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Title: Autoxidative degradation of unsaturated fatty acid esters
Author: Leeves, Nigel John
Awarding Body: University of London
Current Institution: Royal Holloway, University of London
Date of Award: 1985
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The autoxidative degradation of methyl cis-9-octadecenaote, methyl cis-9-cis-12-octadecadienoate and methyl cis-9-cis-12-cis-l5 octadecatrienoate promoted by both transition metal ions and photoinitiators produce volatile products. These were collected by cryogenic and chemical traps, then analysed by glc, HPLC and gc-ms. The major products so identified included; 3-heptanone, heptanal and octanal from methyl cis-9-octadecenoate, hexanal,2-hexenal and 2-heptenal from methyl cis-9-cis-12-octadecadienoate, and propanal, 1-penten-3-ol and 1-penten-3-one from methyl linolenate. Methyl octanoate was found to be a product common to the autoxidation of the three methyl esters. The major products are explained by -scissions of alkoxy radicals. The quantity of volatile compounds produced was found to depend on both the degree of unsaturation and the type of promotor. Volatile products were observed during the promoted autoxidative crosslinking of polyester resins (alkyd resins). The products so formed corresponded to the fatty acids present in the resins. Time lapse infrared spectroscopy was used to observe chemical changes occurring in the drying resin films. Hydroperoxides are the primary autoxidation products and their rate of formation was shown to depend upon the promotor used. Benzoyloxyethyl cis-9-cis-12-octadecadienoate, a model alkyd, was synthesised and autoxidised. The volatile products formed were the same as those observed from methyl cis-9-cis-12-octadecadienoate. Alkyds having a high proportion of non-esterified hydroxyl groups may be crosslinked in the presence of strong acids. This has been shown to be an autoxidative process where the hydroperoxides are decomposed by the acid to give acetal type linkages.2-Hydroxyethyl linoleate, 2-hydroxyethyllinolenate and a series of variable hydroxyl content alkyds were prepared. The volatile products isolated from the alkyds were similar to those produced using transition metal promotors but the 2-hydroxyethyl esters produced only acetal type compounds.6,9-Pentadecadiene, 8-methyl-6,9-pentadecadiene and 8,8-dimethyl-6,9-pentadecadiene were synthesised and autoxidised. The composition and quantity of 'volatile products' depended upon the degree of allylic substitution.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Organic Chemistry