The Kinetics and Mechansim of the Hydrolysis of p-Nitrophenyl Isothiocyanate Promoted by Soft Metal Ions

DOI: 10.1039/P29910000303

Source and publish data:

Journal of the Chemical Society. Perkin transactions II p. 303 - 306 (1991)

Update date:2022-08-11

Topics:

Authors:

Satchell, Derek P. N.

Satchell, Rosemary S.

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Article abstract of DOI:10.1039/P29910000303

The hydrolysis of p-nitrophenyl isothiocyanate in aqueous acid solution is powerfully promoted by the Ag+ and Hg2+ ions.The organic product is p-nitroaniline.The mercury-promoted reaction is first order in isothiocyanate and in , and has ΔH(excit.) = 56 +/- 2kJ mol^-1, ΔS(excit.) = -53 +/- 4 J K^-1 mol^-1, and k_H2O/k_D2O = 1.12 +/- 0.05 at 25.0 deg C.The behaviour with silver is similar: promotion is principally first order in , but in H2O there is evidence for a small kinetic term in 2. ΔH(excit.) = 59 +/- 2kJ mol^-1 and ΔS(excit.) = -88 +/- 3 J K^-1 mol^-1 for the first-order reaction, and ΔH(excit.) = 25 +/- 5 kJ mol^-1 and ΔS(excit.) = -202 +/- 12 j K^-1 mol^-1 for the route second order in .Use of D2O removes the second-order term, and k_H2O/k_D2O = 1.07 +/- 0.06 for the route involving one Ag+ ion pre-equilibrium, followed by a rate-determining attack of water to give the soft metal derivative of the corresponding thiocarbamic acid as a rapidly decomposition intermediate.