When treated with KOCMe3 in THF, fluorohydrin p-tosylates afford fluoro olefins, e.g., Z- or E-Me(CH2)4CF:CH(CH2)4Me, in high yields. Fluorohydrins are readily and stereoselectively accessible by antiperiplanar addn. of HF to oxiranes. Terminal epoxides give preferentially 2-fluoro-1-alkanols with HF-pyridine mixt. in PhMe, while mainly 1-fluoro-2-alkanols result from reaction with Huenig's hydrofluoride (i.e., the adduct of HF and (Me2CH)2NEt. With 2-hydroxymethyl-substituted oxiranes, 3-fluoro-1,2-alkanediols are obtained predominantly if not exclusively. [on SciFinder (R)]