A simple McGowan specific volume correction for branching in hydrocarbons and its consequences for some other solvation parameter values
A simple McGowan specific volume correction for branching in hydrocarbons and its consequences for some other solvation parameter values
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DOI：
10.1016/j.chemosphere.2011.04.042
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发表时间：
2011-08-01
期刊：
影响因子：
8.8
通讯作者：
Parsons, John R.
中科院分区：
文献类型：
--
作者：
van Noort, Paul C. M.;Haftka, Joris J. H.;Parsons, John R.
由于与环境相关的化合物（如燃料、燃料添加剂、表面活性剂）存在大量的支链异构体，线性烷烃和支链烷烃之间以及具有支链烷基的化合物之间的分子性质差异具有相关性。对于支链烷烃蒸汽压，麦高恩比容是一个很差的预测器。因此，本研究推导了分支数和相邻分支对数对McGowan比容的修正，以改进支链烷烃蒸汽压的预测。与McGowan比体积相比，这种分支校正还使支链/烷烃溶剂的可及体积、辛醇/水分配系数、空气/十六烷分配系数、水溶性以及烷基支链取代脂肪烃的空气/十六烷分配系数更符合相应的线性烃性质。即使对于在非末端碳上有取代基的取代脂肪烃的空气-十六烷分配系数，对含有取代基的碳进行分支校正也会使这些分配系数更符合线性化合物的分配系数。使用分支校正麦高恩比体积重新计算的非线性脂肪族醚、胺和醇的亚伯拉罕A和B溶剂化参数值，与先前报道的使用未校正麦高恩比体积获得的实验值相比，更接近基于线性脂肪族醚、胺和醇值的化学期望值。通过比较两种不同的线性溶剂化能量关系（一种包含麦高恩比体积项，另一种不包含麦高恩比体积项）对烷基苯和烯烃分配系数的估计，表明sp(2)碳上的烷基不需要支链校正。使用分支校正麦高恩比体积的主要优点是，其他溶剂化参数的值在化学上变得更加一致。(C) 2011 Elsevier Ltd.版权所有。
Differences in molecular properties between linear and branched alkanes as well as between compounds with branched alkyl groups is of relevance due to the large number of branched isomers of environmentally relevant compounds (e.g. fuels, fuel additives, surfactants). For branched alkane vapor pressures, the McGowan specific volume is a poor predictor. Therefore, in this study a correction on the McGowan specific volume is derived in terms of the number of branches and the number of pairs of vicinal branches to improve the prediction of branched alkane vapor pressures. This branching correction also brought branched/alkane solvent accessible volumes, octanol/water partition coefficients, air/hexadecane partition coefficients, and aqueous solubilities as well as alkyl-branched substituted aliphatic hydrocarbon air/hexadecane partition coefficients more in line with corresponding linear hydrocarbon properties when compared on a McGowan specific volume basis. Even for air-hexadecane partition coefficients of substituted aliphatic hydrocarbons with substituents at non-terminal carbons, application of the branching correction to the carbon bearing the substituent caused these partition coefficients to be more in line with those for linear compounds. Values for the Abraham A and B solvation parameters for nonlinear aliphatic ethers, amines, and alcohols, recalculated using branching corrected McGowan specific volumes, turned out to be closer to chemical expectations based on linear aliphatic ether, amine and alcohol values compared to previously reported experimental values obtained using uncorrected McGowan specific volumes. A comparison of alkylbenzene and alkene partition coefficient estimates from two different linear solvation energy relations, one containing a McGowan specific volume term and one without such a term, suggests that no branching correction is needed for alkyl groups at sp(2) carbons. The main advantage of using branching corrected McGowan specific volumes is that the values of other solvation parameters become chemically more consistent. (C) 2011 Elsevier Ltd. All rights reserved.