NEW MATERIAL:The compound of formula I (R is H or 1W10C alkyl).

EXAMPLE: trans-4-Butyl-trans-4"- ( 3, 4-difluorophenyl ) -trans-octadecahydro-p-terphenyl.

USE: A liquid crystal substance having positive dielectric anisotropy and exhibiting liquid crystal phase over a wide temperature range.

PROCESS: The objective compound of formula I can be prepared by reacting 4- methoxybromobenzene with metallic Mg and then with the compound of formula II, dehydrating with KHSO4, reducing in the presence of Raney nickel catalyst, separating and recrystallizing the trans-isomer of formula III, demethylating with hydrobromic acid, catalytically reducing in the presence of an Ru catalyst, oxidizing with CrO3, reacting with a Grignard reagent, dehydrating with KHSO4, and finally catalytically reducing in the presence of a Raney Ni catalyst.