Theoretical Study of the Nitroalkane Thermolysis. 1. Computation of the Formation Enthalpy of the Nitroalkanes, Their Isomers and Radical Products

Abstract

The gas phase enthalpies of formation of mono-, di-, tri-, tetranitromethane and nitroethane, as well as of their nitrite and aci-form isomers were calculated using different multilevel (G2, G3, G2M(CC5)) and density functional theory (DFT)-based (B3LYP, MPW1B95 and MPWB1K) techniques. The enthalpies of the C-N bond dissociation and isomerization of these nitroalkanes were also calculated. The calculated values of the formation and reaction enthalpies were compared with the experimental data when these data were available. It was found that only the G3 procedure gave accurate (within 1 kcal/mol) results for the formation enthalpy of nitroalkanes, their isomers, and radical products. The G3 procedure and two new hybrid meta DFT methods proposed by Truhlar's group (Zhao, Y.; Truhlar, D. J. Phys. Chem. A 2004, 108, 6908) showed good results for the reaction enthalpies of the nitromethane isomerization and the C-N bond dissociation. Our calculation results were used to analyze thermodynamics of the dissociation and isomerization reactions of the poly nitro-substituted methanes.

Comment on “Studies on Thermodynamic Properties of FOX-7 and Its Five Closed-Loop Derivatives”

“… a The Gaussian 09 implementation W1Usc (UCCSD­(T) instead of ROCCSD­(T) along with a small spin contamination correction) of the W1 method was employed for open-shell atoms. b The most reliable experimental values summarized in refs − . c Reference , calculated using the atomization energy approach. …”

Nitro-, Cyano-, and Methylfuroxans, and Their Bis-Derivatives: From Green Primary to Melt-Cast Explosives

“…Due to natural hindrances with the combustion calorimetry of high-energy compounds, solid-state formation enthalpies are often calculated using quantum chemical values for the gas-phase thermochemistry and empirical estimations for sublimation enthalpy. The latter values generally lie in the narrow range on the enthalpic scale, while the former values are prone to error accumulation and require highly accurate levels of theory [53].…”

“…Molecules 2020, 25, x FOR PEER REVIEW 9 of 19 estimations for sublimation enthalpy. The latter values generally lie in the narrow range on the enthalpic scale, while the former values are prone to error accumulation and require highly accurate levels of theory [53].…”

Thermal Stability Evaluation of Nitroalkanes with Differential Scanning Calorimetry

“…34,42 Further studies have indicated that isomerization of nitromethane into nitrite should be taken into consideration, as well as the secondary reactions of the nitro-substituted radicals and the contribution of other primary unimolecular reactions, like isomerization to nitrites and aci-forms. 43 In addition to those methods, the latest development of molecular simulation as a predictive tool, such as, quantitative structure−activity/property relationships, represents an alternative way of predicting physical and chemical properties of energetic materials, like decomposition enthalpies (theoretical decomposition enthalpies). 44,45 Together with theoretical and computational methods, experimental methods are used to characterize the thermal properties of chemicals, especially for compounds involved in industrial processes.…”