Chaikin Artem V, Rozov Timofey P, Ryzhako Alexander S, Moshchenkov Andrey D, Otlyotov Arseniy A, Minenkov Yury
N.N. Semenov Federal Research Center for Chemical Physics RAS, Kosygina Street 4, 119991, Moscow, Russian Federation; Department of Chemistry, Lomonosov Moscow State University, 119991, Moscow, Russian Federation.
N.N. Semenov Federal Research Center for Chemical Physics RAS, Kosygina Street 4, 119991, Moscow, Russian Federation.
J Mol Graph Model. 2025 Nov;140:109106. doi: 10.1016/j.jmgm.2025.109106. Epub 2025 Jun 4.
An automated reaction-based approach coupled with DLPNO-CCSD(T)/CBS calculations was used to derive enthalpies of formation (ΔH) of 32 short-chain chlorinated paraffins (SCCPs) containing 10-13 C atoms and 3-11 Cl atoms. Absolute entropies (S) were obtained using B3LYP-D3(BJ)/def2-TZVP optimized geometries and vibrational frequencies in the framework of the modified and scaled rigid rotor - harmonic oscillator (msRRHO) approximation. Conformational corrections to entropies were estimated using the CREST program and GFNn-xTB/FF methods. Examination of the performance of fast semiempirical methods reveals them to be suitable for the express evaluation of molecular entropies (mean unsigned deviation MUD = 2.3 cal mol K), while only PM6 method reproduces reference ΔH with MUD = 2.4 kcal mol, approximately within the estimated average error limits (2.8 kcal mol). In contrast, simple Benson's group additivity method (GA) yields ΔH values with MUD = 0.8 kcal mol but turns out to significantly overestimate entropies with MUD = 20.4 cal mol K. The obtained datasets of reliable ΔH and S values can be used for the further development of fast and efficient methods for the gas-phase thermochemistry evaluations of medium-sized molecules with rich conformational landscapes.
一种基于反应的自动化方法与DLPNO-CCSD(T)/CBS计算相结合，用于推导32种短链氯化石蜡（SCCP）的生成焓（ΔH），这些短链氯化石蜡含有10-13个碳原子和3-11个氯原子。绝对熵（S）是在修正和缩放的刚性转子-谐振子（msRRHO）近似框架下，使用B3LYP-D3(BJ)/def2-TZVP优化的几何结构和振动频率获得的。使用CREST程序和GFNn-xTB/FF方法估计熵的构象校正。对快速半经验方法性能的检验表明，它们适用于分子熵的快速评估（平均无符号偏差MUD = 2.3 cal·mol⁻¹·K⁻¹），而只有PM6方法能以MUD = 2.4 kcal·mol⁻¹再现参考ΔH，大约在估计的平均误差范围内（2.8 kcal·mol⁻¹）。相比之下，简单的本森基团加和法（GA）得到的ΔH值的MUD = 0.8 kcal·mol⁻¹，但结果表明它显著高估了熵，MUD = 20.4 cal·mol⁻¹·K⁻¹。所获得的可靠ΔH和S值数据集可用于进一步开发快速有效的方法，用于对具有丰富构象景观的中等大小分子进行气相热化学评估。
