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Title: Accurate Thermochemical Properties for Energetic Materials Applications. II. Heats of Formation of Imidazolium-, 1,2,4-Triazolium-, and Tetrazolium-Based Energetic Salts fromIsodesmic and Lattice Energy Calculations.

Abstract

The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. A computational approach to the prediction of the heats of formation (ΔHf°’s) of solid-state energetic salts from electronic structure and volume-based thermodynamics (VBT) calculations is described. The method uses as its starting point reliable ΔHf°’s for energetic precursor molecules and ions. The ΔHf°’s of more complex energetics species such as substituted imidazole, 1,2,4-triazole, and tetrazole molecules and ions containing amino, azido, and nitro (including methyl) substituents are calculated using an isodesmic approach at the MP2/complete basis set level. On the basis of comparisons to experimental data for neutral analogues, this isodesmic approach is accurate to <3 kcal/mol for the predicted cation and anion ΔHf°’s. The ΔHf°’s of the energetic salts in the solid state are derived from lattice energy (UL) calculations using a VBT approach. Improved values for the ∝ and β parameters of 19.9 (kcal nm)/mol and 37.6 kcal/mol for the UL equation were obtained on the basis of comparisons to experimental UL’s for a series of 23 saltsmore » containing ammonium, alkylammonium, and hydrazinium cations. The total volumes are adjusted to account for differences between predicted and experimental total volumes due to different shapes of the ions (flat vs spherical). The predicted ΔHf°’s of the energetic salts are estimated to have error bars of 6-7 kcal/mol, on the basis of comparisons to established experimental ΔHf°’s of a subset of the salts studied. Energetic salts with the highest positive ΔHf°’s are predicted for azido-containing cations, coupled with heterocyclic anions containing nitro substituents. The substitution of functional groups on carbon versus nitrogen atoms of the heterocyclic cations has interesting stabilization and destabilization effects, respectively.« less

Authors:
; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
921378
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physical Chemistry B, 111(18):4788-4800; Journal Volume: 111; Journal Issue: 18
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; IMIDAZOLES; TRIAZOLES; TETRAZOLES; FORMATION HEAT; AZIDO COMPOUNDS; NITRO COMPOUNDS; SALTS; Environmental Molecular Sciences Laboratory

