| Résumé | The Hammett equation correlates the effects of Y on many different chemical properties of YC6H4ZX families of compounds. One of the most surprising is that the Z-X bond dissociation enthalpy (BDE), a homolytic property, can be correlated for some 4-YC6H4ZX families with electrophilic substituent constants, (Y), which were largely derived from the rates of the heterolytic SN1 solvolyses of para-substituted cumyl chlorides. Although there is no Hammett correlation of the C-X BDEs in 4-YC6H4CH2X (X = H, halide, OPh) families, there are good correlations of N-X BDEs with (Y) in 4-YC6H4NHX (X = H, CH3, OH, F) and excellent correlations of O-X BDEs with (Y) in 4-YC6H4OX (X = H, CH3, CH2Ph) families. The reasons for this varied behavior are discussed. |
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