Ethyl nitrate activation energy

Siddall and his co-workers (46) have examined the barriers to rotation of a series of 2,6-disubstituted anilides. Af-Ethyl-A/-(2,6-xylyl)formamide (9) was recrystallized as a uranyl nitrate complex, and one isomer, which at equilibrium was favored by a factor of 3 1, was enriched up to a 30 1 ratio. The kinetics of rotation were examined at 0 to 29°C. The Arrhenius activation energy was 26 3 kcal/mol and log A was 18.5 2.4 hr-1. Siddall and Gamer (47) were able to obtain an almost pure isomer (which also predominated at equilibrium 1.3 1 for the ethyl compound and 1.1 1 for the methyl compound) of Ar-alkyl- V-(2-methyl-4,6-dibromophenyl)-l-naphthamide (10). The half-lives of... 

Using their own data on the decomposition of ethyl nitrate between 180 and 215°C under pressures of 30-50 mm Hg, Adams and Bawn [17] have calculated the activation energy E and the constant B ... 

The first step in the pyrolysis of the alkyl nitrates has been supposed to be O N bond fission to give NO2 and an alkoxy radical. The activation energy is 39-5 kcal for methyl nitrate and 39-9 or 34-6 kcaP <> for ethyl nitrate. If the latter value for ethyl nitrate is taken, and assumed to be i)(EtO -NO2) a value for the heat of formation of the ethoxy radical in good agreement with that given by Rebbert and Laidler is obtained, so apparently we may put D(MeO -NO2) =40 kcal, and i)(EtO -NO2) =34 kcal. In the opinion of the present author, however, the mechanism of the reaction is not sufficiently well established to allow this to be done. The discrepancy between the result of Adams and Bawn and that of Phillips 390 is large and may well be because of the different pressure ranges in which these authors worked. A further examination of the effect of pressure on rate constant is necessary before it can be taken as established that the reaction is of the first order. 

Most of the ethyl nitrate decomposes in the high temperature region (740—800 °K) of the flame where it is believed that unimolecular thermal decomposition [129] is the rate controlling process. The rate equation given above corresponds to a unimolecular reaction in its low-pressure region and the pre-exponential term suggests that the activation energy is distributed over about 10 square terms. 

It has been observed that the activation energy for thermal decomposition of ethyl nitrate is substantially reduced in the presence of lead oxide or copper surfaces. Above 200° C approximately, the thermolysis of ethyl nitrate becomes much more complex and detonation in the gas phase is common. In the range 242-260° C the reaction was found to be half-order, with an overall rate coefficient" k = 10 - exp(—46,800)/J 7 mmole. l . sec apparently the initiation step is unaltered but the subsequent radical chain mechanism affects the overall rate of decomposition. 

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