Electronegativity and resonance parameters from the geometry of monosubstituted benzene rings |
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Authors: | Campanelli Anna Rita Domenicano Aldo Macchiagodena Marina Ramondo Fabio |
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Institution: | (1) Department of Chemistry, University of Rome “La Sapienza”, 00185 Rome, Italy;(2) Department of Chemistry, Chemical Engineering and Materials, University of L’Aquila, 67100 L’Aquila, Italy; |
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Abstract: | Reference values of the structural substituent parameters, S
E and S
R, measuring the electronegativity and resonance effects, respectively, of functional groups (Campanelli et al. J Phys Chem
A 107:6429–6440, 2003) have been determined from the benzene ring geometries of 100 Ph–X species, including different conformations of the same
molecule. Geometries have been obtained by quantum chemical calculations at the HF/6-31G*, HF/6-311++G**, and B3LYP/6-311++G**
levels of theory. The substituent parameters from HF/6-311++G** calculations are in close agreement with those determined
at the HF/6-31G* level. Using the B3LYP density functional yields S
E and S
R values which—in general—correlate well with the corresponding HF values. Exceptions occur with some charged groups, and,
in the case of S
E, with a few dipolar groups having very high or low electronegativities. S
R values from B3LYP calculations are about 22% smaller than the corresponding HF values. The variations of the benzene ring
geometry caused by electronegativity, resonance, and steric effects are illustrated in some detail. |
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Keywords: | |
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