Deck 21: Amines

Question 1

Which of the following are radical inhibitors?

A) None of these are correct.
B) Vitamin E
C) BHT
D) Both of these choices are correct.

Answer 1

Both of these choices are correct.

Question 2

The proposed reaction between chlorofluorocarbons and ozone involves what type of mechanism?

A) Substitution mechanism
B) Elimination mechanism
C) Electrophilic aromatic substitution
D) Radical mechanism

Answer 2

Radical mechanism

Question 3

The proposed reaction of the oxidation of unsaturated lipids involves what type of mechanism?

A) Substitution mechanism
B) Radical mechanism
C) Elimination mechanism
D) Electrophilic aromatic substitution

Answer 3

Radical mechanism

Question 4

Which of the following statements about the stereochemistry of halogenation reactions is true?

A) The configuration at a stereogenic center of a product must change even if a reaction does not occur at a stereogenic center.
B) An achiral starting material always gives an achiral product only.
C) An achiral starting material always gives either an achiral or a racemic product.
D) An achiral starting material always gives a racemic product only.

Question 5

What is the product of the following reaction?

A) III
B) IV
C) II
D) I

Question 6

What is the product of the following reaction?

A) II
B) I
C) IV
D) III

Question 7

Which of the following statements about the propagation steps in the chlorination of ethane is true?

A) The second of the propagation steps is rate-determining because its transition state is at higher energy.
B) The first of the propagation steps is rate-determining because its transition state is at lower energy.
C) Radical chlorination consists of two propagation steps.
D) The energy diagram for the propagation steps has three energy barriers.

Question 8

Which of the following statements about carbon radicals isnot true?

A) A carbon radical issp² hybridized.
B) Carbon radicals are classified as primary, secondary, tertiary, or quaternary.
C) The geometry of a carbon radical is trigonal planar.
D) The unhybridizedp orbital in a carbon radical contains the unpaired electron.

Question 9

Which of the following statements about radicals and radical reactions isnot true?

A) A radical is formed by homolysis of a covalent bond.
B) Most radicals are unstable.
C) A radical contains an atom that has an octet of electrons.
D) Half-headed arrows are used to show the movement of lone electrons.

Question 10

Which of the following statements about chlorination is true?

A) The transition state resembles the product.
B) The more stable radical is formed faster.
C) A mixture of products results.
D) The rate-determining step in chlorination is endothermic.

Question 11

A possible reaction of ethane with chlorine is shown below.


This reaction could conceivably occur by the following chain mechanisms [1], [2], and [3]. Determine DH for step [1].
Bond dissociation energies (kcal/mol):

$\begin{array}{|l|l|}\hline \text { Bond A-B } & \Delta \mathrm{H} \\\hline \mathrm{Cl}-\mathrm{Cl} & 58 \\\mathrm{CH}_{3}-\mathrm{H} & 104 \\\mathrm{CH}_{3} \mathrm{CH}_{2}-\mathrm{H} & 98 \\\mathrm{CH}_{3}-\mathrm{CH}_{3} & 88 \\\mathrm{CH}_{3}-\mathrm{Cl} & 84 \\\mathrm{H}-\mathrm{Cl} & 103 \\\hline\end{array}$

A)-5 kcal/mol
B) None of the choices are correct.
C) +58 kcal/mol
D) -28 kcal/mol

Question 12

A possible reaction of ethane with chlorine is shown below.


This reaction could conceivably occur by the following chain mechanisms [1], [2], and [3]. Determine DH for step [2].
Bond dissociation energies (kcal/mol):

$\begin{array}{|ll|}\hline \text { Bond } \mathrm{A}-\mathrm{B} & \Delta \mathrm{H} \\\hline \mathrm{Cl}-\mathrm{Cl} & 58 \\\mathrm{CH}_{3}-\mathrm{H} & 104 \\\mathrm{CH}_{3} \mathrm{CH}_{2}-\mathrm{H} & 98 \\\mathrm{CH}_{3} \mathrm{CH}_{3} & 88 \\\mathrm{CH}_{3} \mathrm{CH}_{2}-\mathrm{Cl} & 81 \\\mathrm{H}-\mathrm{Cl} & 103 \\\hline\end{array}$

A) +58 kcal/mol
B) -28 kcal/mol
C)-5 kcal/mol
D) None of the choices are correct.

Question 13

What is the product of the following reaction?

A) II
B) III
C) I
D) IV

Question 14

A possible reaction of ethane with chlorine is shown below.
This reaction could conceivably occur by the following chain mechanisms [1], [2], and [3]. The chain propagating step(s) is (are) ________.

A) Only [1] and [2]
B) Only [2] and [3]
C) Only [3]
D) Only [1] and [3]

Question 15

Which of the following statements about radicals is true?

A) The higher the bond dissociation energy for a C-H bond, the more stable the resulting carbon radical.
B) Cleavage of a stronger bond forms the more stable radical.
C) The stability of a radical increases as the number of alkyl groups bonded to the radical carbon decreases.
D) Less stable radicals generally do not rearrange to more stable radicals.

Question 16

Which of the following statements is (are) true about free radical halogenation of alkanes?

A) The chain-initiating step involves cleavage of a carbon-hydrogen bond to afford a carbon radical and a hydrogen atom.
B) The first of the chain-propagating steps is rate-determining.
C) The reaction proceeds by way of a flatsp² hybridized free radical.
D) Statements (The first of the chain-propagating steps is rate-determining) and (The reaction proceeds by way of a flatsp² hybridized free radical) are both true.