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Josep M Anglada - One of the best experts on this subject based on the ideXlab platform.
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the reaction of formaldehyde Carbonyl Oxide with the methyl peroxy radical and its relevance in the chemistry of the atmosphere
Physical Chemistry Chemical Physics, 2013Co-Authors: Josep M Anglada, Santiago Olivella, Albert SoleAbstract:The reaction of formaldehyde Carbonyl Oxide (H2COO) with the methyl peroxy radical (CH3OO), a prototype of the reactions of Carbonyl Oxides with alkyl peroxy radicals of potential interest in atmospheric chemistry, has been investigated by means of quantum-mechanical electronic structure methods (CASSCF, CASPT2, UQCISD, and UCCSD(T)) and DFT functionals (B3LYP, BH&HLYP, M05 and M06-2X). Two reaction paths have been found for the lowest-barrier reaction, namely the CH3OO radical addition to the carbon atom of H2COO leading to the formation of the CH3OOCH2OO radical adduct. Both pathways begin with the formation of a pre-reactive complex with binding energies of 5.39 and 5.13 kcal mol−1. The corresponding transition states are predicted to lie 2.64 and 0.25 kcal mol−1, respectively, below the energy of the reactants and the rate constant of the global reaction is calculated to be 3.74 × 10−12 cm3 molecules−1 s−1 at 298 K. Since the CH3OOCH2OO radical adduct is formed with an internal energy excess of about 45 kcal mol−1, it can decompose unimolecularly into formaldehyde and the CH2(O)OOCH radical. This unimolecular decomposition involves an intramolecular H-atom transfer followed by the decomposition of the CH2OOCH2OOH radical intermediate. Kinetic calculations based on the collision–reaction master equation employing the MultiWell Program Suite reveal that the CH3OOCH2OO radical adduct is stabilized in 86.9%, whereas 13.10% of the reaction corresponds to the formation of H2CO plus the CH2(O)OOH radical. It is concluded that the methyl peroxy radical addition to substituted Carbonyl Oxides might be the source of low volatility oligomers observed in secondary organic aerosols in chamber studies.
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effects of the substituents on the reactivity of Carbonyl Oxides a theoretical study on the reaction of substituted Carbonyl Oxides with water
Physical Chemistry Chemical Physics, 2011Co-Authors: Josep M Anglada, J W Gonzalez, Miquel TorrentsucarratAbstract:The reactions between fifteen Carbonyl Oxides and water have been investigated with the aim of contributing to a better understanding of the effects of the substituents in the reactivity of Carbonyl Oxides. We have employed density functional theory and large scale ab initio methods (CCSD(T), CASSCF, and CASPT2), combined with transition state theory, to investigate the addition of water to Carbonyl Oxide and, for those Carbonyl Oxides having a methyl substituent in syn, the hydrogen transfer from the methyl group to the terminal oxygen of Carbonyl Oxide. In this case, the water acts as a catalyst and this reaction can contribute to the atmospheric formation of a hydroxyl radical. Carbonyl Oxides with electron withdrawing substituents and zwitterionic character have low energy barriers and react fast, whereas Carbonyl Oxides with electron releasing substituents have high energy barriers and react slowly. The position of the substituents plays also an important role and Carbonyl Oxides having a hydrogen atom substituent in syn react faster than Carbonyl Oxides having a hydrogen atom substituent in anti. The differences in the reactivity of different substituted Carbonyl Oxides raise up to ten orders of magnitude and the branching ratios for the two different reactions investigated are also reported.
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the gas phase reaction of Carbonyl Oxide with hydroxyl radical in presence of water vapor a theoretical study on the reaction mechanism
Computational and Theoretical Chemistry, 2011Co-Authors: Alex Mansergas, Manuel F Ruizlopez, Javier Gonzalez, Josep M AngladaAbstract:Abstract The effect of water vapor on the reaction mechanism of Carbonyl Oxide with hydroxyl radical has been investigated by using theoretical methods. Our calculations predict that the addition of the HO radical to the carbon atom of H 2 COO is the most favorable reaction path, as also found for the reaction without water. The water molecule produces a stabilizing effect close to 4 kcal/mol. The fate of the reaction is the peroxy radical complex H 2 C(OH)OO···H 2 O, which can decompose into H 2 CO + H 2 O + HO 2 . Therefore, this reaction mechanism corresponds to the inverse process of the water-assisted oxidation of formaldehyde by the hydroperoxyl radical. The abstraction of a hydrogen atom from Carbonyl Oxide has been investigated too and has been shown to involve a quite high energy barrier suggesting that such a process cannot occur in tropospheric conditions. Finally, we have studied the addition of water to Carbonyl Oxide assisted by the hydroxyl radical and the results highlight an important catalytic effect of the later species.
