Organic Chemistry wade

Organic Chemistry, 7e (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 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: 3.1 5) 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

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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: E Diff: 3 Section: 3.2 7) A series of compounds, like the n-alkanes, that differ only by the number of –CH2– groups, is called a(n) __________ series. Answer: homologous Diff: 2 Section: 3.2 8) 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 9) 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: 3.3

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10) 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 11) Provide an acceptable name for (CH3CH2CH2)3CH. Answer: 4-propylheptane Diff: 1 Section: 3.3 12) Provide the name of the compound below.

Answer: 3-fluoro-2,2-dimethylhexane Diff: 1 Section: 3.3 13) Provide the name of the compound below.

Answer: 2,3,6,7-tetramethylnonane Diff: 1 Section: 3.3

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14) Provide an acceptable name for the following compound.

Answer: 4,4-dichloro-6-isopropyl-3-methylnonane Diff: 2 Section: 3.3 15) Provide an acceptable name for the [(CH3)3C]2CHCH3. Answer: 2,2,3,4,4-pentamethylpentane Diff: 2 Section: 3.3 16) Provide the IUPAC name of (CH3CH2)3CH. Answer: 3-ethylpentane Diff: 2 Section: 3.3 17) Provide the IUPAC name of (CH3)2CHCH2CH2C(CH3)3. Answer: 2,2,5-trimethylhexane Diff: 2 Section: 3.3 18) Provide the name of the compound shown.

Answer: 2,2,7-trichloro-4-ethyl-6-isobutyl-7,10-dimethyldodecane Diff: 3 Section: 3.3 19) Provide an acceptable name for the alkane shown below. CH3CH2CH2CH2CH2CH3 Answer: hexane or n-hexane Diff: 1 Section: 3.3 4

20) Provide an acceptable name for the alkane shown below.

Answer: 2,5-dimethylheptane Diff: 1 Section: 3.3 21) Draw an acceptable structure for 4-tert-butyloctane. Answer:

Diff: 1 Section: 3.3 22) Draw an acceptable structure for 3-ethyl-3-methylhexane. Answer:

Diff: 1 Section: 3.3 23) Draw an acceptable structure for 4-isopropyl-2-methylheptane. Answer:

Diff: 1 Section: 3.3 24) Predict the molecular formula of 4-ethyl-5,5-dimethyldodecane. Answer: C16H34 Diff: 2 Section: 3.3

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Answer: 5-sec-butyl-2,2-dimethylnonane or 2,2-dimethyl-5-(1-methylpropyl)nonane Diff: 2 Section: 3.3 26) Provide an acceptable name for the alkane shown below.

Answer: 4-isopropyldecane or 4-(1-methylethyl)decane Diff: 2 Section: 3.3 27) Provide an acceptable name for the alkane shown below.

Answer: 3-ethyl-4,4-dimethylheptane Diff: 2 Section: 3.3 28) Draw an acceptable structure for 6-ethyl-2,6,7-trimethyl-5-propylnonane. Answer:

Diff: 2 Section: 3.3

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Answer: 2,2,3,6-tetramethylheptane Diff: 2 Section: 3.3 30) Provide an acceptable name for the alkane shown below.

Answer: 6-ethyl-2-methyl-5-propyldecane Diff: 2 Section: 3.3 31) Provide an acceptable name for the alkane shown below.

Answer: 5-ethyl-2,2-dimethylheptane Diff: 2 Section: 3.3 32) Give structures for the three isomers with molecular formula C5H12 and provide the common name of each. Answer:


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Answer: 3-ethyl-7-methyl-5-propylnonane Diff: 3 Section: 3.3 34) Draw an acceptable structure for 4-ethyl-6-(1,2-dimethylpropyl)decane. Answer:

Diff: 3 Section: 3.3 35) Draw an acceptable structure for 1-ethyl-2-(2,2-dimethylpentyl)cyclopentane. Answer:

Diff: 3 Section: 3.3 36) 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 37) 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 8

38) A branched alkane generally melts at a __________ temperature than the n-alkane containing the same number of carbons. Answer: lower Diff: 2 Section: 3.4 39) __________ is the n-alkane of greatest molecular weight which is a gas at room temperature and pressure. Answer: Butane Diff: 2 Section: 3.4 40) 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 41) 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 42) Which intermolecular force is primarily responsible for the interactions among alkane molecules? Answer: van der Waals or London forces Diff: 2 Section: 3.4 43) 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

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44) 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 45) 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 46) __________ 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 47) 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 48) 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 49) Name the two major steps in the refining of crude oil into usable hydrocarbon products. Answer: 1. fractional distillation 2. cracking (catalytic cracking and/or hydrocracking) Diff: 2 Section: 3.5

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50) In the complete combustion of heptane, how many moles of water are produced? Answer: 8 Diff: 2 Section: 3.6 51) 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 52) 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 53) 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 54) 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

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55) 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 56) Draw a Newman projection of the most stable conformation of 2-methylpropane. Answer:

Diff: 2 Section: 3.7 57) Define the term conformation. Answer: Conformations are different arrangements of the same molecule formed by rotations about single bonds. Diff: 2 Section: 3.7 58) Use a sawhorse structure to depict the eclipsed conformer of ethane. Answer:

Diff: 2 Section: 3.7 59) 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

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60) 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 61) For the compound represented by the Newman projection above, what is the dihedral angle between the methyl groups in the conformer that has the smallest molecular dipole moment? A) 0° B) 30° C) 60° D) 120° E) 180° Answer: C Diff: 3 Section: 3.8 62) 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 63) 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

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64) Draw the Newman projection of the lowest energy conformation that results from rotation about the C2-C3 bond of 2-methylbutane. Answer:

Diff: 2 Section: 3.8 65) Draw the Newman projection of the lowest energy conformation that results from rotation about the C2-C3 bond of 2,2-dimethylbutane. Answer:

Diff: 2 Section: 3.8 66) 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 67) Consider rotation about the C3-C4 bond of hexane, and draw the Newman projection for the most stable conformation. Answer:


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Use the following Newman projection for the question(s) below.

