Extraction CHM142L

CHM145L Organic Chemistry 1 Laboratory 2nd Quarter SY 2014-2015

Extraction Miranda, Marilyn  1, de Guzman, Anne K. 2 Professor, School of Chemical Engineering, Chemistry an d Biotechnology, Mapua Institute of Technology; 2Student, Chm142L/B21, School of Chemical Engineering, Chemistry and Biotechnology, Mapua Institute of Technology

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ABSTRACT Extraction is the physical process by which a compound or a mixture of compounds is transferred from one phase into another. In this experiment, a liquid-liquid extraction was performed. Liquid-liquid extractions usually involve water and an organic solvent. Most common organic solvents (i.e. diethyl ether, ethyl acetate, toluene, methylene chloride) are immiscible and are much less polar than water. A general rule of thumb for solubility states that like dissolves like. Polar compounds are more soluble in polar solvents than in nonpolar solvents, and vice versa. The selective solubility of different compounds in polar versus nonpolar solvents allows the separation of the compounds in a mixture by liquid-liquid extraction. This experiment aims to know the effect of number of extractions to the distribution coefficient and percentage yield. Adipic acid was mixed with ether in a separatory funnel and extracted. The distribution coefficient and percentage yield was later computed and compared with adipic acid extracted twice. The group obtained incorrect values for distribution coefficient and percentage yield due to incorrect computation which was of course, amended. By the end of this experiment, it was determined that double extraction is more efficient than single extraction alone as double extraction increases the distribution coefficient and the percentage yield. Generally, the experiment was satisfactory since the objectives were met a ccordingly. This experiment aims aims to know the effect of number of extractions to the distribution coefficient and percentage yield. Keywords: Keywords: extraction, liquid-liquid extraction, solubility, distribution coefficient, percentage yield

INTRODUCTION Chemists often extract an organic compound derived from other reaction or syntheses. syntheses. Extraction is a process in which one selectively dissolves an organic compound in an acceptable solvent. Organic acids and bases can be separated from each other by using a variety of aqueous solutions. The solutions have varying levels of pH which in turn effects the solubility of the organic compound. Therein lies the basis for extraction; the factor of solubility. Extraction has many real world applications. Numerous organic compounds are extracted from plants for medicinal purposes such as morphine from the opium poppy, aspirin from willow bark, and digitalis (a heart drug) from foxglove to name a few. Or to keep it simple, when you steep a tea bag in boiling water, add a bay leaf to a pot of soup, or wash a load of laundry, you are performing a solid/liquid extraction, in which a solution containing several

Experiment 06│ Group  No.2│ Date November 28,2014

components is mixed with a second, immiscible liquid, for the purpose of extracting one component of the solution into the second solvent. We have seen that recrystallization is used to purify solids that are contaminated by relatively small amounts of impurities. By contrast, the technique of extraction is a more “coarse” or preliminary technique, in that it can be used to separate one compound from another or from large amounts of impurities. Most uncharged organic molecules are more soluble in organic solvents than in water. If the organic solvent itself is not very soluble in water, then when the solvent or one of its solutions is mixed with water, two layers will form, and the solvents are said to be immiscible. The layers are called

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CHM145L Organic Chemistry 1 Laboratory 2nd Quarter SY 2014-2015

the organic layer and the aqueous layer. If the two layers are shaken together, small amounts of the components of the organic layer will dissolve in (or be extracted into) the aqueous layer, and small amounts of the aqueous layer components will dissolve (be extracted into) the organic layer, establishing equilibrium between the two layers. Thus, if a neutral compound C is initially dissolved in one layer (phase), it will be distributed, or “partitioned,” between the two layers at equilibrium. This experiment aims to know the effect of number of extractions to the distribution coefficient and percentage yield.

RESULTS and DISCUSSIONS

MATERIALS AND METHODS

The reason why the test tube containing salt formed two layers is the salting-out effect, in which the solubility of a nonelectrolyte in water is decreased when an electrolyte, like salt is added.

