extraction chm142l

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

Experiment 06 Group No.2 Date November 28,2014 1 of 4

Extraction Miranda, Marilyn 1, de Guzman, Anne K. 2

1Professor, School of Chemical Engineering, Chemistry and Biotechnology, Mapua Institute of Technology; 2Student, Chm142L/B21, School of Chemical Engineering, Chemistry and Biotechnology, Mapua Institute of Technology

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 accordingly. This experiment aims

to know the effect of number of extractions to the distribution coefficient and percentage yield.

Keywords: extraction, liquid-liquid extraction, solubility, distribution coefficient, percentage yield

INTRODUCTION

Chemists often extract an organic compound derived from other reaction or 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

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



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.

MATERIALS AND METHODS

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 n-amyl 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.

RESULTS and DISCUSSIONS

For the first part of the experiment, our observation is written below:

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.

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

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.

The micro test tube with distilled water, aqueous crystal violet and n-amyl alcohol only didnt 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.

Volume of NaOH used for titration

Original 1% sample 44 mL

Solution, extracted once 31.4 mL

Solution extracted twice 23.7 mL

Weight of Adipic acid in grams

Original Solution 0.1608 g

Solution, extracted once 0.1147 g

Solution, extracted twice 0.0866 g

Distribution coefficient

Single extraction 0.4019

Double Extraction 1.7136

Percentage yield

Single extraction 28.67%

Double extraction 46.14%



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 groups calculations below:

Weight of Adipic Acid in grams

Original Solution

Solution, extracted once

Solution, extracted twice

Distribution Coefficient



Percent yield



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.



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.

extraction chm142l

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