s-Triazines. Part IV. Kinetic and pKa studies of 2,4-dichloro-6-(N-methylpyrrol-2-yl)-s-triazine and its hydrolysis products

Abstract

The kinetics of hydrolysis of the title dichloro-s-triazine (I) and its 2-oxo-analogue (II) have been measured by u.v. absorption spectroscopy and pH-stat methods in the pH/H₀ range 12·3 to –5·7. pK_a Data for (II) and the 2,4-dioxo-analogue (III) are compared with those for the analogous hydrolysis products of cyanuric chloride. Rate coefficients for the attack of hydroxide and water on (I) and (II), together with the pK_a values of the substrates, can be used to rationalise the observed rate profiles. This leads to an interpretation of the mechanism of hydrolysis of (I) and (II) in terms of rate-determining nucleophilic attack on an electron-deficient carbon atom without the intervention of a previously suggested hydrated intermediate.