Abstract

Shashi Kala Pandit and Shashi Prabha

The hydrolysis of the highly stable mono-4-chloro-2,6-dimethylphenyl hydrogen phosphate has been kinetically pursued in the acid medium, 0.1 to 7.0 M-H CI at 90 °C in the aqueous phase. The ester exhibits typical features like: (i) an optimum rate at the usual 4.0M, HCI. (ii) first order rate-coefficients in substrate, (iii) the sole presence and contribution of the conjugate acid form, with specific acid catalysis, (iv) P-O bond fission, and(v) SN2 (P) pathway involving a transition state, justified by Arrhenius parameters etc. Insptte of showing the negative salt effect, the reactivity is promoted by Ca .65 times incomparison to the similarly-substituted 2,4,6-trichiorophenyI phosphate. This aspect is explained in terms of +1 effect and no-bond resonance of the two-o-Me-substituents, This monoester differs from the related di-and tri-esters which both exhibit zero order rate-coefficients. The highest rates of this monoester are attributed to the steric acceleration of the two ortho-alkyI groups in the arylmatnx.

Hydrolysis; Chloro - Xylenyl; Hydrolysis; Temperature

[ View HTML Full Text]