KINETIC STUDIES USING SEMI-EMPIRICAL SELF- CONSISTENT FIELD (SCF) MOLECULAR ORBITAL (MO) METHOD: PART I1 [I] A MODIFIED NEGLECT OFDIATOMIC OVERLAP (MNDO) STUDY OF THE PYROLYSES OF CHLOROETHYL VINYL ETHERS

The effect of monochloro and dichloro substitution into the ethyl portion on the pyrolysis of ethyl vinyl ether has been studied. This involved four possible monosubstituted derivatives and six disubstituted derivatives. For the monochloro derivatives, B- chloro substitution enhanced the rate constant while a- chloro substitution depressed it noticeably. For the dichloro derivatives, substitution of both chlorine atoms on the same carbon atom, whether aor S hardly made any difference, while for substitution on different carbon atoms, substrate resulting in transdichloroetbene is facilitated relative to that resulting in the cis product. These results are interpreted in terms of the effect of the substituent(s) on the electronic charge density distributions over the key atoms in transition state geometries calculated.