The carbonyl fluoride (CF2O) is one of the significant atmospheric molecules, and its hydrolysis reaction has been considered the most potential removal process in the earth's troposphere. In this ...article, the hydrolysis reaction of CF2O assisted by H2O, basic (NH3 and CH3NHCH3), and acidic (H2SO4, HCOOH, and CF3COOH) catalysts have theoretically investigated using quantum chemical methods. These catalysts significantly decrease the hydrolysis reaction of barrier height by 20.4–28.8 kcal mol−1. Here two H‐transfer mechanisms have been identified in these catalyzed hydrolytic reactions as asynchronous collaborative caused by base molecules and the synchronous collaborative led by H2O and acid molecules. In addition, the rate coefficient and relative rate of all catalytic reactions have calculated using conventional transition state theory (TST) over a temperature range of 280–320 K. The results show that H2SO4 has the best catalytic effect without considering the concentration of catalyst molecules in the atmosphere. On the contrary, a high concentration of HCOOH (10 ppbv) is dominant in the catalytic reaction when considered the concentrations of catalyst molecules. In this work, it was identified that the catalytic efficiencies of H2O, acid and base molecules upon addition reaction between CF2O and H2O is not only related to their catalytic mechanisms but also depending upon their concentrations in the atmosphere.
This is the first detailed theoretical work on the kinetics and mechanism of the gas‐phase hydrolysis reaction of CF2O assisted by base and acid molecules. The mechanisms of the catalytic reaction of the two most important synchronous and asynchronous collaborative have also been explored and reported for the first time. The present results will provide a specific example of how the hydrolysis of CF2O assisted by H2O, base and acid occurs by two different mechanisms.
Abstract
The carbonyl fluoride (CF
2
O) is one of the significant atmospheric molecules, and its hydrolysis reaction has been considered the most potential removal process in the earth's troposphere. ...In this article, the hydrolysis reaction of CF
2
O assisted by H
2
O, basic (NH
3
and CH
3
NHCH
3
), and acidic (H
2
SO
4
, HCOOH, and CF
3
COOH) catalysts have theoretically investigated using quantum chemical methods. These catalysts significantly decrease the hydrolysis reaction of barrier height by 20.4–28.8 kcal mol
−1
. Here two H‐transfer mechanisms have been identified in these catalyzed hydrolytic reactions as asynchronous collaborative caused by base molecules and the synchronous collaborative led by H
2
O and acid molecules. In addition, the rate coefficient and relative rate of all catalytic reactions have calculated using conventional transition state theory (TST) over a temperature range of 280–320 K. The results show that H
2
SO
4
has the best catalytic effect without considering the concentration of catalyst molecules in the atmosphere. On the contrary, a high concentration of HCOOH (10 ppbv) is dominant in the catalytic reaction when considered the concentrations of catalyst molecules. In this work, it was identified that the catalytic efficiencies of H
2
O, acid and base molecules upon addition reaction between CF
2
O and H
2
O is not only related to their catalytic mechanisms but also depending upon their concentrations in the atmosphere.
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•The cycloaddition of CH2OO to CO bond of CH2 = C(CH3)CHO is the favorable pathway.•Compared to the saturated system CH2OO + CH3CH(CH3)CHO, the title system shows a lowering of ...reactivity.•The overall rate constant is increasing as the temperature decrease over the range 200–400 K.•The final dominant decomposition products are methacrylic acid, formaldehyde, formic acid, and methacrolein.
The comprehensive mechanism and kinetics for CH2OO with methacrolein (CH2 = C(CH3)CHO, MACR) reaction were investigated at the CCSD(T)/6-311+G(2df,2p)//M06-2X/6-311+G(2df,2p) level of theory. The results show that three kinds of mechanisms including cycloaddition, oxidation and insertion have been identified. Among them, the cycloaddition of CH2OO adding to CO bond of MACR is more favorable, which occurs via a deeply submerged barrier leading to the formation of energized secondary ozonide (SOZ). The nascent SOZ mainly further decomposes into methacrylic acid and formaldehyde or formic acid and methacrolein, in which formic acid generation follows stepwise and concerted mechanism involving a catalysis for rearrangement of CH2OO by methacrolein. The calculated rate constant for the title reaction at 300 K using canonical variational transition state theory with small curvature tunneling correction is 1.00 × 10−12 cm3 molecule−1 s−1, which is close to the experimental value of (4.4 ± 1.0) × 10−13 cm3 molecule−1 s−1. The results reveal that the reaction provides a new pathway to produce organic acids. However, the contribution of acids from this reaction is small as its relative lower rate, compared to atmospheric CH2OO loss occurring through the hydrolysis of CH2OO + (H2O)n (n = 1–2).
The addition reaction of CH
2
OO + H
2
O → CH
2
(OH)OOH without and with X (X = H
2
CO
3
, CH
3
COOH and HCOOH) and H
2
O 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 CH
2
OO + H
2
O → CH
2
(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 CH
2
OO···H
2
O is favourable one. Water-assisted CH
2
OO + H
2
O → CH
2
(OH)OOH can occur by H
2
O moiety of (H
2
O)
2
or the whole (H
2
O)
2
forming cyclic structure with CH
2
OO, where the latter form is more favourable. Because the concentration of H
2
CO
3
is unknown, the influence of CH
3
COOH, HCOOH and H
2
O were calculated within 0-30 km altitude of the Earth's atmosphere. The results calculated within 0-5 km altitude show that H
2
O 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 CH
2
OO + HCOOH, the rate of CH
2
OO···H
2
O + HCOOH is much slower.
