Ch6 Nucleophilic Alkyl Reactions Verified Test Bank

Package title: Solomons Test Bank

Course Title: Solomons 13e

Chapter Number: 6

Question type: Multiple choice

1) Select the rate law for the following reaction, e.g.,

CH₃CH₂CH₂CHBrCH₃ + OH^  CH₃CH₂CH₂CHOHCH₃ + Br ^-

( RBr )

A) Rate = k [RBr]

B) Rate = k [RBr] [OH^]

C) Rate = k [RBr]² [OH^]

D) Rate = k [RBr] [OH^]²

E) Rate = k [RBr]² [OH^]²

Topic: Reaction kinetics

Section: 6.5

Difficulty Level: Easy

2) The rate equation for a nucleophilic substitution reaction of a secondary alkyl chloride (R-Cl) with I^ ion would be:

A) Rate = k [RCl]

B) Rate = k [I^]

C) Rate = k [RCl][I^]

D) Rate = k [RCl]²[I^]

E) Rate = k [RCl][I^]²

Topic: Reaction Kinetics

Section: 6.5

Difficulty Level: Easy

3) Consider the S_N2 reaction of butyl bromide with OH^- ion.

CH₃CH₂CH₂CH₂Br + OH^-  CH₃CH₂CH₂CH₂OH + Br^-

Assuming no other changes, what effect on the rate would result from simultaneously doubling the concentrations of both butyl bromide and OH- ion?

A) No effect.

B) It would double the rate.

C) It would triple the rate.

D) It would increase the rate four times.

E) It would increase the rate six times.

Topic: Reaction kinetics

Section: 6.5

Difficulty Level: Medium

4) Consider the S_N2 reaction of 2-iodopentane with CH₃CO₂ ion.

Assuming no other changes, what effect on the rate would result from simultaneously doubling the concentrations of both 2-iodopentane and sodium acetate?

A) No effect.

B) It would double the rate.

C) It would triple the rate.

D) It would increase the rate four times.

E) It would increase the rate six times.

Topic: Reaction kinetics

Section: 6.5

Difficulty Level: Medium

5) Consider the S_N2 reaction of 1-chloro-5-methylhexane with CN ion.

Assuming no other changes, what effect on the rate would result from simultaneously doubling the concentrations of both 1-chloro-5-methylhexane and NaCN?

A) No effect.

B) It would double the rate.

C) It would triple the rate.

D) It would increase the rate four times.

E) It would increase the rate six times.

Topic: Reaction kinetics

Section: 6.5

Difficulty Level: Medium

6) The reaction,

has the following thermodynamic values at 27.0 ºC: H = -75.3 kJ mol^-1;

S = 54.4 J K^-1 mol^-1. What is the value of G for this reaction?

A) -73.8 kJ mol^-1

B) -76.8 kJ mol^-1

C) -59.0 kJ mol^-1

D) +91.6 kJ mol^-1

E) -91.6 kJ mol^-1

Topic: Free energy changes

Sections: 6.7

Difficulty Level: Easy

7) Select the potential energy diagram that represents an exothermic (exergonic) reaction.

A) I

B) II

C) III

D) IV

E) V

Topic: Free energy diagrams

Section: 6.7

Difficulty Level: Easy

8) Select the potential energy diagram that represents a single-step endothermic (endergonic) reaction.

A) I

B) II

C) III

D) IV

E) V

Topic: Free energy diagrams

Section: 6.7

Difficulty Level: Easy

9) Select the potential energy diagram that represents a two-step endothermic (endergonic) reaction.

A) I

B) II

C) III

D) IV

E) V

Topic: Free energy diagrams

Section: 6.7

Difficulty Level: Easy

10) The difference in the bond energies of reactants and the transition state of a reaction is designated by the notation:

A) H

B) H^‡

C) G

D) G^‡

E) S^‡

Topic: Free energy diagrams

Section: 6.7

Difficulty Level: Easy

11) An increase in the temperature at which a reaction is carried out increases

A) the collision frequency.

B) the fraction of molecules with proper orientation.

C) the fraction of molecules with energy greater than E_act.

D) More than one of these choices.

E) None of these choices.

Topic: Activation energy

Section: 6.7

Difficulty Level: Medium

12) Which will be true for any actual or potential nucleophilic substitution reaction?

A) H is positive.

B) H is negative.

C) G^‡ is positive.

D) G is positive.

E) G is negative.

Topic: Transition state theory

Section: 6.7

Difficulty Level: Medium

13) Increasing the temperature of a chemical reaction usually increases greatly the rate of the reaction. The most important reason for this is that increasing the temperature

A) increases the collision frequency.

