Partition coefficients of ketones, phenols, aliphatic and aromatic acids, and esters in n-hexane/nitromethane
ABSTRACT Liquid-liquid partition is used in sample preparation and in countercurrent and liquid-liquid chromatographic separations.
Partition coefficients are widely used in toxicology, environmental, and analytical chemistry. The K
determination procedure for the n-hexane/nitromethane system was optimized and partition coefficients for 99 ketones, esters and trimethylsilyl derivatives
of phenols, aliphatic and aromatic acids were determined. For 130 compounds, K
values were predicted using mathematical relationships between K
and other physicochemical and structural parameters.
KeywordsPartition coefficients–n-Hexane/nitromethane system–Structure-partitioning relationships
- SourceAvailable from: Andreas M. Zissimos[Show abstract] [Hide abstract]
ABSTRACT: The use of gas-liquid chromatographic (GLC) retention data to obtain sets of solute descriptors is outlined, with reference to the schemes of Laffort and of Weckwerth. The method of Snyder and Dolan to obtain a set of solute descriptors from reverse phase high performance chromatographic (RP-HPLC) measurements is described. The work of Abraham on the construction of solvation parameters, or descriptors, from water-solvent partitions, GLC retention data and RP-HPLC data is considered in some detail. A comparison is made between the schemes of Laffort, Weckwerth and Abraham, and it is shown that the latter two yield exactly the same fits for a test data set of gas-methanol partition coefficients, although the distribution of chemical information amongst the terms in the multiple linear regressions is not quite the same. A comparison between the above 'experimental' descriptors and theoretical descriptors is made, and it is shown that the experimental Abraham and the theoretical Klamt descriptors encode almost the same chemical information. It is concluded that for processes that entail transfer of a solute from one phase to another, only a small number of solute descriptors, no more than five or six, is needed to provide a reasonably accurate analysis of the process.Journal of Chromatography A 06/2004; 1037(1-2):29-47. · 4.26 Impact Factor
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ABSTRACT: Partition coefficients for 69 varied compounds were determined for the n-hexane-acetonitrile partition system and combined with 74 partition coefficients for (largely) terpenes, esters and alkylaromatic compounds determined by Isidorov and coworkers and 27 extraction p-values determined by Bowman and Beroza to derive a general model for the distribution of neutral compounds in the biphasic system. The partition coefficients, logK(p), were correlated through the solvation parameter model giving logK(p) = 0.097(+/- 0.049) + 0.189(+/-0.041)E - 1.332(+/-0.056)S - 1.649(+/-0.055)A - 0.966(+/-0.074)B + 0.773(+/-0.040)V with a multiple correlation coefficient of 0.985, standard error of the estimate 0.114, and Fischer statistic 1087. The solute descriptor E is the excess molar refraction, S is the dipolarity/polarizability, A and B are the overall hydrogen-bond acidity and basicity, respectively, and V is McGowan's characteristic volume. The model is expected to be able to estimate further values of the partition coefficient to about 0.1 log units and is applicable to a wide range of compounds except for n-alkylcarboxylic acids, which have higher partition coefficients than predicted, most likely due to the formation of oligomers (e.g. dimers) in the n-hexane layer.Journal of Chromatography A 03/2006; 1104(1-2):82-90. · 4.26 Impact Factor
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ABSTRACT: The efficiency of using combinations of retention indices and partition coefficients (Kp) with a hexane: acetonitrile system has been demonstrated by taking as an example the essential oil from Artemisia pallens Wall. Preliminary partition of the components between the two partly mixing liquids provides information by which components can be attributed to the appropriate homologous series. The use of group constants (j), which are functions of both partition coefficients and GC retention indices, in the practice of identifying the components of essential oils is reported for the first time.Phytochemical Analysis 03/2001; 12(2):87-90. · 2.45 Impact Factor