Enthalpies of formation of the benzyloxyl, benzylperoxyl, hydroxyphenyl radicals and related species on the potential energy surface for the reaction of toluene with the hydroxyl radical

2019 ◽  
Author(s):  
Oscar Ventura ◽  
Martina Kieninger ◽  
Zoi Salta ◽  
Agnie M. Kosmas ◽  
Vincenzo Barone
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Hydroxyl Radical ◽  
Related Species ◽  
Energy Surface ◽  
Closed Shell ◽  
Experimental Information ◽  
Enthalpies Of Formation ◽  
Isodesmic Reactions ◽  
Benzyl Radical

<p></p><p>The reaction of toluene (T) with OH<sup>●</sup> produces addition products as well as the benzyl radical (TR). TR can react with OH<sup>●</sup> or O<sub>2</sub> to produce oxygenated species, for many of which there is no experimental information available. We present here theoretically determined heats of formation (HFs) of 17 such species using the non-isodesmic reactions on the potential energy surface (PES) of TR+O<sub>2</sub> and T+OH<sup>●</sup>+O<sub>2</sub>. For those species the experimental HFs of which are known, we obtained a good correlation between experimental and theoretical values at the G4 (r<sup>2</sup>=0.999) and M06/cc-pVQZ (r<sup>2</sup>=0.997) levels, thus showing the goodness of the methods used. Previously unknown HFs of other radicals (benzyloxyl, spiro [1,2-dioxetane benzyl], hydroxyphenyl, and benzylperoxyl) and closed shell species (salicylic alcohol, benzo[b]oxetane and p-hydroxy cyclohexa-2,5-dienone) were later determined using those methods.<b></b></p><br><p></p>

scholarly journals Enthalpies of formation of the benzyloxyl, benzylperoxyl, hydroxyphenyl radicals and related species on the potential energy surface for the reaction of toluene with the hydroxyl radical

2019 ◽  
Author(s):  
Oscar Ventura ◽  
Martina Kieninger ◽  
Zoi Salta ◽  
Agnie M. Kosmas ◽  
Vincenzo Barone
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Hydroxyl Radical ◽  
Related Species ◽  
Energy Surface ◽  
Closed Shell ◽  
Experimental Information ◽  
Enthalpies Of Formation ◽  
Isodesmic Reactions ◽  
Benzyl Radical

<p></p><p>The reaction of toluene (T) with OH<sup>●</sup> produces addition products as well as the benzyl radical (TR). TR can react with OH<sup>●</sup> or O<sub>2</sub> to produce oxygenated species, for many of which there is no experimental information available. We present here theoretically determined heats of formation (HFs) of 17 such species using the non-isodesmic reactions on the potential energy surface (PES) of TR+O<sub>2</sub> and T+OH<sup>●</sup>+O<sub>2</sub>. For those species the experimental HFs of which are known, we obtained a good correlation between experimental and theoretical values at the G4 (r<sup>2</sup>=0.999) and M06/cc-pVQZ (r<sup>2</sup>=0.997) levels, thus showing the goodness of the methods used. Previously unknown HFs of other radicals (benzyloxyl, spiro [1,2-dioxetane benzyl], hydroxyphenyl, and benzylperoxyl) and closed shell species (salicylic alcohol, benzo[b]oxetane and p-hydroxy cyclohexa-2,5-dienone) were later determined using those methods.<b></b></p><br><p></p>

Theoretical Determination of Enthalpies of Formation of Benzyloxy, Benzylperoxy, Hydroxyphenyl Radicals and Related Species in the Reaction of Toluene with the Hydroxyl Radical

2018 ◽  
Author(s):  
Oscar Ventura ◽  
Martina Kieninger ◽  
Zoi Salta ◽  
Agnie M. Kosmas
Keyword(s):  
Related Species ◽  
Theoretical Data ◽  
Closed Shell ◽  
Experimental Information ◽  
Enthalpies Of Formation ◽  
Phenyl Radical ◽  
Theoretical Determination ◽  
Isodesmic Reactions ◽  
Benzyl Radical

<p>Reaction of toluene (T) with HO<sup>●</sup> produces addition products and the benzyl radical (TR). TR can react with HO<sup>●</sup> or O<sub>2</sub> to produce oxygenated species, for many of which there is no experimental information. We present here theoretically determined heats of formation (HFs) of 17 such species using non-isodesmic reactions of TR+O<sub>2</sub> and T+HO<sup>●</sup>+O<sub>2</sub>. For experimentally known HFs, we obtained a reasonable correlation between experimental and theoretical data for G4 (r2=0.999) and M06/cc-pVQZ (r2=0.997) results. Previously unknown HFs of other radicals (benzyloxy, spiro [1,2-dioxetane benzyl], hydroxyphenyl, and benzylperoxy) and closed shell species (salicylic alcohol, benzo[b]oxetane and p-hydroxy cyclohexa-2,5-dienone) were calculated using these methods. The species studied and the enthalpies of formation obtained were: salycilic alcohol, -69.7 ± 3.4 kcal/mol; benzyloxy radical, 28.4 ± 3.4 kcal/mol; hydroxyphenyl radical, 37.3 ± 3.4 kcal/mol; benzo[b]oxetane, 23.7 ± 3.4 kcal/mol; spiro [1,2-oxoetane phenyl] radical, 57.3 ± 3.4 kcal/mol; p-hydroxy cyclohexan-2,5-dienone, -42.1 ± 3.4 kcal/mol; and benzylperoxy radical, 28.5 ± 3.2 kcal/mol.</p>

scholarly journals Isomerization and Fragmentation Reactions on the [C2SH4] Potential Energy Surface. The Metastable Thione-S-Methylide Isomer

