at 30 u00b0 c and the solvent is p chlorophenol unless otherwise indicated fiber tensile properties are reported in customary units first with si units in parentheses they are measured using the procedures shown in morgan u s pat no 3 827 998 on fibers that have been conditioned for at least one hour at least three breaks are averaged thermooptical test tot is described in u s pat no 4 066 620 polymers that pass this test are considered to be optically anisotropic the 3 4 39 diacetoxybenzophenone used in subsequent polymerizations was prepared in stages starting from m anisic acid it was converted first to m anisoyl chloride then to 3 4 39 dimethoxybenzophenone then to 3 4 39 dihydroxybenzophenone and finally to 3 4 39 diacetoxybenzophenone this example provides the details of one such conversion and except for changes in scale was the general procedure for all such preparations a mixture of 100 g of m anisic acid 0 658 mole 250 g thionyl chloride 2 10 mole and 5 ml dimethylformamide was heated under reflux in a round bottom flask with desiccant in the top of the condenser for exclusion of atmospheric moisture excess thionyl chloride was distilled from the product using a rotary film evaporator at about 200 torr 26 6 kpa the m anisoyl chloride was then isolated by fractional distillation through a 25 cm vigreux column at 109 u00b0 c 12 torr 1 6 kpa yield was 90 g.