68) Without any change in conformation, translate the Newman projection shown above to a perspective structure. Answer:

Diff: 3 Section: 3.8 69) 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 70) Provide a representation of the gauche conformer of butane. Answer:

Diff: 3 Section: 3.8 71) From the perspective of viewing down the C2–C3 bond, draw the Newman projection of the most stable conformation of 2,3-dimethylbutane. Answer:


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72) 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 73) 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 74) 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 75) Provide an acceptable name for the following compound.

Answer: isobutylcyclopentane or 2-methylpropylcyclopentane Diff: 2 Section: 3.10

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76) Provide the name of the compound below.

Answer: sec-butylcycloheptane Diff: 2 Section: 3.10 77) Give the IUPAC name for the cycloalkane shown below.

Answer: trans-1-ethyl-2-methylcyclopentane Diff: 1 Section: 3.10 78) Give the IUPAC name for the cycloalkane shown below.

Answer: cis-1-isopropyl-3-methylcycloheptane Diff: 1 Section: 3.10 79) 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

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80) 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 81) 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 82) 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 83) 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

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84) 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 85) 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 86) The twisted boat conformation of cyclohexane is actually a slightly lower energy conformation than the boat conformation. Which of the following acurately describes one factor involved in this structural behavior ? A) lower angle strain B) lower torsional strain C) fewer unfavorable steric factors D) increased rotational freedom E) lower bond strain Answer: C Diff: 1 Section: 3.13 87) 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

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88) 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 89) Draw the chair conformer of cyclohexane. Label the axial hydrogens (Ha) and the equatorial hydrogens (He). Answer:

Diff: 1 Section: 3.13 90) 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?

A) The Ks are equal. B) The K where X = CH3 is greater. C) The K where X = CH(CH3)2 is greater. D) The Ks differ only slightly and are both less than 1. Answer: C Diff: 2 Section: 3.14

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91) The energy difference between the axial and equatorial conformers of methylcyclohexane is: A) < 0.1 kcal/mol B) 0.9 kcal/mol C) 1.7 kcal/mol D) 2.5 kcal/mol E) > 5.0 kcal/mol Answer: C Diff: 3 Section: 3.14 92) 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: E Diff: 1 Section: 3.15 93) 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: A Diff: 2 Section: 3.15 94) 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: D Diff: 2 Section: 3.15

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95) 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: A Diff: 2 Section: 3.15 96) In the lowest energy conformation of the compound below, how many alkyl substituents are equatorial?

A) 0 B) 1 C) 2 D) 3 E) 6 Answer: C Diff: 2 Section: 3.15 97) In the lowest energy conformation of the compound below, how many alkyl substituents are axial?

A) 0 B) 1 C) 2 D) 3 E) 6 Answer: A Diff: 2 Section: 3.15 22

98) 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: F Diff: 2 Section: 3.15 99) 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: C Diff: 3 Section: 3.15 100) Which of the following correctly lists the confromations of cis-1,4-di-t-butylcylcohexane in order of increasing energy? A) chair < boat < twist boat < half-chair B) twist boat < boat < chair < half-chair C) chair < twist boat < half-chair < boat D) boat < chair < twisted boat < half-chair E) half-chair < chair < boat < twisted boat Answer: B Diff: 3 Section: 3.15 101) Draw the most stable conformation of cis-1-t-butyl-4-methylcyclohexane. Answer:


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102) Draw the most stable conformation of the cyclohexane derivative shown.

Answer:

Diff: 2 Section: 3.15 103) Draw the most stable conformation of cis-1,4-dipropylcyclohexane. Answer:

Diff: 2 Section: 3.15 104) Draw the most stable conformation of trans-1,4-dipropylcyclohexane. Answer: Diff: 2 Section: 3.15 105) Draw the most stable conformation of trans-1,2-dimethylcyclohexane. Answer: Diff: 2 Section: 3.15 106) Draw the most stable conformation of cis-1,2-dimethylcyclohexane. Answer:


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107) Draw the most stable conformation of trans-1-tert-butyl-3-ethylcyclohexane. Answer:

Diff: 2 Section: 3.15 108) Draw the most stable conformation of cis-1-ethyl-3-methylcyclohexane. Answer:

Diff: 2 Section: 3.15 109) Draw the most stable conformation of cis-1-ethyl-4-isopropylcyclohexane. Answer:

Diff: 2 Section: 3.15 110) 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: B Diff: 2 Section: 3.16 111) Which of the following describes the compound below?

A) bridged bicyclic B) fused bicyclic C) spiro bicyclic D) bridged tricyclic Answer: A Diff: 2 Section: 3.16

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112) Provide an acceptable name for the compound below.

Answer: Bicyclo[2.1.1]hexane Diff: 2 Section: 3.16 113) Provide an acceptable structure for spiro [4.4]nonane. Answer:

Diff: 3 Section: 3.16 114) Draw the most stable conformation of trans-decalin. Answer:


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Organic Chemistry wade

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