B) decreases the probability factor.

C) increases the fraction of collisions with energy greater than E_act.

D) decreases the energy of activation.

E) makes the reaction more exothermic.

Topic: Activation Energy

Section: 6.7

Difficulty Level: Easy

14) What product(s) would you expect to obtain from the following S_N2 reaction?

A) I

B) II

C) An equimolar mixture of I and II.

D) III

E) None of these choices.

Topic: Predicting products

Section: 6.8

Difficulty Level: Easy

15) The major product of the following reaction would be:

A) I

B) II

C) III

D) IV

E) An equimolar mixture of I and II.

Topic: Predicting products

Section: 6.8

Difficulty Level: Easy

16) A true statement about the transition state(s) of an S_N2 reaction is:

A) The two transition states are of unequal energy.

B) The transition states precede and follow an unstable reaction intermediate.

C) The single transition state represents the point of maximum free energy of the reaction.

D) Existence of this transition state implies an exothermic reaction.

E) The transition state will always have a net charge of -1.

Topic: Generalities

Sections: 6.7 and 6.8

Difficulty Level: Hard

17) The rate equation for a nucleophilic substitution reaction of a tertiary alkyl bromide (R-Br) with I^ ion would be:

A) Rate = k [RBr]

B) Rate = k [I^]

C) Rate = k [RBr][I^]

D) Rate = k [RBr]²[I^]

E) Rate = k [RBr][I^]²

Topic: Reaction Kinetics

Section: 6.9 and 6.10

Difficulty Level: Easy

18) Consider the reaction of 2-chloro-2-methylpentane with sodium iodide.

Assuming no other changes, how would it affect the rate if one simultaneously doubled the concentration of 2-chloro-2-methylpentane and sodium iodide?

A) No effect.

B) It would double the rate.

C) It would triple the rate.

D) It would quadruple the rate.

E) It would increase the rate five times.

Topic: Reaction Kinetics

Section: 6.9 and 6.10

Difficulty Level: Hard

19) If the rate of reaction of [0.1 M] sodium cyanide with [0.1 M] 2-bromo-2-methylpropane is 1.2 x 10^-3 M/s, what would be the effect on the overall rate if the concentration of sodium cyanide is increased to [0.2 M] and the concentration of the alkyl bromide is decreased to [0.05 M]?

a) the rate will increase by a factor of 2

b) the rate will decrease by a factor of 2

c) the rate will increase by a factor of 10

d) the rate will decrease by a factor of 10

e) the rate will remain unchanged

Topic: Reaction kinetics

Section: 6.9 and 6.10

Difficulty Level: Medium

20) The hybridization state of the charged carbon in a carbocation is ___.

A) sp⁴

B) sp³

C) sp²

D) sp

E) s

Topic: Carbocations

Section: 6.11

Difficulty Level: Easy

21. The p orbital of a methyl cation, CH₃⁺, contains how many electrons?

A) 0

B) 1

C) 2

D) 3

E) 4

Topic: Carbocations

Section: 6.11

Difficulty Level: Easy

22) The p orbital of the charged carbon in the isopropyl cation, (CH₃)₂CH⁺, contains how many electrons?

A) 0

B) 1

C) 2

D) 3

E) 4

Topic: Carbocations

Section: 6.11

Difficulty Level: Easy

23) Consider the substitution reaction that takes place when (R)-3-bromo-3-methylhexane is treated with methanol. Which of the following would be true?

A) The reaction would take place only with inversion of configuration at the stereogenic center.

B) The reaction would take place only with retention of configuration at the stereogenic center.

C) The reaction would take place with racemization.

D) No reaction would take place.

E) The alkyl halide does not possess a stereogenic center.

Topic: Predicting mechanism, stereochemistry of SN reactions

Sections: 6.8 and 6.12

Difficulty Level: Medium

24) Which of the following alkyl bromide isomers would most readily undergo an S_N2 reaction?

a) bromocyclobutane

b) 4-bromo-1-butene

c) 3-bromo-1-butene

d) 1-bromo-1-butene

e) All will react at the same rate.

Topic: Synthesis, reagent selection

Section: 6.13

Difficulty Level: Hard

25) Which alkyl chloride, though primary, is essentially unreactive in S_N2 reactions?

A)

B)

C)

D)

E)

Topic: Steric hindrance

Sections: 6.13

Difficulty Level: Easy

26) Which alkyl halide would be most reactive in an S_N1 reaction?

