Centro de Investigação em Química, Department of Chemistry and Biochemistry, Faculty of Science, University of Porto, Rua do Campo Alegre, 687, P-4169-007 Porto, Portugal.
J Org Chem. 2011 May 20;76(10):3754-64. doi: 10.1021/jo200018r. Epub 2011 Apr 12.
Thermodynamic properties of 3- and 4-phenoxyphenol have been determined by using a combination of calorimetric and effusion techniques as well as by high-level ab initio molecular orbital calculations. The standard (p° = 0.1 MPa) molar enthalpies of formation in the condensed and gas states, Δ(f)H(m)°(cr or l) and Δ(f)H(m)°(g), at T = 298.15 K, of 3- and 4-phenoxyphenol were derived from their energies of combustion in oxygen, measured by a static bomb calorimeter, and from the enthalpies of vaporization or sublimation derived respectively by Calvet microcalorimetry for the 3-phenoxyphenol and by Knudsen effusion technique for the 4-phenoxyphenol. The theoretically estimated gas-phase enthalpies of formation were calculated from high-level ab initio molecular orbital calculations at the G3(MP2)//B3LYP level of theory. Furthermore, this composite approach was also used to obtain information about the gas-phase acidities, gas-phase basicities, proton and electron affinities, adiabatic ionization enthalpies, and, finally, O−H bond dissociation enthalpies. The good agreement between the G3MP2B3-derived values and the experimental gas-phase enthalpies of formation for the 3- and 4-phenoxyphenol gives confidence to the estimate concerning the 2-phenoxyphenol isomer, which was not experimentally studied, and to the estimates concerning the radical and the anion. Additionally, the experimental values of gas-phase enthalpies of formation were also compared with estimates based on the empirical scheme developed by Cox.
通过组合量热法和逸出技术以及高级从头算分子轨道计算，确定了 3- 和 4- 苯氧基苯酚的热力学性质。在 T = 298.15 K 下，3- 和 4- 苯氧基苯酚的标准（p° = 0.1 MPa）凝聚态和气态摩尔生成焓，Δ(f)H(m)°(cr 或 l)和Δ(f)H(m)°(g)，是由它们在氧气中的燃烧能，通过静态弹量热计测量得出的，以及由 Calvet 微量热计分别为 3- 苯氧基苯酚和 Knudsen 逸出技术为 4- 苯氧基苯酚得出的汽化或升华焓得出的。理论上估计的气相生成焓是根据 G3(MP2)//B3LYP 理论水平的高级从头算分子轨道计算计算得出的。此外，这种组合方法还用于获得气相酸度、气相碱度、质子和电子亲和能、绝热电离焓以及最终的 O-H 键离解焓的信息。G3MP2B3 衍生值与 3- 和 4- 苯氧基苯酚的实验气相生成焓之间的良好一致性，使人们对未进行实验研究的 2- 苯氧基苯酚异构体以及自由基和阴离子的估计值充满信心。此外，气相生成焓的实验值还与基于 Cox 开发的经验方案的估计值进行了比较。