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reaction mechanism between Carbonyl Oxide and hydroxyl radical a theoretical study
Journal of Physical Chemistry A, 2006Co-Authors: Alex Mansergas, Josep M AngladaAbstract:The reaction mechanism of Carbonyl Oxide with hydroxyl radical was investigated by using CASSCF, B3LYP, QCISD, CASPT2, and CCSD(T) theoretical approaches with the 6-311+G(d,p), 6-311+G(2df, 2p), and aug-cc-pVTZ basis sets. This reaction involves the formation of H2CO + HO2 radical in a process that is computed to be exothermic by 57 kcal/mol. However, the reaction mechanism is very complex and begins with the formation of a pre-reactive hydrogen-bonded complex and follows by the addition of HO radical to the carbon atom of H2COO, forming the intermediate peroxy-radical H2C(OO)OH before producing formaldehyde and hydroperoxy radical. Our calculations predict that both the pre-reactive hydrogen-bonded complex and the transition state of the addition process lie energetically below the enthalpy of the separate reactants (ΔH(298K) = −6.1 and −2.5 kcal/mol, respectively) and the formation of the H2C(OO)OH adduct is exothermic by about 74 kcal/mol. Beyond this addition process, further reaction mechanisms have ...
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reaction modes of Carbonyl Oxide dioxirane and methylenebis oxy with ethylene a new reaction mechanism
Journal of Physical Chemistry A, 2002Co-Authors: Ramon Crehuet, Josep M Anglada, Dieter Cremer, Josep Maria BofillAbstract:The reaction modes of the three isomers, Carbonyl Oxide (A), dioxirane (B), and methylenebis(oxy) (C), with ethylene (E) were investigated by using CASPT2, CCSD(T), and B3LYP with a 6-311+G(2d,2p) basis set. Contrary to general expectations, A prefers to react with E via a [4+2] cycloaddition reaction (activation enthalpy ΔH#(298) = 1.0 kcal/mol) to yield 1,2-dioxolane (MA2) (reaction enthalpy, −65.0 kcal/mol) rather than via an epoxidation reaction (ΔH#(298) = 11.3 kcal/mol) leading to oxirane and formaldehyde. Epoxidation by B is slower in view of an activation enthalpy of 13.7 kcal/mol; however, it should proceed stereochemically similar as in the case of A. Biradicals C and E can undergo a pseudo-[4+2] cycloaddition reaction (ΔH#(298) = 1.8 kcal/mol), which leads to 1,3-dioxolane (MC2) in a strongly exothermic reaction (ΔHR(298) = −84.5 kcal/mol). The results obtained lead to a mechanistic reconsideration of epoxidation reactions observed in the course of the ozonolysis. They also provide a general ba...
V.d. Komissarov - One of the best experts on this subject based on the ideXlab platform.
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Flash Photolysis of Diphenyldiazomethane in the Presence of Organic Sulfides
High Energy Chemistry, 2002Co-Authors: A.m. Nazarov, S. L. Khursan, P. V. Krupin, A. S. Kanchurin, V.d. KomissarovAbstract:The flash photolysis of diphenyldiazomethane in acetonitrile, benzene, and n -decane solutions saturated with air resulted in the formation of diphenyl Carbonyl Oxide Ph_2COO which decayed in combination reactions. In the presence of organic sulfides, the transfer of the terminal oxygen atom of Ph_2COO to the sulfur atom was observed. The kinetics of this reaction was studied. The absolute rate constants ( k _6, dm^3 mol^–1 s^–1) of the reactions of Ph_2COO with sulfides at 295 K (acetonitrile as a solvent) varied from 4.1 × 10^2 (Me_2S) to 8.1 × 10^4 (Ph_2S). The solvent effect on the reaction kinetics and product composition was studied. The mechanism of the process was discussed.
