scholarly journals Alternative mechanisms of the primary act of gas-phase monomolecular thermal decomposition of N-methyl-N’-methoxydiazene-N-oxide according to the data of quantum chemical calculations

2021 ◽  
Vol 2052 (1) ◽  
pp. 012030
Author(s):  
E V Nikolaeva ◽  
G M Khrapkovskii ◽  
I V Aristov ◽  
D L Egorov ◽  
A G Shamov

Abstract The mechanisms of the primary act of thermal decomposition of the simplest representative of the series of alkoxy-NNO-azoxy compounds – N-methyl-N’-methoxydiazene-N- oxide are studied using quantum-chemical density functional methods PBE, B3LYP, wB97XD with different sets of basic functions, as well as the composite G4 method. It is shown that the most probable channel of its thermal destruction, leading to the formation of experimentally observed reaction products, is isomerization because of rotation of the OCH3 group around the NO bond with the subsequent transfer of the CH3 group between oxygen atoms. In this case, the transfer of the CH3 group is the limiting reaction of the thermal decomposition of N-methyl-N’-methoxydiazene-N-oxide as a whole.

2016 ◽  
Vol 71 (12) ◽  
pp. 1253-1260 ◽  
Author(s):  
Sebastian Blomeyer ◽  
Christian G. Reuter ◽  
Diego M. Gil ◽  
María E. Tuttolomondo ◽  
Aída Ben Altabef ◽  
...  

AbstractThe structural and conformational properties of 2,2,2-trichloroethylacetate, H3CCO2CH2CCl3, have been determined in the gas phase using gas electron diffraction (GED). The experimental measurements were complemented by MP2 and DFT quantum-chemical calculations. Two conformers separated by a shallow rotational barrier have been identified, one of C1 (syn-gauche) and the other of Cs symmetry (syn-anti). All calculations indicate that syn-gauche is preferred in terms of enthalpy, whereas syn-anti seems to be slightly more stable regarding Gibbs free energy. In the gas-phase structure determination, dynamic models based on different potential energy surface scans were used. The one from dispersion-corrected density functional theory, predicting a preference of syn-gauche by 1.7kJmol−1, was found to describe the experimental data best. One- and two-conformer models had to be rejected due to correlations and unrealistically large amplitudes. Experimentally determined structural parameters are in good agreement with both, quantum-chemical calculations as well as GED data for related compounds. Interacting quantum atoms (IQA) analyses revealed that interplay between the carbonyl group and the hydrogen as well as chlorine atoms of the trichloroethyl group accounts for most of the stabilisation of the C1 conformer. With intramolecular symmetry-adapted perturbation theory (I-SAPT) analyses it was possible to further elucidate the nature of dominant interactions in the two conformers. Herein, preference of syn-gauche can for the most part be attributed to electrostatic and to some extent to induction and dispersion interplays. In contrast this conformer is severely destabilised through steric repulsion. These results were supported by NBO analyses.


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