A kinetic study of chlorine-isotopic exchange between lithium chloride and di- and tri-nitro-derivatives of m- and p-dichlorobenzenes

Abstract

The kinetics of chlorine-isotopic exchange between di- or tri-nitro-derivatives of m- or p-dichlorobenzene with Li³⁶Cl have been measured. Second-order rate constants for 1,3-dichloro-4,6-dinitrobenzene increase in the sequence of solvents: isopropyl alcohol acetylacetone < sulpholan < dimethyl sulphoxide < 97:3 (v/v) diethyl ketone–n-butanol < acetone < hexamethylphosphoramide < diethyl ketone. No exchange was observed for dioxan or glacial acetic acid solutions. Water exerts a strong retarding effect on the rate of exchange of this substrate in acetone solution. Rate-constants relative to 1-chloro-2,4-dinitrobenzene = 1·00, at 298 K in anhydrous acetone solution were: 1,3-dichloro-2,4-dinitrobenzene 0·019, 1,4-dichloro-2,6-dinitrobenzene 0·61, 1,3-dichloro-4,6-dinitrobenzene 26, and 1,3-dichloro-2,4,6-trinitrobenzene 32,000. With 1,3-dichloro-2,4-dinitro- and 1,4-dichloro-2,6-dinitro-benzene only the 1-chloro-groups undergo exchange, under the conditions used.