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Theoretical study of the gas-phase thermolysis of 3-methyl-1,2,4,5-tetroxane
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Cyclic organic peroxides are a broad and highly sought-after class of peroxide compounds that present high reactivity and even explosive character. The unusually high reactivity of these peroxides can generally be attributed to the rupture of O-O bonds. Cyclic diperoxides are a very interesting series of substituted compounds in which tetroxane is the most prominent member. Gas-phase thermolysis of the simplest substituted member of the series [3-methyl-1,2,4,5-tetroxane or methylformaldehyde diperoxide (MFDP)] has been observed to yield one acetaldehyde, one formaldehyde, and one oxygen molecule as reaction products. DFT at the 6-311 + G** level of theory using the BHANDHLYP correlation-exchange functional was applied via the Gaussian09 program to calculate the critical points of the potential energy surface (PES) of this reaction. Equatorial and axial isomers were studied. The singlet state PES of MFDP was calculated, and an open diradical structure was found to be the first intermediate in a stepwise reaction. Two PESs were subsequently obtained: singlet state (S) and triplet state (T) PESs. After that, two alternative stepwise reactions were found to be possible: 1) one in which either an acetaldehyde, or 2) formaldehyde molecule is initially formed. For second one, exothermic reactions were observed for both the S and T PESs. The reaction products include a oxygen molecule in either S or T state, with the T reaction being the most exothermic. When calculations were performed at the CASSCF(10,10)/6-311 + G** level, spin-orbit coupling permitted S to T crossing at the open diradical intermediate stage, a non-adiabatic reaction was observed, and lower activation energies and higher exothermicity were generally seen for the T PES than for the S PES. These results were compared with the corresponding results for tetroxane. The spin-orbit coupling of MFDP and tetroxane yielded identical values, so it appears that the methyl substituent does not have any effect on this coupling.
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... In previous papers, the thermolysis reactions of 1,2,4,5tetroxane [formaldehyde diperoxide (FDP)] [14] and 3-methyl-1,2,4,5-tetroxane [methyl formaldehyde diperoxide (MFDP)] [15] were investigated. In the leader compound of the series, FDP, the gas-phase thermolysis reaction was studied by kinetic experiments and theoretical DFT methods [14]. ...
... The first methyl derivative of FDP corresponds to MFDP, in which the gas-phase thermolysis reaction was also theoretically studied at the same electronic level as FDP [15]. In this molecule, axial (ax) and equatorial (eq) isomers were also studied. ...
... The procedure to determine the electron density is quite close to the previous papers [14,15], nonetheless, it is described here for the sake of completeness. Reactant, intermediates, and products were calculated using the DFT method with the 6-311+G** basis set, with the BHandHLYP [16][17][18] correlation exchange functional, and using the Gaussian 09 program [19]. ...
Organic peroxides are interesting compounds with a broad range of properties from antimalarial and antimicrobial activities to explosive character. In this work the gas-phase thermolysis reaction mechanism of the 3,6-dimethyl-1,2,4,5-tetroxane (DMT) is studied by DFT calculations, considering axial–axial, axial–equatorial, and equatorial–equatorial position isomers. The critical points of the singlet (S) and triplet (T) potential energy surfaces (PES) are calculated. Three mechanisms are considered: i) S-concerted, ii) S-stepwise, and iii) T-stepwise. The first intermediate of the reaction through S-stepwise-PES is a diradical open structure, o, yielding, as products, two molecules of acetaldehyde and one of O2 in the S state. The S-stepwise-mechanism gives exothermic reaction energies (Er) in the three position isomers. The S-concerted mechanism yields very high activation energies (Ea) in comparison with those of the S-stepwise mechanism. In the T-stepwise mechanism, a triplet open structure (T-o) is first considered, yielding an Er 12 kcal mol–1 more exothermic than that of the S-mechanisms. The S-o and T-o are similar in structure and energies; therefore, a crossing from the S- to T-PES is produced at the o intermediate as a consequence of a spin–orbit coupling. The highest Ea is the first step after o intermediate, and thus it is considered the rate limiting step. Therefore, the Er at the T-PES is more in agreement with the Er of the exothermic experimental diperoxide products. Ea, Er, and O···O distances are studied as a function of the number of methyl groups and the position isomerization.
... The results of density functional calculations with full geometry optimization also supported the stepwise mechanism of formaldehyde diperoxide and the methyl diperoxide decomposition through intermediate diradical species. [9,10] The values of the activation parameters (ΔH # =102.9 ± 1 kJ mol -1 and ΔS # = -49.8 ± 1.1 J mol -1 K -1 ) were determined using the Eyring equation, whose graphical representation is linear (r 2 = 0.9990) in the temperature range ( 36ºC). ...
The thermal decomposition reaction of benzaldehyde diperoxide (DFT; 0.001 mol L-1) in nitromethane solution studied in the temperature range of 130.0-166.0 °C, follows a first-order kinetic law up to at least 60% DFT conversion. The organic products observed were benzaldheyde and benzoic acid. A stepwise mechanism of decomposition was proposed where the first step is the homolytic unimolecular rupture of the O-O bond. The activation enthalpy and activation entropy for DFT in nitromethane were calculated (DH# = 106.3 ± 1.0 kJ mol-1 and DS# = -58.6 ± 1.1 J mol-1K-1) and compared with those obtained in other solvents to evaluate the solvent effect.
The present volume in "The Chemistry of Functional Groups" series deals with functional groups which include the -0-O- bond, i.e., organic peroxides, hydroperoxides, acyl peroxides, peroxy acids and esters and ozonides. These should have treated the following subjects: NMR; ESR and CIDNP; Analytical methods; Elcctrocliemistry; Chemiluminescence; Biological formation and reactions; Safety and toxicity.
