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.