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2.7 Vitamins

2.7.1 Liposoluble Vitamins. Retinol, vitamin A (271), is liable to photo-induced geometrical isomerisation and oxidation,251 as it is generally the case for polyenes. The composition of the photostationary mixture of geometric isomers has been determined for a related compound, retinoic acid (272) (used as keratolytic).252

R= COOH

Vitamins D have offered to organic photochemistry one of the most exciting fields of research, and the unravelling of the geometric isomerisation and electrocyclic cyclisation reactions occurring from various vitamins and provitamins of this group has been of great value for the advancement of this science.253

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