In a system
XC6H4GY
this is
conjugation involving the substituent
X,
the benzene ring and the side-chain connective-plus-reaction site
GY, i.e. either
X
is a
+R
group and
GY
is a
-R
group, or
X
is a
-R
group and
GY
is a
+R
group. In Hammett correlations this situation can lead to the need to apply exalted
substituent constants
or
, respectively, as in electrophilic or nucleophilic aromatic substitution, respectively.
The term '
through resonance' is synonymous. Cross
conjugation has also been used to describe the interactions occurring in 2-phenylallyl and similar
systems.
Source:
PAC, 1994, 66, 1077
(Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994))
on page 1101
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.
