Dolbier HW Solutions 207

Dolbier HW Solutions 207 - 201 NUCLEOPHILIC SUBSTITUTION...

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Since the reaction of the bromide with NaSCH 2 CH 3 proceeds with inversion of con f guration at the stereogenic center, and since the f nal product has the same con f guration as the starting alcohol, the conversion of the alcohol to the bromide must proceed with inversion of con f gu- ration. ( d ) The conversion of 2-butanol to sec -butyl methanesulfonate does not involve any of the bonds to the stereogenic center, and so it must proceed with 100% retention of con f guration. Assuming that the reaction of the methanesulfonate with NaSCH 2 CH 3 proceeds with 100% inversion of con f guration, we conclude that the maximum rotation of sec -butyl ethyl sul f de is the value given in the statement of part ( b ), that is, 6 25 ° . Since the sul f de produced in part ( c ) has a rotation of 1 23 ° , it is 92% optically pure. It is reasonable to assume that the loss of optical purity occurred in the conversion of the alcohol to the bromide, rather than in the re- action of the bromide with NaSCH 2 CH 3 . If the bromide is 92% optically pure and has a rota-
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