2020 ◽  
Author(s):  
Zoi Salta ◽  
Marc E. Segovia ◽  
Aline Katz ◽  
Nicola Tasinato ◽  
Vincenzo Barone ◽  
...  
Keyword(s):  
Potential Energy ◽  
Transition State ◽  
Potential Energy Surface ◽  
Density Functional ◽  
Energy Surface ◽  
Computational Study ◽  
Experimental Information ◽  
Reaction Scheme ◽  
Ring Closure ◽  
Complete Analysis

Thione S-methylide (TSM), the parent species of the thiocarbonyl ylide family, is a 1,3-dipolar, planar species on the [C2SH4] potential energy surface (PES), which has not shared the richness of studies dedicated to its isomers, the cyclic thiirane (THI), and the keto-enol pair vinyl thiol (VTH)/thioacetaldehyde (THA). While the conrotatory ring closure reaction toward THI was studied in the ‘90s, no complete analysis of the PES is available in the literature. In the present paper, we report a computational study of the reaction scheme linking all species on that PES. We employ several levels of calculation, ranging from density functional theory (DFT), through CCSD(T) based composite schemes, to CASSCF/CASPT2 multi-reference procedures, to find the best description of TSM, its isomers, and the transition states (TSs) ruling their interconversion. Fragmentation of TSM, THA and THI were investigated and compared to the available experimental information. We found that the B2PLYP-D3 functional, contrary to M06-2XD3 or B97X-D, describes well the geometry of both TSM and the transition state connecting it to THI. The reverse barrier, from THI to TSM, amounts to 52.2 kcal mol-1 (to be compared to 17.6 kcal mol-1 for the direct one), thus explaining why, in general, thiocarbonyl ylides cannot be prepared from thiiranes. Conversion of THI to VTH implies also a large barrier, explaining why the reaction has been observed only at high temperatures. The fragmentation of THI to S(3P) or S(1D) and ethylene was also explored, together with the decomposition to H2S plus acetylene. Open species, both in triplet and singlet states, were identified as intermediates in the fragmentations, and their energies were found to be lower than the transition state for the isomerization of THI to VTH, thus explaining the preference for fragmentation over isomerization at relatively low temperatures.

scholarly journals Isomerization and Fragmentation Reactions on the [C2SH4] Potential Energy Surface. The Metastable Thione-S-Methylide Isomer

2020 ◽  
Author(s):  
Zoi Salta ◽  
Marc E. Segovia ◽  
Aline Katz ◽  
Nicola Tasinato ◽  
Vincenzo Barone ◽  
...  
Keyword(s):  
Potential Energy ◽  
Transition State ◽  
Potential Energy Surface ◽  
Density Functional ◽  
Energy Surface ◽  
Computational Study ◽  
Experimental Information ◽  
Reaction Scheme ◽  
Ring Closure ◽  
Complete Analysis

Thione S-methylide (TSM), the parent species of the thiocarbonyl ylide family, is a 1,3-dipolar, planar species on the [C2SH4] potential energy surface (PES), which has not shared the richness of studies dedicated to its isomers, the cyclic thiirane (THI), and the keto-enol pair vinyl thiol (VTH)/thioacetaldehyde (THA). While the conrotatory ring closure reaction toward THI was studied in the ‘90s, no complete analysis of the PES is available in the literature. In the present paper, we report a computational study of the reaction scheme linking all species on that PES. We employ several levels of calculation, ranging from density functional theory (DFT), through CCSD(T) based composite schemes, to CASSCF/CASPT2 multi-reference procedures, to find the best description of TSM, its isomers, and the transition states (TSs) ruling their interconversion. Fragmentation of TSM, THA and THI were investigated and compared to the available experimental information. We found that the B2PLYP-D3 functional, contrary to M06-2XD3 or B97X-D, describes well the geometry of both TSM and the transition state connecting it to THI. The reverse barrier, from THI to TSM, amounts to 52.2 kcal mol-1 (to be compared to 17.6 kcal mol-1 for the direct one), thus explaining why, in general, thiocarbonyl ylides cannot be prepared from thiiranes. Conversion of THI to VTH implies also a large barrier, explaining why the reaction has been observed only at high temperatures. The fragmentation of THI to S(3P) or S(1D) and ethylene was also explored, together with the decomposition to H2S plus acetylene. Open species, both in triplet and singlet states, were identified as intermediates in the fragmentations, and their energies were found to be lower than the transition state for the isomerization of THI to VTH, thus explaining the preference for fragmentation over isomerization at relatively low temperatures.

Sign in / Sign up

Export Citation Format

Share Document