Abstract Cohydrolysis of phenyltrichlorosilane with phenyl (fluoro) dichloro-and phenyl (difluoro)-chlorosilanes and thermolysis of the formed siloxanes leading to the formation of phenyl (difluoro) chlorosilane are studied. The scheme of thermal decomposition of disiloxanes possessing fluorine atoms in the 1, 3 positions is suggested. The scheme is based on the intermediate formation of an active four-membered cyclic complex closed by ...