Adamantane undergoes degradation in its reaction with diiodine at 250degreesC. At 200degreesC, 1,3-dimethyladamantane produces traces of 4,6-dehydro-1,3-dimethyladamantane. 3,5-Dimethyladamantan-1-ol at 200degreesC forms 6,10-, 6,8-, and 2,10-dehydro-3,5-dimethyladamantan-1-ols (7 : 2 : 1) in 40% yield. Steric factors have a determining effect on the ratio of dehydrogenation products, whereas the electronic influence of the hydroxyl group through the adamantane ring system activates hydrogen atoms in certain positions of the adamantane skeleton.