Participation of an elimination mechanism in alkaline hydrolyses of alkyl N-phenylcarbamates
- 1 January 1973
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 9,p. 1244-1247
- https://doi.org/10.1039/p29730001244
Abstract
Second-order rate constants for alkaline hydrolysis of alkyl N-phenylcarbamates and alkyl and aryl N-methyl-N-phenylcarbamates have been measured. Together with results from an earlier paper the alkaline hydrolysis of aryl and alkyl N-phenylcarbamates is related linearly with pKa(7–16) of the leaving alcohol and phenol (β=–1·15); the fully substituted carbamates have β=–0·25. These results are interpreted to mean that alkyl N-phenylcarbamates hydrolyse in alkali via an elimination type of process. It is estimated that a changeover from an elimination (E1cB) to a bimolecular substitution (SN2) mechanism occurs when the pKa of the leaving alcohol exceeds 17. A discussion of the factors favouring SN2 or E1cB mechanisms in alkaline hydrolysis is given.Keywords
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