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Determination of the Absolute Rate Constants of Reactions between Diphenyl Carbonyl Oxide and Alcohols by Flash Photolysis
Kinetics and Catalysis, 2002Co-Authors: A.m. Nazarov, S. L. Khursan, I. A. Kalinichenko, S. Kh. Ziganshina, V.d. KomissarovAbstract:The rate constants of the reactions of diphenyl Carbonyl Oxide Ph_2COO with a number of alcohols and water in acetonitrile, benzene, and n -decane solutions (295 K) were measured by flash photolysis. The rate constants vary over a range from 400 (triphenylmethanol in a MeCN solution) to 2.5 × 10^5 l mol^–1 s^–1 (adamantanol in a benzene solution). α-Methoxydiphenylmethyl hydroperOxide is the reaction product of Ph_2COO and MeOH. The absence of a kinetic isotope effect and the dependence of the logarithms of the rate constants on the first ionization potentials of alcohols are indicative of the formation of a C–O bond at the rate-limiting step of the reaction.
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Kinetics, mechanism, and products of the reaction of diphenylCarbonyl Oxide with carboxylic acids
Russian Chemical Bulletin, 2002Co-Authors: A.m. Nazarov, E. M. Chainikova, S. L. Khursan, V.d. KomissarovAbstract:The kinetics of the reactions of acetic, benzoic, formic, oxalic, malic, tartaric, trifluoroacetic, and hydrochloric acids with diphenylCarbonyl Oxide Ph_2COO was studied. The Carbonyl Oxide Ph_2COO was generated by flash photolysis of diphenyldiazomethane Ph_2CN_2 in solutions of acetonitrile and benzene at 295 K. The apparent rate constants of the reaction range from 4.6·10^8 for (COOH)_2 in MeCN to 7.5·10^9 L mol^–1 s^–1 for acetic acid in a benzene solution. The reaction mechanism was proposed, according to which at the first stage the Carbonyl Oxide is reversibly solvated by the solvent. Then the solvated Carbonyl Oxide reacts with the acid molecule by the mechanism of insertion at the O—H bond.
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The Reactivity of Diphenyl Carbonyl Oxide in Reactions with Alcohols
Kinetics and Catalysis, 2001Co-Authors: A.m. Nazarov, G.a. Yamilova, V.d. KomissarovAbstract:The reactivities of ten alcohols in the reactions with diphenyl Carbonyl Oxide Ph_2COO is characterized by the ratio k ^OH _ 33 / k _31, where k ^OH _ 33 and k _31are the rate constants of Ph_2COO reactions with an alcohol and diphenyldiazomethane PH_2CN_2, respectively. The values of k ^OH _ 33 / k _31range between 0.6 × 10^–2for MeOH to 6.0 for iso -PrOH at 70°C in acetonitrile. The donation of electron density to the alcohol hydroxyl group favors the attack of Ph_2COO; that is, Ph_2COO reacts as an electrophile.
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Solvent effects on the absorption spectrum and recombination kinetics of diphenylCarbonyl Oxide
Russian Chemical Bulletin, 2001Co-Authors: S. L. Khursan, A.m. Nazarov, E. M. Chainikova, V.d. KomissarovAbstract:The absorption spectra and rate constants of diphenylCarbonyl Oxide recombination in a series of solvents and their binary mixtures were determined by flash photolysis. An increase in the solvent polarity causes hypsochromic shift of the maximum in the absorption spectrum of Ph_2COO. The analysis of the solvent effect on the recombination rate constant in terms of the four-parameter Koppel—Palm equation shows that the reactivity of Carbonyl Oxide depends on both specific and non-specific solvations. Quantum chemical B3LYP/6-31G(d) calculations of H_2COO and PhHCOO Carbonyl Oxides as well as the complexes of H_2COO with acetonitrile and ethylene in different media were performed using a polarized continuum model.
Yasuki Endo - One of the best experts on this subject based on the ideXlab platform.
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Conformational preferences of Criegee intermediates: Isopropyl substituted Carbonyl Oxide.
The Journal of Chemical Physics, 2018Co-Authors: Carlos Cabezas, Jean-claude Guillemin, Yasuki EndoAbstract:Three conformers of the isopropyl-substituted Criegee intermediate, (CH3)2CHCHOO, have been observed by Fourier transform microwave spectroscopy. The transient species was produced using a pulsed electric discharge of a gas mixture of 1,1-diiodo-2-methylpropane/O2 diluted in Ar or Ne. The use of different carrier gases in the supersonic expansion reveals the difference of the collisional relaxation process between anti-conformers. The conformational relaxation pathways have been investigated theoretically and are presented as well. In light of these results, the previous study on the ethyl-substituted Criegee intermediate, where the absence of one of the four possible conformers was associated with collisional relaxation processes, has been re-examined. Here we report the detection of a new conformer of the ethyl-substituted Criegee intermediate observed using Ne as the seeding gas.Three conformers of the isopropyl-substituted Criegee intermediate, (CH3)2CHCHOO, have been observed by Fourier transform microwave spectroscopy. The transient species was produced using a pulsed electric discharge of a gas mixture of 1,1-diiodo-2-methylpropane/O2 diluted in Ar or Ne. The use of different carrier gases in the supersonic expansion reveals the difference of the collisional relaxation process between anti-conformers. The conformational relaxation pathways have been investigated theoretically and are presented as well. In light of these results, the previous study on the ethyl-substituted Criegee intermediate, where the absence of one of the four possible conformers was associated with collisional relaxation processes, has been re-examined. Here we report the detection of a new conformer of the ethyl-substituted Criegee intermediate observed using Ne as the seeding gas.
