CHEMICAL EXTRACTION OF A MIXTURE PURPOSE: The purpose of this experiment is to:

Question

CHEMICAL EXTRACTION OF A MIXTURE PURPOSE: The purpose of this experiment is to: 1. 2. Learn about the practical and theoretical aspects involved in the extraction process. Separate a mixture containing a carboxylic acid, an amine, and a neutral compound by a process called "chemically active extraction. BACKGROUND n is the removal of a substance (solute) from one solvent phase by another solvent. w hen a compound is shaken in a separa solvent, the compound distributes itself between the two solvents. Extraction is frequently used in organic chemistry to remove one or more components tory funnel with two immiscible solvents, such as water and an o from a mixture. In later experiments, you will use this technique to obtain a reaction product free of unreacted starting material and by- often How much solute dissolves in each phase depends on differences of solubility of the solute in each solvent. The ratio of the concentrations of solute in each solvent at a particular temperature is a constant called the distribution coefficient or partition coefficient (K). A rough estimate of K can be made by using the ratio of the solubilities of the solute in the two solvents 20 g/100 mL Ksconeinsolvet! . solubility insolventI in solvent 2 eg. K4.0 when K extract from H20 using ether 1.0 or less, the extraction will be difficult. Assuming you had 5.0 g of material to then x=4.0 g K = 4.0 = Rg/100mL ether mL HO 1st extraction2.8 g Thus, one single extraction with 100 mL ether removes 4.0 g or 80% of solute from Ho. Compared with three successive extractions with 33.3 mL portions of ether: 2nd extraction1.2g 3rd extraction 0.5g 4.5 g or 90% extracted multiple extractions with smaller portions of extracting solvent are more efficient than a single extraction with a large portion of solvent Extraction requires the use of two mutually immiscible solvents: an aqueous solvent and an organic solvent with only very slight water solubility. Common solvents for extraction of an aqueous solution are ing extracted; non-reactive with the solute or solvent being extracted (except in a chemically-active shown in Table 1. The "ideal extracting solvent should be: immiscible with the solution extraction); have a large K for the solute, be relatively volatile so that the solvent can be non-toxic, non-flammable, and inexpensive. Table 1 Common Organic Solvents for Extraction of Aqueous Solutions Lighter than Water n water er Ether, Pentane, Hexane Petroleum ether, Toluene Dichloromethane, chloroform Carbon tetrachloride 51

Explanation / Answer

Hi

Initially, organic extraction relies on the principle of like dissolves like that is: polar components dissolves in polar solvents (usually water) & non polar solvents ( organic) dissolves nonpolar components.

& during extraction, denser solvent lies in the bottom of separating funnel & the lighter one on the top.

1. To improve the efficacy or yield, compound has to be repeatedly extracted with suitable solvent for 2 or more times and the collected fractions are united to remove the solvent

2. If an organic acid is there, it forms a salt with NaOH and enters into aqueous layer instead of ether layer, where we can collect organic base. Where as if organice base is there, it forms salt with HCl, an acid & hence collected in aqueous layet& in ether only organic acid will be there.

3. If that is the case, just add water to the solution mixture in separating funnel & observe which layer is increasing in quantity. If upper layer quantity increases, it is clear that, water is at top & in bottom, denser organic solvent.

If lower layer increases, water is at bottom, where as lighter organic layer is on top.

4. If considerable water quantity is there in organic extract, use separation funnel again to separate the two solutions & then use drying agent to remove water from organic layer.

5. Generally, potassium salts are not used as drying agents as K+ ions can be easily exchanged with acid groups of organic compounds & results in salts which enter the aqueous layer instead of the organic layer.

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