A computational study of bond dissociation enthalpies in haloethenes |
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Authors: | Gantasala N Srinivas M Schwartz |
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Institution: | Department of Chemistry, University of North Texas, P.O. Box 305070, Denton, TX 76203-5070, USA |
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Abstract: | Carbon–hydrogen bond dissociation enthalpies (BDEs) were computed for all haloethenes, C2H4?nXn (n=0–3, X=F, Cl, Br, I), at the B3LYP/6-311+G(3df,2p) level using isodesmic reactions. It was found that C–H bond strengths in the monohaloethenes varied substantially, by as much as 18 kJ mol?1, dependent upon the bond's stereochemical position relative to the halogen. BDEs in the dihaloethanes varied in the order CX2CH–H>(E)-CHXCX–H>(Z)-CHXCX–H. Trends in the computed bond enthalpies were discussed and explained on the basis of relative steric repulsions and hyperconjugative delocalization interactions, as determined from Natural Bond Orbital analysis. |
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Keywords: | Bond dissociation enthalpies Bond strengths Haloethenes DFT |
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