u00b0 c while stirring using the water bubbler to maintain a slight positive pressure of hcl a by product of the reaction in the flask after 1 5 hrs the mixture is cooled and excess phenol and hcl are removed under vacuum the product is purified to remove residual phenol by dissolving in a minimum of boiling methanol ca 100 ml adding 500 ml water and boiling with vigorous stirring for about 2 hrs while continuing the stirring the mixture is allowed to cool to room temperature and filtered the solid product is dried under vacuum the resulting tan powder is dissolved in boiling chcl 3 and crystallized therefrom giving 101 7 g of light beige crystals of 4 4 39 bis 1 4 hydroxyphenyl 1 methylethyl biphenyl bp dipbp m p 195 u00b0 6 u00b0 c the yield is 67 of theoretical this is a new bisphenol not previously known to the art the method of making aromatic polyesters from bisphenols is well known and conditions for the reaction include 1 temperatures within the liquid ranges e g from about 70 u00b0 to about 300 u00b0 c preferably from about 0 u00b0 to about 50 u00b0 c 2 solvents for the reaction such as aliphatic and aromatic hydrocarbons and their halogenated derivatives e g xylene toluene sulfolane dichloroethane chloroform methyl chloroform chlorobenzenes and the like 3 reactants preferably employed in the solvent at concentrations of from about one to about 50 percent by weight based on the total reaction mixture and 4 ratios of bisphenol to terephthalic.