Chapter 3 Flashcards by Allison Krause

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

E) both A and C

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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.

A) alkanes

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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

D) 2n + 2

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A bicyclic alkane contains 12 carbon atoms. How many hydrogen atoms does it contain?
A) 20
B) 22
C) 24
D) 26
E) 28

B) 22

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

C) 2

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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

E) 62

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How many secondary (2°) carbons are found in 5-ethyl-3,3,4-trimethylheptane?
A) 1
B) 4
C) 2
D) 3
E) 6

D) 3

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

C) 4

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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.

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

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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

D) a lower; weaker

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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

A) 2,3-dimethylbutane

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

Answer: (CH3)3CCH2CH2CH3

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

C) methane.

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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

B) propane and butane

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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

C) C5C8

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

Answer: Catalytic cracking

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

C) 11

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

E) torsion strain

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

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

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

Answer: anti

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

C) gauche and anti

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

A) cyclooctane

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

B) cyclohexane

Which of the following cycloalkanes has the smallest heat of combustion per CH2 group?
A) cyclopropane
B) cyclobutane
C) cyclopentane
D) cyclohexane
E) cycloheptane

D) cyclohexane

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.

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

``` 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 ```

B) cis-1,2-dimethylcyclopentane

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

C) fewer unfavorable steric factors in the twisted boat

``` 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 ```

D) on C-1 and C-4.

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

D) chair

``` 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 ```

E) 6

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.

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

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.

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

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.

A) The two chair conformations are equal in energy.

``` 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. ```

F) Both A and C are correct.

``` 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 ```

C) cis 1,3-difluorocyclohexane

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

B) twist boat

``` 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 ```

B) bicyclo[2.2.1]heptane