The main products of the 185 nm photolysis of neat liquid tetrahydropyran are pent-4en-l-ol (7) (0 = 0.40), 2-(5'-hydroxypentyl)tetrahydropyran (10) (0.21), valeraldehyde (6) (0.13), and pentan-l-ol (8) (0.08). These products are thought to be formed via the biradical '0(0112)40112, and/or through intramolecular (6, 7, 8) and intermolecular (10) photoreactions. In the case of 10, the probabilit...