Comparison of Vitamins a and A2 by Distillation

Physical and Chemical Determination of Vitamin A

“…It was also found to possess direct absorption at the correspondingly longer ultraviolet wave length of 345 to 350 µ together with another band in the region of 290 µ. Gillam et al judged that vitamin Aa had the same formula as vitamin Ai except that it had two or more carbon atoms or one more ethylene group. Contradictory evidence has been recently obtained (1939) by Gray to indicate that the differences may be explained by the presence of merely one additional double bond and that vitamins Ai and Aa therefore have the same number of carbon atoms (20).…”

“…Although vitamins Ai and Aa differ considerably in their ultraviolet absorptions and antimony trichloride values (19,20), the absorptions of the cyclized compounds have been found by independent investigators to be identical. However, it would appear that these cyclized compounds are not identical, since Embree and Shantz ( 16) have proposed a quantitative determination of each of the constituent vitamins when mixed, based on the differences of their respective adsorptions on alumina.…”

ABSORPTION SPECTRA OF CAROTENOIDS; STRUCTURE OF VITAMIN A2

“…Vitamin Ai is easily dehydrated to an anhydro compound; Oppenauer oxidation of the alcohol or aldehyde gives a C^-aldehyde very similar in absorption characteristics to the aldehyde of vitamin A2 and reducible to an alcohol similar to or identical with A2 (13,14). Vitamin A2, isolated in pure form by Shantz (4), distills in a high vacuum at a temperature only about 3°h igher than Ai (15) and is so similar to in chromatographic characteristics and ease of dehydration that it must be an allylic alcohol of nearly the same molecular weight. From a comparison with the distillation characteristics (elimination maxima) of saturated and unsaturated fatty acids, Gray and Cawley ( 16) concluded that A2 has the same number of carbon atoms as Ai but contains one additional conjugated double bond!…”

High-Vacuum Still in Medicine

“…The half-succinate gave an elimination curve with a maximum at 173°C ., the double succinate of vitamin A failed to distill completely at 250°C ., and the submaximum at 120°C. showed that not all of the reaction mixture had become esteri-TEMPERATURE Dye Class Vitamin A6-alcohol (16) Vitamin A6-acetate (15) Vitamin A&-palmitate (15) Vitamin A&-naphthoate Vitamin A6-half-succinate (9) Vitamin A&-succinate (9) Vitamin A 6-fish liver esters (16) Vitamin A 6-rat liver esters (15) Vitamin A26 (14) Cyclized vitamin A6 (12) Subvitamin A6 (9) 0-Carotene6 (9) a-Carotene (5) Xanthophyll (9) D2 (!S)-Calciferol6 D3 (18) (Windaus)6…”