"The principal olefin formed in the
decomposition of quaternary ammonium hydroxides that contain different primary
alkyl groups is always ethylene, if an ethyl group is present." Originally given in this limited
form by A. W. Hofmann, the rule has since been extended and modified as follows: "When
two or more
alkenes can be produced in a β-
elimination reaction, the alkene having the smallest number of
alkyl groups attached to the double bond carbon atoms will be the predominant product." This orientation
described by the Hofmann rule is observed in
elimination reactions of quaternary ammonium salts and tertiary sulfonium salts, and in certain
other cases.
Source:
PAC, 1994, 66, 1077
(Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994))
on page 1121
Cite as:
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by
A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997).
XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic,
J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8.
https://doi.org/10.1351/goldbook.
