33G 



VII. ACIDS, AMIDES, ALDEHYDES AND HYDROCARBONS 



benzene.^™ In fact, it is known that this isomer is formed when phenol 

 or catechol is oxidized with peracetic acid.^^^"^^'''^^^ Further evidence that 

 as-c/s-muconic acid is the first isomer to be derived from benzene is sug- 

 gested by the results of Hayaishi and Hashimoto, ^^^ who found that an 

 enzyme called pyrocatecase, which was separated from Pseudomonas spp., 

 oxidized catechol to czs-m-muconic acid, which could be isolated in the 

 crystalline state in high yield. The third variety of muconic acid (cis- 

 trans) has recently been found to originate when the cis-cis acid is recrystal- 

 lized from water.^i^ This observation casts doubt upon much of the earlier 

 work, which indicated that the cis-cis variety was present. The structures 

 of these several types of muconic acid and of galactose are given below. 



HCOH 

 HCOH 



HOCH 



I 

 HOCH I 



HC 1 



O 



CH2OH 

 Galactose 



Drummond and Finar^^* also showed that, when the cis-cis acid was dis- 

 solved in "benzene urine," it was spontaneously changed to the trans-trans 

 type, although the cis-cis-muconic acid could be recovered under suitable 

 conditions. It was also observed that when the sodium cfs-as-muconate 

 was injected into rabbits which had received benzene, the amount of the 

 trans-trans acid isolated was greater than that obtained when only benzene 

 was given. "^ This suggests that the in vivo change of the cis-cis to the 

 trans-trans form occurs under these conditions. However, when benzene 

 is not being metabolized, the cis-cis form fails to be changed to its geo- 

 metrical isomer. The explanation for this is not immediately forthcoming. 

 However, in subsequent studies, Parke and Williams^^* failed to note any 

 in vivo isomerization of any of the three isomers of muconic acid when 

 they were injected into rabbits. As much as 50 to 65% of the unchanged 



219 J. A. Elvidge, R. P. Linstead, P. Sims, and B. A. Orkin, /. Che7n. Soc. 1950, 2235- 

 2241. 



"0 O. Hayaishi and K. Hashimoto, J. Biochem. (Japan), 37, 371-374 (1950). 



