The catalytic effects of H₂CO₃, CH₃COOH, HCOOH and H₂O on the addition reaction of CH₂OO + H₂O → CH₂(OH)OOH

<p>The addition reaction of CH₂OO + H₂O <b>→</b> CH₂(OH)OOH without and with X (X = H₂CO₃, CH₃COOH and HCOOH) and H₂O was studied at CCSD(T)/6-311+ G(3df,2dp)//B3LYP/6-311+G(2d,2p) level of theory. Our results show that X can catalyse CH₂OO + H₂O → CH₂(OH)OOH reaction both by increasing the number of rings, and by adding the size of the ring in which ring enlargement by COOH moiety of X inserting into CH₂OO···H₂O is favourable one. Water-assisted CH₂OO + H₂O → CH₂(OH)OOH can occur by H₂O moiety of (H₂O)₂ or the whole (H₂O)₂ forming cyclic structure with CH₂OO, where the latter form is more favourable. Because the concentration of H₂CO₃ is unknown, the influence of CH₃COOH, HCOOH and H₂O were calculated within 0–30 km altitude of the Earth's atmosphere. The results calculated within 0–5 km altitude show that H₂O and HCOOH have obvious effect on enhancing the rate with the enhancement factors are, respectively, 62.47%–77.26% and 0.04%–1.76%. Within 5–30 km altitude, HCOOH has obvious effect on enhancing the title rate with the enhancement factor of 2.69%–98.28%. However, compared with the reaction of CH₂OO + HCOOH, the rate of CH₂OO···H₂O + HCOOH is much slower.</p

Computational study of the decomposition mechanisms of ammonium dinitramide in the gas phase

<p>CBS-QB3 method has been employed to determine the geometries, the vibrational frequencies of the reactants, the products and the transition states involved in intramolecular hydrogen-transfer and decomposition reactions of the free gas-phase H₃N···HN(NO₂)₂ (ADN^*). The results show that the intramolecular hydrogen-transfer reaction of ADN^* is more feasible than that of HDN. ADN^* and its hydrogen-transfer isomers ADN^*-IIa,b,c decompose along four channels to form NH₃ + HONO + 2NO (P_I), ȮH + ṄO₃ + N₂ + NH₃ (P_II), ȮH + ṄO₂ + N₂O + NH₃ (P_III), and HNO₃ + N₂O + NH₃ (P_IV), respectively. It has been found that the dominant decomposition channels are P_I and P_III. The hydrogen-transfer reaction can reduce the barrier of elimination of NO₂ and forming N₂O reactions in ADN^* and HDN. The decomposition of ADN^*-IIc to form NO₂ and N₂O is more feasible than that of the gas-phase HDN. The rate constants (<i>k</i>) of rate-determining step of ADN^* show that <i>k</i>_PI and <i>k</i>_PIII are higher than <i>k</i>_PIV and <i>k</i>_PII. Compared with HDN-IIc → N₂O+ȮH+ṄO₂, <i>k</i>_PIII of ADN^*-IIc is significantly higher than that of <i>k</i>^HDN-IIc. These results reveal that NH₃ (as a chaperon) has a certain influence on the decomposition mechanisms and kinetics of ADN^*.</p