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Conformational preferences of Criegee intermediates Isopropyl substituted Carbonyl Oxide
Journal of Chemical Physics, 2018Co-Authors: Carlos Cabezas, Jean-claude Guillemin, Yasuki EndoAbstract:Three conformers of the isopropyl-substituted Criegee intermediate, (CH3)(2) CHCHOO, have been observed by Fourier transform microwave spectroscopy. The transient species was produced using a pulsed electric discharge of a gas mixture of 1,1-diiodo-2-methylpropane/O-2 diluted in Ar or Ne. The use of different carrier gases in the supersonic expansion reveals the difference of the collisional relaxation process between anti-conformers. The conformational relaxation pathways have been investigated theoretically and are presented as well. In light of these results, the previous study on the ethyl-substituted Criegee intermediate, where the absence of one of the four possible conformers was associated with collisional relaxation processes, has been re-examined. Here we report the detection of a new conformer of the ethyl-substituted Criegee intermediate observed using Ne as the seeding gas. Published by AIP Publishing.
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fourier transform microwave spectroscopy of dimethyl substituted criegee intermediate ch3 2coo
Journal of Chemical Physics, 2016Co-Authors: Masakazu Nakajima, Yasuki EndoAbstract:Pure rotational transitions of the dimethyl-substituted Criegee intermediate (dimethyl Carbonyl Oxide, acetone Oxide), (CH3)2COO, were observed in the discharge plasma of a C(CH3)2I2/O2 gas mixture by Fourier-transform microwave spectroscopy. The observed spectra show small splittings due to the internal rotations of the two methyl groups. Precise rotational constants of the molecule and the barrier heights of the methyl internal rotations were experimentally determined.
Miquel Torrentsucarrat - One of the best experts on this subject based on the ideXlab platform.
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effects of the substituents on the reactivity of Carbonyl Oxides a theoretical study on the reaction of substituted Carbonyl Oxides with water
Physical Chemistry Chemical Physics, 2011Co-Authors: Josep M Anglada, J W Gonzalez, Miquel TorrentsucarratAbstract:The reactions between fifteen Carbonyl Oxides and water have been investigated with the aim of contributing to a better understanding of the effects of the substituents in the reactivity of Carbonyl Oxides. We have employed density functional theory and large scale ab initio methods (CCSD(T), CASSCF, and CASPT2), combined with transition state theory, to investigate the addition of water to Carbonyl Oxide and, for those Carbonyl Oxides having a methyl substituent in syn, the hydrogen transfer from the methyl group to the terminal oxygen of Carbonyl Oxide. In this case, the water acts as a catalyst and this reaction can contribute to the atmospheric formation of a hydroxyl radical. Carbonyl Oxides with electron withdrawing substituents and zwitterionic character have low energy barriers and react fast, whereas Carbonyl Oxides with electron releasing substituents have high energy barriers and react slowly. The position of the substituents plays also an important role and Carbonyl Oxides having a hydrogen atom substituent in syn react faster than Carbonyl Oxides having a hydrogen atom substituent in anti. The differences in the reactivity of different substituted Carbonyl Oxides raise up to ten orders of magnitude and the branching ratios for the two different reactions investigated are also reported.
A.m. Nazarov - One of the best experts on this subject based on the ideXlab platform.
