The term orthoprene is here presented as a designation for derivatives of butadiene-1, 3 having a single substituent and that in the 2-position (111). Isoprene is the historically important member of this class and (except for a single reference'to ethylbutadiene) it was the only one known until the discovery of chloroprene2 and bromoprene. The extraordinarily superior properties of these compounds from the standpoint of rubber synthesis prompted ...