Donetsk National Technical University, 58 Artema Str., 83000 Donetsk, Ukraine.
J Phys Chem B. 2012 Aug 2;116(30):8996-9006. doi: 10.1021/jp303617n. Epub 2012 Jul 13.
An approach to calculation of the threshold temperature for spontaneous clusterization of substituted alkanes (amines, nitriles, alcohols, thioalcohols, saturated and unsaturated carboxylic acids, α-amino acids, carboxylic acid amides, and melamine derivatives) at the air/water interface with dependence on the alkyl chain length was developed. In the framework of this approach, four schemes for the description of the temperature dependencies of the thermodynamic parameters of clusterization of the concerned amphiphilic compounds were proposed. They use the data obtained previously in the framework of quantum chemical semiempirical PM3 method and differ from each other by the degree of their theoretical accuracy. It was shown that the threshold temperature for spontaneous clusterization of the regarded classes of substituted alkanes can be described using a fractionally linear function in dependence on the alkyl chain length. It was found that, in agreement with the presented experimental data, the effect of the alkyl chain elongation of the substituted alkanes by two methylene units correlates with the decrease of the subphase temperature (ΔT) by 10-20 K. The general shape of the obtained dependencies indicates that the difference in the ΔT values for the amphiphilic molecules decreases with increasing alkyl chain length. This implies that the contribution of the intermolecular CH···HC interactions between the alkyl chains of monolayer molecules should be a decisive factor.
开发了一种计算取代烷烃（胺、腈、醇、硫醇、饱和和不饱和羧酸、α-氨基酸、羧酸酰胺和三聚氰胺衍生物）在空气/水界面自发聚集的阈温的方法，该方法与烷基链长度有关。在该方法的框架内，提出了四种描述所关注的两亲化合物聚集的热力学参数的温度依赖性的方案。它们使用以前在量子化学半经验 PM3 方法框架内获得的数据，并且彼此之间的理论准确性不同。结果表明，取代烷烃类自发聚集的阈温可以用分数线性函数来描述，该函数与烷基链长度有关。结果表明，与提出的实验数据一致，取代烷烃的烷基链延长两个亚甲基单元的效应与亚相温度（ΔT）降低 10-20 K 相关。所得到的依赖性的一般形状表明，两亲分子的ΔT 值的差异随烷基链长度的增加而减小。这意味着单层分子的烷基链之间的分子间 CH···HC 相互作用的贡献应该是一个决定性因素。