A) I

B) II

C) III

D) IV

E) V

Topic: Kinetics

Section: 6.13

Difficulty Level: Easy

27) Reaction of (R)-2-chloro-4-methylhexane with excess NaI in acetone gives racemic 2-iodo-4-methylhexane. What is the explanation that best describes this transformation?

a) an S_N2 reaction has occurred with inversion of configuration

b) racemization followed by an S_N2 attack

c) an S_NI reaction has taken over resulting in inversion of configuration

d) an S_N1 reaction has occurred due to carbocation formation

e) an S_N1 reaction followed by an S_N2 “backside” attack

Topic: Kinetics and Mechanism

Section: 6.8, 6.13

Difficulty Level: Easy

28) An increase in the kinetic energy of reacting molecules results in

A) a decrease in reaction rate.

B) an increase in the probability factor.

C) a decrease in the probability factor.

D) an increase in the reaction rate.

E) no changes.

Topic: Transition State theory

Sections: 6.7 and 6.13

Difficulty Level: Medium

29) Which alkyl halide would you expect to undergo an S_N2 reaction most slowly?

A) 1-bromohexane

B) 1-bromo-2-methylpentane

C) 1-bromo-3-methylpentane

D) 1-bromo-4-methylpentane

E) 1-bromo-2,2-dimethylbutane

Topic: Kinetics

Sections: 6.8 and 6.13

Difficulty Level: Medium

30) Identify the nucleophile in the following reaction:

2 H₂O + RX 🡪 ROH + H₃O⁺ + X^

A) X-

B) H₃O⁺

C) ROH

D) H₂O

E) RX

Topic: Generalities, nucleophiles

Sections: 6.3 and 6.13

Difficulty Level: Easy

31) Which of the following is not a nucleophile?

A) H₂O

B) CH₃O^-

C) NH₃

D) NH₄⁺

E) All are nucleophiles.

Topic: Generalities, nucleophiles

Sections: 6.3 and 6.13

Difficulty Level: Easy

32) Ambident nucleophiles are ones which can react with a substrate at either of two nucleophilic sites. Which of the following is not an ambident nucleophile?

A) I

B) II

C) III

D) IV

E) V

Topic: Nucleophiles

Sections: 6.3 and 6.13

Difficulty Level: Easy

33) Identify the nucleophile in the following reaction:

2R’OH + RX 🡪 ROR’ + [R’OH₂]⁺ + X^-

A) X^

B) [R’OH₂]^

C) ROR’

D) R’OH

E) RX

Topic: Generalities, nucleophiles

Sections: 6.3 and 6.13

Difficulty Level: Medium

34) Which is the strongest nucleophile?

A) OH^-

B) CH₃CH₂O^-

C)

D) CH₃CH₂OH

E) H₂O

Topic: Nucleophiles

Sections: 6.3 and 6.13

Difficulty Level: Medium

35) Rank the following in terms of nucleophilic strength:

a) I>II>III>IV>V

b) V>IV>III>II>I

c) I>IV>II>III>V

d) V>I>IV>II>III

e) I>II>IV>V>III

Topic: Nucleophiles

Sections: 6.3 and 6.13

Difficulty Level: Medium

36) Which S_N2 reaction would you expect to take place most rapidly? Assume that the concentrations of the reactants and the temperature are the same in each instance.

A)

B)

C)

D)

E)

Topic: Nucleophilicity, leaving groups

Sections: 6.3, 6.8, 6.13

Difficulty Level: Medium

37) Which is not a polar aprotic solvent?

A)

B)

C)

D)

E)

Topic: Generalities, solvent effects

Section: 6.13

Difficulty Level: Easy

38) Which is a polar aprotic solvent?

A) 2-methylhexane

B) CCl₄

C) NH₃(l)

D) CH₃CH₂CH₂OCH₂CH₂CH₃

E) 2-methyl-2-propanol

Topic: Generalities, solvent effects

Section: 6.13

Difficulty Level: Easy

39) Consider an SN2 reaction of NaSH in a polar aprotic solvent with (CH3)2CHCH2CH2X. What would be the relative order of reactivity for the following X substituents?

I. X = I   II. X = Br   III. X = Cl   IV X = F

a) I > II > III > IV

b) II > I > IV > III

c) IV > III > II > I

d) III > I > II > IV

e) None of these choices.

Topic: Generalities, solvent effects

Section: 6.13

Difficulty Level: Easy

40) Which is the weakest nucleophile in polar aprotic solvents?

A) I^-

B) Br^-

C) Cl^-

D) F^-

E) All of these choices are equally strong nucleophiles, regardless of the type of solvent used.

Topic: Generalities, solvent effects

Sections: 6.13

Difficulty Level: Easy

41) Which is the weakest nucleophile in polar protic solvents?

