A chemical reaction, the principal product of which is
isomeric with the principal reactant. An
intramolecular isomerization that involves the breaking or making of bonds is a special case of
a
molecular rearrangement. Isomerization does not necessarily imply
molecular rearrangement (e.g. in the case of the interconversion of conformational isomers).
Source:
PAC, 1994, 66, 1077
(Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994))
on page 1129