Question

1. Consider the S_N2 reaction of butyl bromide with hydroxide ion , Assuming no other changes, what effect on the reaction rate would result from simultaneously doubling the concentrations of both butyl bromide and hydroxyl ion

1. No effect (B)It would double the rate (C)it would increase the rate six times

(D) It would increase the rate four times.

   2. Which alky halide would you expect to undergo S_N1 hydrolysis most rapidly? (A) (CH₃)₃C-I

(B) (CH₃)₃C-Br (C) (CH₃)₃C-Cl (D) (CH₃)₃C-F

3. Which of the following alkyl halides would you expect to be most reactive in a unimolecular .

Reaction? (A) C₆H₁₁CH₂CH₂CH₂Br (B) C₆H₁₁CHCH₃CH₂Br (C) C₆H₁₁CH₂CHBrCH₃

(D) C₆H₁₁CBr(CH₃)₂

   4. An increase in the kinetic energy of reacting moleules results in: (A) a decrease in reaction rate

(B) an increase in the probability factor (C)an increase in the reaction rate (D) no change

5. Select the rate law for a second order reaction: (A) rate = k[RX] (B) rate = k[RX]²[OH^-]

(C) rate = k[RX][OH^-] (D) rate k[RX]²[OH^-]²

6. S_N1 reactions of the type, Nu^- + RL ----- Nu-R + L^- are favored (A) when tertiary alkyl

halides are used. (B) by using a high concentration of the nucleophile (C)by use of polar

   aprotic solvent (D)by none of the above

7. Which alkyl halide would give the highest yield of the elimination product when treated with sodium ethoxide in ethanol? A)ethyl bromide (B)tertiary butyl bromide

(CH₃)₃C-F 8. Which of the following reactions proceeds with inversion of configuration at the carbon bearing the leaving group? (A)S_N 1 (B)E1 (C) S_N 2 (D) E2

9. Which of the following reactions proceeds with racemization at the carbon bearing the leaving group? (A)S_N1 (B)E1 (C) S_N2 (D) E2

10. Identify the leaving group in the reaction , CH₃OH + C H₃OH₂⁺ -------- CH₃O⁺HCH₃ + H₂O

(A) CH₃OH (C)CH₃OCH₃ (C) H₂O (D) None of these

11. Which of the following is NOT a nucleophile? (A) NH₄⁺ (B)H₂O (C)NH₃ (D) CH₃O^-

12. Select the strongest nucleophile for an S_N2 reaction. (A)RO^- (B) OH^- (C)H₂O (D )RCO₂^-

13. Which is the strongest nucleophile? (A)OH^- (B) CH₃CH₂O^- (C)CH₃CH₂OH (D) H₂O

14. Which of the following is NOT a good leaving group? (A)CH3O^- (B) Cl^- (C) Br^- (D) I^-

15. Which is the most reactive nucleophile in dimethyl sulfoxide (DMF), a polar aprotic solvent

   (A) F^- (B) I^- (C) Br^- (D) Cl^-

16. 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

17. The p-orbital of a methyl cation, CH3+, contains how many electrons? (A) 0 (B) 1 (C)2 (D) 3

18. The hybridization state of the charged carbon in a carbocation is(A) sp⁴ (B)sp³ (C)sp² (D)s

19. Which is a TRUE statement concerning the transition state of the rate-determining step of the S_N1 reaction? (A) structurally, it closely resembles the carbocation intermediate

   (B) Both bond-breaking and bond-making are occurring

(C) Formation of the transition state is an exothermic reaction

(D) The transition state is at energy minimum

20, You want to convert 2-chloropentane(an alky halide) into 1-pentene (an alkene). Which of the following reagents would you choose? (A)NaOH/water (B)KOH/methanol

   (C)CH₃ONa/CH₃OH (D) (CH₃)₃COK/(CH₃)₃COH

21. Elimination reactions are favored over nucleophilic substitution reactions:

(A) at high temperature

   (B)when tert-butoxide ion is used

   (C) when 3o alkyl halides are used as substrates

   (D) in all of these cases

22. Which is NOT a polar aprotic solvent? (A)acetone (B) acetonitrile (C)DMF (D)methanol

23. The relative nucleophilicities of species do not necessarily parallel the relative basicity of the same species because:

(A) not all nucleophiles are bases, and vie versa

(B) nucleophilicity is a thermodynamic matter, whereas basicity is a matter of kinetics

(C) basicity is a thermodynamic matter, whereas nucleophilicity is a matter of kinetics

(D) experimental measurements of sufficient accuracy are not available to make the comparisons

Answer 1