EXPERIMENT 2:EXTRACTIONCHEM200 LABORATORY

EXTRACTION

• A process that involves the transfer of material from one vehicle to another

• The amount of material that will be transferred depends on its relative affinity in the two vehicles.

PURPOSE

• Used to isolate a substance from a solid mixture and this is usually applied in the isolation of compounds from natural resources.

• The separation of a dissolved substance from a solution

• Removal of soluble impurities from mixtures

• Removal of undesired by-products of a reaction.

ALKALOIDS

• Organic bases containing nitrogen, characterized by their bitter taste.

• N-containing heterocyclic compounds

• Very weakly polar/Hydrophobic

• Favors solubility in non-polar solvent

N

N

nicotine

N

O O

OO

cocaine

ON

N

N

N

O

caffeine

N

NN

O

HN

O

xanthine

NH

NN

O

N

O

theophylline

N

NN

O

HN

O

theobromine

METHYLXANTHINES

ON

N

N

N

O

caffeine

Tannins

water-soluble polyphenolics

Chlorophyll green pigment

TEA (CAMELLA SINENSIS)FlavonoidPolyheterocyclic compounds w/c gives tea its color

ALKALOID

Cellulosestructural carbohydrate

CAFFEINE CONTENT

Drink Caffeine content (mg)

Coffee 80-125 per cup

Coffee, decaf 2-4 per cup

Tea 30-75 per cup

Cocoa 5-40 per cup

Milk chocolate 6 per ounce

Coca-cola 46 per 12 ounces

Starbucks (grande) 330

Red bull (8.4 fl. oz.) 80

Monster (16 fl. oz) 160

Tea leaves treated with

base

Aqueous solution –

added with DCM

Aqueous solution

Organic layer (caffeine,

chlorophyll)

Organic layer dehydrated by NaSO4

Residue (cellulose)

SOLUBILITY COEFFICIENT

KD (solubility coefficient) – ratio of solute in the two solvent

Caffeine was extracted from 10.0 grams of tea leaves (containing 0.5% caffeine) by solid-liquid extraction using 100.0 ml of water and liquid-liquid extraction using DCM. Initial tests on the solubility of the caffeine on the two solvents require 2.5 ml of DCM and 20.0 ml of distilled water to completely solubilize 100.0 mg of caffeine.

1. Compute for KD

2. How much caffeine can be extracted by single extraction using 60.0 ml of DCM?

3. How much caffeine can be extracted by two successive extraction using 30.0 ml of DCM per extraction procedure?

FORMULA FOR MULTIPLE EXTRACTION

Xi = amount left in aqueous layer

X0 = original amount in aqueous layer

Vaq = volume of aqueous layer

Vorg = volume of organic layer

i = number of extractions