Stage 1. Extraction of Piperine
Starting reagents and materials:- 400 ml of 88% ethanol
- 300 g of ground black pepper
- Potassium hydroxide (KOH)
- 180 mm diameter filter papers
- Soxhlet extractor (500 ml)
- Measuring cups
- Funnel
- Heater
Pour 300 ml of 88% ethanol into a 500 ml flask.
Place 60 g of ground black pepper in a paper extraction sleeve (180 mm in diameter).
Assembling the apparatus for piperine extraction, the flask with ethanol was heated, and the reflux condenser was cooled.
Each portion of pepper (60 g) was extracted until the condensing ethanol becomes colorless. Then, a new extraction was performed on the next portions of black pepper, each weighing 60 g, with the addition of 20 ml of fresh ethanol. In total, 5 extractions were carried out from portions of ground black pepper weighing 60 g each, which corresponds to the maximum saturation of ethanol with piperine.
Place 60 g of ground black pepper in a paper extraction sleeve (180 mm in diameter).
Assembling the apparatus for piperine extraction, the flask with ethanol was heated, and the reflux condenser was cooled.
Each portion of pepper (60 g) was extracted until the condensing ethanol becomes colorless. Then, a new extraction was performed on the next portions of black pepper, each weighing 60 g, with the addition of 20 ml of fresh ethanol. In total, 5 extractions were carried out from portions of ground black pepper weighing 60 g each, which corresponds to the maximum saturation of ethanol with piperine.
Stage 2: Piperine Precipitation
Reagents and Materials:
- Ethanol extract of black pepper obtained in Stage 1
- 24 g of potassium hydroxide (KOH)
- 216 ml of 88% ethanol
- 1 liter of distilled water
- Chemical beakers
- Filter papers
- Funnel
Potassium hydroxide (KOH) was dissolved in ethanol. The obtained black pepper extract was filtered through a paper filter directly into the prepared KOH solution.
The obtained solution was heated to 60-70℃.
In the heated solution, water was gradually added in portions (about 1 liter) until the formation of yellow precipitate of piperine ceases.
The obtained suspension was cooled in a freezer until the next day and the precipitated residue was filtered out.
The filtered precipitate of piperine was dried in a desiccator over alkali or under a heat gun until a constant mass was achieved. The precipitate should have a slight pepper odor and a melting point of 127-128°C.
The yield of piperine is 17 g.
Stage 3: Alkaline Hydrolysis of Piperine to Piperic acid
Reagents and Materials:
- 17 g of piperine
- 193.8 g of KOH
- 500 ml of ethanol (EtOH)
- 900 ml of 14% HCl
- Magnetic stirrer with heating
- Chemical beakers
- 1-liter flask
- Reflux condenser
- Funnel
- Filter papers
Ethanol, KOH, and piperine were added to a 1-liter flask. The mixture was stirred until dissolved and heated at 70-80°C for 10 hours.
The resulting warm suspension of potassium piperate was transferred to a beaker, and hydrochloric acid was added until complete precipitation of piperic acid occurs.
The precipitated light-yellow piperic acid was filtered through a dense paper filter. Glass filters with porosity of 160 and 100 do not filter the precipitate, while a filter with porosity of 60 gets clogged.
Piperic acid was dried in a desiccator or under a heat gun until a constant mass was achieved. The acid is a yellow powder with a slight pepper odor.
The yield of piperic acid is 12 g.
Stage 4: Oxidation of Piperic Acid to Piperonal using Copper(II) Hydroxide (UNSUCCESSFUL)
Reagents and Materials:
- 12 g of piperic acid
- 41 g of NaOH
- 62 g of CuSO4·5H2O
- 500 ml of water (250 ml for Copper(II) sulfate and 250 ml for alkali)
- 150 ml of DCM
- Chemical beakers
- Magnetic stirrer with heating
- Reflux condenser
The solution of copper sulfate was mixed while adding the alkali solution, and then piperic acid was added. The solution was heated for 8 hours under a reflux condenser at a temperature of 80-90°C.
After 8 hours, based on the odor of heliotrope and a slight pepper odor, it is presumed that piperic acid and piperonal are in equilibrium in the resulting reaction mixture. An attempt was made to remove the formed heliotropin by steam distillation and to extract from the reaction mixture with dichloromethane. The dichloromethane was dried with sodium sulfate and evaporated. As a result, the yield of the oil-like, non-crystallizing substance with the corresponding heliotrope odor was less than 1 g. The alkaline reaction mixture also contained unreacted piperic acid in the form of sodium piperate. The method was unsuccessful in reproducing the oxidation of piperic acid using Cu(OH)2.
These results allow to understand that extraction method piperine is valid. Also, synthesis of piperic acid from piperine gives decent yield. But Cu(OH)2 isn`t work well as oxidizer of piperic acid in piperonal synthesis.
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