Hydrolysis rate constants for 18 chlorinated methanes, ethanes, ethenes, and propanes have been measured in dilute aqueous solutions within the temperature range of 0-180 "C and at pH values of 3-14. Arrhenius parameters were determined for both neutral and alkaline hydrolysis reactions. Reactivity of these compounds in basic solutions increases in accord with the expected acidity of the most reactive hydrogen atom in the molecule. Neutral hydrolysis appears to depend on both the C-Cl bond strength and the degree of steric hindrance a t the reaction site. Only a neutral hydrolysis process occurs for CC14, l,l,ltrichloroethane, and 2,2-dichloropropane. The chlorinated ethenes and hexachloroethane react only with hydroxide under severe conditions and exhibit no neutral hydrolysis. Some of these compounds eliminate HCl, whereas others substitute OH for C1 to form alcohols that may react further to give aldehydes or carboxylic acids as products. Environmental hydrolysis half-lives (25 OC, pH 7) range from 36 h for 2,2-dichloropropane to 1850 years for CHC13 and to over lo6 years for C&16 and the ethenes.

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Methyl bromide degradation in sea water can be described by a summation of the hydrolysis and chloride ion exchange reactions. Laboratory experiments covered chloride concentrations of 0.1 to 1.0 mol/1, and temperatures from 20 to 60°C. The first‐order hydrolysis rate constant is and the second‐order chloride ion exchange rate constant deduced from the experiments is At a sea water surface temperature of 21.9 °C and a chloride concentration of 0.56 mol/1, the calculated degradation half‐life of methyl bromide in sea water is 4 days. At 35 °C, τ1/2 = 22 hr.

Abstract-New experimental data on the hydrolysis of dilute solutions of carbon tetrachloride (CCl 4 ) indicate clearly that the reaction is first-order in CCl 4 , a conclusion contrary to the classic work of Fells and Moelwyn-Hughes. These historical data have been reanalyzed and shown to be consistent with first-order kinetics. A new determination of the Arrhenius parameters confirm an environmental half-life of 40 years for CCl 4 .

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