Chiral dopants of the formula ##STR1## in which n represents the number 0 or 1; R.sup.3 denotes a group of the general formula ##STR2## A.sup.1, A.sup.2 and A.sup.3, independently of one another, represent 1,4-phenylene which is unsubstituted or substituted by halogen, cyano and/or methyl and in which 1 or 2 CH groups may be replaced by nitrogen, or represent trans-1,4-cyclohexylene, trans-1,3-dioxane-2,5-diyl or naphthalene-2,6-diyl, and ring A.sup.2 additionally represents 1,4-biphenylene; Z.sup.1 and Z.sup.4, independently of one another, denote a single covalent bond or --CH.sub.2 CH.sub.2 --; Z.sup.2 and Z.sup.3, independently of one another, denote a single covalent bond, --CH.sub.2 CH.sub.2 --, --COO--, --OOC--, --CH.sub.2 O--, --OCH.sub.2 --, --C.tbd.C--, --(CH.sub.2).sub.4 --, --(CH.sub.2).sub.3 O--, --O(CH.sub.2).sub.3 -- or the trans-form of --CH.dbd.CH--CH.sub.2 CH.sub.2 --, --CH.sub.2 CH.sub.2 --CH.dbd.CH--, --CH.dbd.CH--CH.sub.2 --O-- or --O--CH.sub.2 --CH.dbd.CH--; with the proviso that, if R.sup.3 denotes a group of the formula II, at least one of the groups Z.sup.2 and Z.sup.3 denotes --(CH.sub.2).sub.4 --, --(CH.sub.2).sub.3 --O--, --O--(CH.sub.2).sub.3 -- or the trans-form of --CH.dbd.CH--CH.sub.2 --CH.sub.2 --, --CH.sub.2 --CH.sub.2 --CH.dbd.CH--, --CH.dbd.CH--CH.sub.2 --O-- or --O--CH.sub.2 --CH.dbd.CH--; R.sup.1, R.sup.5 and R.sup.6 denote hydrogen, alkyl, phenyl or alkoxycarbonyl; R.sup.2 denotes alkyl, phenyl or alkoxycarbonyl; R.sup.4 denotes halogen, cyano, trifluoromethyl, trifluoromethoxy or alkyl in which one --CH.sub.2 --CH.sub.2 -- may be replaced by --CH.dbd.CH-- and/or one or two non-adjacent methylene groups may be replaced by --O--, --COO-- and/or --OOC-- and/or one methylene group methylene group may be replaced by --CHX--; X denotes halogen, cyano or methyl; and the dioxolane ring shown in the formula I is in optically active form, liquid-crystalline mixtures which contain such dopants, and their use for optical and electrooptical purposes.