Prediction of Reaction Rate Constants of Hydroxyl Radical With Organic Compounds

Abstract

In this work we have performed a QSAR study of atmospheric reactions with hydroxyl radical, at the B3LYP level of theory with 6-31G(d) basis set. Molecular descriptors selected by applying multiple linear stepwise regression (MLR) analysis were used to predict the reaction rate constants (-logk OH ) of OH radicals with organic compounds in the atmosphere, including 98 alkenes and 80 aromatic compounds. For setting our reactions, we have calculated 98 alkenes and 80 aromatic compounds. A four-descriptor MLR model (rms = 0.102 and R 2 = 0.938) for 98 alkenes was developed based on the number of R=CHX functional group counts, E HOMO parameter, and Fukui indices of the double-bonded C atoms. We found vinyl chemicals with conjugated double bonds and electron-donor substituents are the most reactive systems; while alkenes with multiple halogen substitutions are the least reactive molecules. Additionally, a three-descriptor MLR model (rms = 0.282 and R 2 = 0.910) was built to predict OH radical rate constants for 80 aromatic compounds, which was dominated by the E HOMO parameter, a topological descriptor for steric hindrance, and the most positive net atomic charge on hydrogen atoms. Aromatics with electron-donor and electron-acceptor groups, respectively, possess high and low degradation rates. The halogen aromatics are less reactive, especially for aromatics with multiple halogen substitutions. In comparison to existing models, the two models obtained in this paper show better statistical quality.

Salicylic Acid Boosts the TiO2 and ZnO-Mediated Photodegradation of Paracetamol

“…It is worth noting that the reactivity of aromatic compounds with HO•, a powerful oxidant, and electrophilic species, increases in the presence of hydroxyl substituents, i.e., electron-donor groups, which are present in salicylic acid and paracetamol. On the other hand, electron-withdrawing groups decrease reactivity 19,26,27 . In our study, the carboxylate group in salicylic acid is a strong electron-withdrawing group, and the amide in paracetamol, a moderated one.…”

“…Acetophenone is a pollutant, and studies about its photodegradation have been reported 11,31,32 . On the other hand, 4-aminoacetophenone was never studied in this context, but the presence of the amino group makes this compound more susceptible to oxidation and electrophilic attack 19,26 . Therefore, it should be expected 4-aminoacetophenone as more reactive, or at least similar to benzophenone.…”

An improved protein lipid overlay assay for studying lipid–protein interactions

“…Lipid structure simulation and calculations were performed as previously reported [4,19]. Briefly, the molecular structures of lipids were drawn using Chem-BioDraw Ultra 12.0, transferred to the ChemBio3D Ultra 12.0 module, and pre-optimized using the MM2 force field calculation until the minimum rms error was < 0.100 kcal/mol/Å to generate the lowest energy conformation.…”

Assessing the hydroxyl radical and volatilization roles in aquatic fate estimations of sulfur heterocycles: Dibenzothiophene derivatives

“…In addition, Lundstedt et al [27] observed that lowmolecular-weight PAHs and heterocycles degraded more rapidly than the high-molecular-weight compounds and that the presence of alkyl substituents or nitrogen atoms in the aromatic rings reduced the degradation rates. Among derivatives of benzene, those with large alkyl side chains such as tert-butyl or n-propyl that impose more steric hindrance for reaction with Á OH as well as being less thermodynamically stable were predicted to be less reactive than those with smaller and more stable alkyl groups such as methyl, vinyl, and isopropyl [28]. For example, toluene was more reactive than tert-butylbenzene, and styrene was more reactive than ethylbenzene [28].…”

“…Among derivatives of benzene, those with large alkyl side chains such as tert-butyl or n-propyl that impose more steric hindrance for reaction with Á OH as well as being less thermodynamically stable were predicted to be less reactive than those with smaller and more stable alkyl groups such as methyl, vinyl, and isopropyl [28]. For example, toluene was more reactive than tert-butylbenzene, and styrene was more reactive than ethylbenzene [28]. Our results are consistent with these predictions.…”