In the first part of our experiment entitled Salting-out Effect , two micro test tubes were filled with 3 ml distilled water. A drop of 0.003 M aqueous crystal violet and 0.50 ml of namyl alcohol were added in each test tube. After shaking the test tubes, sodium chloride was introduced to one of the test tubes and the results were observed and compared. In the second part entitled Determination of a Distribution Coefficient and Percentage Yield of Extraction, 10 ml of 10% adipic acid was added with a drop of phenolphthalein and titrated with 0.05 M NaOH up to a light endpoint. The volume of NaOH used for titration was later used to obtain the weight of the acid in the original solution. 10 ml of adipic was transferred in the quick fit separatory funnel and mixed with 10 ml of ether before extracting the acid. A drop of phenolphthalein was added to the extracted aqueous layer and titrated with 0.05 M NaOH. The organic layer was drawn off and placed in a separate bottle with the label “Ether extract”. The next part involved double extraction. Again, 10 ml of adipic acid was transferred in the quick fit separatory funnel and mixed with 5 ml of ether. The aqueous solution was extracted while the organic solution was drawn off and transferred to the bottle labelled “Ether extract”. The aqueous layer previously extracted was placed again in the separatory funnel, mixed with another 5 ml of fresh ether and extracted. . A drop of phenolphthalein was added to the extracted aqueous layer and titrated with 0.05 M NaOH. The results were recorded and used for further observations.

Experiment 06│ Group  No.2│ Date November 28,2014

For the first part of the experiment, our observation is written below: The micro test tube with distilled water, aqueous crystal violet and n-amyl alcohol only didn’t form a layer separating the two components. In the second test tube with salt, it forms a layer with water at the bottom and the top as violet colored substance. In the second test tube, the color is much lighter than that of the first test tube.

The data obtained from the part 2 of the experiment is shown in tabular form below: Table 1 Determination of a Distribution Coefficient and Percentage Yield of Extraction

Volume of NaOH used for titration Original 1% sample Solution, extracted once Solution extracted twice Weight of Adipic acid in grams Original Solution Solution, extracted once Solution, extracted twice Distribution coefficient Single extraction Double Extraction Percentage yield Single extraction Double extraction

44 mL 31.4 mL 23.7 mL 0.1608 g 0.1147 g 0.0866 g 0.4019 1.7136 28.67% 46.14%

 A quantitative measure of the how an organic compound will distribute between aqueous and organic phases is called the distribution or partition coefficient. It is the ratio, K, of the solubility of solute dissolved in the organic layer to the solubility of material dissolved in the aqueous layer.

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CHM145L Organic Chemistry 1 Laboratory 2nd Quarter SY 2014-2015

Solution, extracted once

Since the distribution coefficient is a ratio, unless K is very large, not all of a solute will reside in the organic layer in a single extraction. Usually two, three, or four extractions of the aqueous layer with an organic solvent are carried out in sequence in order to remove as much of the desired product from the aqueous layer as possible. The effectiveness of multiple small volume extractions versus one large volume extraction is demonstrated by the group’s calculations below:

Solution, extracted twice

Percent yield

Weight of Adipic Acid in grams Original Solution Solution, extracted once

Solution, extracted once

Solution, extracted twice

Solution, extracted twice

By comparing the obtained values for percentage yield and distribution coefficient of each of the extractions it can be interpreted that by extracting twice, the amount of the acid acquired was greater than extracting only once. Thus, the number of extractions increases the percentage yield and the partition or distribution coefficient.

Distribution Coefficient

Experiment 06│ Group  No.2│ Date November 28,2014

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CHM145L Organic Chemistry 1 Laboratory 2nd Quarter SY 2014-2015

CONCLUSIONS AND RECOMMENDATIONS The group achieved the data correctly except for the distribution coefficient and percentage yield due to error in computation which was later corrected. At the end of the experiment, it was determined that double or multiple extractions is more efficient to perform to obtain higher percentage yield and distribution coefficient and attain as much of the desired product from the layer. Certain precautions which are as follows must be observed when performing the experiment: A protective mask must be worn when dealing with toxic compounds such as ether. When shaking the separatory funnel, the barrel must be pointed away from the holder and his neighbours. Also, the stop cock must be opened after vigorously shaking to release the internal pressure. REFERENCES 1. Zachary Fijal, Constantinos Loukeris, Zhaleh Naghibzadeh, John Walsdorf, (n.d.) Liquid-liquid Extraction (University of Illinois at Chicago) 2. Barnard College, Department of Chemistry (n.d.) Extraction 3.

Experiment 06│ Group  No.2│ Date November 28,2014

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