ChemInform Abstract: AN ESTIMATE OF THE STABILIZATION ENERGY OF THE BENZYL RADICAL VIA HF(+) INFRARED CHEMILUMINESCENCE FROM C6H5CH3+F - HF(+)+C6H5CH2.

This work reports density functional and composite model chemistry calculations performed on the reactions of toluene with the hydroxyl radical. Both experimentally observed H-abstraction from the methyl group and possible additions to the phenyl ring were investigated. Reaction enthalpies and heights of the barriers suggest that H-abstraction is more favorable than ●OH addition to the ring. The calculated reaction rates at room temperature and the radical-intermediate product fractions support this view. This is somehow contradictory with the fact that, under most experimental conditions, cresols are observed in a larger concentration than benzaldehyde. Since the accepted mechanism for benzaldehyde formation involves H-abstraction, a contradiction arises that begs for an explanation. In this first part of our work we give the evidences that support the preference of hydrogen abstraction over ●OH addition and suggest an alternative mechanism which shows that cresols can actually arise also from the former reaction and not only from the latter.

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A Reinvestigation of the Deceptively Simple Reaction of Toluene with ●OH, and the Fate of the Benzyl Radical. I. a Combined Thermodynamic and Kinetic Study on the Competition Between ●OH Addition and Hydrogen Abstraction Reactions.

10.26434/chemrxiv.8281283 ◽

2019 ◽

Author(s):

Zoi Salta ◽

Agnie M. Kosmas ◽

Marc E. Segovia ◽

Martina Kieninger ◽

Oscar Ventura ◽

...

Keyword(s):

Density Functional ◽

Room Temperature ◽

Hydrogen Abstraction ◽

Reaction Rates ◽

Composite Model ◽

Alternative Mechanism ◽

Radical Intermediate ◽

Experimental Conditions ◽

Methyl Group ◽

Benzyl Radical

This work reports density functional and composite model chemistry calculations performed on the reactions of toluene with the hydroxyl radical. Both experimentally observed H-abstraction from the methyl group and possible additions to the phenyl ring were investigated. Reaction enthalpies and heights of the barriers suggest that H-abstraction is more favorable than ●OH addition to the ring. The calculated reaction rates at room temperature and the radical-intermediate product fractions support this view. This is somehow contradictory with the fact that, under most experimental conditions, cresols are observed in a larger concentration than benzaldehyde. Since the accepted mechanism for benzaldehyde formation involves H-abstraction, a contradiction arises that begs for an explanation. In this first part of our work we give the evidences that support the preference of hydrogen abstraction over ●OH addition and suggest an alternative mechanism which shows that cresols can actually arise also from the former reaction and not only from the latter.

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Properties and Reactivity of First and Second Row Hydrides. IV. Interactions Between Hydrides and Their Radical Ions

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19930001 ◽

1993 ◽

Vol 58 (1) ◽

pp. 1-10 ◽

Cited By ~ 1

Author(s):

Rudolf Zahradník

Keyword(s):

Radical Cations ◽

Stabilization Energy ◽

Hydrogen Atom Abstraction ◽

Type Ii ◽

Radical Ions ◽

Reaction Products ◽

Ion Molecule Reactions ◽

Heats Of Reaction ◽

Experimental Values ◽

Easy Differentiation

The energies and heats of ion-molecule reactions have been calculated (MP4/6-31G**//6-31G** or better level) and compared with the experimental values obtained from the heats of formation. Two main types of reactions have been studied: (i) AHn + AHn+• ↔ AHn+1+ + AHn-1• (A = C to F and Si to Cl), (ii) AHn + BHm+• ↔ AHn+1+ + BHm-1• or AHn-1+• + BHm+1+ (A and B = C to F). In contrast to (i), processes of type (ii) permit easy differentiation between the proton transfer and hydrogen atom abstraction mechanisms. A third type of interaction involves reactions with radical anions (A = Li to F); comparison was made with analogous processes with radical cations. A brief comment is made about the influence of the level of computational sophistication on the energies and heats of reaction, as well as on the stabilization energy of a hydrogen bonded intermediate, a structure which is similar to that of the reaction products.

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