In the previous paper, the authors suggested the presence of the aromatic ο-substituted compound in the cyclic monomer obtained from heated linseed oil in the presence of alkali.
In order to certify the presence of the aromatic ο-substituted compound, this study was made by using ethyl-β-eleostearate prepared form tung, oil.
Ethyl-β-eleostearate was heated at 250°C, for 10 hours in the stream of carbon dioxide. Heated ester was separated into non urea adduct forming ester and urea adduct forming ester by urea adduct separation.
Cyclic monomer was obtained from non urea adduct forming ester by vacuume distillation.
When GLC and IR spectra of this cyclic monomer were compared with those of the cyclic monomer of the first report obtained from heated linseed oil, the similarity was observed.
IR spectra of this cyclic monomer indicated the presence of aromatic ο-substituted compound and cyclohexadiene structure. The positions of the both compounds on the GLC chart were ascertained by selective hydrogenation of this cyclic monomer.
In the case of cyclic monomer obtained from ethyl-β-eleostearate heated under severe condition at 310°C for 10 hours, it was found in the GLC and IR spectra that the amount of aromatic ο-substituted compound increased, while the amount of cyclohexadiene compound decreased.
With regard to the mechanism of the formation of aromatic ο-substituent, cyclohexadiene is farmed by the cyclization of ethyl-β-eleostearate, and aromatic ο-substituent is formed by disproportionation reaction of cyclohexadiene.
From the result of the experiment on ethyl-β-eleostearate, it can be concluded that, when linseed oil is heated under the presence of alkali, (1) linolenic acid in linseed oil is isomerized to conjugated triene, (2) cyclization and (3) disproportionation reaction occure and aromatic ο-substituted compound is formed.
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