A) I^-

B) Br^-

C) Cl^-

D) F^-

E) All of these choices are equally strong nucleophiles, regardless of the type of solvent used.

Topic: Generalities, solvent effects

Sections: 6.13

Difficulty Level: Easy

42) Which ion is the strongest nucleophile in aqueous solution?

A) F^-

B) Cl^-

C) Br^-

D) I^-

E) All of these choices are equally strong.

Topic: Generalities, solvent effects

Sections: 6.13

Difficulty Level: Easy

43) Which ion is the strongest nucleophile in an aprotic solvent such as dimethylsulfoxide?

A) I^-

B) Br^-

C) Cl^-

D) F^-

E) All of these choices are equal.

Topic: Nucleophile, solvent effects

Sections: 6.13

Difficulty Level: Medium

44) Which alkyl halide would you expect to react most slowly when heated in aqueous solution?

A) (CH₃)₃C-F

B) (CH₃)₃C-Cl

C) (CH₃)₃C-Br

D) (CH₃)₃C-I

E) All of these choices would react at the same rate.

Topic: Leaving groups

Sections: 6.4 and 6.13

Difficulty Level: Easy

45) Considering the relative solvation of reactants and the transition states of substitution reactions of these reactants, predict which general type of reaction would be most favored by the use of a polar solvent.

A) Y: + RX  RY⁺ + X:^-

B) Y:^- + RX  RY + X:^-

C) Y: + RX⁺  RY⁺ + X:

D) Y:^- + RX⁺  RY + X:

E) RX⁺  R⁺ + X:

Topic: Generalities, solvent effects

Sections: 6.13

Difficulty Level: Medium

46) Which is the most reactive nucleophile in DMF (structure shown below)?

A) F^-

B) Cl^-

C) Br^-

D) I^-

E) All of these choices are equally reactive.

Topic: Nucleophile, solvent effects

Sections: 6.3, 6.13

Difficulty Level: Easy

47) Which of these species, acting in a protic solvent, exhibits greater nucleophilic activity than expected on the basis of its basicity?

A) OH^-

B) CH₃O^-

C) SH^-

D) Cl^-

E) H₂O

Topic: Nucleophile, solvent effects

Sections: 6.3, 6.13

Difficulty Level: Medium

48) Which S_N2 reaction will occur most rapidly in a mixture of water and ethanol?

A) I^- + CH₃CH₂–Br  CH₃CH₂–I + Br^-

B) I^- + CH₃CH₂–Cl  CH₃CH₂–I + Cl^-

C) I^- + CH₃CH₂–F  CH₃CH₂–I + F^-

D) Br^- + CH₃CH₂–Cl  CH₃CH₂–Br + Cl^-

E) Br^- + CH₃CH₂–F  CH₃CH₂–Br + F^-

Topic: Leaving groups, nucleophiles

Sections: 6.3, 6.13

Difficulty Level: Medium

49) Which S_N2 reaction will occur most rapidly in aqueous acetone solution? Assume concentrations and temperature are the same in each instance.

A) HO^- + CH₃-Cl  CH₃OH + Cl^-

B) HO^- + CH₃CH₂-Cl  CH₃CH₂OH + Cl^-

C) HO^- + (CH₃)₂CH-Cl  (CH₃)₂CHOH + Cl^-

D) HO^- + (CH₃)₃C-Cl  (CH₃)₃COH + Cl^-

E) HO^- + (CH₃)₃CCH₂-Cl  (CH₃)₃CCH₂OH + Cl^-

Topic: Predicting mechanism, kinetics

Sections: 6.3, 6.13

Difficulty Level: Medium

50) The relative nucleophilicities of species do not necessarily parallel the relative basicities of the same species because

A) not all nucleophiles are bases, and vice versa.

B) experimental measurements of sufficient accuracy are not available to make the comparisons.

C) nucleophilicity is a thermodynamic matter; basicity is a matter of kinetics.

D) basicity is a thermodynamic matter; nucleophilicity is a matter of kinetics.

E) Actually, the relative values do parallel one another.

Topic: Nucleophilicity

Sections: 6.3, 6.13

Difficulty Level: Hard

51) Which of the following is not true concerning the strength of a nucleophile?

a) Nucleophilicity may not parallel basicity.

b) Negatively charged nucleophiles are always more reactive than their conjugate acids.

c) The greater the strength of a nucleophile, the faster an S_N2 reaction will occur.

d) Strong bases are always good nucleophiles

e) None of these answer choices are correct.

