Process for the preparation of silane esters of tertiary alcohols

An alkoxysilane of the formula ##STR4## wherein R is hydrogen, an alkyl radical of 1 to 4 carbon atoms or an alkenyl radical of C.sub.2 -C.sub.10, R' is alkyl of 1 to 8 carbon atoms and R" is tertiary alkyl of 4 to 8 carbon atoms, a is 1 or 2, b is 1 or 2 and a plus b does not exceed 3, which is at least 94% pure, produced by a process comprising the steps of:

• A. contacting in the liquid phase and without contacting in the gas phase halogen silane of the formula R.sub.a SiX.sub.4-a wherein R is hydrogen, alkenyl of C.sub.2 -C.sub.10 or alkyl of C.sub.1 -C.sub.4, a is 1 or 2 and X is halogen, with a primary or secondary alcohol having the formula R'OH wherein R' is an alkyl group, an alkylene group or a polyhydroxyalkylene group having a terminal hydroxy alkyl group;
• said alcohol present in an amount not in excess of a 10% stoichiometric excess whereby to produce a halogen alkoxysilane as an intermediate;
• B. thereafter contacting said halogen alkoxysilane while in the reaction mixture of step A with an alcohol of the formula R'OH wherein R' is a tertiary alkyl group of C.sub.4 -C.sub.8 in the presence of an acid binding agent.