Microsomal dechlorination of chloroethanes: Structure-reactivity relationships

Abstract

1. The dechlorination rates of six haloethanes were investigated in vitro, using liver microsomes derived from rats treated with Aroclor 1254.

2. The compounds studied were 1,1-dichloroethane, 1,2-dichloroethane, 1,1,1-tri-chloroethane, 1,1,2,2-tetrachloroethane, 1,1,1-trifluoro-2-chloroethane and hexachloro-ethane.

3. Dechlorination kinetics (K_m and V_max) were measured at various substrate concentrations.

4. Electron densities in the molecules for which dechlorination data are available were calculated by the MINDO/3 method.

5. A previously reported overall correlation between electronic parameters and dechlorination rate was not confirmed, but rather a separate relationship between these parameters for each of three structural classes (RCH₂Cl, RCHCl₂ and RCCl₃) was observed.

6. On the basis of these observations, possible reaction mechanisms and their toxicological implications are discussed.