Accurate Prediction of Enthalpies of Formation of Organic Azides by Combining G4 Theory Calculations with an Isodesmic Reaction Scheme

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2013-08, Vol.117 (31), p.6835-6845
• Main Authors: Dorofeeva, Olga V, Ryzhova, Oxana N, Suntsova, Marina A
• Format: Article
• Language: English
• Subjects: Azides (organic); Consistency; Deviation; Enthalpy; Formations; Mathematical analysis; Physical chemistry; Systematic errors
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp404484q

Accurate gas-phase enthalpies of formation (Δf H 298 °) of 29 azides are recommended by combining G4 theory calculations with an isodesmic reaction approach. The internal consistency over a set of Δf H 298 ° values was achieved by sequential adjustment of their values through the isodesmic reactions. The HN3 was chosen as a key reference compound. Of the experimental data available for 16 compounds, our predictive values agree well with 9 of them, while the deviations from 25 to 55 kJ/mol are observed for 7 compounds; possible systematic errors in the experimental data for phenyl azide, 2-azidoethanol, azidocyclopentane, azidocyclohexane, 3-azido-3-ethylpentane, 2-azido-2-phenylpropane, and 1-azidoadamantane are discussed. The recommended enthalpies of formation of organic azides were used as reference values to estimate the enthalpy of formation of four nitrogen-rich carbon nitrides. The calculations do not support the high value of the solid-state enthalpy of formation of TAAT (4,4′,6,6′-tetra­(azido)­azo-1,3,5-triazine); its value is estimated to be 300–400 kJ/mol lower than that measured experimentally.