Ro-vibrational Spectra of the Simplest Deuterated Criegee Intermediate CD2OO

Criegee intermediates are of signi cance in the atmospheric chemistry.In this work,the rovibrational spectra of the simplest deuterated Criegee intermediate,CD2OO,were studied by a vibrational self-consistent eld/virtual con guration interaction(VSCF/VCI)method based on a nine-dimensional accurate potential energy surface and dipole surface for its ground electronic state.The calculated fundamental vibrational frequencies and rotational constants are in excellent agreement with the available experimental results.These data are useful for further spectroscopic studies of CD2OO.Especially,the rotational constants for excited vibrational levels are essential for experimental spectral assignments.However,the infrared intensities from di erent resources,including the current computation,the experiment,and previous calculations at the NEVPT2 and B3LYP levels,deviate signi cantly.

Multiple evaluations of atmospheric behavior between Criegee intermediates and HCHO: Gas-phase and air-water interface reaction

Given the high abundance of water in the atmosphere,the reaction of Criegee intermediates(CIs)with(H_(2)O)_(2) is considered to be the predominant removal pathway for CIs.However,recent experimental findings reported that the reactions of CIs with organic acids and carbonyls are faster than expected.At the same time,the interface behavior between CIs and carbonyls has not been reported so far.Here,the gas-phase and air-water interface behavior between Criegee intermediates and HCHO were explored by adopting high-level quantum chemical calculations and Born-Oppenheimer molecular dynamics(BOMD)simulations.Quantum chemical calculations evidence that the gas-phase reactions of CIs+HCHO are submerged energy or low energy barriers processes.The rate ratios speculate that the HCHO could be not only a significant tropospheric scavenger of CIs,but also an inhibitor in the oxidizing ability of CIs on SO_(x) in dry and highly polluted areas with abundant HCHO concentration.The reactions of CH_(2)OO with HCHO at the droplet’s surface follow a loop structure mechanism to produce i)SOZ(■),ii)BHMP(HOCH_(2)OOCH_(2)OH),and iii)HMHP(HOCH_(2)OOH).Considering the harsh reaction conditions between CIs and HCHO at the interface(i.e.,the two molecules must be sufficiently close to each other),the hydration of CIs is still their main atmospheric loss pathway.These results could help us get a better interpretation of the underlying CIs-aldehydes chemical processes in the global polluted urban atmospheres.

Reaction mechanism and kinetics of Criegee intermediate and hydroperoxymethyl formate

The reaction mechanism and kinetics of the simplest Criegee intermediate CH_(2)OO reaction with hydroperoxymethyl formate(HPMF)was investigated at high-level quantum chemistry calculations.HPMF has two reactive functional groups,-C(O)OH and-OOH.The calculated results of thermodynamic data and rate constants indicated that the insertion reactions of CH_(2) OO with-OOH group of HPMF were more favorable than the reactions of CH_(2)OO with-C(O)OH group.The calculated overall rate constant was 2.33×10^(−13) cm^(3)/(moleculesec)at 298 K and the rate constants decreased as the temperature increased from 200 to 480 K.In addition,we also proved the polymerization reaction mechanism between CH_(2)OO and-OOH of HPMF.This theoretical study interpreted the previous experimental results,and supplied the structures of the intermediate products that couldn’t be detected during the experiment.

Spectroscopic characterization and photochemistry of the Criegee intermediate CF_(3)C(H)OO

Criegee intermediates(CIs),also known as carbonyl oxide,are reactive intermediates that play an important role in the atmospheric chemistry.Investigation on the structures and reactivity of CIs is of fundamental importance in understanding the underlying mechanism of their atmospheric reactions.In sharp contrast to the intensively studied parent molecule(CH_(2)OO)and the alkyl-substituted derivatives,the knowledge about the fluorinated analogue CF_(3)C(H)OO is scarce.By carefully heating the triplet carbene CF_(3)CH in an O2-doped Ar-matrix to 35 K,the elusive carbonyl oxide CF_(3)C(H)OO in syn-and anti-conformations has been generated and characterized with infrared(IR)and ultraviolet-visible(UV-vis)spectroscopy.The spectroscopic identification is supported by^(18)O-labeling experiments and quantum chemical calculations at the B3 LYP/6-311++G(3df,3pd)and MP2/6-311++G(2d,2p)levels.Upon the long-wavelength irradiation(λ>680 nm),both conformers of CF_(3)C(H)OO decompose to give trifluoroacetaldehyde CF_(3)C(H)O and simultaneously rearrange to the isomeric dioxirane,cyclic-CF_(3)CH(OO),which undergoes isomerization to the lowest-energy carboxylic acid CF_(3)C(O)OH upon UV-light excitation at 365 nm.The O_(2)-oxidation of CF_(3)CH via the intermediacy of CF_(3)C(H)OO and cyclic-CF_(3)CH(OO)might provide new insight into the mechanism for the degradation of hydro-chlorofluorocarbon CF_(3)CHCl_(2)(HCFC-123)in the atmosphere.