Unformatted text preview: 6-47 (b) continued Better to do SN2 on a methyl carbon:
C H3 CH3 CH3 C H3 - X U CH3 - C-O - CH3 C H3 ?
I -O �
+ I CH3 I 6-48 (a) SN2-second order: reaction rate doubles ( b) SN2-second order: reaction rate increases six times (c) Virtually all reaction rates, including this one, increase with a temperature increase. 6-49 This is an SN I reaction; the rate law depends only on the substrate concentration, not on the nucleophile concentration.
(a) no change in rate (b) the rate triples, dependent only on [ t-butyl bromide ] (c) Virtually all reaction rates, including this one, increase with a temperature increase. 6-50 The key to this problem is that iodide ion is both an excellent nucleophile AND leaving group. Substitution on chlorocyclohexane is faster with iodide than with cyanide (see Table 6-3 for relative nucleophilicities). Once iodocyclohexane is formed, substitution by cyanide is much faster on iodocyclohexane than on chlorocyclohexane because iodide is a better leaving group than chloride. So fast reactions involving iodide replace a slower single reaction, resulting in an overall rate increase. two o6-51 (a) 0- Cl + -CN moderate rate .. Cl + -I fast
---- �� .. 0- 0+ CN 1 -CN fast ---- �� .. 0- CN + - 1 recycles-only a small amount needed (catalyst) (c) (d) rearrangement 6-52 (a) rearrangement 1 20 ...
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