CHE 275 NUCLEPHILIC SUBSTITUTUIN CHAP 8 ASSIGN 1. Which best depicts the partial charges on methyl bromide and sodium methoxide? 2. Which of the following would be the best (most reactive) nucleophile in a reaction with iodomethane (CH 3I) in a polar protic solvent? A. I B. Br C. Cl D. F The type of nucleophile would make no difference in the rate of this reaction. 3. Provide an IUPAC name for the following molecule. A. (2R, 4R )-2-bromo-4-methylheptane B. (2R, 4R )-4-methyl-2-bromoheptane C. (4R, 6R )-6-bromo-4-methylheptane D. (4S, 6R )-6-bromo-4-methylheptane (2R, 4S )-2-bromo-4-methylheptane 4. What product(s) would you expect from the following reaction? 5. The halogens are quite typically very useful leaving groups in the S N2 reaction. f the following, which is the best leaving group? A. F B. Cl C. Br D. I both B and C are equally correct 1 P a g e
6. What problem could you anticipate when attempting the following reaction? (Pinane ring numbering is shown.) A. Cyanide is too poor a nucleophile to displace a bromide ion. B. The hydrogen at C3 prevents the reaction from occurring. C. The hydrogens at C2 prevent the reaction from occurring. D. The product has the wrong stereochemistry at C3 for typical reaction of a 2 bromide. The geometry of the pinane ring prevents the backside attack required to obtain the product shown. 7. Consider the following S N2 reaction shown below. If the concentration of NaCN is quadrupled, what will happen to the rate of the reaction? A. rate will be unaffected B. rate will quadruple C. rate will double D. rate will be cut in half rate will increase by a factor of 16 8. Predict the major product of the following reaction. 9. Which one is not true for the S N2 reaction: A + B products? A. Rate = k[a][b] B. Reactivity order is RI > RBr > RCl C. The reaction proceeds with racemization. D. The process is concerted (bond making and bond breaking occurring simultaneously). 2 P a g e
10. Which of the following reactions may proceed by an S N2 mechanism? A. B. C. D. 11. To ensure that the elimination reaction (shown below) proceeds through an E2 mechanism, which of the following reagents should be utilized as the base? A. NaCH 2CH 3 B. HCH 2CH 3 C. HCH 3 D. H 2 NaCN 12. What reaction conditions would be necessary to effect the following transformation? This reaction cannot possibly take place!!! 13. Which of the following compounds would undergo S N2 most rapidly? A. 1-chloropentane B. 2-chloropentane C. 2-chloro-2-methylbutane D. neopentylchloride 3 P a g e
14. Which of the five following compounds would you expect to react most rapidly with methanol to do the following reaction? 15. The following reaction (as written) most likely proceeds through what mechanism? A. S N2 B. S N1 C. E2 D. E1 Free-radical halogenation 16. Which of the following structures would be an intermediate (short-lived, reactive species) in the reaction shown? 17. In the following reaction, if the concentration of HCH 2CH 3 is tripled, what will happen to the rate of the reaction? A. Triple B. Decrease by a factor of 3 C. Increase by a factor of 6 D. No change in rate Increase by a factor of 9 18. Why is it that alkoxides of tertiary alcohols tend to cause E2 reactions in reactions with 1 halides far more than do alkoxides of 1 or 2 alcohols? A. Tertiary alkoxides are stronger bases than alkoxides of 1 or 2 alcohols. B. Tertiary alkoxides are better nucleophiles than alkoxides of 1 or 2 alcohols. C. Tertiary alkoxides provide a more polar environment than do alkoxides of 1 or 2 alcohols. D. Tertiary alkoxides are poorer nucleophiles than alkoxides of 1 or 2 alcohols. Tertiary alkoxides provide a less polar environment than do alkoxides of 1 or 2 alcohols. 19. Which compound would undergo E1 reaction the fastest? A. 1-chlorobutane B. 2-chlorobutane C. 2-chloro-2-methylbutane D. neopentylchloride 4 P a g e
20. What product would you expect to be formed in the reaction of the (R) bromide shown? 21. Predict the major product of the following reaction. 22. Which species of each pair would be the better leaving group? Group I Group II A H or B H 2 C CH 3C or D CH 3CH 2 A. A and C B. A and D C. B and C D. B and D 23. Which of the following reactions would not lead to the formation of the indicated product? A. CH 3CH 2 + CH 3H CH 3CH 2CH 3 + H B. CH 3S Na+ + CH 3CH 2I CH 3CH 2SCH 3 + NaI C. NaN 3 + CH 3CH 2CH 2Br CH 3CH 2CH 2N 3 + NaBr D. (CH 3) 2NH + CH 3Br (CH 3) 3N + + H + + Br 5 P a g e
24. Which product would you expect to predominate in the reaction of (S)-3-bromohexane with sodium acetate? 25. Which of the following would be true of the reaction shown? A. The rate of the reaction depends only on the alkyl bromide concentration. B. The rate of the reaction depends only on the methanol concentration. C. The rate of the reaction depends on both the alkyl halide concentration and the methanol concentration. D. The rate of the reaction depends on the concentration of neither reactant. There is no way to predict what the rate would depend on. 26. Which of the following does not correctly describe S N2 reactions of alkyl halides? A. Tertiary halides react faster than secondary halides. B. Rate of reaction depends on the concentrations of both the alkyl halide and the nucleophile. C. The mechanism consists of a single step with no intermediates. D. The transition state species has a pentavalent carbon atom. 27. What is the leaving group in the following reaction? A. H B. H 2 C. CH 3CH 2 + D. C1 6 P a g e
28. What is the major product of the following reaction? 29. Give the product(s) of the following reaction? A. A B. B C. C D. a mixture of A and B 30. In the solvolysis of t-butyl chloride, a minor product is 2-methylpropene, which results from the: A. E2 mechanism with H acting as the base. B. E2 mechanism with H 2 acting as the base. C. E1 mechanism with H acting as the base. D. E1 mechanism with H 2 acting as the base. 7 P a g e
31. Considering the S N1, S N2, E1, and E2 mechanisms, the energy diagram shown below corresponds to A only the S N1 mechanism. B both the S N1 and E1 mechanisms. C. only the S N2 mechanism. D. both the S N2 and E2 mechanisms. 32. Starting with 1-methylcyclohexene, which of the following reaction sequences is the best synthesis of the azide shown below? 33. Iodide ion is rather unusual in that it is both a good nucleophile and a good leaving group. Which of the following graphs represents what you expect when (S )-(+)-2-iodobutane is treated with sodium iodide? 8 P a g e
34. An optically pure 2 alcohol with a specific rotation of +24 was converted to the tosylate with p-toluenesulfonyl chloride. Subsequent treatment of the tosylate with H ion yielded a 2 alcohol. What is the specific rotation of that alcohol? H R CHH + CH 3 S 2 Cl R C S CH 3 R' R' R CHH + S CH 3 H R' A. +24 B. -24 C. 0 D. +12 12 NAME DATE ANSWER SHEET CHE 275 CHAP 8 ASSIGN 1. 11. 21. 31. 2. 12. 22. 32. 3. 13. 23. 33. 4. 14. 24. 34. 5. 15. 25. 35. 6. 16. 26. 36. 7. 17. 27. 37. 8. 18. 28. 38. 9. 19. 29. 39. 10. 20. 30. 40. SS I 2016 9 P a g e