A process for preparing a metal oxide having groups of the general formula I --O.sub.1+n--SiR.sup.1.sub.2-n--CH.sub.2--Y (I) which involves reacting a solid having OH groups on the surface with silanes of the general formula II RO.sub.1+n--SiR.sup.1.sub.2-n--CH.sub.2--Y (II) where Y is a functional group --NR.sup.x.sub.2, --OC(O)C(R).dbd.CH.sub.2, -halo, or --NCO. The reaction takes place rapidly and at reasonable temperatures and avoids production of significant quantities of decomposition products or byproducts, providing a metal oxide with a high proportion of Y functional groups.