chapter 7 (wade)

1) Which of the following statements best describes the relative bond dissociation energies of the sigma and pi bonds present in the carbon-carbon double bond of an alkene? A) sigma > pi B) pi > sigma C) sigma = pi D) cannot be estimated

A

10) Consider molecules with the formula C10H16. Which of the following structural features are not possible within this set of molecules? A) 2 triple bonds B) 1 ring and 1 triple bond C) 2 rings and 1 double bond D) 2 double bonds and 1 ring E) 3 double bonds

A

107) Predict the major product of the reaction shown below. A) 2,3-dimethyl-2-butene B) 2,3-dimethyl-1-butene C) 3,3-dimethyl-1-butene D) None of the above

A

51) Using Zaitsev's rule, choose the most stable alkene among the following. A) 1-methylcyclohexene B) 3-methylcyclohexene C) 4-methylcyclohexene D) They are all of equal stability according to Zaitsev's rule.

A

53) Using Zaitsev's rule, choose the most stable alkene among the following. A) 1,2-dimethylcyclohexene B) 1,6-dimethylcyclohexene C) cis-3,4-dimethylcyclohexene D) They are all of equal stability according to Zaitsev's rule.

A

56) Which of the following alkenes has the smallest molar heat of hydrogenation (ie, releases the least heat upon hydrogenation)? A) 2,3-dimethyl-2-butene B) 2-methyl-2-butene C) trans-2-butene D) cis-2-butene E) 1-hexene

A

77) Which of the following alkenes is the major product when 2-bromo-2-methylpentane is treated with potassium tert-butoxide in tert-butanol? A) 2-methylpent-1-ene B) 2-methylpent-2-ene C) (E)-4-methylpent-2-ene D) (Z)-4-methylpent-2-ene E) 4-methylpent-1-ene

A

62) Which has the smaller heat of hydrogenation, (E)-2-pentene or (Z)-2-pentene? What is the structural origin of this difference?

(E)-2-pentene has the smaller heat of hydrogenation. There is less steric strain between the alkyl substituents in the (E)-isomer than in the (Z)-isomer.

59) The trans isomers of cycloalkenes with rings containing fewer than __________ atoms are unstable at room temperature.

8

58) The compound produced when 3-methylpent-2-ene undergoes hydrogenation in the presence of a platinum catalyst is __________.

3-methylpentane

11) How many elements of unsaturation are implied by the molecular formula C6H12? A) 0 B) 1 C) 2 D) 3 E) 4

B

12) How many elements of unsaturation do molecules with a molecular formula of C6H6Cl6 have? A) 0 B) 1 C) 2 D) 3 E) 4

B

17) A newly isolated natural product was found to have the molecular formula C15H28O2. By hydrogenating a sample of the compound, it was determined to possess one p bond. How many rings are present in the compound? A) 0 B) 1 C) 2 D) 3 E) 4

B

20) A chemist has isolated a new natural product and determined its molecular fromula to be C24H40O4. In hydrogenation experiments the chemist found that each mole of the natural product reacted with two moles of H2. How many rings are present in the structure of the new natural product? A) 2 B) 3 C) 4 D) 5 E) 6

B

4) What two atomic orbitals or hybrid atomic orbitals overlap to form the C-H bond in ethylene? A) C sp3 + H s B) C sp2 + H s C) C sp + H s D) C p + H s

B

52) Using Zaitsev's rule, choose the most stable alkene among the following. A) hex-1-ene B) (E)-hex-2-ene C) (Z)-hex-2-ene D) They are all of equal stability according to Zaitsev's rule.

B

54) Consider the constitutional isomers 2-methylbut-1-ene, 2-methylbut-2-ene, and 3-methylbut-1-ene. When each of these alkenes is subjected to catalytic hydrogenation (H2, Pt), a single product results. Which of the following best describes the structural relationship among these products? A) The products are cis-trans isomers. B) The products are identical. C) The products are constitutional isomers. D) The products are enantiomers. E) The products are diastereomers.