Topic: Nucleophilicity

Sections: 6.3, 6.13

Difficulty Level: Hard

52) Which of the following solvents will best promote a nucleophilic reaction between NaCN and 1-bromopropane?

a) H₂O/MeOH mixture

b) H₂O

c) MeCN

d) HF(aq)

e) running with no solvent

Topic: Predicting mechanism, solvent effects

Sections: 6.3, 6.13

Difficulty Level: Medium

53) Which of the following nucleophiles will react the fastest with tert-butyl bromide in ethanol?

a) F^-

b) Br^-

c) I^-

d) Cl^-

e) All react at about the same rate.

Topic: Predicting mechanism, kinetics, solvent effectsh

Sections: 6.3, 6.13

Difficulty Level: Hard

54) Which of the following nucleophiles will react the fastest with 1-bromoptopane in ethanol?

a) SH^-

b) OH^-

c) H₂O

d) H₂S

e) All react at about the same rate.

Topic: Predicting mechanism, nucleophilicity, solvent effects

Sections: 6.3, 6.13

Difficulty Level: Medium

55) Which S_N2 reaction would take place most rapidly?

A)

B)

C)

D)

E)

Topic: Kinetics, nucleophilicity

Sections: 6.3, 6.8, 6.13

Difficulty Level: Medium

56) Which of the following is a feasible substitution reaction?

A) CH₃CH₂Cl + NaBr  CH₃CH₂Br + NaCl

B) CH₃CH₃ + NaCN  CH₃CH₂CN + NaH

C) CH₃CH₂Cl + NaOH  CH₂=CH₂ + H₂O + NaCl

D) More than one of these choices.

E) None of these choices.

Topic: Leaving group

Sections: 6.2, 6.4, 6.13

Difficulty Level: Easy

57) Identify the leaving group in the following reaction.

A) C₆H₅S^-

B) Na⁺

C) CH₃CH₂I

D) C₆H₅SCH₂CH₃

E) I^-

Topic: Generalities, leaving group

Sections: 6.4 and 6.13

Difficulty Level: Easy

58) Identify the leaving group in the following reaction.

A) CH₃OH

B) CH₃OH₂⁺

C) CH₃OCH₃

D) H₂O

E) None of these choices.

Topic: Leaving groups

Sections: 6.4 and 6.13

Difficulty Level: Easy

59) Which nucleophilic substitution reaction would be unlikely to occur?

A) HO^ + CH₃CH₂–I  CH₃CH₂–OH + I^

B) I^ + CH₃CH₂–H  CH₃CH₂–I + H^

C) CH₃S^ + CH₃–Br  CH₃S–CH₃ + Br^

D) All of these choices would be unlikely to occur.

E) None of these choices would be unlikely to occur.

Topic: Leaving groups

Sections: 6.4 and 6.13

Difficulty Level: Easy

60) Which of the following would be most reactive in an S_N2 reaction?

A)

B)

C)

D)

E)

Topic: Leaving groups

Sections: 6.4 and 6.13

Difficulty Level: Easy

61) Which of the following is the poorest leaving group?

A) H^

B) CH₃O^

C) H₂O

D) OH^

E) NH₂^

Topic: Generalities, leaving group

Sections: 6.4 and 6.13

Difficulty Level: Medium

62) Which of the following is not a good leaving group?

A) C₂H₅O^

B) Cl^

C) I^

D) CH₃CO₂^

E) All of these choices are good leaving groups.

Topic: Leaving groups

Sections: 6.4 and 6.13

Difficulty Level: Medium

63) Which nucleophilic substitution reaction is not likely to occur?

A) I^ + CH₃CH₂–Cl  CH₃CH₂–I + Cl^

B) I^ + CH₃CH₂–Br  CH₃CH₂–I + Br^

C) I^ + CH₃CH₂–OH  CH₃CH₂–I + OH^

D) CH₃O^ + CH₃CH₂–Br  CH₃CH₂–OCH₃ + Br^

E) OH^ + CH₃CH₂–Cl  CH₃CH₂–OH + Cl^

Topic: Leaving groups

Sections: 6.3, 6.4, 6.13

Difficulty Level: Medium

64) S_N2 reactions of the type, Nu^- + RL  Nu-R + L^-, are favored

A) when tertiary substrates are used.

B) by using a high concentration of the nucleophile.

C) by using a solvent of high polarity.

D) by the use of weak nucleophiles.

E) by none of these choices.

Topic: Generalities

Sections: 6.8, 6.13

Difficulty Level: Easy

65) Which of the following statements is (are) true of an S_N2 reaction of (R)-2-bromobutane with hydroxide ion?

A) Doubling the hydroxide ion concentration would double the rate of the reaction. (Assume that all other experimental conditions are unchanged.)

B) The major product would be (S)-2-butanol.

