The seed oil of Melia (Azadirachta) indica has been critically re‐examined particularly with reference to fatty acid composition, using the gas chromatograph as a means of analytical control.
Behenic acid has been discovered as a component and the presence of myristic acid and lignoceric acid verified. The limitations of some earlier methods of analysis are illustrated. A suitably purified neem oil has been successfully reduced to the corresponding saturated and unsaturated alcohols by a selective sodium reduction procedure of potential industrial value.
The reduction products and their acetyl esters have been examined by gas‐liquid chromatography. A comparison is made between the results obtained from methyl esters as derivatives and those obtained from the alcohols and their acetates.
Modified processes are detailed for the preparation of highly purified brassidic acid, from the fatty acids of rape oil, by making use of urea complexes.A study of the changes occurring during, and of the oxidation products of, the catalytic oxidation of brassidic acid by gaseous oxygen a t 120" and 73" with uranyl brassidate as catalyst has shown that there is little rupture of the carbon chain, the main products being dihydroxybehenic acid and an oily monomeric complex containing keto-hydroxy-or keto-unsaturated derivatives. Brassidic acid hydroperoxide is more stable than that of erucic acid, a t moderate temperature, and the trans-acid is again generally less susceptible to oxidation than the cis-isomer. The results of high-temperature oxidation have confirmed existing vien-s on the mechanism of oxidation of inonoethenoid fatty acids.
A solvent extraction process using light petroleum has been adopted for preparation of pure ricinoleic acid from castor oil.The non‐catalytic and catalytic autoxidation of ricinoleic acid by gaseous oxygen at 120° has been studied in relation to the type and concentration of catalyst, and complex changes occurring have been investigated.The products of autoxidation at 120° using uranium and cobalt soap catalysts have been examined and the mechanism of the reaction is discussed in relation to the end products.Ricinoleic acid forms hydroperoxides which yield scisson products on decomposition. At 120° degradation of the molecule occurs with evolution of carbon dioxide and water and it is probable that rupture occurs at the ethenoid linkage and at hydroperoxide groups. Complex, oily components of high molecular weight are formed by recombination of scisson products. In the absence of oxygen, ricinoleic acid esterifies but does not dehydrate at 120°.
The methods of preparation of highly purified erucic acid and its esters have been studied. Catalytic oxidation of the pure acid and of methyl and n-propyl erucate a t various temperatures has been investigated, and the nature of the complex changes occurring studied. The oxidations a t high temperatures result in rapid hydroperoxide decomposition followed by some dimerisation, and there is evidence that a t moderate temperatures the mechanism may follow a different course, as in the case of other monoethenoid fatty acids, The composition of the oxidation products varies considerably with conditions of oxidation and, in oxidations of the esters, the presence of the terminal alkyl group apparently has considerable influence, not only on the rate of entry of the oxygen, but also on that of decomposition of the hydroperoxides.
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