AB-INITIO STUDY OF THE ADDITION OF SELECTED FREE-RADICALS TO MONOFLUOROETHYLENE AND 1,1'-DIFLUOROETHYLENE

We report the results of a comprehensive ab initio investigation of th e addition reactions of H-., (OH)-O-., (NH2)-N-., and (CH3)-C-. radica ls to monofluoroethylene (MFE) and 1,1-difluoroethylene (DFE), conside ring attack at both carbon atoms. The attack angles of (OH)-O-. and (N H2)-N-. are reduced by including electron correlation at the MP2 level , while those of H-. and (CH3)-C-. remain relatively constant. Reactio n barriers, computed up to the PMP4-(SDTQ)/6-311G*//UMP2/6-311G** lev el, are reduced 5-8 kcal/mol by inclusion of spin projection technique s. This reduction is offset 0-2 kcal/mol by consideration of zero poin t vibrational energies (ZPVEs). In contrast, heats of reaction are cha nged by <1 kcal/mol by spin projection but increased 3-6 kcal/mol by Z PVE contributions. The calculated relative reactivities of the four ra dicals with MFE and DFE agree with experimental data, but discrepancie s appear when the predicted regioselectivity of (OH)-O-. and (NH2)-N-. is compared. Although the calculated isotropic hyperfine splitting co nstants of the radical products are in reasonable accord with experime ntal data for species with well defined minima, they demonstrate large differences for radicals having greater conformational flexibility.