title: Experimental and theoretical study of the structures and enthalpies of formation of 3H-1,3-benzoxazole-2-thione, 3H-1,3-benzothiazole-2-thione, and their tautomers.
abstract: This paper reports an experimental and theoretical study of the structures and standard (p(o) = 0.1 MPa) molar enthalpies of formation of 3H-1,3-benzoxazole-2-thione and 3H-1,3-benzothiazole-2-thione. The enthalpies of combustion and sublimation were measured by rotary bomb combustion calorimetry and the Knudsen effusion technique, and gas-phase enthalpies of formation values at T = 298.15 K of (42.0 +/- 2.7) and (205.5 +/- 3.8) kJ x mol(-1) for 3H-1,3-benzoxazole-2-thione and 3H-1,3-benzothiazole-2-thione, respectively, were determined. G3-calculated enthalpies of formation are in excellent agreement with the experimental values. The present work discusses the question of tautomerism explicitly for both compounds and compares the energetics of all the related species. A comparison of the theoretical results with the structural data is also reported.
authors.affiliation: Instituto de Química Física Rocasolano, CSIC, Serrano 119, 28006 Madrid, Spain. victoriaroux@iqfr.csic.es
authors.forename: Maria Victoria
authors.initials: MV
authors.lastname: Roux
authors.forename: Manuel
authors.initials: M
authors.lastname: Temprado
authors.forename: Pilar
authors.initials: P
authors.lastname: Jiménez
authors.forename: Concepción
authors.initials: C
authors.lastname: Foces-Foces
authors.forename: Rafael
authors.initials: R
authors.lastname: Notario
authors.forename: Archana R
authors.initials: AR
authors.lastname: Parameswar
authors.forename: Alexei V
authors.initials: AV
authors.lastname: Demchenko
authors.forename: James S
authors.initials: JS
authors.lastname: Chickos
authors.forename: Carol A
authors.initials: CA
authors.lastname: Deakyne
authors.forename: Joel F
authors.initials: JF
authors.lastname: Liebman
mesh_terms: D052160:Benzothiazoles / Q000737:chemistry*; D001583:Benzoxazoles / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004583:Electrons; D005740:Gases / Q000737:chemistry; D007536:Isomerism; D008958:Models, Molecular; D008968:Molecular Conformation; D011789:Quantum Theory; D013816:Thermodynamics; D013871:Thiones / Q000737:chemistry*
chemical_list: C551673:3H-1,3-benzothiazole-2-thione; D052160:Benzothiazoles; D001583:Benzoxazoles; D005740:Gases; D013871:Thiones; C508121:benzoxazolethione