C) Doubling the concentration of (R)-2-bromobutane would double the rate of the reaction. (Assume that all other experimental conditions are unchanged.)

D) All of these choices.

E) Two of these choices.

Topic: Generalities

Sections: 6.8, 6.13

Difficulty Level: Medium

66) Which nucleophilic substitution reaction would be likely to occur (although probably not in excellent yield, due to competing elimination)?

A) HO^ + CH₃CH₂CH₂CHICH₃  CH₃ CH₂CH₂CHOHCH₃ + I^

B) Cl^ + CH₃CH₂CH₂CH₂–OH  CH₃CH₂CH₂CH₂–Cl + OH^

C) CH₃S^ + CH₃CH₂CH₂–OCH₃  CH₃S–CH₂CH₂CH₃ + OCH₃^

D) All of these choices are likely to occur.

E) None of these choices are likely to occur.

Topic: Predicting products

Sections: 6.8, 6.13

Difficulty Level: Medium

67) Which of the following statements is (are) true of S_N1 reactions of alkyl halides in general?

A) The rate of an S_N1 reaction depends on the concentration of the alkyl halide.

B) The rate of an S_N1 reaction depends on the concentration of the nucleophile.

C) S_N1 reactions of alkyl halides are favored by polar solvents.

D) The rate of an S_N1 reaction depends on the concentration of the alkyl halide and S_N1 reactions of alkyl halides are favored by polar solvents.

E) The rate of an S_N1 reaction depends on the concentration of the alkyl halide and the concentration of the nucleophile, and S_N1 reactions of alkyl halides are favored by polar solvents.

Topic: Generalities

Sections: 6.12, 6.13

Difficulty Level: Easy

68) Which of the following statements is (are) true of S_N1 reactions of alkyl halides in general?

A) The rate of an S_N1 reaction depends on the concentration of the alkyl halide.

B) The rate of an S_N1 reaction depends on the concentration of the nucleophile.

C) S_N1 reactions of alkyl halides occur faster in polar aprotic solvents (compared to protic solvents).

D) The rate of an S_N1 reaction depends on the concentration of the alkyl halide and S_N1 reactions of alkyl halides occur faster in polar aprotic solvents (compared to protic solvents).

E) The rate of an S_N1 reaction depends on the concentration of the alkyl halide and the concentration of the nucleophile, and S_N1 reactions of alkyl halides occur faster in polar aprotic solvents (compared to protic solvents).

Topic: Generalities

Sections: 6.12, 6.13

Difficulty Level: Easy

69) S_N1 reactions of the type, Nu^- + RL  Nu–R + L^-, are favored

A) when tertiary substrates are used.

B) by using a high concentration of the nucleophile.

C) when L^- is a strong base.

D) by use of a non-polar solvent.

E) by none of these choices.

Topic: Generalities

Sections: 6.12, 6.13

Difficulty Level: Easy

70) S_N1 reactions of the following type:

Nu:^- + R-X  R-Nu + :X^-

are favored

A) by the use of tertiary substrates (as opposed to primary or secondary substrates).

B) by increasing the concentration of the nucleophile.

C) by increasing the polarity of the solvent.

D) by use of a strong base.

E) by more than one of these choices.

Topic: Generalities

Sections: 6.12, 6.13

Difficulty Level: Medium

71) S_N1 reactions of the following type:

Nu:^- + R-X  R-Nu + :X^-

are favored

A) by the use of tertiary substrates (as opposed to primary or secondary substrates).

B) by increasing the concentration of the nucleophile.

C) by increasing the polarity of the solvent.

D) by use of a weak nucleophile.

E) by the use of tertiary substrates (as opposed to primary or secondary substrates) and by use of a weak nucleophile.

Topic: Generalities

Sections: 6.12, 6.13

Difficulty Level: Hard

Question type: True/false

72) In a highly exergonic S_N2 reaction we can assume the transition state is similar to the products formed in the reaction.

Topic: Hammond Postulate

Sections: 6.7 and 6.10

Difficulty Level: Hard

73) An endergonic S_N2 reaction will have a have a higher energy of activation (G^‡) than an exergonic S_N2 reaction.

Topic: Free energy diagrams

Sections: 6.7 and 6.8

Difficulty Level: Medium

74) Increasing the temperature of a reaction will speed up the overall rate as this will increase the energy of activation for reaction.

Topic: Temperature and rate

Section: 6.7

Difficulty Level: Medium

75) Racemic mixtures form in S_N1 reactions when leaving group departure results in a loss of chirality followed by subsequent attack of the nucleophile.

