Radical equilibrium studies; the thermodynamic parameters of n ‐propyl

The azoethane-sensitized thermal reaction of isobutene has been studied at 526-565 K.The initial concentrations of azoethane and isobutene were in the ranges of 1.40-10.5 X and 6.78-26.6 X mol/dm3, respectively. From the initial rates of formation of ethane and 2-methylpentane the heat of formation of the 2-methyl-2-pentyl radical was determined. The result obtained is q(2-methyl-2-pentyl) = 0.8 f 2.0 kcal/mol. The entropy of the radical, obtained from statistical mechanical calculations and experimentally, is S0(2-methyl-2-pentyl) = 92.8 f 1.5 cal/mol-K. The results support the high heat of formation of the t -butyl radical suggested by different authors.

Section: Mation Of Ethane and I-cgh14 Ismentioning

confidence: 99%

“…A useful method to obtain such data for the higher alkyl radicals is radical equilibrium studies [2]. In such studies the heat of formation of the radicals is derived from the experimentally determined equilibrium constant K p of the reaction errors made in the determination of Kp contribute only moderately to the overall error in AHY(R2).…”

Section: Introductionmentioning

confidence: 99%

The azoethane‐initiated thermal reaction of isobutene. Heat of formation of the 2‐methyl‐2‐pentyl radical

Serés¹,

Görgényi²,

Farkaš³

1983

“…Azomethane was prepared in our laboratory using the method previously described [9]. Propane was research grade supplied by Phillips Petroleum Go.…”

Section: Methodsmentioning

confidence: 99%

Photolysis of azomethane–propane mixtures. Arrhenius parameters for the hydrogen abstraction reactions of methyl with azomethane and with propane

Durban

Marshall

1980

Self Cite

Mixtures of up to 14% azcjmethane in propane have been photolyzed using mainly 366 nm radiation in the ranges of 323-453 K and 25-200 torr. Detailed measurements were made of the yields of nitrogen, methane, and ethane. Other products observed were isobutane, n-butane, ethene, and propene. A detailed mechanism is proposed and shown to account for the observed variation of product yields with experimental conditions. The quantum yield of the molecular processis found to be given by the temperature-independent equationThe values of rate constants obtained are log k3(cm3/mol sec) = 12.03 f 0.15 -40.8 f 1.1 kJlmoll(2.3RT) log k4(cm3/mol sec) = 11.42 f 0.15 -40.7 f 1.1 kJlmoll(2.3RT) where the reactions are (3) (4)and it is assumed that the rate constant for the reactionis given by log k5(cm3/mol sec) = 13.4

Radical equilibrium studies. II. The thermodynamic parameters of s−butyl

Marshall

Page

1979

Self Cite

The thermal decomposition of azomethane in the presence of propene has been investigated in the range of 568438°K a t reactant partial pressures of up to about 7 torr in the presence of a t least 170 torr of argon. The elementary reactions taking place in such conditions are discussed in detail. It is shown that a situation approaching equilibrium is attained between the processes (2) s -C~H~ CH3 + C3HsValues are obtained for the equilibrium constant K:!, which can be described by the equation log K:! (atm) = 7.66 -26.1 kcal/mol/(2.3RT) Using the best available thermodynamic parameters for methyl and propene, it is concluded that those for s-butyl are in need of adjustment. We recommend the values (300°K) = 13.8 f 1.0 kcal/mol and Sgm (1 atm standard state) = 75.6 f 3.0 cal/mol-K together with group additivity values of the heat capacity. A comparison of measured values of K:! with values calculated from independent measurements of k:! and k-2 shows a discrepancy of about a factor of 3.5.