Theoretical studies on the elimination of hydrogen fluoride from alkyl fluoride and its substituent effect

Abstract

The reaction mechanism of the a, a and a, /3 elimination of hydrogen fluorides from alkyl fluorides has been studied theoretically. For fluoroethane as a reactant, the transition state (1s) optimized at the level of the 6-31~** basis set shows that the Q, /3 elimination proceeds via a four membered-ring TS with a barrier height 64.6 kcal/mol, while the a, a elimination, via a three-membered ring TS with a 83.7 kcal/mol barrier. Four substituents, CH,, CN, F, and NH,, were used to investigate the substituent effect of elimination by using the 3-21c basis set. The calculated barriers show that NH,-substituted alkyl fluorides favor both the a, Q and a, @ elimination and these two reactions would be expected to proceed simultaneously. 0 19% John WiIey & Sons, Inc.carbene and hydrogen halide (X represents the The pyrolysis of alkyl halides in the vapor phase has been extensively studied by experimentalists [ 1-51. However, there are very limited theoretical studies [6,