-5-tertbutylcycloheptane
D) 1-bromo-4-tert-butyl-5-chlorocycloheptane
E) 1-tert-butyl-4-bromo-7-chlorocycloheptane
Answer: B
Diff: 3
Section: 3.10
LO: 6.1
MCAT LO: MCAT6.1
93) Given the following heats of combustion per CH2 group within the structure, which cyclic alkane has essentially no angle strain? (Ref: long-chain Alkane = 659 kJ/mol)
A) cyclobutane = 686 kJ/mol
B) cyclopentane = 664 kJ/mol
C) cyclohexane = 659 kJ/mol
D) cycloheptane = 662 kJ/mol
E) cyclooctane = 663 kJ/mol
Answer: C
Diff: 1
Section: 3.12
LO: 3.5
94) Which of the following cycloalkanes exhibits the greatest molar heat of combustion?
A) cyclooctane
B) cycloheptane
C) cyclohexane
D) cyclobutane
E) cyclopropane
Answer: A
Diff: 2
Section: 3.12
95) Which of the following correctly ranks the cycloalkanes in order of increasing ring strain per methylene?
A) cyclopropane < cyclobutane < cyclohexane < cyclopentane
B) cyclohexane < cyclopentane < cyclobutane < cyclopropane
C) cyclohexane < cyclobutane < cyclopentane < cyclopropane
D) cyclopentane < cyclopropane < cyclobutane < cyclohexane
E) cyclopropane < cyclopentane < cyclobutane < cyclohexane
Answer: B
Diff: 2
Section: 3.12
LO: 3.5
96) Which of the following cycloalkanes has the smallest heat of combustion per CH2 group?
A) cyclopropane
B) cyclobutane
C) cyclopentane
D) cyclohexane
E) cycloheptane
Answer: D
Diff: 2
Section: 3.12
LO: 3.5
97) Which of the following statements regarding cyclobutane is correct?
A) The lowest energy conformation of cyclobutane is a planar one in which all of the bond angles is 90°.
B) The lowest energy conformation of cyclobutane is known as the chair conformation.
C) The lowest energy conformation is one in which the bond angles are slightly less than 90° even though this increases angle strain.
D) The lowest energy conformation is one in which the bond angles are greater than 90° so that angle strain is significantly reduced.
E) None of the above statements is correct.
Answer: C
Diff: 3
Section: 3.12
LO: 3.5
98) Which has the greatest molar heat of combustion?
A) trans-1,2-dimethylcyclopentane
B) cis-1,2-dimethylcyclopentane
C) trans-1,3-dimethylcyclopentane
D) methylcyclohexane
E) cycloheptane
Answer: B
Diff: 3
Section: 3.12
LO: 3.5
99) Describe the sources of angle strain and torsional strain present in cyclopropane.
Answer: The angle strain arises from the compression of the ideal tetrahedral bond angle of 109.5° to 60°. The large torsional strain occurs since all C—H bonds on adjacent carbons are eclipsed.
Diff: 3
Section: 3.12
LO: 3.5
100) The twisted boat conformation of cyclohexane is actually a slightly lower energy conformation than the boat conformation. Which of the following accurately describes one factor involved in this structural behavior?
A) lower angle strain in the boat
B) higher torsional strain in the twisted boat
C) fewer unfavorable steric factors in the twisted boat
D) increased rotational freedom in the boat
E) lower bond strain in the boat
Answer: C
Diff: 1
Section: 3.13
LO: 3.5
101) Draw the chair conformer of cyclohexane. Label the axial hydrogens (Ha) and the equatorial hydrogens (He).
Answer:
Diff: 1
Section: 3.13
LO: 3.7
102) In the boat conformation of cyclohexane, the "flagpole" hydrogens are located ______.
A) on the same carbon
B) on adjacent carbons
C) on C-1 and C-3
D) on C-1 and C-4
E) none of the above
Answer: D
Diff: 2
Section: 3.13
LO: 3.7
103) Which of the following correctly lists the conformations of cyclohexane in order of increasing energy?
A) chair < boat < twist < half-chair
B) half-chair < boat < twist < chair
C) chair < twist < half-chair < boat
D) chair < twist < boat < half-chair
E) half-chair < twist < boat < chair
Answer: D
Diff: 3
Section: 3.13
LO: 3.7
104) Consider the equilibrium shown below. When one looks at the equilibrium where X = CH3 and the one where X = CH(CH3)2, how do the values of the equilibrium constants (Ks) compare?