s (-OH groups) A vicinal diol is a diol with two hydroxyl groups in vicinal positions, that is, attached to adjacent atoms. Examples include 1,2-ethanediol or ethylene glycol HO-(CH2)2-OH, a common ingredient of antifreeze products; and propane-1,2-diol or propylene glycol, HO-CH2-CH(OH)-CH3. A geminal diol has two hydroxyl groups bonded to the same atom. Examples include methanediol H2C(OH)2 and 1,1,1,3,3,3-hexafluoropropane-2,2-diol (F3C)2C(OH)2, the hydrated form of hexafluoroacetone. Exampl… (More on Glycol)