113947-94-7Relevant articles and documents
Transfer of the Diethoxyphosphoryl Group between Imidazole and Aryloxy Anion Nucleophiles
Ba-Saif, Salem,Williams, Andrew
, p. 2204 - 2209 (1988)
Rate constans have been measured for reaction of imidazole with aryl diethyl phosphate (k1) and of aryloxy anions with N-(diethoxyphosphoryl)imidazolium ion (k-1) in aqueous solution at 25 deg C; they obey the following linear Broensted equations: log k1 = -1.02pKArOH + 1.83 (n = 6, r = 0.989); log k-1 = 0.85pKArOH - 0.48 (n = 10, r = 0.957).The value of βeq (1.87) obtained from βlg and βnuc supports a previously determined value (1.83) for the transfer of the neutral phosphoryl group from phenolate ion nucleophiles.The pKaof (diethoxyphosphoryl)imidazolium ion is 6.04.The equilibrium constant for reaction of 4-nitrophenyl diethyl phosphate with imidazole is 5.9 x 10-6; in the case of the aryl ester from phenol with pKArOH = 4.34 the equilibrium constant is calculated to be unity.The Broensted βeq data are used to calibrate effective charges derived from previously measured βlg values for attack of nucleophiles at phosphorus bearing phenolate ion leaving groups.
