Abstract: A method to manufacture acryloxypropylsilane to a high degree of purity is achieved by hydrosilation of (A) allyl acrylate or allyl methacrylate by (B) a hydrosilane compound, using (C) a platinum-containing compound as the catalyst and (D) an organic phosphorus compound as the promoter. The acryloxypropylsilane product is expressed by General Formula ICH.sub.2 .dbd.CR.sup.1 COOCH.sub.2 CH.sub.2 CH.sub.2 SiR.sup.2.sub.n R.sup.3.sub.3-n (Formula I)where R.sup.1 represents a hydrogen or methyl group, R.sup.2 represents a hydrolyzable group, R.sup.3 represents an aryl, alkenyl or aryl group of carbon number 1-12, and n is 0, 1, 2, or 3.

Abstract: A process is disclosed for producing a diorganopolysiloxane by polymerizing a cyclic siloxane expressed by the following general formula (2) ##STR1## wherein R.sup.3 represents methyl group, ethyl group, or phenyl group, and p is an integer of 3 or 4,by an anion living polymerization using a lithium trialkylsilonolate or an alkyl lithium as a polymerization initiator and then terminating the anion living polymerization with an acid or a chlorosilane derivative, the improvement comprising treating a diorganopolysiloxane which is modified with a silanol at both its terminals and included in the cyclic siloxane as impurities, with an acetylating agent.