Correlations of Charges of Substituent Active Region in C-substituted Tetrazoles with Their Gas-phase Acidity,Hammett Constants,and Charge Distribution in Tetrazolic Rings

摘要

Electron distribution was investigated in molecules of 5C-substituted tetrazoles by means of Natural Population Analysis.The analysis of the impact of substituents on the excess of pi electrons in the ring and on the uniformity of their distribution produced similar results as were recently reported for derivatives of p-benzoic acid.The significant correlation coefficients of the two properties with the Hammett constants have been found.The more uniform the n electron distribution,measured by means of standard deviation of pi electrons amounts localized on individual atoms in the ring,the more acidic is the molecule.On the other hand,an increase of the pi electron number in the ring brings about an opposite effect.No correlation was found between the substituent charges and the Hammett constants.However,a new variable,namely charge of the substituent active region,composed of charge of a substituent added to charge of the ring C_(ipso)atom,was highly correlated with the Hammett constants,as well as with charge of acidic hydrogen of the>N-H group.The results prove that the set of charges of the substituent active region may be perceived as a theoretical equivalent of the experimental set of Hammett constants and that it is closely related to properties of this group of compounds.