Study on the addition of hydrogen fluoride to 2′,2′-difluorostyrenes

2,2,2-Trifluoroethylarenes were obtained in good yield from the addition of KF to 2′,2′-difluorostyrenes in the presence of crown ether. A linear regression line obtained from correlation between log(reaction rate) and Hammett constants with slope of +4.28 suggested that this addition process is very sensitive to the substituents on the phenyl ring.