15597ch07113-13110/22/0520:20Pag0124 124.chapter 7 FURTHER REACTONS OF HALOALKANES:UNIMOLECULAR SUBSTTTUTION AND PATHWAYS OF ELIMINATION (b)Rates of (1)and ()will be the same.rly so.((sand E1.and they be very close.Rate of ()ill depend on the concentration of the base because of of bimolecular elimination. 40.(a-CH:E2 (b)No reaction.Poor leaving group (e)Racemie CH,CH2CHOHCH,SNI (e)(CHa)2CHCH2CH2OCH2CH Sx2 (f)Racemic CH:CH2C(CH)CH,CH-CH:SNl (g)No reaction,except for reversible proton transfer NC- -CH-CH-CH-CN E2 and Sx2 (i)(S)-CH,CH2CHSHCH3 Sx2 (j) (k)(CH)CCH=CH,E2 (D)No reaction.Poor nucleophile 41. Reagent Haloalkane H,0 NaSeCH, NaOCH, KOC(CH, CH,CI no reaction CH,SeCH, CHaOCH CH.CH.CHCI n0 reactio可 CH.CH.CHOCH,S2 CH,OC(CH)Sx2 CHCH-CH: (CH:CHO (CH:)CHO CHCH-CHE2 CH;CH (CH:)CC (CH3)C= (CHa)C-CHa)E1 (CHa)C-CHa]EI 43.(a)Poorly.CH,CH-CHCH and CH,CH,CH-CH,are important products. (b)Not at all.No reaction:poor nucleophile.(b) Rates of (1) and (2) will be the same, or nearly so. (1) is SN1 and (2) is SN1 and E1, and they have the same rate-determining step; if the reaction mixtures are similar in polarity, the rates will be very close. Rate of (3) will depend on the concentration of the base because of the occurrence of bimolecular elimination. 40. (a) (b) No reaction. Poor leaving group. (c) Racemic CH3CH2CHOHCH3 SN1 (d) (e) (CH3)2CHCH2CH2OCH2CH3 SN2 (f ) Racemic (g) No reaction, except for reversible proton transfer. (h) (i) (S)OCH3CH2CHSHCH3 SN2 (j) (k) (CH3)CCHPCH2 E2 (l) No reaction. Poor nucleophile. 41. Reagent Haloalkane H2O NaSeCH3 NaOCH3 KOC(CH3)3 CH3Cl no reaction CH3SeCH3 CH3OCH3 CH3OC(CH3)3 SN2 CH3CH2CH2Cl no reaction CH3CH2CH2SeCH3 CH3CH2CH2OCH3 CH3CHPCH2 (CH3)2CHCl (CH3)2CHOH (CH3)2CHSeCH3 CH3CHPCH2 CH3CHPCH2 (CH3)3CCl (CH3)3COH (CH3)3CSeCH3SN1 (CH3)2CPCH2 (CH3)2CPCH2 and and (CH3)2CPCH2}E1 (CH3)2CPCH2}E1 42. See answer to Problem 41. Secondary halides give higher E2/E1 ratios than do tertiary halides (secondary carbocations form less readily than tertiary). 43. (a) Poorly. CH3CHPCHCH3 and CH3CH2CHPCH3 are important products. (b) Not at all. No reaction; poor nucleophile. SN1 E2 SN2 OCH3 CH2CH3 SN1 NC CH2CH2CH2CN E2 and SN2 CH2CH2CH2CN and CH3CH2C(CH3)CH2CH2CH3 SN1 I E2 CH2 E2 124 • Chapter 7 FURTHER REACTIONS OF HALOALKANES: UNIMOLECULAR SUBSTITUTION AND PATHWAYS OF ELIMINATION E2 SN2 1559T_ch07_113-131 10/22/05 20:20 Page 124