Kinetic evidence for the coexistence of zwitterionic ([T.sup.[plusmn]], neutral ([T.sup.0]) and anionic ([T.sup.-]) intermediates during rearrangement of S-(2-oxotetrahydrofuran-3-yl)-N-(4-methoxyphenyl)isothiuronium bromide to 5-(2-hydroxyethyl)-2-(4-methoxyphenylimino)-1,3-thiazolidin-4-one

The kinetics and mechanism of rearrangement of S-(2-oxotetrahydrofuran-3-yl)-N-(4-methoxyphenyl)isothiuronium bromide into 5-(2-hydroxyethyl)-2-[(4-methoxyphenyl)imino]-1,3-thiazolidin-4-one are analyzed under pseudo-first-order reaction conditions in aqueous buffer solutions and in diluted HCl. The coexistence of all three kinetically detectable intermediates is very rare and is because of enhanced stability of these intermediates necessitating participation of an acid for progression to products.