SUPPRESSION OF THE RATE OF HYDROLYSIS OF T-AMYLCHLORIDE AT THE CONSOLUTE COMPOSITION OF ISOBUTYRIC ACID PLUS WATER

We have measured the rate of hydrolysis of t-amylchloride in the solve nt, isobutyric acid + water, prepared at its consolute composition. Th e consolute temperature of the mixture depends upon the initial amount of t-amylchloride, being 32.3 degrees C when 100 mu l are added to 25 ml of the solvent and 36.46 degrees C when 150 mu l are added. In bot h cases, however, we found that the specific rate of reaction is suppr essed over a temperature range of about 0.2 degrees C on either side o f the local consolute temperature, T-c. These observations serve to de monstrate the concept of 'critical slowing down' in chemical kinetics. The decrease in specific rate with temperature, T, could be fitted by \T - T-c\(-x) with x = 0.63 +/- 0.28. Within the experimental error, this value of the exponent is consistent with the value (x = 0.80) pre dicted theoretically on the basis of the principle of universality. (C ) 1998 Elsevier Science B.V. All rights reserved.