Introduction
As early as 1849, piperine was hydrolyzed with aqueous Sodium hydroxide, and later with Nitric acid, to yield a volatile base piperidine and piperic acid. Spring and stark used ethanolic potassium hydroxide for hydrolysis of piperin. The presence of two double bonds in piperic acid was proved by its catalytic reduction to tetrahydropiperic acid and by the preparation of tetrabromopiperic acid by bromination with bromine in carbon disulfide.
The structure of Piperic acid oxidation by Potassium permanganate to yield Oxalic acid, Piperonal, and Piperonylic acid.
Mild oxidation (KMnO4 in basic solution) yields piperonal, piperonylic acid, and tartaric acid. Piperine can synthesized from the chloride of piperic acid and piperidine.
In the following degradation, piperine is treated with ethanolic potassium hydroxide, yielding piperic acid and piperidine.
Procedure
1. Piperine 1 g and 10 mL potassium hydroxide alcoholic 10% are refluxed for 90 min.
2. The ethanolic solution is evaporated to dryness under reduced pressure, and the receiver being cooled in an ice salt bath.
3. The solid potassium piperinate is suspended in hot water and acidified with hydrochloric acid.
4. The voluminous yellow precipitate is collected on a Buchner funnel, wash with cold water.
5. Recrystallized from ethanol to yield piperic acid as yellow needles (mp 216-217°C).
6. The strongly basic ethanolic distillate in the receiver is saturated with hydrochloric acid and evaporated to dryness to give piperidine hydrochloride.
7. Recrystallization with ethanol (mp 244°C).
0 comments:
Post a Comment