a decarboxylation process for coupling aromatic compounds wherein cyclic hydrocarbons and heterocyclic compounds having at least one labile ring hydrogen are reacted with the mono silver salts of aromatic carboxylic acids , or mono silver salts of unsaturated compounds such as α , β - ethylenically unsaturated acid compounds , or silver trifluoroacetate , or the mono silver salts are reacted with themselves , by heating to temperatures of 100 ° to 500 ° c . at pressures of 0 . 1 to 10 atmospheres , or by irradiating the reactants with ultraviolet light of 200 to 400 nanometers at temperatures of - 30 ° to 100 ° c . the resulting dimers , trimers , polysubstituted polyphenyls , polyheterocyclics and trifluoromethylated aromatics are useful as heat transfer media , as intermediates for high molecular weight polymers , pesticides and petroleum additives , and as scintillation counters .