The Gas-Phase Reactivity of h5-cyclopentadienylcobalt
ion (CpCo.+) toward Saturated Hydrocarbons
Using Fourier-transform Mass Spectrometry (FT-MS)
H.C. Michelle Byrd and Charles M. Guttman, Polymers Division, Standards
and Data, Gaithersburg, MD 20899
Douglas P. Ridge, University of Delaware, Department of Chemistry
and Biochemistry, Newark, DE 19716
By volume, polyethylenes, polypropylenes and their
derivatives are the most widely used of all synthetic polymers. Their chemical
structure and composition, molecular mass, and molecular-mass distribution
(MMD) are critical in determining performance properties. The potential
for quick and direct measurement of chemical composition and MMDs makes
mass spectrometry especially attractive to the polymer industry. However,
mass spectral analysis of saturated polyolefins has been plagued by the
ineffectiveness of conventional methods of cationization due to the lack
of polar groups, unsaturation and aromaticity. Selection of a suitable
ionizing reagent is crucial for successful MS analysis.
The selective reactivity of the h5-cyclopentadienylcobalt
ion (CpCo.+) may provide a suitable
cationization reagent for saturated hydrocarbons analysis by mass spectrometry.
Therefore, the CpCo.+ ion reactivity
toward linear alkanes was examined in the gas-phase using FT-MS. Loss of
two hydrogen molecules from the adduct ion was found to dominate all reactions
( > 80 %).
Furthermore, the dehydrogenation reaction rate increases with increasing
chain length, approaching the collision rate. These initial results suggest
that the CpCo.+ ion may be a promising
cationization reagents of larger saturated polyethylenes.