Methyl oleate and methyl elaidate were autoxidized in the conditions free from natural antioxidants and metals. The autoxidation of methyl oleate gave the rate 10.4 times as fast as that found for methyl elaidate in comparison of the induction period, and 2.2 times in comparison of the rate of the oxidative weight increase and the hydroperoxide formation rate after the induction period. Results from analyses of the various autoxidation products from oleate and elaidate showed that the autoxidation products from oleate were formed in a shorter interval of autoxidation in comparison with those from elaidate, but the amount of the autoxidation products from oleate was similar to that from elaidate if the autoxidation products were compared at the same autoxidation level (oxidative weight gains). These results showed that the different rates of the autoxidation between oleate and elaidate resulted from the different affinity of oxygen molecule with the olefinic double bond of substrates (equations 7 and 8).
Methyl linoleate and its trans, trans isomer, methyl linolenate, and a mixture of methyl eicosapentaenoate and methyl docosahexaenoate (50 : 50%) were autoxidized in the conditions free from natural antioxidants and metals. Their autoxidations gave the induction period of 49, 52, 18 and 11h, and showed the oxidation rates of 3.61, 3.08, 5.24 and 9.41×10-5mol/h, respectively, at the autoxidation level after the induction period (specified as the time required to gain 10mg by weight). Relative autoxidation rates derived from the induction periods were almost similar to the ratio of the number of the active methylene group, but those from the oxidation rates were equal to the ratio of unsaturation degree. In comparison with the oxidation rate of methyl oleate, the abstraction of hydrogen from the active methylene groups by peroxyl radicals was superior by 1.54×10-5mol/h in the rate to that from α-methylene groups. An Increase in the unsaturation degree of autoxidation substrates permitted the rapid and large formation of hydroperoxides, radicals, polymers, α, β, γ, δ-unsaturated carbonyls and etc. But in comparison at the same autoxidation level (weight gains) free from oxidative polymerization and decomposition, the amounts of these autoxidation products were similar each other. These data showed that the rate-determing step during induction period of autoxidation was the abstraction of hydrogen from the active methylene groups by oxygen molecules, and after the induction period was the diffusion of peroxyl radicals. The geometric isomeric effect that methyl linoleate was autoxidized easier than the trans, trans isomer was observed. This effect suggested the interaction of the oxygen molecule with the double boud of substrates in initiating the chain reaction.
Conjugated methyl cis, trans-and trans, trans-octadecadienoates were autoxidized in the conditions free from natural antioxidants and metals. The autoxidation of conjugated cis, trans-and trans, trans-isomers gave the induction period of 17 and 27h, and showed the oxidative weight increase rate 0.661 and 0.615mg/h at the autoxidation level after the induction period (specified as the time required to gain 10mg by weight). In comparison with methyl linoleate, the autoxidation of conjugated isomers gave the shorter induction period, but showed the lower oxidative weight increase rate. Results from analyses of the various autoxidation products from the conjugated isomers showed that the products from cis, trans-isomer were formed in a shorter interval of autoxidation in comparison with those from trans, trans-isomer, but the amount of products from the former was almost the same to that from the latter if the products were compared at the same autoxidation level (oxidative weight gains). Differences on the autoxidation products from conjugated isomers, such as conjugated dienes, radicals, isolated trans double bonds and etc, showed that the large parts of the conjugated isomers were autoxidized by the addition of oxygen molecules to olefinic double donbs. It was concluded that the different rates of the autoxidation between conjugated cis, trans-and trans, trans-isomers resulted from the geometric isomeric effect of olefinic double bonds upon the addition of oxygen molecules.
In the previous papers, the authors previously reported on the results of collaborative tests with regard to a standardization of the fat stability test on the autoxidation by using soybean oil. In this paper, the authors report on investigations concerning the stability test made on the autoxidation by using refined lard as follows : 1. Results of AOM test Average AOM value of 6 laboratories was 16.2h, showing that deviations among them were small except for a specific laboratory. 2. Results of Oven test The peroxide value (POV) measured by these laboratories were varied widely especially at the long standing period. A reason of this was considered as the differences of the inconsistencies on the thermostat specifications, not that the differences of the POV determination method and the sampling conditions. 3. Results of organoleptic evaluation The results of organoleptic evaluation were comparatively consistent among collaborators. The correlation between the organoleptic evaluation and the POV was as given hereunder : POV (meq/kg) Flavor score Response 01.3 5 Odorless, Fresh oil 1.32.0 4 Slightly grassy, Flavor reversion, Nutty 2.35.0 3 Slightly rancid, Heavy flavor reversion 5.38.0 2 Rancid, Viscous taste 8.0> 1 Strong rancid, Pungent smell 4. Results of test on weighing method When the collaborators followed different specifications of thermostat, the deviations on the results obtained were very big. The greatest cause of deviations on the test by weighing method certainly consisted in various and uneven specifications of thermostat and difference of heat capacity. In the case of using the same thermostat, the deviation lessened. Therefore, if the specifications of the thermostat is unified, the standardization will be realized.
Micro-synthesis of zinc O, O-diisobutyldithiophosphate [32P] (ZDDP [32P]) was successfully attained with a yield of 33.9% from phosphorus [32P] pentasulfide and isobutyl alcohol. Because of the new experimental technique in this work, the time required to obtain the final product was remarkably shortened. It now takes less than 48h, which is quite satisfactory considering the very fast decay of phosphorus [32P]. Specific activity of the ZDDP [32P] obtained was 4.71 mCi/g-phosphorus, and the purity of the product was chemically and radiochemically high enough to be applied to ordinary tracer experiments. IR, elemental analyses, and autoradiography were employed to obtain the above conclusion.
Alkylethylmethylsulfonium iodide (alkyl : C12H25, C16H33, C18H37) were prepared, refined, and identified by elementary analysis etc. Physico-chemical properties of aqueous solutions of the above samples were measured. Depressions of the surface tension and durabilities of emulsification of liquid paraffin and wettabilities to cotton cloth were fairly large. The amounts of sedimented CaCO3 in the dilute aqueous solution of the samples tended to decrease with the increase of the length of alkyl chains of the samples. The results indicated that the above samples were excellent as surfactants. And then, the antibacterial and antimold actions of the samples were examined. From these results obtained, it was recognized that antimicrobial actions of the samples were superior than pentachlorophenol.