B

71) Alkenes __________. A) are relatively polar compounds B) have lower boiling points than alcohols of similar molecular weight C) are reasonably soluble in water D) both A and B E) none of the above

B

76) Which of the following alkenes is the major product when 2-bromo-2-methylpentane is treated with sodium ethoxide in ethanol? A) 2-methylpent-1-ene B) 2-methylpent-2-ene C) (E)-4-methylpent-2-ene D) (Z)-4-methylpent-2-ene E) 4-methylpent-1-ene

B

14) Which of the following molecular formulas corresponds to a monocyclic saturated compound? A) C6H6 B) C3H7Br C) C3H7N D) C3H8O

C

15) How many elements of unsaturation are implied by the molecular formula C5H8O? A) 0 B) 1 C) 2 D) 3 E) 4

C

16) How many elements of unsaturation are implied by the molecular formula C7H11Cl? A) 0 B) 1 C) 2 D) 3 E) 4

C

3) Which of the following best approximates the CCC bond angle of propene? A) 90° B) 109° C) 120° D) 150° E) 180°

C

5) What two atomic orbitals or hybrid atomic orbitals overlap to form the C-C σ bond in ethylene? A) C sp3 + C sp3 B) C sp3 + C sp2 C) C sp2 + C sp2 D) C sp3 + C p E) C sp2 + C p

C

73) Which of the alkyl chlorides listed below undergoes dehydrohalogenation in the presence of a strong base to give pent-2-ene as the only alkene product? A) 1-chloropentane B) 2-chloropentane C) 3-chloropentane D) 1-chloro-2-methylbutane E) 1-chloro-3-methylbutane

C

72) Which has the higher boiling point, cis- or trans-hex-3-ene? Briefly explain your choice.

Cis-Hex-3-ene has the higher boiling point since it has a net molecular dipole moment while the trans-isomer does not. The presence of a permanent molecular dipole allows for stronger intermolecular attractions.

104) In the group shown below, which of the following alcohols is (are) likely to yield a product where skeletal rearrangement has occurred when treated with sulfuric acid? 3-methyl-3-pentanol, 3,3-dimethyl-2-butanol, 2,2-dimethylcyclohexanol A) 3-methyl-3-pentanol only B) 3,3-dimethyl-2-butanol only C) 2,2-dimethylcyclohexanol only D) both 3,3-dimethyl-2-butanol and 2,2-dimethylcyclohexanol E) None of these three alcohols is prone to rearrangement.

D

13) How many elements of unsaturation do molecules with a molecular formula of C8H4N2 have? A) 2 B) 4 C) 6 D) 8 E) 10

D

2) Carbon-carbon single bonds tend to be __________ and __________ than carbon-carbon double bonds. A) shorter, stronger B) longer, stronger C) shorter, weaker D) longer, weaker

D

74) Dehydrohalogenation of 2-bromobutane in the presence of a strong base proceeds via which of the following mechanistic pathways? A) SN1 B) SN2 C) E1 D) E2 E) none of the above

D

75) Dehydrohalogenation of an alkyl halide by treating it with a strong base to yield an alkene product typically occurs by what reaction mechanism? A) SN1 B) SN2 C) E1 D) E2 E) free radical

D

78) Which of the following statements applies to the E2 mechanism? A) It occurs with inversion of stereochemistry. B) It occurs with racemization of stereochemistry. C) It proceeds through the more stable carbocation intermediate. D) The C-H and C-X bonds that break must be anti. E) Use of a bulky base gives the more highly substituted alkene product.

D

18) How many elements of unsaturation are implied by the molecular formula C5H5NO2? A) 0 B) 1 C) 2 D) 3 E) 4

E

19) How many elements of unsaturation are implied by the molecular formula C8H11N? A) 0 B) 1 C) 2 D) 3 E) 4

E

55) Which of the following alkenes has the largest molar heat of hydrogenation (ie, releases the most heat upon hydrogenation)? A) 2,3-dimethyl-2-butene B) 2-methyl-2-butene C) trans-2-butene D) cis-2-butene E) 1-hexene

E

6) What two atomic orbitals or hybrid atomic orbitals overlap to form the C-C π bond in ethylene? A) C sp3 + C sp3 B) C sp3 + C sp2 C) C sp2 + C sp2 D) C sp2 + C p E) C p + C p

E

90) Provide the name of the major alkene product that results when (2S,3S)-2-bromo-3-methylpentane is treated with sodium methoxide in methanol.

E)-3-methyl-2-pentene