https://doi.org/10.1351/goldbook.C01404
In a system XC6H4GY this is @C01267@ 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 \(\sigma ^{+}\) or \(\sigma ^{-}\), respectively, as in electrophilic or nucleophilic aromatic substitution, respectively. The term 'through @R05326@' is synonymous. Cross @C01267@ has also been used to describe the interactions occurring in 2-phenylallyl and similar systems.