Theoretical study on the mechanism of the N2H4 plus O2 reaction on the singlet and triplet potential energy surfaces

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

“…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 . 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 . Depending on the level of theory employed, the energy barrier ranges from 24 to 30 kcal mol –1 when considering O 2 in its most stable triplet state.…”

“…In a chain mechanism, the experimental apparent activation energy E a is generally a weighted average of the standard state enthalpies of all the intermediate, transition state, and product entities involved in the reaction mechanism. , Assuming that the first proton abstraction reaction is the rate-determining step of the hydrazine and DEHA O 2 scavenger process in solution, the overall agreement between our activation energies Ẽ a and the experimental estimates suggests that the subsequent chain steps are rapid and lead to intermediate stable compounds that possess similar stability as the initial reactants. That hypothesis is supported by the quantum chemistry data presented by Asgharzade et al, which show that the most stable forms of the reactants and of the intermediate states of the hydrazine/O 2 reaction in the gas phase [resulting in the HNNH and H 2 N 2 (OH) 2 compounds] exhibit nearly isoenergetic behavior within a few 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. 10 Depending on the level of theory employed, the energy barrier ranges from 24 to 30 kcal mol −1 when considering O 2 in its most stable triplet state. Jappinen et al 5 recently adopted the aforementioned firstorder rate-limiting mechanism to interpret high-temperature kinetic data regarding the O 2 scavenger process of hydrazine, DEHA, and erythorbic acid in a recirculation water loop of a pressurized water reactor (PWR).…”

The atmospheric relevance of primary alcohols and imidogen reactions

“…Therefore, hydroxyl radicals as a key atmospheric scavenger are the main sink for alcohols in the air. Also, it has been proved that other species such as HO 2 72 – 75 , O 76 – 81 , O 2 82 – 84 , O 3 85 – 88 , N 89 , 90 , H 91 – 93 , F 94 – 98 , Cl 95 , 99 – 102 , NH 103 – 106 , NH 2 107 , 108 , NO 109 , 110 , H 2 O 111 , 112 , NO 2 109 , 113 , 114 , NO 3 109 , 115 – 118 , CH 3 72 , 119 , 120 and Criegee intermediates 121 , 122 have good contributions in eliminating atmospheric pollutants. Therefore, we must remember this point in mind that the role of other oxidants like NH can not be ignored because, in the absence of hydroxyl radicals, the principal task of these species is the elimination of pollutants from the air of living environments.…”