Topic: S_N1 stereochemistry

Section: 6.12

Difficulty Level: Medium

Question type: text-entry

76) As we go down Group 7A of the periodic table, the size of the halogen atom increases; accordingly, the carbon-halogen bond length gets ___ and the bond strength gets ___.

Topic: Bond length, bond strength, leaving groups

Section: 6.4

Difficulty Level: Easy

77) In the S_N2 reaction, the unstable arrangement of atoms in which both the nucleophile and the leaving group are partially bonded to the same carbon atom is called the ___.

Topic: Transition state theory

Section: 6.6

Difficulty Level: Easy

78) In order for colliding species to react, they must ___ and ___.

Topic: Activation energy, transition state theory

Section: 6.7

Difficulty Level: Medium

79) What final product is likely to be obtained through the following series of reactions?

Topic: Multistep synthesis, acid-base reactions, S_N2

Sections: 6.8

Difficulty Level: Medium

80) When 5-bromo-1-pentanol is treated with sodium hydride in diethyl ether, the product is analyzed to be C₅H₁₀O. Propose a likely structure for this product, suggesting a reasonable mechanistic pathway for its formation.

Topic: Acid-base reactions, intramolecular S_N2

Sections: 6.8

Difficulty Level: Hard

81) Draw the potential energy diagram that represents an exothermic reaction between a tertiary alkyl halide and methanol. Briefly explain your rationale.

Topic: Free energy diagrams

Sections: 6.7 and 6.10

Difficulty Level: Hard

82) A nucleophile in an S_N2 reaction must approach from the ___ of the carbon atom attached to the leaving group since the electrons in the nucleophile’s HOMO begins to overlap with the ___ of the carbon atom attached to the leaving group.

Topic: SN2 mechanism

Section 6.6

Difficulty Level: Medium

83) The stabilizing effect of alkyl substituents on carbocations can be explained through ___.

Topic: Carbocation stability

Section: 6.11

Difficulty Level: Medium

84) Typically, increasing the concentration of the nucleophile of an S_N1 reaction has no impact on the rate of the reaction. The reason for this is that ___.

Topic: S_N1 kinetics

Section: 6.12

Difficulty Level: Easy

85) The substitution mechanism whose rate depends primarily on the relative stability of the intermediate carbocation is the ___.

Topic: Carbocation stability

Sections: 6.11 and 6.12

Difficulty Level: Easy

86) A reaction in which the nucleophile is a molecule of the solvent is referred to as a ___ reaction.

Topic: Solvolysis

Section: 6.12

Difficulty Level: Easy

87) A student has isolated a chiral alkyl halide (shown below) with a specific rotation of [] = +22.1^o. The student decided to store the compound in the solvent MeOH overnight. However, reanalysis of the alkyl halide showed a new chemical formula of C₁₁H₁₆O with a specific rotation of [] = 0^o. Suggest a mechanism to justify these results.

Topic: Solvolysis

Sectioin: 6.12

Difficulty Level: Medium

88) The substitution mechanism whose rate depends primarily on the degree of steric hindrance around the leaving group is the ___.

Topic: Steric hindrance

Section: 6.13

Difficulty Level: Medium

89) Increasing the concentration of either of the reactants of an S_N2 reaction increases the rate of the reaction. The primary reason for this is that increasing the concentration increases ___.

Topic: Activation energy, kinetics

Sections: 6.7 and 6.13

Difficulty Level: Hard

90) The relative nucleophilicity of the halide ions in polar aprotic solvents is observed to be markedly different from that in protic solvents. Explain briefly.

Topic: Nucleophilicity, solvent effects

Sections: 6.3 and 6.13

Difficulty Level: Hard

91) Typically alkyl chlorides are slow in S_N2 reactions with sodium methoxide in methanol, however the rate of the reaction can be greatly increased with a small addition of NaI. Explain.

R-Cl + I^- 🡪 Cl^- + R-I + MeO^- 🡪 R-OMe + I^-

Topic: Nucleophilicity, solvent effects

Sections: 6.3 and 6.13

Difficulty Level: Hard

92) What final product is likely to be obtained through the following series of reactions?

Topic: Multistep synthesis, acid-base reactions, S_N2

Sections: 6.14

Difficulty Level: Medium

93) What final product is likely to be obtained through the following series of reactions?

Topic: Multistep synthesis, acid-base reactions, S_N2, hydrogenation

Sections: 6.14, 4.16

Difficulty Level: Hard

94) Select the potential energy diagram that represents a two-step exothermic (exergonic) reaction.

A) I

B) II

C) III

D) IV

E) V

Topic: Free energy diagrams

Section: 6.7

Difficulty Level: Easy

95) Which alkyl chloride, though primary, would be expected to be most reactive in S_N2 reactions?

