2,2'-Biphenyldicarboxylic anhydride 2,2'-Diphenyldicarboxylic anhydride 6050-13-1 Biphenyl-2,2'-dicarboxylic anhydride Dibenz(c,e)oxepin-5,7-dione Diphenic anhydride EINECS 227-950-0 NSC 116225 NSC 67689