Mechanistic and kinetic study on the ozonolysis of n-butyl vinyl ether, i-butyl vinyl ether and t-butyl vinyl ether

Ozonolysis of ketoprofen in polluted water: Reaction pathways, kinetics, removal efficiency, and health effects

Ketoprofen (KET), as a non-steroidal anti-inflammatory drug frequently detected in aqueous environments, is a threat to human health due to its accumulation and low biodegradability, which requires the transformation and degradation of KET in aqueous environments. In this paper, the reaction process of ozone-initiated KET degradation in water was investigated using density functional theory (DFT) method at the M06-2X/6-311++g(3df,2p)//M06-2X/6-31+g(d,p) level. The detailed reaction path of KET ozonation is proposed. The thermodynamic results show that ozone-initiated KET degradation is feasible. Under ultraviolet irradiation, the reaction of ozone with water can also produce OH radicals (HO·) that can react with KET. The degradation reaction of KET caused by HO· was further studied. The kinetic calculation illustrates that the reaction rate (1.99 × 10-1 (mol/L)-1 sec-1) of KET ozonation is relatively slow, but the reaction rate of HO· reaction is relatively high, which can further improve the degradation efficiency. On this basis, the effects of pollutant concentration, ozone concentration, natural organic matter, and pH value on degradation efficiency under UV/O3 process were analyzed. The ozonolysis reaction of KET is not sensitive to pH and is basically unaffected. Finally, the toxicity prediction of oxidation compounds produced by degradation reaction indicates that most of the degradation products are harmless, and a few products containing benzene rings are still toxic and have to be concerned. This study serves as a theoretical basis for analyzing the migration and transformation process of anti-inflammatory compounds in the water environment.

Matrix isolation study of the early intermediates in the ozonolysis of selected vinyl ethers

The Criegee mechanism of the ozonolysis reaction of vinyl ethers has been observed by matrix isolation FTIR spectroscopy.

Computational study on the mechanisms and rate constants of the OH-initiated oxidation of ethyl vinyl ether in atmosphere

The hydroxylation reactions of ethyl vinyl ether (EVE) in the present of O2 and NO are analyzed by using MPWB1K/6-311++G(3df,2p)//MPWB1K/6-31+G(d,p) level of theory. According to the calculated thermodynamic data, the detailed reaction mechanisms of EVE and OH are proposed. All of the ten possible reaction pathways are discussed. The major products of the title reaction are ethyl formate and formaldehyde, which is in accordance with experimental detection. The rate constants of the primary reactions over the temperature of 250-400K and the pressure range of 100-2000Torr are computed by employing MESMER program. At 298K and 760Torr, OH-addition channels are predominate and the total rate constant is ktot=4.53×10(-11)cm(3)molecule(-1)s(-1). The Arrhenius equation is obtained as ktot=6.27×10(-12)exp(611.5/T), according to the rate constants given at different temperatures. Finally, the atmospheric half life of EVE with respect to OH is estimated to be 2.13h.

The atmospheric degradation reaction of dehydroabietic acid (DHAA) initiated by OH radicals and O3

Dehydroabietic acid (DHAA) is the major marker compound emitted from the burning of conifer. In this paper, the atmospheric mechanism of DHAA initiated by OH radicals and O3 was studied at the MPWB1K/6-31+G(d,p)//MPWB1K/6-311+G(3df,2p) level. For OH radicals, two types of reactions including OH addition and hydrogen abstraction were investigated. The cycloaddition reactions of O3 were considered. The rate constants over the temperature range of 200-400 K were calculated with the Rice-Ramsperger-Kassel-Marcus (RRKM) theory. At 298 K and under the pressure of 760 Torr, the whole rate constants are 0.89×10(-11) cm(3) molecule(-1) s(-1) and 2.29×10(-20) cm(3) molecule(-1) s(-1) for DHAA+OH and DHAA+O3, respectively. This study can be regarded as an attempt to investigate the OH-initiated and O3-initiated photochemical reaction mechanisms of DHAA in the atmosphere.