Synthesis and purification of fatty acids by the pyrolysis of esters

Abstract

simple olefins, particularly those that were not sensitive to acid catalyzed rearrangements. It was recently reported however that if carbonization were avoided, this reaction could also be used for the synthesis of strained olefins (1). Thus 1,2-dimethylene-4-cyclohexene, an isomer of o-xylene, was prepared in a 92% yield by the pyrolysis of a diacetate (3) while the decomposition of the corresponding quaternary ammonium hydroxide gave only o-xylene (8). Since the pyrolysis of esters is such an excellent method for the synthesis of unsaturated compounds, it appeared likely that pyrolysis should also be useful for the synthesis of acids. For this reason a research program was initiated to determine in which cases the pyrolysis of esters was superior in some respects to the conventional hydrolysis for the preparation of acids or their derivatives. Although titration of the liberated acid has often been used to determine the extent of pyrolysis, very little has been published about the use of this reaction for the preparation of acids. Ratchford, Rchberg, and Fisher prepared acrylic and methacrylic acids in high yields by the pyrolysis of the corresponding esters (10, 11). Halbig developed a synthesis of formic acid which involved the pyrolysis of tert-amyl formate (6).