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Ab-initio MO study of electronic substituent effects in nitriles

Abstract:

Ab-initio MO calculations using a 4-31G basis were performed for R-CNs with R = H, Cl, CCH, CN, NO, CH3, NH2 and COH. It was found that substitution produced larger changes in σ than in π bonds of CN and that the C of that group exhibited a complicated two-way charge transfer with both R and N. Good correlation was found between changes in π population of CN and resonance parameters but not between the changes in sigma population and inductive parameters. The changes upon substitution in σ, and in σ plus π populations showed a good correlation with the difference in electronegativity (ΔEN) between R and CN thus indicating that those changes are determined by ΔEN. It was also found that the electronegativity scale based on the analysis of the population at H in XH molecules produced better correlations with changes in population than other scales. © 1984.