The standard molar enthalpies of combustion and sublimation of benzothiazino-benzothiazine and benzoxazino-benzoxazine

• Published in: The Journal of chemical thermodynamics Vol. 29; no. 5; pp. 565 - 574
• Main Authors: Gudiño, Ramón, Torres, Luis Alfonso, Campos, Myriam, Santillán, Rosa Luisa, Farfán, Norberto
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.05.1997; Elsevier
• Subjects: benzothiazino-benzothiazine; benzoxazino-benzoxazine; Chemical thermodynamics; Chemistry; Elements, mineral and organic compounds; enthalpy of combustion; Enthalpy of formation; enthalpy of sublimation; Exact sciences and technology; General and physical chemistry; Thermodynamic properties; Enthalpy of formation; enthalpy of combustion; benzoxazino-benzoxazine; enthalpy of sublimation; benzothiazino-benzothiazine; Heat of combustion; Sulfur nitrogen heterocycle; Aromatic compounds; Heat of sublimation; Enthalpy; Tetracyclic compound; Thermodynamic properties; Organic compounds; Oxygen nitrogen heterocycle
• ISSN: 0021-9614; 1096-3626
• DOI: 10.1006/jcht.1996.0176

The compoundscis-5a,6,11a,12-tetrahydro[1,4]benzothiazino[3,2-b][1,4]benzothiazine(BTB) and 5a,6,11a,12-tetrahydro[1,4]benzoxazino[3,2-b][1,4]benzoxazine(BOB) have been studied by oxygen bomb combustion calorimetry and by the Knudsen effusion method using a quartz-crystal microbalance. Based on the experimental results, the standard molar enthalpies of formation of the solid and gaseous compounds were determined. A summary of experimental and derived results at the temperatureT=298.15 K is shown below: [Table] From a group-contribution scheme and from the experimental results, the group-contribution terms to the standard molar enthalpies of formation of the gaseous compounds for the molecular groups {C–(S)(N)(C)(H)} and {C–(O)(N)(C)(H)} were calculated as –76.1 kJ·mol−1and –42.7 kJ·mol−1, respectively. It is concluded that the standard molar enthalpy of formation in the gas phase is decreased by (340.4±9.0) kJ·mol−1when two Cb–S bonds and two C–S bonds are substituted by two Cb–O bonds and two C–O bonds in the compound BTB to obtain BOB; here Cbrefers to a carbon atom in the benzene ring.