A theoretical study of the gas-phase pyrolysis of nitroethylene

Шамов, А. Г.; Храпковский, Г. М.

doi:10.1070/mc2001v011n04abeh001423

Cited by 19 publications

(17 citation statements)

References 11 publications

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“…On the other hand, an 8312 kJ mol !1 error is also possible in calculation of the activation enthalpy; thus, the agreement between the calculated and experimental reaction barriers is quite reasonable. It is important that 6-31G(d), 6-311 ++ G(df,p), and QCISD(T)/6-31G(d) calculations give very close activation enthalpies of the reaction [31], which also confirms the reliability of the calculation results.…”

Section: Radical Decompositionsupporting

confidence: 56%

“…10) can decompose by two pathways (Scheme 4, with the relative energies given at structures and reaction barriers, at arrows; values in kJ mol !1 ). The first pathway involves isomerization (28) into compound XX with the half-chair conformation, followed by formation of a five-membered ring [XXII, reaction (30)], nitro3nitrite rearrangement [XXIII, reaction (31)], and elimination of HNO 2 [reaction (32)]. The second pathway via biradical XXI is more energetically favorable according to the available data.…”

Section: ääääääääääääääääääääääääáääääääääääääääääáäääääääääääääääáäämentioning

confidence: 94%

“…For the neutral molecule of I, we considered above two alternative routes to the aci form and found that the barriers of these reactions are so high that their occurrence as alternative pathways of gas-phase monomolecular decomposition is improbable (Table 1) [31]. However, the barrier of reaction (4) is considerably lower than the activation enthalpy of process (5).…”

Section: ääääääääääääääääääääääääáääääääääääääääääáäääääääääääääääáäämentioning

confidence: 97%

“…As for the neutral molecule of I [31], we examined six major pathways (20)3(25) of monomolecular decomposition of its radical cation: (25) Examination of the geometric structure of radical cation of I revealed existence of two different confor- mations: that with the C 4 C 3 N 2 O 1 dihedral angle of 60o (Fig. 8, structure Ic; its energy is taken as zero) and a planar conformation (Fig.…”

Section: Decomposition Of Nitroethylene Radical Cationmentioning

confidence: 99%

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Mechanism of gas-phase decomposition of nitroethylene: A theoretical study

2004

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Calculations by the B3LYP density functional method with various basis sets and by the QCISD(T)/6-31G(d) ab initio method showed that the main pathway of monomolecular gas-phase decomposition of nitroethylene is that involving a cyclic intermediate, 4H-1,2-oxazete 2-oxide; the barrier of its formation (201.9, 203.9, and 216.5 kJ mol !1 , as estimated by various methods) reasonably agrees with the experimental value (191.9 kJ mol !1 ). The barriers of alternative pathways of gas-phase decomposition of nitroethylene are considerably higher. The barriers of reactions involving radical cations are considerably lower than those of the similar reactions involving molecules. Among all the considered pathways of nitroethylene decomposition, bimolecular pathways are the most favorable energetically.Two major pathways of gas-phase decomposition of aliphatic nitro compounds have been proved experimentally: homolytic cleavage of the C3N bond with generation of free radicals and elimination of HNO 2 [13 4]. The molecular mechanism is realized at relatively low temperatures (up to 350oC) with mononitroalkanes containing a hydrogen atom in the a position relative to the nitro group, and also with halonitroalkanes RCH 2 CHXNO 2 (X = Hlg) [2, 3]. Gasphase decomposition of nitroethylene I and other a-nitroolefins is presumed to occur by a similar mechanism [2, 3, 5]. For mononitroalkanes, the molecular mechanism of HNO 2 elimination is confirmed by data on the composition of products in the initial steps of decomposition [1,2] and by the results of quantumchemical calculations [6 38]. Data on the composition of products formed in the initial steps of decomposition of I are lacking; therefore, the molecular mechanism for this compound is just a hypothesis. Published results of quantum-chemical studies of nitroethylene decomposition [9,10] are apparently insufficient to make any definite conclusions on the primary step of the monomolecular gas-phase decomposition or to cast doubt on the suggested pathway of HNO 2 elimination. In [11,12], we found that the barrier to elimination of HNO 2 from a molecule of I [223.9 kJ mol !1 according to B3LYP/6-311++G(df,p) calculations] significantly exceeds the experimental activation energy of the gas-phase decomposition (191.9 kJ mol !1 ).In this work, we studied theoretically various alternative pathways of monomolecular decomposition of

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Section: Radical Decompositionsupporting

confidence: 56%

Section: ääääääääääääääääääääääääáääääääääääääääääáäääääääääääääääáäämentioning

confidence: 94%

Section: ääääääääääääääääääääääääáääääääääääääääääáäääääääääääääääáäämentioning

confidence: 97%

Section: Decomposition Of Nitroethylene Radical Cationmentioning

confidence: 99%

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Mechanism of gas-phase decomposition of nitroethylene: A theoretical study

2004

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“…Karle and collaborators studied by means of MP2, MP4, and G2 methods its unimolecular decomposition [2], whereas Zhang et al investigated ground-state isomerization reactions and the first five electronic transitions at DFT/ B3LYP/6-31G* and TD-DFT-B3LYP/6-31G* levels of theory, respectively [11]. Shamov and Khrapkovskii considered the pyrolysis mechanism of nitroethylene through B3LYP/6-31G(d) functional [12]. Khrapkovskii and Shamov reviewed quantum chemical data on gas-phase decomposition mechanisms of C-nitro compounds including nitroethylene [13].…”

Section: Introductionmentioning

confidence: 98%

Electronic spectra of nitroethylene

Borges

Barbatti

Aquino

et al. 2011

Int J of Quantum Chemistry

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A systematic study of the electronic excited states of nitroethylene (C₂H₃NO₂) was carried out using the approximate coupled-cluster singles-and-doubles approach with the resolution of the identity (RI-CC2), the time dependent density functional theory with the CAMB3LYP functional (TDDFT/CAMB3LYP) and the DFT multireference configuration interaction (DFT/MRCI) method. Vertical transition energies and optical oscillator strengths were computed for a maximum of 20 singlet transitions. Semiclassical simulations of the ultraviolet (UV) spectra were performed at the RI-CC2 and DFT/MRCI levels. The main features in the UV spectrum were assigned to a weak n-π* transition, and two higher energy π_CC+O−π* bands. These characteristics are common to molecules containing NO2 groups. Simulated spectra are in good agreement with the experimental spectrum. The energy of the bands in the DFT/MRCI simulation agrees quite well with the experiment, although it overestimates the band intensities. RI-CC2 produced intensities comparable to the experiment, but the bands were blue shifted. A strong π_CC+O−π* band, not previously measured, was found in the 8–9 eV range

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