The preparation of sixteen dimethylene linked compounds is described [14 incorporating the cyclobutane ring and 2 incorporating the spiro[3.3]heptane ring], and a comparison is made between the transition temperatures of these compounds and those of the corresponding esters.1This comparison once again highlights the fact that the cyclobutane ring should be regarded, in terms of its ability to promote nematic thermal stability, as a “chain stiffener” rather than as a ring system.