Characterization and reactivity of hybrid organosilicate mesoporous sieves

Vinyl-MCM-41 has been synthesized by a direct synthesis from the corresponding organosiloxane precursors. The location of vinyl groups on the internal channel surfaces of the mesoporous silicate sieves was confirmed by small angle neutron scattering (SANS) experiments using contrast matching techniques. To investigate further modification of the vinyl groups, bromination reactions were carried out on vinyl-MCM-41 samples in dichloromethane, carbon tetrachloride, and in a gas-phase reaction. With dichloromethane as a solvent, the bromination rate increased with increasing pore diameter. A strong dependence of the reaction rate on the presence and type of solvent molecules was observed. While gas-phase bromination was complete within 40 minutes, the reaction required several days for completion in dichloromethane and was even slower in the nonpolar solvent, carbon tetrachloride.