title: Experimental and Computational Thermochemistry of 3- and 4-Nitrophthalic Anhydride.
abstract: In order to understand the influence that the position of the nitro group on the aromatic ring has on the relative stability of two isomers, the standard enthalpies of formation of 3- and 4-nitrophthalic anhydride in the gaseous phase, at T = 298.15 K, were obtained by experimental thermochemistry and theoretical studies. The standard enthalpies of formation in the crystalline phase, at T = 298.15 K, were obtained by combustion calorimetry and the enthalpies of sublimation by the Knudsen method. For the theoretical calculations, a standard ab initio molecular orbital method at the G3 level was used. The enthalpies of formation in the gaseous phase were obtained from atomization and isodesmic reactions. A theoretical study of the molecular and electronic structures of these compounds was also performed. Differences of -9.7 kJ·mol-1, for 3-nitrophthalic anhydride, and -2.6 kJ·mol-1for 4-nitrophthalic anhydride, were found from a comparison between our theoretical and experimental results.
authors.affiliation: Facultad de Ciencias Químicas de la Benemérita Universidad Autónoma de Puebla , 14 Sur y Avenida San Claudio, C.P. 72570, Puebla Pue, México.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: García-Castro
authors.affiliation: Facultad de Ciencias Químicas de la Benemérita Universidad Autónoma de Puebla , 14 Sur y Avenida San Claudio, C.P. 72570, Puebla Pue, México.
authors.forename: Patricia
authors.initials: P
authors.lastname: Amador
authors.affiliation: Facultad de Ciencias Químicas de la Benemérita Universidad Autónoma de Puebla , 14 Sur y Avenida San Claudio, C.P. 72570, Puebla Pue, México.
authors.forename: Julio M
authors.initials: JM
authors.lastname: Hernández-Pérez
authors.affiliation: Facultad de Ciencias Químicas de la Benemérita Universidad Autónoma de Puebla , 14 Sur y Avenida San Claudio, C.P. 72570, Puebla Pue, México.
authors.forename: Adrián E
authors.initials: AE
authors.lastname: Medina-Favela
authors.affiliation: Facultad de Ciencias Químicas de la Benemérita Universidad Autónoma de Puebla , 14 Sur y Avenida San Claudio, C.P. 72570, Puebla Pue, México.
authors.forename: Henoc
authors.initials: H
authors.lastname: Flores