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A DFT study of permanganate oxidation of toluene and its ortho-nitroderivatives.

Adamczyk P, Wijker RS, Hofstetter TB, Paneth P - J Mol Model (2014)

Bottom Line: Acceptable results have been obtained using IEFPCM/B3LYP/6-31+G(d,p) calculations with zero-point (ZPC) and thermal corrections, as validated by comparison with the experimental data.All favored reactions are characterized by the Gibbs free energy of activation, ΔG(≠), of about 25 kcal mol(-1).Methyl group oxidations are exothermic by about 20 kcal mol(-1) while ring oxidations are around thermoneutrality.

View Article: PubMed Central - PubMed

Affiliation: Institute of Applied Radiation Chemistry, Faculty of Chemistry, Lodz University of Technology, Zeromskiego 116, 90-924, Lodz, Poland.

ABSTRACT
Calculations of alternative oxidation pathways of toluene and its ortho-substituted nitro derivatives by permanganate anion have been performed. The competition between methyl group and ring oxidation has been addressed. Acceptable results have been obtained using IEFPCM/B3LYP/6-31+G(d,p) calculations with zero-point (ZPC) and thermal corrections, as validated by comparison with the experimental data. It has been shown that ring oxidation reactions proceed via relatively early transition states that become quite unsymmetrical for reactions involving ortho-nitrosubstituted derivatives. Transition states for the hydrogen atom abstraction reactions, on the other hand, are late. All favored reactions are characterized by the Gibbs free energy of activation, ΔG(≠), of about 25 kcal mol(-1). Methyl group oxidations are exothermic by about 20 kcal mol(-1) while ring oxidations are around thermoneutrality.

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Transition state structures of methyl group oxidation in modeled oxidation reactions of 2-nitrotoluene and 2,6-dinitrotoluene with permanganate
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Fig4: Transition state structures of methyl group oxidation in modeled oxidation reactions of 2-nitrotoluene and 2,6-dinitrotoluene with permanganate

Mentions: As illustrated in Fig. 4 geometries of the transition states of the methyl group oxidation of the considered nitroderivatives are significantly different. In the case of 2,6-dinitrotoluene the structure is almost symmetric and very similar to the one observed in the corresponding toluene oxidation. In the case of 2-nitrotoluene, however, the permanganate anion is rotated about 90 degrees relative to the Cm-C1 bond. Changes of the dihedral angle Φ throughout the 2,6-dinitrotoluene oxidation molecule are similar to those observed in the case of toluene. In the case of 2-nitrotolune, however, these changes are negligible; the dihedral angle changes from −85° in reactants complex to −94° in the transition state to −81° in the product.Fig. 4


A DFT study of permanganate oxidation of toluene and its ortho-nitroderivatives.

Adamczyk P, Wijker RS, Hofstetter TB, Paneth P - J Mol Model (2014)

Transition state structures of methyl group oxidation in modeled oxidation reactions of 2-nitrotoluene and 2,6-dinitrotoluene with permanganate
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3936135&req=5

Fig4: Transition state structures of methyl group oxidation in modeled oxidation reactions of 2-nitrotoluene and 2,6-dinitrotoluene with permanganate
Mentions: As illustrated in Fig. 4 geometries of the transition states of the methyl group oxidation of the considered nitroderivatives are significantly different. In the case of 2,6-dinitrotoluene the structure is almost symmetric and very similar to the one observed in the corresponding toluene oxidation. In the case of 2-nitrotoluene, however, the permanganate anion is rotated about 90 degrees relative to the Cm-C1 bond. Changes of the dihedral angle Φ throughout the 2,6-dinitrotoluene oxidation molecule are similar to those observed in the case of toluene. In the case of 2-nitrotolune, however, these changes are negligible; the dihedral angle changes from −85° in reactants complex to −94° in the transition state to −81° in the product.Fig. 4

Bottom Line: Acceptable results have been obtained using IEFPCM/B3LYP/6-31+G(d,p) calculations with zero-point (ZPC) and thermal corrections, as validated by comparison with the experimental data.All favored reactions are characterized by the Gibbs free energy of activation, ΔG(≠), of about 25 kcal mol(-1).Methyl group oxidations are exothermic by about 20 kcal mol(-1) while ring oxidations are around thermoneutrality.

View Article: PubMed Central - PubMed

Affiliation: Institute of Applied Radiation Chemistry, Faculty of Chemistry, Lodz University of Technology, Zeromskiego 116, 90-924, Lodz, Poland.

ABSTRACT
Calculations of alternative oxidation pathways of toluene and its ortho-substituted nitro derivatives by permanganate anion have been performed. The competition between methyl group and ring oxidation has been addressed. Acceptable results have been obtained using IEFPCM/B3LYP/6-31+G(d,p) calculations with zero-point (ZPC) and thermal corrections, as validated by comparison with the experimental data. It has been shown that ring oxidation reactions proceed via relatively early transition states that become quite unsymmetrical for reactions involving ortho-nitrosubstituted derivatives. Transition states for the hydrogen atom abstraction reactions, on the other hand, are late. All favored reactions are characterized by the Gibbs free energy of activation, ΔG(≠), of about 25 kcal mol(-1). Methyl group oxidations are exothermic by about 20 kcal mol(-1) while ring oxidations are around thermoneutrality.

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