Abstract: Thiophene derivatives of formula (I) ##STR1## wherein X and Y are the same or different O, S or N--R.sup.3,Z is a C.sub.1 -C.sub.6 -alkylene residue that may be substituted by R.sup.1 and R.sup.2,R.sup.1, R.sup.2 are the same or different hydrogen, or --(CH.sub.2).sub.n --OR.sup.4, --CH.dbd.CH.sub.2 or ##STR2## n is 1 to 10, R.sup.3 is aryl, C.sub.1-18 -alkyl or H,R.sup.4 is SO.sub.3.sup.- (H.sup.+,Na.sup.+,K.sup.+,Li.sup.+) or --(CH.sub.2 --CH.sub.2 --O).sub.m --R.sup.5,m is 1 to 10 andR.sup.5 is alkyl with 1 to 6 C atoms,wherein compounds in which X and Y are both O and R.sup.1 and R.sup.2 are both hydrogen atoms are excluded, are suitable for the preparation of polythiophenes which can be used as organic electrical conductors.