REACTIONS OF SUBSTITUTED BORYL RADICALS WITH NITROALKANES - EPR, KINETIC, AND PRODUCT STUDIES

The radical-initiated reaction of amine-boranes and phosphine-boranes, LBH(3) (L = R(3)N, R(3)P) with aliphatic nitro compounds has been inv estigated in order to explore the possibility of reducing tertiary nit roalkanes to the corresponding hydrocarbons. In all the examined cases boroxy nitroxides, RN(O-.)OBLH(2), resulting from the addition of lig ated boryl radicals, LBH(2)(.), to an oxygen atom of the nitro group w ere detected and characterized by EPR spectroscopy. This reaction occu rs at room temperature with a rate constant of 1.5 x 10(7) M(-1) s(-1) for LBH(2)(.) = Me(3)NBH(2)(.) and RNO(2) = Me(3)CNO(2). The boroxy n itroxides from tertiary nitroalkanes decay by a fragmentation reaction occurring with cleavage of the nitrogen-oxygen bond, rather than of t he carbon-nitrogen bond as would be required for the reduction to the corresponding alkane to take place. The Arrhenius parameters for this fragmentation have been determined in few cases.