Process for preparing a compound of the formula (I) R1-S(O).sub.x--S(O).sub.yR2 in which R1 represents a molecular hydrocarbon radical which can be substituted and/or interrupted by one or more atoms and/or by one or more groups containing one or more atoms, said atoms being selected from N, O, P, S, Si and X, where X represents a halogen; R2, independently of R1, represents a carbon-containing group or a molecular hydrocarbon radical which can be substituted and/or interrupted by one or more atoms and/or by one or more groups containing one or more atoms, said atoms being selected from N, O, P, S, Si and X, where X represents a halogen, and x and y are selected from 0 and 1 in such a way that the sum of x and y is not more than 1, characterized in that a compound of formula (II) R1-S(O).sub.x--R3-Si(R4)(R5)(R6) in which R3 represents a hydrocarbon chain of two carbon atoms, which is optionally unsaturated and/or substituted, and R4, R5 and R6, which are identical or different, each represent, independently of one another, a hydrocarbon group, is reacted with a compound of formula (VII) R2-S(O).sub.y--X in which X represents a halogen, intermediate compounds, and compounds prepared.