Solvent Extraction PDF

Solvent Extraction Organic chemistry Solvent Extraction Extraction It’s a method of separation & purification of organic compounds depends on the ability of the compound to dissolve in two immiscible solvents. e.g., H2O & CH3Cl Immiscible solvents are mixtures of liquids Insoluble in each other Solv...

Solvent Extraction Organic chemistry Solvent Extraction Extraction It’s a method of separation & purification of organic compounds depends on the ability of the compound to dissolve in two immiscible solvents. e.g., H2O & CH3Cl Immiscible solvents are mixtures of liquids Insoluble in each other Solvent Extraction Extraction with immiscible solvents is generally employed for: 1. 2. 3. 4. Isolation of dissolved compounds from solution. Isolation of solid compounds from mixtures. Removal of undesirable impurities From mixtures (washing). Sometimes it's used in organic chemistry laboratories to remove an organic compound from a solution when the use of distillation is not convenient. Solvent Extraction Choosing a solvent for extraction: 1. 2. 3. 4. 5. 6. Readily dissolve the compound to be extracted. Have a low b.p. so it can be readily removed. Does not react with solute or other solvent Not flammable or toxic Show little or no water solubility (immiscible with water). Inexpensive. No solvent meets all these criteria, for ex., ether is probably the most common solvent used for extraction but it is flammable Solvent Extraction Diethyl ether Ether, C4H10O, Colorless liquid, Boiling point 34.6 oC, Density 0.7134 g / ml, Solubility in water 69g/L Ether: 1. Has a high solvating power for hydrocarbons and O containing compounds. 2. Is highly volatile , b.p. 34.6 oC. So that it can be easily removed from the extract at low temp. 2O (C2H5) Solvent Extraction Ether is used extensively as an extracting solvent. It's very slightly soluble in water & it's efficiency in use can be ↑ by the addition of a small amount of an ionizable salt, NaCl , to the water layer. This lead to an ↑ in the polarity of this solution that result in a ↓ in the solubility of a non polar compound This is known as "salting out" process. Solvent Extraction SALTING OUT In aqueous solutions of organic molecules, salt is added to separate the organic material from the salty aqueous phase. Solvent Extraction Partition coefficient: is the ratio of concentrations of a compound in the two phases of a mixture of 2 immiscible liquids at equilibrium. Normally one of the solvents is aqueous while the 2nd is organic. Solvent Extraction Solvent Extraction Where: C org: Concentration of the solute in the organic layer W: Concentration of the solute in the aqueous layer Wt. org : Weight of the solute in the organic layer Wt. W : Weight of the solute in the aqueous layer Org : Volume of the organic solvent V W : Volume of the aqueous solvent. Solvent Extraction Name of experiment: Solvent Extraction Aim of experiment: Separation of 4-hydroxybenzaldehyde from an unknown mixture containing NaCl and 4-hydroxybenzaldehyde Properties of the compounds to be separated Hydroxybenzaldehyde-4: Molecular formula: C7H6O2 molar mass:122.12 g/mol ,Yellow-tan powder, Soluble in ether, Slightly soluble in water, Sublimes. Sodium chloride: Molecular formula: NaCl, molar mass :58.44 g/mol, Ionic compound, Colorless crystals, Soluble in water. Solvent Extraction Solvent Extraction 1- Transfer an unknown sample to a separatory Funnel ; add 20ml of ether & 20 ml of Distilled water. 2- Shake gently for 15 – 20 minutes until No further pressure is released From the funnel stem. 3- Leave for 5 – 10 minutes to complete separation of the 2 layers. The stopper must be removed, then separate the 2 layers. 4- Dry the ethereal layer