Hydrochloric Acid → 3',4',7-Trihydroxyflavylium chloride

Participants

Reaction Steps

At 0° C., hydrochloric acid (generated by dropwise addition of H2SO4 to NaCl) was bubbled in a two-necked flask containing 12 g (0.079 mol) of 3,4-dihydroxyacetophenone, 10.88 g (0.079 mol) of 2,4-dihydroxybenzaldehyde and 100 ml of ethyl acetate distilled beforehand. The product started to precipitate after 30 minutes. The bubbling was continued for another 1 hour and then the reaction was stopped. The solution was kept at −18° C. for 3 days and then it was filtered. The filtrate was evaporated and it was taken up in ether; the product precipitated. It was separated from the ether, dissolved in hot methanol and then it was added slowly to an equivalent volume of acetone. The solution was placed in a refrigerator and the product started to precipitate. After filtration, the filtrate was evaporated, dissolved in a minimum of methanol and then ether was added until a precipitate appeared. The procedure was thus repeated several times until precipitate no longer appeared. The purity of the 3′,4′,7-trihydroxyflavylium chloride precipitate thus obtained with a yield of 75% was checked by HPLC (high-performance liquid chromatography).

Provenance & Evidence