Cao Chao-Tun, Cao Chenzhong
Key Laboratory of Theoretical Organic Chemistry and Function Molecule, Ministry of Education, School of Chemistry and Chemical Engineering, Hunan University of Science and Technology, Xiangtan 411201, China.
ACS Omega. 2023 Feb 8;8(7):6492-6506. doi: 10.1021/acsomega.2c06856. eCollection 2023 Feb 21.
Changes in various physicochemical properties ( ) of noncyclic alkanes can be roughly classified as linear and nonlinear changes. In our previous study, the NPOH equation was proposed to express nonlinear changes in the properties of organic homologues. Until now, there has been no general equation to express nonlinear changes in the properties of noncyclic alkanes involving linear and branched alkane isomers. This work, on the basis of NPOH equation, proposes a general equation to express nonlinear changes in the physicochemical properties of noncyclic alkanes, including a total of 12 properties, boiling point, critical temperature, critical pressure, acentric factor, heat capacity, liquid viscosity, and flash point, named as the "NPNA equation", as follows: ln( ) = + ( - 1) + ( ) + (ΔAOEI) + (ΔAIMPI), where , , , and are coefficients, and represents the property of the alkane with carbon atom number. , , ΔAOEI, and ΔAIMPI are number of carbon atoms, sum of carbon number effects, average odd-even index difference, and average inner molecular polarizability index difference, respectively. The obtained results show that various nonlinear changes in the properties of noncyclic alkanes can be expressed by the NPNA equation. Nonlinear and linear change properties of noncyclic alkanes can be correlated with four parameters, , , ΔAOEI, and ΔAIMPI. The NPNA equation has the advantages of uniform expression, usage of fewer parameters, and high estimation accuracy. Furthermore, using the above four parameters, a quantitative correlation equation can be established between any two properties of noncyclic alkanes. Employing the obtained equations as model equations, the property data of noncyclic alkanes, involving 142 critical temperatures, 142 critical pressures, 115 acentric factors, 116 flash points, 174 heat capacities, 142 critical volumes, and 155 gas enthalpies of formation, a total of 986 values, were predicted, which have not be experimentally measured. NPNA equation not only can provide a simple and convenient estimation or prediction method for the properties of noncyclic alkanes but also can provide new perspectives for studying quantitative structure-property relationships of branched organic compounds.
非环烷烃各种物理化学性质（ ）的变化可大致分为线性变化和非线性变化。在我们之前的研究中，提出了NPOH方程来表示有机同系物性质的非线性变化。到目前为止，还没有一个通用方程来表示涉及直链和支链烷烃异构体的非环烷烃性质的非线性变化。这项工作在NPOH方程的基础上，提出了一个通用方程来表示非环烷烃物理化学性质的非线性变化，该方程涵盖了总共12种性质，包括沸点、临界温度、临界压力、偏心因子、热容、液体粘度和闪点，命名为“NPNA方程”，如下所示：ln( ) = + ( - 1) + ( ) + (ΔAOEI) + (ΔAIMPI)，其中 、 、 和 是系数， 表示具有 个碳原子数的烷烃的性质。 、 、ΔAOEI和ΔAIMPI分别是碳原子数、碳数效应之和、平均奇偶指数差和平均分子内极化率指数差。所得结果表明，非环烷烃性质的各种非线性变化可用NPNA方程表示。非环烷烃的非线性和线性变化性质可以与四个参数 、 、ΔAOEI和ΔAIMPI相关联。NPNA方程具有表达统一、使用参数少和估算精度高的优点。此外，利用上述四个参数，可以建立非环烷烃任意两种性质之间的定量相关方程。以所得方程作为模型方程，对非环烷烃的性质数据进行了预测，这些数据包括142个临界温度、142个临界压力、115个偏心因子、116个闪点、174个热容、142个临界体积和155个气体生成焓，共计986个值，均未经过实验测量。NPNA方程不仅可以为非环烷烃的性质提供一种简单方便的估算或预测方法，还可以为研究支链有机化合物的定量构效关系提供新的视角。
