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The hydrolysis of phosphoranes in aqueous dioxane
Author(s) -
Queen A.,
Lemire A. E.,
Janzen A. F.
Publication year - 1981
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550130407
Subject(s) - chemistry , hydrolysis , enthalpy , aqueous solution , kinetic isotope effect , hydrolysis constant , kinetic energy , entropy (arrow of time) , activation energy , kinetics , organic chemistry , computational chemistry , thermodynamics , reaction rate constant , physics , deuterium , quantum mechanics
The entropy of activation for the hydrolysis of pentaphenoxyphosphorane in 25% aqueous dioxane is −188 J/mol deg. The enthalpy of activation is 22.5 kJ/mol, which is small for the relatively slow reaction. This suggests that the reaction is a multistep process having a preliminary equilibrium with a negative heat of reaction. This conclusion is supported by the results obtained for the hydrolysis of C 6 H 5[OCH(CF 3 ) 2 ] 2 . A kinetic isotope effect k H2O / k D2O of 3.46 was found for the latter reaction. Orders in water were obtained, and a mechanism of hydrolysis is proposed.