Triptycene-1-carboxylic acid (9, 10-o-benzenoanthracene-9-carboxylic acid) has been prepared and with it a number of other triptycene derivatives. The acyl peroxide prepared from this acid decomposes in benzene at 80" somewhat faster than benzoyl peroxide. The readiness of formation of the triptycyl free radical under these conditions is indicated by the appearance of about 4070 of triptycene among the products, which is supplanted by a ...