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Internet Electronic Journal of Molecular Design - IEJMD, ISSN 1538-6414, CODEN IEJMAT
| ABSTRACT - Internet Electron. J. Mol. Des. July 2003, Volume 2, Number 7, 475-491 |
QSPR with TAU Indices: Water Solubility of Diverse Functional Acyclic Compounds
Kunal Roy and Achintya Saha
Internet Electron. J. Mol. Des. 2003, 2, 475-491
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Abstract:
The topochemically arrived unique (TAU) scheme, developed in valence electron mobile
(VEM) environment, is unique in that it unravels specific contributions of functionality,
branching, shape and size factors to the physicochemical property or biological activity
while most other indices give mainly a global contribution of the molecule. QSPR/QSAR
studies with TAU indices on different physicochemical properties/biological activities of
diverse functional compounds will explore the usefulness of TAU indices in modeling
studies. The present communication attempts to correlate water solubility, ln S, of 193
diverse functional acyclic compounds with different TAU indices, namely
T, TR, F, B,
NV, NP, NI,
NX, and NY.
Sometimes, TAU relations have been improved further upon
inclusion of suitable indicator or integer variables. The statistical quality of the QSPR
model has been judged by statistical parameters such as predicted
variance Q2, explained
variance Ra2, correlation coefficient R,
and variance ratio F. This study shows that TAU
indices, along with appropriate indicator variables, can predict up to 91.4% and explain
91.9% of the variance of water solubility. The relations can unravel specific contributions
of molecular bulk (size), functionality, branching and shape parameters to the water
solubility of diverse functional compounds. In general, water solubility increases with
increase in functionality and branching, and decreases with increase in molecular bulk.
Further, halocarbons and hydrocarbons specifically show reduced water solubility. Some
of the hydrocarbons and halogen compounds act as outliers. The TAU index is an
important tool in exploring structure-property relationships in view of its potential to
unravel specific contributions of different structural parameters like molecular bulk,
shape factors, branching, functionality and carbon skeletal structure.
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