Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Theoretical Model for the Carboxylic Group Acidity Constant Based on Connectivity Index 3χv
Ante MilicevicNenad Raos
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2013 Volume 86 Issue 5 Pages 594-599


We developed a regression model for prediction of COOH acidity constant on 19 amino and 16 aliphatic monocarboxylic acids. As variables we employed two subsummations of 3χv index terms, 3χv(chain) and 3χv(side). The calculation of 3χv(chain) includes only atoms constituting the main chain in a molecule, whereas the calculation of 3χv(side) includes atoms from the side chains. The model yielded r = 0.998, S.E. = 0.053 and r = 0.974, S.E. = 0.017, for amino and aliphatic monocarboxylic acids, respectively. As a test set we used three amino acids, valine, leucine, and isoleucine, predicting their pKa values with root-mean-square error, rms = 0.07 (I = 0) and 0.10 (I = 0.1 mol kg−1).

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© 2013 The Chemical Society of Japan
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