Citation Formats

Gutowski, Keith E, Rogers, Robin D, and Dixon, David A. Accurate Thermochemical Properties for Energetic Materials Applications. II. Heats of Formation of Imidazolium-, 1,2,4-Triazolium-, and Tetrazolium-Based Energetic Salts fromIsodesmic and Lattice Energy Calculations.. United States: N. p., 2007. Web. doi:10.1021/jp066420d.
Gutowski, Keith E, Rogers, Robin D, & Dixon, David A. Accurate Thermochemical Properties for Energetic Materials Applications. II. Heats of Formation of Imidazolium-, 1,2,4-Triazolium-, and Tetrazolium-Based Energetic Salts fromIsodesmic and Lattice Energy Calculations.. United States. doi:10.1021/jp066420d.
Gutowski, Keith E, Rogers, Robin D, and Dixon, David A. Thu . "Accurate Thermochemical Properties for Energetic Materials Applications. II. Heats of Formation of Imidazolium-, 1,2,4-Triazolium-, and Tetrazolium-Based Energetic Salts fromIsodesmic and Lattice Energy Calculations.". United States. doi:10.1021/jp066420d.
@article{osti_921378,
title = {Accurate Thermochemical Properties for Energetic Materials Applications. II. Heats of Formation of Imidazolium-, 1,2,4-Triazolium-, and Tetrazolium-Based Energetic Salts fromIsodesmic and Lattice Energy Calculations.},
author = {Gutowski, Keith E and Rogers, Robin D and Dixon, David A},
abstractNote = {The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. A computational approach to the prediction of the heats of formation (ΔHf°’s) of solid-state energetic salts from electronic structure and volume-based thermodynamics (VBT) calculations is described. The method uses as its starting point reliable ΔHf°’s for energetic precursor molecules and ions. The ΔHf°’s of more complex energetics species such as substituted imidazole, 1,2,4-triazole, and tetrazole molecules and ions containing amino, azido, and nitro (including methyl) substituents are calculated using an isodesmic approach at the MP2/complete basis set level. On the basis of comparisons to experimental data for neutral analogues, this isodesmic approach is accurate to <3 kcal/mol for the predicted cation and anion ΔHf°’s. The ΔHf°’s of the energetic salts in the solid state are derived from lattice energy (UL) calculations using a VBT approach. Improved values for the ∝ and β parameters of 19.9 (kcal nm)/mol and 37.6 kcal/mol for the UL equation were obtained on the basis of comparisons to experimental UL’s for a series of 23 salts containing ammonium, alkylammonium, and hydrazinium cations. The total volumes are adjusted to account for differences between predicted and experimental total volumes due to different shapes of the ions (flat vs spherical). The predicted ΔHf°’s of the energetic salts are estimated to have error bars of 6-7 kcal/mol, on the basis of comparisons to established experimental ΔHf°’s of a subset of the salts studied. Energetic salts with the highest positive ΔHf°’s are predicted for azido-containing cations, coupled with heterocyclic anions containing nitro substituents. The substitution of functional groups on carbon versus nitrogen atoms of the heterocyclic cations has interesting stabilization and destabilization effects, respectively.},
doi = {10.1021/jp066420d},
journal = {Journal of Physical Chemistry B, 111(18):4788-4800},
number = 18,
volume = 111,
place = {United States},
year = {Thu Mar 01 00:00:00 EST 2007},
month = {Thu Mar 01 00:00:00 EST 2007}
}
  • The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. The heats of formation of 1H-imidazole, 1H-1,2,4-trizazole, 1H-tetrazole, CH3NO2, CH3N3, CH3NH2, CH2- CHNO2, HClO4, and phenol, as well as cations and anions derived from some of the molecules have been calculated using ab initio molecular orbital theory. These molecules are important as models for compounds used for energetic materials synthesis. The predicted heats of formation of the heterocycle-based compounds aremore » in excellent agreement with available experimental values and those derived from proton affinities and deprotonation enthalpies to <1 kcal/mol. The predicted value for the tetrazolium cation differs substantially from the experimental value, likely due to uncertainty in the measurement. The heats of formation of the nitro and amino molecules, as well as phenol/phenolate, also are in good agreement with the experimental values (<1.5 kcal/mol). The heat of formation of CH3N3 is predicted to be 72.8 kcal/mol at 298 K with an estimated error bar of (1 kcal/mol on the basis of the agreement between the calculated and experimental values for ¢Hf(HN3). The heat of formation at 298 K of HClO4 is -0.4 kcal/mol, in very good agreement with the experimental value, as well as a W2 literature study. An extrapolation of the CCSD(T)/aug-cc-pV- (Q,5) energies was required to obtain this agreement. This result suggests that very large basis sets (gaugcc- pV5Z) may be needed to fully recover the valence correlation energy contribution in compounds containing elements with high formal oxidation states at the central atom. In addition tight d functions are needed for the geometry predictions. Douglas-Kroll-Hess (DKH) scalar relativistic corrections for HClO4 and ClO4 - at the MP2 level with correlation-consistent DKH basis sets were predicted to be large, likely due to the high formal oxidation state at the Cl.« less
  • Quaternary salts based on 1-vinyl-1,2,4-triazole have been synthesized. Alkyl iodides and bromides and dimethyl sulfate served as the quaternizing agent. Polymeric quaternary salts of 1-vinyl-1,2,4-triazole have been obtained by alkylation of its polymer.
  • 1-Methyl-2,3-dihydro-1,2,4-triazolium iodides can be obtained by reacting methylhydrazones with S-methylthioamide hydriodides, by condensing 2-methylamidrazone hydriodides with aldehydes and ketones, or by reacting methyl iodide with 1-alkylidene(or arylidene) benzamidrazones. In solutions these salts are capable of undergoing tautomerism to 1-alkylidene(or arylidene)-2-methylamidrazone hydriodides. The influence of the structural factors on the position of the tautomeric equilibrium has been studied. The free bases obtained by neutralization of the respective salts by an alkali metal hydroxide are heretofore undescribed 1-alkylidene(or arylidene)-2-methylhydrazidoimines or 4-triazolines, depending on their structure. Under the action of oxygen, these compounds are readily oxidized to substituted 1-methyl-1,2,4-triazoles with heating.