Experiement 2. Piperine Extraction

When today's reaction mixture is heated to a reflux, the temperature of the system is kept nearly constant at

~40 oC, boiling temperature of dichloromethane

What role does reflux condenser play in the reflux set up?

water that runs through the condenser cools down solvent vapors so that they condense and return to the reaction flask

all applicable pieces of glassware and equipment that are needed for a typical vacuum filtration set up

buchner funnel

filter paper

rubber sleeve

filtering flask

Which method(s) will you use to determine purity of the isolated piperine

Melting Point Comparison

Dichloromethane is carcinogenic volatile solvent. What precautions should you take when working with DCM?

-work in ventilated area

-use glvoes and PPE

-clean spills immediately

Why is the extraction performed under reflux with a water-cooled condenser

To maintain a constant temperature and prevent solvent loss

After filtration, a drying agent (MgSO4 or Na2SO4) is added until it flows freely. Why is this step necessary before rotary evaporation?

To remove dissolved water that would contaminate the product and hinder recrystallization

In the ethanol-water recrystallization, why is water added to the hot ethanolic solution until precipitation appears

To decrease piperine solubility and induce crystallization in a mixed-solvent system

Why is the mixture hot-filtered through a cotton-plugged funnel before cooling?

To prevent premature crystallization in the funnel and remove charcoal/insolubles efficiently

Why is the filtrate first allowed to cool undisturbed to room temperature before placing it in an ice bath?

Slow cooling favors formation of purer, larger crystals; the ice bath completes crystallization

Why are crystals collected on a pre-chilled Büchner funnel and washed with ice-cold 1:1 ethanol-water?

To minimize product loss by reducing solubility while rinsing away impurities

Why does the procedure forbid using hot plates with exposed heating elements for this experiment?

Because ethyl acetate and ethanol are highly flammable; exposed elements are ignition sources

Why should the product be purified (recrystallized) before measuring its melting point?

Impurities depress and broaden melting ranges, obscuring comparison to the literature value

Why is percent recovery (mass of piperine obtained divided by initial pepper mass) reported instead of percent yield?

Because piperine preexists in the natural material; this is an extraction, not a synthesis with a fixed theoretical yield

Based on the structure of piperine, do you expect it to have better solubility in water or in dichloromethane?

In DCM, because polarity of the molecule matches polarity of DCM

Given the structure of chavicine, what is the relationship between piperine and chavicine?

stereoisomers

If you were to react you piperine in the Bayer test we performed during experiment 1, what result will you expect?

the KMnO4 soultion will turn brown due to presence of free double bonds in piperine (note: aromatic rings do not react with KMnO4)

primary pungent principle of pepper is

piperine

strucutally what is apiperine

amide alkaloid

strucutre of piperine

Alkaloids are

orgnaic large compounds with N atom

-in plants that help with bitter taste and toxic to herbivores

Reflux is a method

heat reaction

mixture at constant temperature without losing solvents or reagents.

pure vs impure compunds vs melting temp

-Pure compounds melt

over a narrow range close to literature values;

-lower/broadened ranges suggest

impurities

Piperine is a

lachrymator- causes tears and eye irritation