326 
Journal of Agricultural Research 
Vol. XXVI, No. 8 
{41) and by Heffter (17), 1 * 3 to an autoxidation of the oleic acid radical, 
followed by a rupture of the moloxid thus formed and further oxidation 
of its cleavage products. These changes might be formulated somewhat 
as follows : 
Oleic acid 
H 
CH 3 (CH 2 ) 7 —C O 
HOOC(CH 2 ) 7 —I + o 
H 
Oleic acid peroxid 
H 
CH 3 (CH 2 ) 7 —c—o 
1)7—C—o 
H 
HOOC(CH 2 ) 7 - 
Pelargonic aldehyde 
H 
CH 3 (CH 2 ) 7 —c=o 
—> + 
Azelaic half aldehyde 
H 
HOOC—(CH 2 ) 7 —C=0 
CH 3 (CH 2 ) 7 CHO+O —> CH 3 (CH 2 ) 7 —COOH Pelargonic acid 
HOOC(CH 2 ) 7 —CHO+O HOOC—(CH 2 ) 7 —COOH Azelaic acid 
Such a scheme would readily account for the peroxid reaction of rancid 
fats, as well as for the presence of pelargonic aldehyde, pelargonic acid, 
azelaic half aldehyde, and azelaic acid. While the other aldehydes and 
acids, whether monobasic or dibasic, previously detected in rancid fats 
would be more difficult to account for on the basis of this scheme, one 
might postulate lhat they owe their origin to the presence in the original 
fat of isomers of oleic acid, or to a migration of the double bond during 
the oxidation. Still other secondary reactions might be pictured whereby 
the oleic acid moloxid is rearranged to form ketoxystearic acid or reacts 
with unchanged oleic acid or with another molecule of the moloxid to 
form dihydroxystearic acid or diketostearic acid. 
While these ideas are not fully borne out by the work which follows, 
they formed the point of attack for the present investigation. At the 
outset it was confidently expected that the substance responsible for the 
rancid odor and for the Kreis test would fit in with this scheme, and in 
this connection azelaic half aldehyde, pelargonic aldehyde, diketostearic 
acid, and ketoxystearic acid were suspected in particular. 
EXPERIMENTAL 
It was originally planned to prepare a considerable quantity of oleic 
acid of unquestionable purity, and, after permitting it to become in¬ 
tensely rancid, to examine it qualitatively for the products formed. 
The preparation of a sufficient quantity of oleic acid of the desired de¬ 
gree of purity, however, proved to be impracticable; also a preliminary 
attempt at the fractionation of a rancid oleic acid indicated that the 
analytical method of procedure would be attended with great difficulties, 
such as might be expected in the separation of small quantities of homolo¬ 
gous acids and aldehydes having but slight differences in physical and 
chemical properties. The original plan was therefore abandoned, and a 
systematic search was made among the known degradation products of 
oleic acid for the substance or substances characteristic of the rancid 
condition, a search which ultimately suggested a compound not previ¬ 
ously recognized as a derivative of oleic acid. 
examination of known oxidation products of oleic acid 
The known oxidation products of oleic acid were examined in a pre¬ 
liminary way as to odor and as to behavior with the Kreis phloroglucin- 
1 A recent article by R. H. Kerr and D. G. Sorber ( 21 ) similarly points to the formation of peroxids of 
the unsaturated fatty acids as the initial stage in the development of rancidity, although oleic acid is not 
mentioned specifically. 
