title: Study of energetics and structure of 1,2,3-benzotriazin-4(3H)-one and its 1H and enol tautomers.
abstract: This paper reports an experimental and computational study on the energetics of 1,2,3-benzotriazin-4(3H)-one. The standard (p° = 0.1 MPa) molar enthalpy of formation of solid 1,2,3-benzotriazin-4(3H)-one, at T = 298.15 K, was derived from its standard massic energy of combustion measured by static bomb combustion calorimetry in oxygen. The Calvet high-temperature vacuum sublimation technique was used to measure the respective standard molar enthalpy of sublimation at T = 298.15 K. From these two experimentally determined thermodynamic parameters, we have calculated the standard molar enthalpy of formation of 1,2,3-benzotriazin-4(3H)-one in the gas phase at T = 298.15 K, (200.9 ± 3.8) kJ·mol(-1). Interrelations between structure and energy for 1,2,3-benzotriazin-4(3H)-one, the tautomer 1,2,3-benzotriazin-4(1H)-one, and the enol tautomer 1,2,3-benzotriazin-4-ol were discussed based on density functional theory (DFT) calculations with the B3LYP hybrid functional and the 6-311++G(d,p) basis set. The gas-phase enthalpy of formation of 1,2,3-benzotriazin-4(3H)-one was estimated from quantum chemical calculations using the G3(MP2)//B3LYP composite method. Nucleus-independent chemical shifts (NICS) were also calculated with the purpose of analyzing the aromaticity of the benzenic and heterocyclic rings of the title molecule and others related tautomerically to it.
authors.affiliation: Centro de Investigação em Química, Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade do Porto, Porto, Portugal. msmirand@fc.up.pt
authors.forename: Margarida S
authors.initials: MS
authors.lastname: Miranda
authors.forename: M Agostinha R
authors.initials: MA
authors.lastname: Matos
authors.forename: Victor M F
authors.initials: VM
authors.lastname: Morais
authors.forename: Joel F
authors.initials: JF
authors.lastname: Liebman
mesh_terms: D007536:Isomerism; D008958:Models, Molecular; D013816:Thermodynamics; D014227:Triazines / Q000737:chemistry*
chemical_list: D014227:Triazines; C102393:1,2,3-benzotriazin-4-one