RELATIONSHIP BETWEEN GAS-CHROMATOGRAPHIC RETENTION INDEXES AND MOLECULAR CONNECTIVITY INDEXES OF CHLORINATED PESTICIDES AND STRUCTURALLY RELATED-COMPOUNDS

The ability of the molecular connectivity model to predict retention indices using both statistical correlation coefficients and correctly predicted elution sequences as criteria of fitness was tested. The tests were performed with chlorinated pesticides and some structurally related compounds. The effect on the retention index of increasing replacement by chlorine of hydrogen atoms bonded to one carbon of the aliphatic part of the molecule was excellently correlated by 1-chi(v), the first-order valence molecular connectivity index, using a quadratic polynomial equation, This equation also fits 1-chi(v) with the retention indices of halobenzenes and halobiphenyl compounds. On the other hand, 1-chi(v) was the most significant connectivity index, using a single linear regression equation to correlate the retention indices of all the compounds. However, 1-chi(v) alone was not sufficient to distinguish significantly some isomers and the correct elution sequence giving a relatively low correlation coefficient. Therefore, other connectivity indices and the consequent use of multiple linear regression equations were necessary in order to represent more completely the molecules and to obtain more accurate results.