Acid catalyzed reactions to fluorosubstituted terminal alkenes and some hydrocarbon alkenes are presented. Addition of open-ion electrophiles to 2-fluorosubstituted terminal alkenes generate cations on the internal number-2 carbon. On the other hand, 1-fluorosubstituted terminal alkenes are less reactive and tend to have the charge develop on the terminal carbon. Calculations show that the carbenium ions from reaction of open-ion electrophiles to 1-fluorosubstituted alkenes are slightly more stable on the terminal carbon compared to the internal number-2 carbon. Triflic acid and perchloric/formic acids were found to be good reagents for acid catalyzed reactions with the 2-fluorosubstituted terminal alkenes. Acid catalyzed reactions with the less reactive 1-fluorosubstituted terminal alkenes did not give products stable to the reaction conditions. Triflic acid catalyzed additions of alcohols to hydrocarbon alkenes are compared to catalysis with boron trifluoride etherate.