title: Diaminobenzenes: an experimental and computational study.
abstract: In the present work, the values of the standard (p(o) = 0.1 MPa) molar enthalpies of formation, in the gaseous phase, at T = 298.15 K, of 1,2-diaminobenzene, 1,3-diaminobenzene, and 1,4-diaminobenzene are reported as 86.6 ± 1.6, 89.6 ± 1.6, and 99.7 ± 1.7 kJ·mol⁻¹, respectively. These values were derived from experimental thermodynamic parameters, namely the standard (p(o) = 0.1 MPa) molar enthalpies of formation, in the crystalline phase, Δf H(m)(o)(cr), at T = 298.15 K, obtained from the standard molar enthalpies of combustion, Δ(c) H(m)(o), measured by static bomb combustion calorimetry, and the standard molar enthalpies of sublimation, at T = 298.15 K, derived from the temperature-vapor pressure dependence, determined by the Knudsen mass loss effusion method. The results were compared with estimates obtained by standard ab initio molecular calculations at the G3(MP2)//B3LYP level. Experimental and calculated data are in very good agreement and show that the 1,2-diaminobenzene is, thermodynamically, the most stable isomer. Finally, proton and electron affinities, basicities and adiabatic ionization enthalpies were also computed at the same level.
authors.affiliation: 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.
authors.forename: Ana Filipa L O M
authors.initials: AF
authors.lastname: Santos
authors.forename: Manuel A V
authors.initials: MA
authors.lastname: Ribeiro da Silva
mesh_terms: D015394:Molecular Structure; D010655:Phenylenediamines / Q000737:chemistry*; D011789:Quantum Theory; D013237:Stereoisomerism; D013816:Thermodynamics
chemical_list: D010655:Phenylenediamines; C034193:1,2-diaminobenzene; C008381:3-phenylenediamine