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•A catalytic effect of H2O and NH3 on the HO + NH3 reaction has been investigated.•Both H2O and NH3 can substantially reduce the energy barriers of the reaction.•The catalytic effect ...of H2O is more obvious than NH3.
A comprehensive investigation of the roles of H2O and NH3 on the HO + NH3 → NH2 + H2O reaction in the troposphere has been carried out by CCSD(T)-F12a/cc-pVDZ-F12//M06-2X/6–311+G(2d,2p) method, and the canonical variational transition state theory with small curvature tunneling correction. The results show that both H2O and NH3 catalyzed reactions prefer the single hydrogen atom transfers (HAT) pathways than the double HAT routes. Meanwhile, the catalytic effect of H2O is more obvious as compared with NH3 with its effective rate constant (k'(WM)) larger by 2–5 orders of magnitude. However, within the temperature range of 213–320 K, the calculated value of k'(WM) is smaller by 5–9 orders of magnitude than the corresponding rate constant of the naked reaction. This result is in agreement with H2O catalyzed OH + CH2CH2, OH + CH2O and OH + CH2NH reactions, where water-assisted reaction cannot accelerate the reaction.
The H2O2 + HO → HO2 + H2O reaction is an important reservoir for both radicals of HO and HO2 catalyzing the destruction of O3. Here, this reaction assisted by NH3 and HCOOH catalysts was explored ...using the CCSD(T)-F12a/cc-pVDZ-F12//M06-2X/aug-cc-pVTZ method and canonical variational transition state theory with small curvature tunneling. Two possible sets of mechanisms, (i) one-step routes and (ii) stepwise processes, are possible. Our results show that in the presence of both NH3 and HCOOH catalysts under relevant atmospheric temperature, mechanism (i) is favored both energetically and kinetically than the corresponding mechanism (ii). At 298 K, the relative rate for mechanism (i) in the presence of NH3 (10, 2900 ppbv) and HCOOH (10 ppbv) is respectively 3–5 and 2–4 orders of magnitude lower than that of the water-catalyzed reaction. This is due to a comparatively lower concentration of NH3 and HCOOH than H2O which indicates the positive water effect under atmospheric conditions. Although NH3 and HCOOH catalysts play a negligible role in the reservoir for both radicals of HO and HO2 catalyzing the destruction of O3, the current study provides a comprehensive example of how acidic and basic catalysts assisted the gas-phase reactions.
The H
O
+ HO → HO
+ H
O reaction is an important reservoir for both radicals of HO and HO
catalyzing the destruction of O
. Here, this reaction assisted by NH
and HCOOH catalysts was explored using ...the CCSD(T)-F12a/cc-pVDZ-F12//M06-2X/aug-cc-pVTZ method and canonical variational transition state theory with small curvature tunneling. Two possible sets of mechanisms, (i) one-step routes and (ii) stepwise processes, are possible. Our results show that in the presence of both NH
and HCOOH catalysts under relevant atmospheric temperature, mechanism (i) is favored both energetically and kinetically than the corresponding mechanism (ii). At 298 K, the relative rate for mechanism (i) in the presence of NH
(10, 2900 ppbv) and HCOOH (10 ppbv) is respectively 3-5 and 2-4 orders of magnitude lower than that of the water-catalyzed reaction. This is due to a comparatively lower concentration of NH
and HCOOH than H
O which indicates the positive water effect under atmospheric conditions. Although NH
and HCOOH catalysts play a negligible role in the reservoir for both radicals of HO and HO
catalyzing the destruction of O
, the current study provides a comprehensive example of how acidic and basic catalysts assisted the gas-phase reactions.
Piezoelectric energy harvesters have been studied extensively because they show considerable promise for use in both military and commercial applications. In order to improve the output capability of ...the piezoelectric energy harvester, the perforated piezoelectric cantilevers were designed in this work. To study how the hole on the cantilever affected the output characteristics, this paper analysed the position and size of the hole separately. The results show that, perforating the cantilever can cause stress concentration of the piezoelectric cantilever, and improve the output capacity.
The H
2
O
2
+ HO → HO
2
+ H
2
O reaction is an important reservoir for both radicals of HO and HO
2
catalyzing the destruction of O
3
. Here, this reaction assisted by NH
3
and HCOOH catalysts was ...explored using the CCSD(T)-F12a/cc-pVDZ-F12//M06-2X/aug-cc-pVTZ method and canonical variational transition state theory with small curvature tunneling. Two possible sets of mechanisms, (i) one-step routes and (ii) stepwise processes, are possible. Our results show that in the presence of both NH
3
and HCOOH catalysts under relevant atmospheric temperature, mechanism (i) is favored both energetically and kinetically than the corresponding mechanism (ii). At 298 K, the relative rate for mechanism (i) in the presence of NH
3
(10, 2900 ppbv) and HCOOH (10 ppbv) is respectively 3-5 and 2-4 orders of magnitude lower than that of the water-catalyzed reaction. This is due to a comparatively lower concentration of NH
3
and HCOOH than H
2
O which indicates the positive water effect under atmospheric conditions. Although NH
3
and HCOOH catalysts play a negligible role in the reservoir for both radicals of HO and HO
2
catalyzing the destruction of O
3
, the current study provides a comprehensive example of how acidic and basic catalysts assisted the gas-phase reactions.
The H
2
O
2
+ HO → HO
2
+ H
2
O reaction is an important reservoir for both radicals of HO and HO
2
catalyzing the destruction of O
3
.
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