Tertiary alcohols with prenyl or geranyl moities, bearing a second oxygen. function in the 3, 4 or 5 position were dehydrated under various conditions: the composition of the olefinic mixture obtained was accounted for, by an intramolecular base relay effect. Basic elimination of analogous dimethylsutfonium salts gave results that could be related to the inductive effect: a correlation between regioselectivity and the Taft constantσI of the ...