Morais Victor M F, Miranda Margarida S, Matos M Agostinha R
Centro de Investigação em Química, Departamento de Química, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre, 687, P-4169-007 Porto, Portugal.
Org Biomol Chem. 2003 Dec 7;1(23):4329-34. doi: 10.1039/b308097h. Epub 2003 Oct 27.
The standard (p(o) = 0.1 MPa) molar energies of combustion in oxygen, at T = 298.15 K, of four liquids: 2-ethylpyridine, 4-ethylpyridine, ethylpyrazine and 2,3-diethylpyrazine were measured by static bomb calorimetry in an oxygen atmosphere. The values of the standard molar enthalpies of vaporization, at T = 298.15 K, were obtained by Calvet microcalorimetry, allowing the calculation of the standard molar enthalpies of formation of the compounds, in the gas phase, at T= 298.15 K: 2-ethylpyridine (79.4 +/- 2.6) kJ mol(-1); 4-ethylpyridine (81.0 +/- 3.4) kJ mol(-1); ethylpyrazine (146.9 +/- 2.8) kJ mol(-1); and 2,3-diethylpyrazine (80.2 +/- 2.9) kJ mol(-1). The most stable geometries of all ethylpyridine and ethylpyrazine isomers were obtained using the density functional theory with the B3LYP functional and two basis sets: 6-31G* and 6-311G**. These calculations were then used to obtain estimates of the enthalpies of formation of all isomers, including those not experimentally studied, through the use of isodesmic reactions. A discussion of the relationship between structure and energetics of the isomers is also presented.
在氧气氛围中，于T = 298.15 K时，采用静态弹式量热法测定了四种液体（2-乙基吡啶、4-乙基吡啶、乙基吡嗪和2,3-二乙基吡嗪）在标准压力（p(o) = 0.1 MPa）下的摩尔燃烧能。通过卡尔维微量热法获得了T = 298.15 K时的标准摩尔汽化焓值，从而得以计算这些化合物在T = 298.15 K气相中的标准摩尔生成焓：2-乙基吡啶为(79.4 ± 2.6) kJ mol⁻¹；4-乙基吡啶为(81.0 ± 3.4) kJ mol⁻¹；乙基吡嗪为(146.9 ± 2.8) kJ mol⁻¹；2,3-二乙基吡嗪为(80.2 ± 2.9) kJ mol⁻¹。使用密度泛函理论中的B3LYP泛函以及6-31G*和6-311G**这两种基组，获得了所有乙基吡啶和乙基吡嗪异构体的最稳定几何结构。然后通过等键反应，利用这些计算结果对所有异构体（包括未进行实验研究的异构体）的生成焓进行了估算。此外，还对异构体的结构与能量学之间的关系进行了讨论。
