In simplest terms, a double bond is formed and part of the molecule is kicked off.
The Chugaev reaction follows this general mechanism and involves the pyrolysis of a xanthate ester. The Cope reaction is another type of this mechanism involving a tertiary amine oxide. The similar reaction of a quaternary ammonium ion with hydroxide ion is known as the Hofmann type of this reaction, which proceeds in an anti-Zaitsev manner. In all of the reactions above, the end result is an alkene. In simplest terms, a double bond is formed and part of the molecule is kicked off. Divided into classes of 1 and 2 according to whether a carbocation is formed, for ten points, this is what mechanism that can occur instead of substitution.
The Chugaev reaction follows this general mechanism and involves the pyrolysis of a xanthate ester.
{elimination} (accept {E2} before “1”)