HYDROCARBONS 329 



benzene than is the lung. When less than 3 ml. (about 2.0 g.) of benzene 

 was given to rabbits, no benzene was found in the urine, although some 

 was detected when larger doses of this hydrocarbon were given. ^^^ How- 

 ever, Parke and Williams '^^ were unable to detect any radioactive un- 

 changed benzene in the urine of rabbits after feeding C^Mabeled benzene, 

 although an average of 32.6% of the ingested material was accounted for 

 in the form of oxidized products (phenol, catechol, quinol, hydroxyquinol, 

 trans-irans-imiconia acid and L-phenylmercapturic acid). The failure to 

 detect unchanged benzene may be related to the size of the dose employed 

 in the latter tests. Almost half of the radioactive benzene fed by Parke 

 and WiUiams"^ could be accounted for as oxidation products. Only 1.5% 

 was excreted as C''*02 over a period of two days following the feeding of 

 this tagged compound. 



b' . Oxidation of Benzene to Phenol : The presence of phenols in normal 

 urine has long been recognized. The most important member of the 

 group is phenol itself (CeHsOH), while the dihydroxybenzenes, catechol (o- 

 dihydroxybenzene) and quinol (p-dihydroxybenzene), and 1,2,4-trihy- 

 droxybenzene (hydroxyquinol), which are grouped under phenols, account 

 for an appreciable proportion of the ingested benzene. In the tests of 

 Parke and Williams ^'^■* with C "-labeled benzene, the following proportion 

 of the administered benzene was isolated as the several phenols: phenol, 

 23.5%; catechol, 2.2%; quinol, 4.8%; and hydroxyquinol, 0.3%. 



A portion of the phenols is eliminated in conjugation with sulfuric acid, 

 while another part may be present in combination with glucuronic acid. 

 A small amount may also appear as the free phenol. The total phenol 

 excretion bj^ normal men on a standard mixed diet is given by Hawk, Oser, 

 and Summerson^" as 0.2 g. per day. 



Schultzen and Naunyn"^ were the first to report the fact that benzene 

 is converted to phenol in the animal body. Mimk^'^ confirmed this finding 

 and, in addition, reported that the level of urinary phenols is increased in 

 proportion to the amount of benzene administered. Since some phenol 

 ordinarily occurs in urine in the absence of preformed benzene in the diet, 

 the latter data were necessary to establish the fact that the source of some 

 of the urinary phenol was benzene itself. The fact that an appreciable 

 proportion of benzene is oxidized to phenol has been amply confirmed by 

 a number of workers. Thus, one-third of the benzene absorbed was con- 



1^8 J. C. Drummond and I. L. Finar, Biochem. J., 32, 79-84 (1938). 

 '"' P. B. Hawk, B. L. Oser, and W. H. Summerson, Practical Physiological Chemistry, 

 13th ed., Blakiston, New York & Toronto, 1954, p. 437. 



i"8 O. Schultzen and B. Naunyn, Arch. Anat. Physiol, 1867, 349-357. 

 "» O. Munk, Arch. ges. Physiol. {P finger's), 12, 142-151 (1876). 



