Term: through-conjugation
https://doi.org/10.1351/goldbook.08214

Definition:
Phenomenon whereby electrons can be delocalized from any of three (or more) groups to any other.

Notes:
1) This may be contrasted with cross-conjugation.
2) In Hammett-type correlations (linear Gibbs-energy relationships), this situation can lead to exalted substituent constants \(\sigma^{+}\) or \(\sigma^{-}\), as in solvolysis of \(\ce{p-CH3OC6H4C(CH3)2Cl}\) or acidity of \(\ce{p-nitrophenol}\), respectively.

Example: <span title="substance">\(\ce{p-XC6H4Y}\)</span>, where an electron pair can be delocalized from electron-donating <span title="substance">\(\ce{X}\)</span> not only to ring carbons but also to electron-withdrawing <span title="substance">\(\ce{Y}\)</span>.

Example: Array

Source: PAC, 2022, 94, 353. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 2021)' on page 518 (https://doi.org/10.1515/pac-2018-1010)

Citation: 'through-conjugation' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.08214

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