Item – Theses Canada

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OCLC number
46552873
Link(s) to full text
LAC copy
LAC copy
Author
Cowley, Nicholas John,1973-
Title
The mechanistic photochemistry of 4-hydroxybenzophenone.
Degree
M. Sc. -- Queen's University at Kingston, 1997
Publisher
Ottawa : National Library of Canada = Bibliothèque nationale du Canada, [1998]
Description
1 microfiche.
Notes
Includes bibliographical references.
Abstract
The photochemical reactions of 4-hydroxybenzophenone with a variety of reactants were studied by UV-visible spectrophotometry and continuous wave (CW) and time-resolved ESR spectroscopy (TR-ESR). The absorption spectra of benzophenone in solvents such as cyclohexane and isopropanol were used to assign the $\pi,\pi\sp*$ and n,$\pi\sp*$ electronic transitions based on the extinction coefficients and the shifts in the absorption maxima with different solvents. A n,$\pi\sp*$ band for 4-hydroxybenzophenone was not clearly identified. Photoreduction at 308 nm of 4-hydroxybenzophenone was not shown with isopropanol or lactic acid, but hydrogen abstraction from 2,6-di-t-butyl phenol to form the 4-hydroxybenzophenone ketyl radical in acetonitrile is suggested. Photoreduction by electron transfer to form the 4-hydroxybenzophenone ketyl radical anion from sulfur-oxygen anions is put forward. Photochemical hydrogen abstraction from 4-hydroxybenzophenone, by quinones and pyruvic acid, to form the 4-hydroxybenzophenone phenoxyl radical is further suggested on the basis a simulated spectrum. These interpretations are based on the chemically induced dynamic electron spin-polarization of the radicals observed, which may be explained by contributions from both the Triplet Mechanism (TM) and the Radical Pair Mechanism (RPM). Hydrogen abstraction from 4-hydroxybenzophenone by di-t-butyl peroxide is consistent with the UV-visible absorption spectra before and after irradiation ($\lambda >300$ nm).
ISBN
0612206203
9780612206205