| Popis: |
A comparative study of radical cation formation from selected polyenes, namely carotenoids (C 40 ) and retinoids (C 20 ), has been carried out by treatment with the Lewis acids BF 3 as its etherate or SbCl 3 . The reaction in chloroform was monitored by vis/NIR and EPR spectroscopy at variable temperature. β,β-Carotene, β,β-caroten-4-ol, retinol (vitamin A), retinyl acetate and anhydroretinol were used as substrates. It is concluded that whereas BF 3 –diethyl etherate or SbCl 3 is capable of effecting one-electron transfers to produce radical cations from the longer polyenes (carotenoids), no radical cations were obtained from the retinoids. The results of SbCl 3 treatment of the retinoids have a bearing on the current studies on the mechanism of the Carr–Price blue colour reaction previously used for quantitative analysis of vitamin A. |
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