A)

B)

C)

D)

E)

Topic: Steric hindrance

Sections: 6.13

Difficulty Level: Easy

96) Which alkyl halide would be unreactive in a nucleophilic substitution reaction?

A) I

B) II

C) III

D) IV

E) V

Topic: Kinetics

Section: 6.13

Difficulty Level: Easy

97) Which alkyl halide would you expect to undergo an S_N2 reaction most rapidly?

A) 1-bromohexane

B) 1-bromo-2-methylpentane

C) 1-bromo-3-methylpentane

D) 1-bromo-4-methylpentane

E) 1-bromo-2,2-dimethylbutane

Topic: Kinetics

Sections: 6.8 and 6.13

Difficulty Level: Medium

98) Identify the electrophile in the following reaction:

2 H₂O + RX 🡪 ROH + H₃O⁺ + X^

A) X-

B) H₃O⁺

C) ROH

D) H₂O

E) RX

Topic: Generalities, nucleophiles

Sections: 6.3 and 6.13

Difficulty Level: Easy

99) Identify the electrophile in the following reaction:

2R’OH + RX 🡪 ROR’ + [R’OH₂]⁺ + X^-

A) X^

B) [R’OH₂]^

C) ROR’

D) R’OH

E) RX

Topic: Generalities, nucleophiles

Sections: 6.3 and 6.13

Difficulty Level: Medium

100) Which S_N2 reaction would you expect to take place most slowly? Assume that the concentrations of the reactants and the temperature are the same in each instance.

A)

B)

C)

D)

E)

Topic: Nucleophilicity, leaving groups

Sections: 6.3, 6.8, 6.13

Difficulty Level: Medium

101) Which is the strongest nucleophile in polar protic solvents?

A) I^-

B) Br^-

C) Cl^-

D) F^-

E) All of these choices are equally strong nucleophiles, regardless of the type of solvent used.

Topic: Generalities, solvent effects

Sections: 6.13

Difficulty Level: Easy

102) Which alkyl halide would you expect to react most rapidly when heated in aqueous solution?

A) (CH₃)₃C-F

B) (CH₃)₃C-Cl

C) (CH₃)₃C-Br

D) (CH₃)₃C-I

E) All of these choices would react at the same rate.

Topic: Leaving groups

Sections: 6.4 and 6.13

Difficulty Level: Easy

103) Which S_N2 reaction will occur most slowly in a mixture of water and ethanol?

A) I^- + CH₃CH₂–Br  CH₃CH₂–I + Br^-

B) I^- + CH₃CH₂–Cl  CH₃CH₂–I + Cl^-

C) I^- + CH₃CH₂–F  CH₃CH₂–I + F^-

D) Br^- + CH₃CH₂–Cl  CH₃CH₂–Br + Cl^-

E) Br^- + CH₃CH₂–F  CH₃CH₂–Br + F^-

Topic: Leaving groups, nucleophiles

Sections: 6.3, 6.13

Difficulty Level: Medium

104) Identify the nucleophile in the following reaction.

A) C₆H₅S^-

B) Na⁺

C) CH₃CH₂I

D) C₆H₅SCH₂CH₃

E) I^-

Topic: Generalities, leaving group

Sections: 6.4 and 6.13

Difficulty Level: Easy

105) Identify the electrophile in the following reaction.

A) C₆H₅S^-

B) Na⁺

C) CH₃CH₂I

D) C₆H₅SCH₂CH₃

E) I^-

Topic: Generalities, leaving group

Sections: 6.4 and 6.13

Difficulty Level: Easy

106) Identify the product in the following reaction.

A) C₆H₅S^-

B) Na⁺

C) CH₃CH₂I

D) C₆H₅SCH₂CH₃

E) I^-

Topic: Generalities, leaving group

Sections: 6.4 and 6.13

Difficulty Level: Easy

107) Identify the electrophile in the following reaction.

A) CH₃OH

B) CH₃OH₂⁺

C) CH₃OCH₃

D) H₂O

E) None of these choices.

Topic: Leaving groups

Sections: 6.4 and 6.13

Difficulty Level: Easy

108) Identify the nucleophile in the following reaction.

A) CH₃OH

B) CH₃OH₂⁺

C) CH₃OCH₃

D) H₂O

E) None of these choices.

Topic: Leaving groups

Sections: 6.4 and 6.13

Difficulty Level: Easy

109) Which of the following is the best leaving group?

A) H^

B) CH₃O^

C) H₂O

D) OH^

E) NH₂^

Topic: Generalities, leaving group

Sections: 6.4 and 6.13

Difficulty Level: Medium