Santos Ana Filipa L O M, Ribeiro da Silva Manuel A V
Centro de Investigação em Química, Department of Chemistry, Faculty of Science, University of Porto, Rua do Campo Alegre, 687, P-4169-007 Porto, Portugal.
J Phys Chem A. 2009 Sep 3;113(35):9741-50. doi: 10.1021/jp905375h.
This paper reports a combined thermochemical experimental and computational study of 2-pyrrolecarboxylic acid and 1-methyl-2-pyrrolecarboxylic acid. Static bomb combustion calorimetry and Knudsen mass-loss effusion technique were used to determine the standard (p degrees = 0.1 MPa) molar enthalpies of combustion, Delta(c)H(m) degrees, and sublimation, Delta(cr)(g)H(m) degrees, respectively, from which the standard (p degrees = 0.1 MPa) molar enthalpies of formation, in the gaseous phase, at T = 298.15 K, were derived. The values obtained were -(286.3 +/- 1.7) and -(291.6 +/- 1.7) kJ x mol for 2-pyrrolecarboxylic acid and 1-methyl-2-pyrrolecarboxylic acid, respectively. For comparison purposes, the gas-phase enthalpies of formation of these two compounds were estimated by G3(MP2)//B3LYP and MP2 approaches, using a set of gas-phase working reactions; the results are in excellent agreement with experimental data. G3(MP2)//B3LYP computations were also extended to the calculation of N-H bond dissociation enthalpies, gas-phase acidities and basicities, proton and electron affinities and adiabatic ionization enthalpies. Moreover, the results are also discussed in terms of the energetic effects of the addition of a carboxylic and of a methyl groups to the pyrrole ring and compared with structurally similar compounds.
本文报道了对2-吡咯甲酸和1-甲基-2-吡咯甲酸的热化学实验与计算相结合的研究。分别采用静态弹式燃烧量热法和克努森质量损失泻流技术测定了标准（p° = 0.1 MPa）摩尔燃烧焓ΔcHm°和升华焓Δcr(g)Hm°，由此推导出在T = 298.15 K时气相中的标准（p° = 0.1 MPa）摩尔生成焓。2-吡咯甲酸和1-甲基-2-吡咯甲酸得到的值分别为-(286.3 ± 1.7) 和-(291.6 ± 1.7) kJ·mol。为作比较，使用一组气相工作反应，通过G3(MP2)//B3LYP和MP2方法估算了这两种化合物的气相生成焓；结果与实验数据高度吻合。G3(MP2)//B3LYP计算还扩展到了N-H键解离焓、气相酸度和碱度、质子和电子亲和能以及绝热电离焓的计算。此外，还根据在吡咯环上添加羧基和甲基的能量效应进行了讨论，并与结构相似的化合物进行了比较。
