Density functional investigation of reaction of borohydride cation BH with propylene

The reactions of BH with propylene (CH 2 CHCH 3 ) to form both the adducts BC 3 H and the H 2 ‐elimination products BC 3 H + H 2 have been investigated at the density functional B3LYP/6‐311G(d,p) level of theory. It is shown that the electrophilic attacks of BH towards two olefinic carbons of H 2 CCHCH 3 and two subsequent 1,3‐H‐shifts may form four low‐lying BC 3 H isomers (with the relative energies in parentheses in kcal/mol): 1 BH · CH 2 CHCH 3 (0.0), 1′ BH · CH 3 CHCH 2 (6.3), 3 BHCH 2 CH 2 CH (4.3), and 4 BHCH(CH 3 ) (5.0), respectively. On the other hand, further H 2 ‐eliminations may also occur easily between BC bonds of isomers 1 and 1′ and between CC bonds of isomers 3 and 4 to form two dissociation products ( P 1 ) HBCHCHCH + H 2 and ( P 2 ) HBC(CH 3 )CH + H 2 , with H 2 ‐elimination from isomer 1 to be energetically most favorable. According to our calculated mechanism, the collisional stabilization processes of low‐lying isomers 1 , 1′ , 3 , and 4 may compete extensively with their H 2 ‐eliminations processes for the title reaction, leading mainly to some linear carborane cations. This study may be helpful for understanding the stereochemical aspects of borohydride cations towards alkylenes. © 2003 Wiley Periodicals, Inc. J Comput Chem 25: 258–264, 2004