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Kinetic evidence for the occurrence of trianionic tetrahedral intermediate in the hydroxide ion‐catalyzed cleavage of 1, 2‐benzisothiazolin‐3‐one‐1, 1‐dioxide (saccharin)
Author(s) -
Khan M. Niyaz,
O M. S. O.
Publication year - 1986
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.550181005
Subject(s) - chemistry , saccharin , tetrahedral carbonyl addition compound , cleavage (geology) , hydroxide , hydrolysis , kinetics , medicinal chemistry , ion , catalysis , reaction rate constant , ionic strength , ionic bonding , stereochemistry , inorganic chemistry , organic chemistry , aqueous solution , nucleophile , medicine , physics , quantum mechanics , engineering , endocrinology , geotechnical engineering , fracture (geology)
The kinetics of hydrolytic cleavage of saccharin has been studied at 60°C within the [ŌH] range of 0.1 to 3.0 M. The observed pseudo first‐order rate constants, k obs , follow an empirical relationship: k obs = B [ŌH] + [ C [ŌH]] 2 . The B and C terms are attributed to the formation of dianionic and trianionic tetrahedral intermediates on the reaction path. It is concluded that the ionized form of saccharin is the major reacting species under the present experimental conditions. The positive ionic strength effect and the negative effect of 1,4‐dioxan on the rate of hydrolysis favor the proposed reaction mechanism. The analysis of the observed activation parameters indicates that the increase in the contribution of C term to k obs causes the slight increase in both Δ H * and Δ S *. A significantly large negative value of Δ S * favors the proposed mechanism.