Conjugation Paths in Monosubstituted 1,2- and 2,3-Naphthoquinones

Optimization of monosubstituted (X = NO, NO2, CN, CHO, Me, OMe, OH, NH2, NHMe, and N(Me)(2)) derivatives of 1,2- and 2,3-naphthoquinone by use of B3LYP with the 6-311+G** basis set applying the GAUSSIAN03 program allowed us to analyze the character of interactions between the substituents and the carbonyl groups. It is shown that only one of two carbonyl groups exhibited substantial substituent effect evidenced by regression of the CO bond length and delocalization index, DI(CO) on the Hammett substituent constants, sigma(p), with a very high correlation coefficient, whereas the other one did not depend in any substantial way on sigma(p). Dependences of conjugation path built up of bonds between substituent and oxygen atoms of carbonyl groups on sigma(p), give more acceptable correlations if the number of bonds in the path is even than in cases when they are odd.