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Kinetics of the hydrolysis of cyclic N ‐substituted sulfamides: 4‐amino‐2‐cyclohexyl‐ and 4‐amino‐2‐phenethyl‐2,3‐dihydro‐3‐oxo‐1,2,5‐thiadiazole 1,1‐dioxides
Author(s) -
Rozas M. F.,
Svartman E. L.,
Mirífico M. V.,
Vasini E. J.
Publication year - 1998
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/(sici)1099-1395(199807)11:7<489::aid-poc29>3.0.co;2-g
Subject(s) - chemistry , hydrolysis , aqueous solution , steric effects , sulfamide , reaction rate constant , medicinal chemistry , acetic acid , oxalic acid , derivative (finance) , protonation , amino acid , stereochemistry , kinetics , organic chemistry , ion , biochemistry , physics , quantum mechanics , financial economics , economics
The hydrolysis reactions of 4‐amino‐2‐phenethyl‐ and 4‐amino‐2‐cyclohexyl‐2,3‐dihydro‐3‐oxo‐1,2,5‐thiadiazole 1,1‐dioxide ( Ia and Ib ) were investigated in the range 24–73 °C in buffered aqueous solutions. The observed rate constants ( k obs ) are independent of pH in the range ca 1–4 pH, but increase with increase in pH above ca 4. A linear log k obs vs pH profile with unit slope is observed from pH ca 4 up to the highest experimental pH ( ca 10). The products are the corresponding new compounds: 2‐amino‐2‐[( N ‐substituted‐sulfamoyl)imino]acetic acid salts. The CN bond of these compounds hydrolyses further, in a slow reaction, to the sulfamide and oxalic acid derivatives. The substrates decompose to the final products without accumulation of the acetic acid derivatives under these experimental conditions. A mechanism is proposed. Rate constants and activation parameters are given for the first reaction step. Owing to steric effects, the reaction rate is higher for the N ‐phenethyl‐substituted derivative than for the 2‐cyclohexyl‐substituted derivative. © 1998 John Wiley & Sons, Ltd.