Authors: Anna Mozrzymas
Publish Date: 2016/11/17
Volume: 295, Issue: 1, Pages: 75-87
Abstract
The molecular connectivity indices were used to derive the simple model relating the critical micelle concentration of cationic chloride gemini surfactants to their structure One index was selected as the best to describe the effect of the structure of investigated compounds on critical micelle concentration consistent with the experimental results This index encodes the information about molecular size the branches and also the information about heteroatoms The selected model can be helpful in designing novel chloride gemini surfactantsThe quantitative structureproperty relationship QSPR studies use the statistical models to estimate the various properties of the chemical compounds from its molecular structure 1 2 3 4 5 6 7 8 9 10 11 12 13 14 In QSPR studies the structure is often represented by different structural descriptors Among the various structural parameters applied to QSPR analysis the topological indices are often used in modeling physical chemical or biological properties 5 6 7 8 9 10 11 12 13 14 The first applications of topological indices in structureproperty relationship studies was proposed by Wiener in 1947 15 and later in the 1975 by Randic16 The generalization of the Randic index are the Kier and Hall molecular connectivity indices 10 The molecular connectivity indices contain considerable information about the structure of the molecule Kier and Hall 10widely described the information encoded by molecular connectivity indices especially on thetopological but also the electronic properties of the moleculeGemini surfactants consist of two hydrophobic tails and two hydrophilic heads connected by the spacer group Due to the binding together of two conventional surfactant molecules by the spacer these compounds have very good properties in aqueous solution The cmc values of these surfactants are significantly lower than those of the corresponding monomeric counterpartsIn the previous paper 12 the QSPR study was performed to derive the model which relates the critical micelle concentration of gemini surfactants to their structure The relationship was developed for a set of 21 cationic bromide gemini surfactants employing the molecular connectivity indices only The previous model contains the secondorder molecular connectivity index which as was suggested in 12 probably encodes the information about the flexibilityIn the present study the 4models were derived The relationships were developed for a set of 23 cationic chloride gemini surfactants also employing only the molecular connectivity indices Just as in the previous study 12 the present models were derived for the molecules of various structures ie the effect of all groups of the molecule on cmc value was taken into account The structure of the investigated compounds are quite different from the previous bromides Also the test compounds differ in structure from previously studied compounds The present study confirms that the onedescriptor model which best estimates the cmc values is that which contains the secondorder molecular connectivity index but the further analysis showed that the model which contains the firstorder valence molecular connectivity index better describes the changes of cmc values of cationic chloride gemini surfactants caused by structure modificationwhere δ i is a connectivity degree ie the number of nonhydrogen atoms to which the ith nonhydrogen atom is bondedm is the order of the connectivity indexk denotes the type of the fragment of the molecule for example path p cluster c and pathcluster pc andn m is the number of fragments of type k and order m
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