The Thermodynamics of Bromination of Toluene and the Heat of Formation of the Benzyl Radical

Benson, Sidney W.; Buss, Jerry H.

doi:10.1021/j150547a023

Cited by 26 publications

(14 citation statements)

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“…Next we needed the standard entropy of the molecule in the gas phase. This was estimated by Benson's bond and group additivity schemes (14,15) [N(C),]). These two estimates were in good agreement.…”

Section: = X[hcon(me)ph (1) + 2meoh (L)]mentioning

confidence: 99%

The tetrahedral intermediate from the hydration of N-methylformanilide

Guthrie¹,

Barker²,

Cullimore³

et al. 1993

Can. J. Chem.

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. Can. J. Chem. 71, 2109Chem. 71, (1993.Heats of hydrolysis of N-methylformanilide dimethyl acetal have been measured in basic solution. The heat of formation of N-methylformanilide was obtained by determining the equilibrium constant in aqueous solution for its formation from formic acid and N-methylaniline as a function of temperature: m : (~) = -33.78 * 1.85 kcal/mol. These data permit the calculation of the heat of formation of N-methylfonnanilide dimethyl acetal, AH;(l) = -72.95 * 1.85 kcal/mol. The free energy of formation of the tetrahedral intermediate in the hydrolysis of N-methylformanilide was calculated by methods we have previously reported. Consideration of the energetics of the intermediates and the known rates of reaction leads to the conclusion that the rate-determining step for alkaline hydrolysis is cleavage of the C-N bond. Operant en solution basique, on a mesurC les chaleurs d'hydrolyse l'acktal dimkthylique de la N-mCthylformanilide. On a obtenu la chaleur de formation de la N-mCthylformanilide en determinant la constante d'kquilibre en fonction de la temperature (en solution aqueuse) pour sa formation 2 partir de l'acide formique et la N-methylaniline: m;(1) = -33,78 * 1,85 kcal/mol. Ces donnCes permettent de calculer la chaleur de formation de I'acCtal dimkthylique de la N-mCthylformanilide, mY(1) = -72,95 * 1,85 kcal/mol. Utilisant des methodes dkcrites anterieurement, on a calculC 1'Cnergie libre de formation de I'intermCdiaire tCtraCdrique implique dans l'hydrolyse de la N-mCthylformanilide. Une considCration des energies des intermediaires et des constantes de vitesse connues mkne i la conclusion que 1'Ctape qui dktermine la vitesse de la reaction de l'hydrolyse alcaline est le clivage de la liaison C-N.[Traduit par la redaction]

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Section: = X[hcon(me)ph (1) + 2meoh (L)]mentioning

confidence: 99%

The tetrahedral intermediate from the hydration of N-methylformanilide

Guthrie¹,

Barker²,

Cullimore³

et al. 1993

Can. J. Chem.

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“…Their value k3a = 7.6 X lo6 I/mol.sec, which was derived from the experimental value of k-sa and a calculated value of the equilibrium constant Kes,, showed that reactions (3) and (4) were not important in their system. These reactions, the mechanism of Benson and Buss [7], had been shown to predominate at pressures near 130 P a by Clyne and Coxon [B] who measured ksa = 1.4 X 107 l/mol-sec.…”

Section: Basco and H U N Tmentioning

confidence: 99%

Mutual combination of ClO radicals

Basco

Hunt

1979

Int J of Chemical Kinetics

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The mutual combination reactionis proposed as the rate-limiting step in the removal of C10 radicals a t moderate pressures. The third-order rate constants measured a t room temperature were kl(Ar) = 3.51 f 0.14 X lo9 lz/mo12.sec, kl(He) = 2.8 X lo9 l2/molZ.sec, and k l ( O 2 ) 0 7.9 X lo9 12/mo12-sec. There is also an independent second-order reaction2C10 -products for which hs = 8 X lo6 I/mol.sec. A new absorption spectrum has been observed in the ultraviolet and attributed to ClzOz. The extinction coefficient for C1202 has been measured a t six wavelengths, and, between 292 and 232 nm, it increases from 0.4 X lo3 to 2.9 X lo3 1/ mol-cm. In the presence of the chlorine atom scavengers OClO or ClzO, ClzOz exists in equilibrium with C10. The equilibrium constant Kel = 3.1 f 0.1 X lo6 l/mol a t 298 K, and, with AS? estimated to be -133 f 11 J/K-mol, AH: = -69 f 3 kJ/mol and AHP(Clz0z) = 136 f 3 kJ/mol.

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“…Benson & Buss (14,29) have surveyed recently all the values derived for dHf(!2)CH2). Their paper is disappointing and confuses the issue.…”

Section: Similarly It Has Been Postulated (158) That Reactions Betwementioning

confidence: 99%

“…In our opinion the problem of D(�CH2-H) needs further independent verification. It seems probable that D(0CH2-Br)�50 kcal./mole, and D(�CH2-H) would ap pear to be ",83 kcal./mole.Although the assumptions underlying the toluene-carrier technique have been questioned by some workers(14,158), we believe that the technique, if properly used, is suitable for the determination of bond dissociation energies. A strong argument in favour of this technique is the good correlation between values obtained by this method and by other techniques.…”

mentioning

confidence: 94%