Autooxidation of diethyl hydroxylamine

Abstract

The autooxidation of diethy1 hydroxylamine (DEHA) has been studied both in solution and in the gas phase between 0" and 60°C. The results obtained are interpreted in terms of a nonchain free radical mechanism in which reaction (1) (1)is the rate-determining step. This reaction is followed by the reaction of H02 radicals with DEHA to give hydrogen peroxide. The initial stoichiometry is given by 2DEHA + 0 2 -2 nitrone + 2H20 which implies that the hydrogen peroxide reacts with DEHA to give water and diethyl nitroxide radicals.The activation energy of reaction (I) is 16.5 f 2 kcal/moI, leading to a dissociation energy of 69.5 i 2 kcal for the 0-H bond in DEHA.The oxidation of DEHA in the gas phase is nearly ten times slower than that observed in chlorobenzene solution under similar experimental conditions. This result is related to the stabilization of the free radicals produced by the solvent.

Early Steps in the O2 Scavenger Process in the Aqueous Phase: Hydrazine vs DEHA

“…The authors reported an apparent activation energy (E a ) for DEHA in chlorobenzene solutions, ranging from 273 to 330 K, to be 16.5 ± 2.0 kcal mol −1 . 6 Remarkably, this value aligns closely with the estimated E a for hydrazine in the aqueous phase at elevated temperatures (from 380 to 573 K) as reported by Buxton and Stuart, which was 16.7 ± 1.2 kcal mol −1 . 9 Interestingly, these orders of magnitude for E a correspond with the energy barrier estimates for the first proton abstraction step of hydrazine in the gas phase, as recently computed by Asgharzade et al using quantum chemistry methods.…”

“…Regarding DEHA for instance, two different scavenger mechanisms have been reported. The first mechanism, proposed by Cáceres et al is based on a rate-determining step of first-order kinetics that yields the HO 2 • radical The authors reported an apparent activation energy ( E a ) for DEHA in chlorobenzene solutions, ranging from 273 to 330 K, to be 16.5 ± 2.0 kcal mol –1 . Remarkably, this value aligns closely with the estimated E a for hydrazine in the aqueous phase at elevated temperatures (from 380 to 573 K) as reported by Buxton and Stuart, which was 16.7 ± 1.2 kcal mol –1 .…”

“…Due to its widespread usage and its toxicity to all living organisms, including humans, there is a pressing need to explore alternatives to hydrazine as a reducing agent. Several alternatives have been investigated, such as carbohydrazide, erythorbic acid, methylethyl-ketoxime, but the compound that has garnered the most interest is diethylhydroxylamine (DEHA). − …”

“…Regarding DEHA for instance, two different scavenger mechanisms have been reported. The first mechanism, proposed by Caćeres et al 6 is based on a ratedetermining step of first-order kinetics that yields the HO 2…”

Increasing the index of covalent oxygen bonding at nitrogen attached to carbon

“…Oxygen and Peroxides Diethylhydroxylamine (DEHA), because of its rapid reaction with alkyl, alkoxy, or peroxy radicals or with air to produce diethyl nitroxide (446), captured interest for its potential as a combatant of photochemical smog brought about by oxidation of nitrogen oxides in the presence of hydrocarbons (eq 336) . 344,345 (C2H5)!^+ Apparently all hydroxylamines with a free hydroxyl group at nitrogen attached to one or two hydrocarbon groups is subject to air oxidation. Nitroxide formation generally required the absence of hydrogen attached to either nitrogen or the a-carbon atom.3346 Such a hindered hydroxylamine (447) is the precursor to 4,4-dimethyloxazolidine-A/-oxy (doxyl) (448) in a new preparation of the latter in four steps from 4,4-dimethyloxazoline (eq 337) .…”