known in the art such as by treating the former with cuprous cyanide in a suitable solvent such as n methyl 2 pyrrolidone at an elevated temperature e g at reflux for about 12 to 24 hours at the end of the reaction period the dicyano compound is precipitated from solution by pouring the reaction mixture into an aqueous alkali metal cyanide solution the crude product may be purified using any technique known in the art hydrolysis of the dicyano compound may be carried out using any technique known in the art and yields the desired pendant heterocyclic terephthalic acid intrinsic viscosity is determined by extrapolation of u03b7 rel 1 c and ln u03b7 rel c to zero concentration in methane sulfonic acid at 30 u00b0 c 2 aminophenol 18 8 g 0 17 mol 2 5 dimethylbenzoic acid 27 0 g 0 18 mol and 215 g of polyphosphoric acid ppa was heated under nitrogen at 145 u00b0 c for 24 hours the reaction mixture after cooling down to about 50 u00b0 c was poured into water to precipitate a heavy oily material the material was extracted repeatedly with methylene chloride the methylene chloride solutions were combined separated dried over magnesium sulfate filtered then evaporated using a rotary evaporator to yield a wet solid the solid was purified by column chromatography on.