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9,10‐Dicyanoanthracene (DCA) and biphenyl (BP) cosensitize the electron‐transfer photooxygenation of epoxides in oxygen‐saturated acetonitrile to form ozonides. These epoxides do not measurably quench the fluorescence of DCA and are, therefore, relatively unreactive under standard photooxygenation conditions with only DCA as sensitizer. However, a dramatic increase in the rate of reaction is observed upon the addition of BP as a non‐light‐absorbing cosensitizer. An investigation of the stereochemistry of the reaction with cis‐ and trans‐2,3‐diphenyloxiranes has shown that both epoxides are converted exclusively to the cis‐ozonide. This striking stereochemical result is consistent with a proposed mechanism involving singlet oxygen addition to an intermediate carbonyl ylide.

Polymeric derivatives of propylene oxide (PO) and higher epoxides are very important in polymer chemistry. Low molecular weight homopolymers of PO and copolymers of PO and ethylene oxide are used in polyurethanes, hydraulic fluids, lubricants, surface active agents, and chemical intermediates. They are known as polyether polyols, polyethers, or polyols. Low molecular weight polyethers are prepared via acid or base catalysis. Propylene oxide is manufactured by either the chlorohydrin process or the peroxidation process. Polymerization mechanisms (anionic, cationic, and coordinate) are described. Details of polyol manufacture are given, such as stoichiometry, processing, removal of catalyst, and stabilization, for example. The most important chemical property of poly(propylene oxide) in polyurethane applications is the primary or secondary hydroxyl end group. Properties of various polyols are given. A number of block and random copolymers are known. Propylene oxide is highly reactive and is a primary irritant. Toxicities of selected epoxides are given.