Chapter 3

Question 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 1

E) both A and C

Question 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 2

A) alkanes

Question 3

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 3

D) 2n + 2

Question 4

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 4

B) 22

Question 5

How many methylene groups are present in 2,4-dimethylhexane?
A) 0
B) 1
C) 2
D) 6
E) 8

Answer 5

C) 2

Question 6

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 6

E) 62

Question 7

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 7

D) 3

Question 8

How many methyl groups are present in 2,4-dimetylhexane?
A) 0
B) 2
C) 4
D) 6
E) 8

Answer 8

C) 4

Question 9

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 9

A) that n-hexane is less dense than water.

Question 10

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 10

D) a lower; weaker

Question 11

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

Answer 11

A) 2,3-dimethylbutane

Question 12

Place the following alkanes in order of increasing boiling point:
CH3(CH2)6CH3, CH3(CH2)5CH3, (CH3)3CCH2CH2CH3

Answer 12

Answer: (CH3)3CCH2CH2CH3

Question 13

Natural gas is primarily composed of
A) oxygen.
B) carbon dioxide.
C) methane.
D) octane.
E) ethanol.

Answer 13

C) methane.

Question 14

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 14

B) propane and butane

Question 15

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 15

C) C5C8

Question 16

________ is the reaction process through which long-chain alkanes are converted into a mixture of short-chain alkanes and alkenes.

Answer 16

Answer: Catalytic cracking

Question 17

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 17

C) 11

Question 18

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 18

E) torsion strain

Question 19

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 19

E) The gauche and anti conformers differ primarily in the amount of nonbonded strain present

Question 20

Arrange the following conformers of butane in order of energy, lowest to highest: eclipsed, totally eclipsed, gauche, and anti.

Answer 20

Answer: anti

Question 21

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 21

C) gauche and anti

Question 22

Which of the following cycloalkanes exhibits the greatest molar heat of combustion?
A) cyclooctane
B) cycloheptane
C) cyclohexane
D) cyclobutane
E) cyclopropane

Answer 22

A) cyclooctane

Question 23

Which of the following correctly ranks the cycloalkanes in order of increasing ring strain per methylene?
A) cyclopropane

Answer 23

B) cyclohexane

Question 24

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 24

D) cyclohexane

Question 25

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 25

C) The lowest energy conformation is one in which the bond angles are slightly less than 90° even though this increases angle strain.

Question 26

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 26

B) cis-1,2-dimethylcyclopentane

Question 27

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 27

C) fewer unfavorable steric factors in the twisted boat

Question 28

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 28

D) on C-1 and C-4.

Question 29

Which of the following correctly lists the conformations of cyclohexane in order of increasing energy?
A) chair

Answer 29

D) chair

Question 30

In the lowest energy chair conformation of cis-1,3-dimethylcyclohexane, how many axial positions are occupied by hydrogen atoms?
A) 2
B) 3
C) 4
D) 5
E) 6

Answer 30

E) 6

Question 31

Which of the following statements is a correct description of the most stable conformation of 1,1,3-trimethylcyclohexane?
A) The methyl group at C-3 is equatorial.
B) C-1 is a tertiary carbon and C-3 is a primary carbon.
C) C-1 is a quaternary carbon and C-3 is a secondary carbon.
D) C-1 is a tertiary carbon and C-3 is a secondary carbon.
E) Both methyl groups at C-1 are equatorial.

Answer 31

A) The methyl group at C-3 is equatorial.

Question 32

Which of the statements below correctly describes the chair conformations of trans-1,4-dimethylcyclohexane
A) The two chair conformations are of equal energy.
B) The higher energy chair conformation contains one axial methyl group and one equatorial methyl group.
C) The lower energy chair conformation contains one axial methyl group and one equatorial methyl group.
D) The higher energy chair conformation contains two axial methyl groups.
E) The lower energy chair conformation contains two axial methyl groups.

Answer 32

D) The higher energy chair conformation contains two axial methyl groups.

Question 33

Which of the statements below correctly describes the chair conformations of trans-1,3-diethylcyclohexane
A) The two chair conformations are equal in energy.
B) The higher energy chair conformation contains two axial ethyl groups.
C) The higher energy chair conformation contains two equatorial ethyl groups.
D) The lower energy chair conformation contains two axial ethyl groups.
E) The lower energy chair conformation contains two equatorial ethyl groups.

Answer 33

A) The two chair conformations are equal in energy.

Question 34

Assuming a chair conformation, which of the following configurations will always have both methyl groups in relative axial/equatorial positions?
A) trans-1,3-dimethylcyclohexane
B) cis-1,3-dimethylcyclohexane
C) cis-1,2-dimethylcyclohexane
D) trans-1,2-dimethylcyclohexane
E) Both B and D are correct.
F) Both A and C are correct.

Answer 34

F) Both A and C are correct.

Question 35

Which of the following difluorocyclohexane isomers has the greatest molecular dipole in its least stable chair conformation?
A) cis 1,2-difluorocyclohexane
B) trans 1,2-difluorocyclohexane
C) cis 1,3-difluorocyclohexane
D) trans 1,3-difluorocyclohexane

Answer 35

C) cis 1,3-difluorocyclohexane

Question 36

Which of the following correctly lists the conformations of cis-1,4-di-t-butylcylcohexane in order of increasing energy?
A) chair

Answer 36

B) twist boat

Question 37

Which of the following is a bridged bicyclic alkane?
A) cis-decalin
B) bicyclo[2.2.1]heptane
C) bicyclo[3.2.0]heptane
D) bicyclo[4.1.0]heptane
E) none of the above

Answer 37

B) bicyclo[2.2.1]heptane