Abstract The standard (po = 0.1 MPa) molar enthalpies of formation, at T = 298.15 K, for 2′,4′-, 2′,5′-, 2′,6′- and 3′,4′-dimethoxyacetophenones, in the condensed phase, were derived from measurements of the standard massic energies of combustion using a static bomb combustion calorimeter. The standard molar enthalpies of sublimation or vaporization, at T = 298.15 K, were determined by high temperature Calvet microcalorimetry. Combining the results measured by these two techniques, the standard molar enthalpies of formation in the gaseous phase, at T = 298.15 K, were derived. Computational studies for the experimentally studied compounds were also performed, as a complement to the experimental work, being also extended to the 2′,3′- and 3′,5′-dimethoxyacetophenone isomers. The gas-phase enthalpies of formation were estimated from high level ab initio molecular orbital calculations, at the G3 level. Group additivity values and corrections for functional group interactions in the benzene ring were derived and used for predicting enthalpies of formation for dimethoxyacetophenones. The applicability of simple group-additivity procedures to tri-substituted benzenes was discussed.

中文翻译：

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二甲氧基苯乙酮的实验和计算热化学研究

摘要 在 T = 298.15 K 时，2',4'-、2',5'-、2',6'- 和 3',4'-二甲氧基苯乙酮的标准 (po = 0.1 MPa) 摩尔生成焓，在凝聚相中，来自使用静态弹式燃烧量热计测量的标准燃烧质量。升华或汽化的标准摩尔焓，在 T = 298.15 K，由高温 Calvet 微量热法测定。结合这两种技术测量的结果，得出了在 T = 298.15 K 时气相中的标准摩尔形成焓。还对实验研究的化合物进行了计算研究，作为对实验工作的补充，还扩展到 2',3'- 和 3',5'-二甲氧基苯乙酮异构体。气相形成焓是根据 G3 水平的高水平从头算分子轨道计算估算的。派生出苯环中官能团相互作用的基团可加性值和校正值，并用于预测二甲氧基苯乙酮的形成焓。讨论了简单的基团加成程序对三取代苯的适用性。