Competition between "Meta Effect" Photochemical Reactions of Selected Benzophenone Compounds Having Two Different Substituents at Meta Positions.
Recent studies conducted on some "meta effect" photochemical reactions focused on aromatic carbonyls having a substitution on one meta position of the benzophenone (BP) and anthraquinone parent compound. In this paper, two different substitutions were introduced with one at each meta position of the BP parent compound to investigate possible competition between different types of meta effect photochemistry observed in acidic solutions containing water. The photochemical pathways of 3-hydroxymethyl-3'-fluorobenzophenone (1) and 3-fluoro-3'-methylbenzophenone (2) were explored in several solvents, including acidic water-containing solutions, using time-resolved spectroscopic experiments and density functional theory computations. It is observed that 1 can undergo a photoredox reaction and 2 can undergo a meta-methyl deprotonation reaction in acidic water-containing solutions. Comparison of these results to those previously reported for the analogous BP derivatives that contain only one substituent at a meta position indicates the introduction of electron-donating (such as hydroxyl) and electron-withdrawing groups (such as F) on the meta positions of BP can influence the meta effect photochemical reactions. It was found that involvement of an electron-donating moiety facilitates the meta effect photochemical reactions by stabilizing the crucial reactive biradical intermediate associated with the meta effect photochemical reactions.
Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, College of Chemistry and Materials Science, Northwest University , 229 Taibai N Road, Xi'an, Shaanxi, People's Republic of China.
Jiani
J
Ma
Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, College of Chemistry and Materials Science, Northwest University , 229 Taibai N Road, Xi'an, Shaanxi, People's Republic of China.
Huai
H
Li
Department of Chemistry, The University of Hong Kong , Pokfulam Road, Hong Kong 11111.
Xiting
X
Zhang
School of Pharmacy, Anhui Medical University , Meishan Road 81, Hefei 230032, People's Republic of China.
Wen-Jian
WJ
Tang
Department of Chemistry, The University of Hong Kong , Pokfulam Road, Hong Kong 11111.
Mingde
M
Li
Department of Chemistry, The University of Hong Kong , Pokfulam Road, Hong Kong 11111.
David Lee
DL
Phillips