ABSTRACT
Although the occurrence of intermolecular hydrogen atom abstraction from solvent by excited ketones was known one hundred years ago, understanding of its intramolecular counterpart was achieved only in the past 40 years. A wide variety of carbonyl compounds undergo photoinduced intramolecular hydrogen atom abstraction to form biradicals, which then undergo two common competing reactions: coupling to produce cyclic alcohols, and disproportionation back to ketone or to various enols. The next chapter of this book is devoted specifically to the chemistry initiated by b-, d-, and more remote intramolecular hydrogen abstractions. The 1,4-biradicals formed by g-hydrogen abstraction undergo unique reactions that other biradicals do not, and they do not disproportionate to enols as other biradicals can. Thus this special chapter.
