Compounds of the formula ##STR1## wherein X.sup.1 denotes fluorine or chlorine and X.sup.2 denotes hydrogen, fluorine or chlorine; R.sup.1 is 3E-alkenyl, 4-alkenyl, 2E-alkenyloxy or 3-alkenyloxy; n stands for the number 0 or 1; one of the groups Y.sup.1 and Y.sup.2 is a single covalent bond, --COO--, --OOC--, --CH.sub.2 CH.sub.2 --, --CH.sub.2 O-- or --OCH.sub.2 -- and the other of the groups Y.sup.1 and Y.sup.2 is a single covalent bond; and rings A.sup.1 and A.sup.2 each individually are substituted or unsubstituted trans-1,4-cyclohexylene, in which optionally 2 non-adjacent CH.sub.2 groups are replaced by oxygen, or substituted or unsubstituted 1,4-phenylene, in which optionally 1 CH group or 2 CH groups is/are replaced by nitrogen; with the proviso that X.sup.2 denotes fluorine or chlorine and/or Y.sup.1 or Y.sup.2 denotes --CH.sub.2 O-- or --OCH.sub.2 -- when simultaneously X.sup.1 is fluorine and R.sup.1 is 3E-alkenyl, and their use for liquid crystalline mixtures and electro-optical purposes.
该化合物的
化学式为##STR1##其中X.sup.1表示
氟或
氯,X.sup.2表示氢,
氟或
氯; R.sup.1是3E-烯基,4-烯基,2E-烯氧基或3-烯氧基; n表示数字0或1; Y.sup.1和Y.sup.2中的一个是单个共价键,--COO--, --OOC--, --CH.sub.2 CH.sub.2 --,--CH.sub.2 O--或--OCH.sub.2--,另一个是单个共价键;环A.sup.1和A.sup.2各自为取代或未取代的反式1,4-
环己烷基,其中可以选择用氧替换2个非相邻的CH.sub.2基团,或取代或未取代的1,4-苯基,其中可以选择用氮替换1个CH基团或2个CH基团; 前提是当同时X.sup.1为
氟且R.sup.1为3E-烯基时,X.sup.2表示
氟或
氯,和/或Y.sup.1或Y.sup.2表示--CH.sub.2 O--或--OCH.sub.2--,并且它们用于液晶混合物和电光用途。