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Flash Photolysis of Diphenyldiazomethane in the Presence of Organic Sulfides
High Energy Chemistry, 2002Co-Authors: A.m. Nazarov, S. L. Khursan, P. V. Krupin, A. S. Kanchurin, V.d. KomissarovAbstract:The flash photolysis of diphenyldiazomethane in acetonitrile, benzene, and n -decane solutions saturated with air resulted in the formation of diphenyl Carbonyl Oxide Ph_2COO which decayed in combination reactions. In the presence of organic sulfides, the transfer of the terminal oxygen atom of Ph_2COO to the sulfur atom was observed. The kinetics of this reaction was studied. The absolute rate constants ( k _6, dm^3 mol^–1 s^–1) of the reactions of Ph_2COO with sulfides at 295 K (acetonitrile as a solvent) varied from 4.1 × 10^2 (Me_2S) to 8.1 × 10^4 (Ph_2S). The solvent effect on the reaction kinetics and product composition was studied. The mechanism of the process was discussed.
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Determination of the Absolute Rate Constants of Reactions between Diphenyl Carbonyl Oxide and Alcohols by Flash Photolysis
Kinetics and Catalysis, 2002Co-Authors: A.m. Nazarov, S. L. Khursan, I. A. Kalinichenko, S. Kh. Ziganshina, V.d. KomissarovAbstract:The rate constants of the reactions of diphenyl Carbonyl Oxide Ph_2COO with a number of alcohols and water in acetonitrile, benzene, and n -decane solutions (295 K) were measured by flash photolysis. The rate constants vary over a range from 400 (triphenylmethanol in a MeCN solution) to 2.5 × 10^5 l mol^–1 s^–1 (adamantanol in a benzene solution). α-Methoxydiphenylmethyl hydroperOxide is the reaction product of Ph_2COO and MeOH. The absence of a kinetic isotope effect and the dependence of the logarithms of the rate constants on the first ionization potentials of alcohols are indicative of the formation of a C–O bond at the rate-limiting step of the reaction.
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Kinetics, mechanism, and products of the reaction of diphenylCarbonyl Oxide with carboxylic acids
Russian Chemical Bulletin, 2002Co-Authors: A.m. Nazarov, E. M. Chainikova, S. L. Khursan, V.d. KomissarovAbstract:The kinetics of the reactions of acetic, benzoic, formic, oxalic, malic, tartaric, trifluoroacetic, and hydrochloric acids with diphenylCarbonyl Oxide Ph_2COO was studied. The Carbonyl Oxide Ph_2COO was generated by flash photolysis of diphenyldiazomethane Ph_2CN_2 in solutions of acetonitrile and benzene at 295 K. The apparent rate constants of the reaction range from 4.6·10^8 for (COOH)_2 in MeCN to 7.5·10^9 L mol^–1 s^–1 for acetic acid in a benzene solution. The reaction mechanism was proposed, according to which at the first stage the Carbonyl Oxide is reversibly solvated by the solvent. Then the solvated Carbonyl Oxide reacts with the acid molecule by the mechanism of insertion at the O—H bond.
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The Reactivity of Diphenyl Carbonyl Oxide in Reactions with Alcohols
Kinetics and Catalysis, 2001Co-Authors: A.m. Nazarov, G.a. Yamilova, V.d. KomissarovAbstract:The reactivities of ten alcohols in the reactions with diphenyl Carbonyl Oxide Ph_2COO is characterized by the ratio k ^OH _ 33 / k _31, where k ^OH _ 33 and k _31are the rate constants of Ph_2COO reactions with an alcohol and diphenyldiazomethane PH_2CN_2, respectively. The values of k ^OH _ 33 / k _31range between 0.6 × 10^–2for MeOH to 6.0 for iso -PrOH at 70°C in acetonitrile. The donation of electron density to the alcohol hydroxyl group favors the attack of Ph_2COO; that is, Ph_2COO reacts as an electrophile.
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Solvent effects on the absorption spectrum and recombination kinetics of diphenylCarbonyl Oxide
Russian Chemical Bulletin, 2001Co-Authors: S. L. Khursan, A.m. Nazarov, E. M. Chainikova, V.d. KomissarovAbstract:The absorption spectra and rate constants of diphenylCarbonyl Oxide recombination in a series of solvents and their binary mixtures were determined by flash photolysis. An increase in the solvent polarity causes hypsochromic shift of the maximum in the absorption spectrum of Ph_2COO. The analysis of the solvent effect on the recombination rate constant in terms of the four-parameter Koppel—Palm equation shows that the reactivity of Carbonyl Oxide depends on both specific and non-specific solvations. Quantum chemical B3LYP/6-31G(d) calculations of H_2COO and PhHCOO Carbonyl Oxides as well as the complexes of H_2COO with acetonitrile and ethylene in different media were performed using a polarized continuum model.