Xiting Zhang, Yan-Bo Guo, Erin Dallin
Aug 25, 2020
Citations
0
Influential Citations
4
Citations
Journal
The Journal of organic chemistry
Abstract
In this work, 2,4'-dichlorobiphenyl (1) yielded 4'-chloro-2-hydroxybiphenyl (2) after photolysis in neutral acetonitrile aqueous (ACN-H2O) solutions. Ultrafast spectroscopic measurements and DFT computations were performed for 2 in ACN and ACN-H2O (v:v, 1:1). These results were compared with previously published results for 2-hydroxybiphenyl (3). The counterparts 2 and 3 went through singlet excited state intramolecular proton transfer (ESIPT) in ACN but behaved differently in ACN-H2O with a dehy-drochlorination process occurring for 2 and an ESIPT taking place for 3. Computational results indicate that the phenol O-H bond elongates after photoexcitation to induce a concerted asynchronously process with the C-Cl bond increasing first followed by an HCl elimination. A biradical intermediate (IM1) then is formed with some spin locating at the phenyl 4'-C radical that appears to favor a hydrogen atom transfer (HAT) process and some spin located on phenoxyl appears to prefer a subsequent ۰CH2CN radical rebound. The hydrogen bond promotes HCl elimination while this is disfavored for ESIPT, making the 4'-Cl extrusion becoming the predominant process in ACN-H2O solutions. The mechanistic investigations have fundamental and significant implications for the understanding of polychlorinated biphenyls photolysis in aqueous environment and hence the photodegradation of these kinds of pollutants in the natural environment.