The kinetics of oxidation of perchloroethylene (PCE), trichloroethylene (TCE), three isomers of dichloroethylene (DCE) and vinyl chloride (VC) by potassium permanganate (KMnO4) Were studied in phosphate-buffered solutions of pH 7 and ionic strength similar to0.05 M and under isothermal, completely mixed and zero headspace conditions. Experimental results have shown that the reaction appears to be second order overall and first order individually with respect to both KMnO4 and all chlorinated ethenes (CEs), except VC. The degradation of VC by KMnO4 is a two-consecutive-step process. The second step, being the rate-limiting step, is of first order in VC and has an activation energy (E-a) of 7.9 +/-1 kcal mol(-1). The second order rate constants at 20 degreesC are 0.035 +/-0.004 M-1 s(-1) (PCE), 0.80 +/-0.12 M-1 s(-1) (TCE), 1.52 +/-0.05 M-1 s(-1) (cis-DCE), 2.1 +/-0.2 M-1 s(-1) (1,1-DCE) and 48.6 +/-0.9 M-1 s(-1) (trans-DCE). The E-a and entropy (DeltaS*) of the reaction between KMnO4 and CEs (except VC) are in the range of 5.8-9.3 kcal mol(-1) and -33 to -36 kcal mol(-1) K-1, respectively. Moreover, KMnO4 is able to completely dechlorinate CEs, and the increase in acidity of the solution due to CE oxidation by KMnO4 is directly proportional to the number of chlorine atoms in CEs.