The thermal decomposition reaction of acetone cyclic diperoxide (ACDP) in 1-octanol (OCT) solution, at the temperatures and initial concentration ranges of 130° -166 °C and (0.94-3.00) × 10-2 mol/L, respectively, follows a pseudo-first order kinetic law. Acetone is the main organic decomposition product observed. The activation parameters values of the initial reaction step (ΔH# = 25.8 ± 0.3 kcal/mol; ΔS# = -19.1 ± 0.6 cal/mol K; Ea = 26.6 ± 0.3 kcal/mol), support a reaction mechanism which includes a homolytic rupture of one peroxidic bond of the ACDP molecule with participation of the solvent and involving a biradical intermediate.
The thermal decomposition of triacetone triperoxide (TATP) was investigated over the temperature range 151 to 230 °C and found to be first order out to a high degree of conversion. Arrhenius parameters were calculated: activation energy, 151 kJ/mol and pre-exponential factor, 3.75×1013 s−1. Under all conditions the principle decomposition products were acetone (about 2 mole per mole TATP in the gas-phase and 2.5–2.6 mole per mole in condensed-phase) and carbon dioxide. Minor products included some ascribed to reactions of methyl radical: ethane, methanol, 2-butanone, ethyl acetate; these increased at high temperature. Methyl acetate and acetic acid were also formed in the decomposition of neat TATP; the former was more evident in the gas-phase decompositions (151 °C and 230 °C) and the latter in the condensed-phase decompositions (151 °C). The decomposition of TATP in condensed-phase or in hydrogen-donating solvents enhanced acetone production, suppressed CO2 production, and slightly increased the rate constant (a factor of 2–3). All observations were interpreted in terms of decomposition pathways initiated by OO homolysis.
Cited By (since 1996):1, Export Date: 20 January 2014, Source: Scopus
Gas-phase thermolysis reaction of formaldehyde diperoxide (1,2,4,5-tetroxane) was performed in an injection chamber of a gas chromatograph at a range of 463–503 K. The average Arrhenius activation energy and pre-exponential factor were 29.3 ± 0.8 kcal/mol and 5.2 × 1013 s−1, respectively. Critical points and reaction paths of the ground singlet and first triplet potential energy surfaces (PES) were calculated, using DFT method at BHANDHLYP/6-311+G∗∗ level of the theory. Also, G3 calculations were performed on the reactant and products. Reaction by the ground-singlet and first-triplet states turned out to be endothermic and exothermic, respectively. The mechanism in three steps seemed to be the most probable one. An electronically non-adiabatic process appeared, in which a crossing, at an open diradical structure, from the singlet to the triplet state PES occurred, due to a spin–orbit coupling, yielding an exothermic reaction. Theoretical kinetic constant coming from the non- adiabatic transition from the singlet to the triplet state agrees with the experimental values.
Imidazole, pyrazole, 1,2,3-triazole, 1,2,4-triazole, and tetrazole based energetic materials are theoretically investigated by employing density functional theory (DFT). Heats of formation (ΔfH0s) for the studied compounds (298 K) in the gas phase are determined at the B3P86/6-311G (d, p) theory level through isodesmic reactions. The bond dissociation energies (BDEs) corresponding to NO2, NH2, CH3, and Cl removal from carbon or nitrogen positions of the azole ring are also calculated at the B3P86/6-311G (d, p) theory level. The substituent effect of electron-withdrawing (NO2, Cl) and electron-donating (NH2, CH3) groups on the Δ(f)H0s and BDEs is discussed. Both electron-withdrawing groups and electron-donating groups (except the CH3 group) dramatically increase the Δ(f)H0s of these energetic materials when the substituent is at an N position on the azole ring. For substitution at a C atom on the azole ring, electron-withdrawing and electron-donating groups have different effects on the Δ(f)H0s for different azole compounds. A correlation is developed for this series of energetics between impact sensitivity h50% and the defined sensitivity index (SI): based on this empirical relationship and its extrapolation, the impact sensitivities of compounds for which experiments are not available are provided. The promising energetic compounds in each groups, which have potentially good energetic performance and low sensitivity, are 1-amino-2,4,5-trinitroimidazole, 1-amino-3,4,5-trinitropyrazole, 1,4-dinitro-1,2,3-triazole, 1,3-dinitro-1,2,4-triazole, 1-nitrotetrazole.
Simple, but beautifully versatile. Perhaps not a description many would choose for hydrogen peroxide, but an accurate one none the less, and this unique book explains the reasons behind the description. Beginning with an historical overview, and guidelines for the safe handling of peroxygens, Applications of Hydrogen Peroxide and Derivatives goes on to cover key activation mechanisms, organic functional group oxidations and the use of hydrogen peroxide with heterogeneous catalysts. The clean-up of environmental pollutants; chemical purification; and extraction of metals from their ores are also discussed in detail, using actual examples from industry. The versatility of this reagent may well prove to be a key to integrated pollution control in the future. This book should therefore be read by academics and industrialists at all levels, to encourage wider applications of the use of hydrogen peroxide in laboratories.
Thermal decomposition of formaldehyde diperoxide (1,2,4,5-tetraoxane) in aqueous solution with an initial concentration of
6.22 × 10−3 M was studied in the temperatures range from 403 to 439 K. The reaction was found to follow first-order kinetic law, and
formaldehyde was the major decomposition product. The activation parameters of the initial step of the reaction (ΔH
≠ = 15.25 ± 0.5 kcal mol−1, ΔS
≠ = −47.78 ± 0.4 cal mol−1K−1, E
a = 16.09 ± 0.5 kcal mol−1) support a mechanism involving homolytic rupture of one peroxide bond in the 1,2,4,5-tetraoxane molecule with participation
of the solvent and formation of a diradical intermediate.