Separating Mixture Of Benzoic Acid And Nitrotoluene Biology Essay


During the vacuum filtration for the recrystaiisation process, some of the product i.e. benzoic acid and in another suction , 4-nitrotoluene just went throught the filter paper and into the Buchner flask. Hence the purified product obtained on hte Buchner funnel was not the total product obtained by separation. Unfortunately, due to lack of time, the process could not be repeated again. Hence the results obtained varied and percentage yield calculated was lower.

The purified products obtained were not allowed to dry completely before their mass was taken. Hence this might slightly affected the results obtained since the mass could might have been slightly higher due to some solvent still present.

During the separation of the 4-nitrotoluene / benzoic acid mixture by means of extraction using the separating funnel, it was quite difficult to stop the run at the interphase between the ether and the aqueous layer. Hence a drop of the ether layer was run out into the conical flask by mistake and hence mixed with the aquoeous layer. This means that there was no complete separation of the two.

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Is is found that extraction is applied to a variety of food products, for example the extraction of sugar from sugar-cane or sugar-beets, the extraction of oil from oil seeds, the extraction of coffee extract from coffee beans, the extraction of various other components such as proteins, vitamins, pigments, essential oils, flavoured compounds, amonsgts others. Hence, the extraction of these products allows their separation from many different materials.

Extraction process can be calssified based on combination of phases (solid, liquid, gas and supercritical fluid). The solid â€" liquid is a type of extraction that is useful for the isolation and purification of naturally occuring sources. On the other hand the liquid â€" liquid is a more common method depending on solubility propertiesof components.

Regarding solvents, it can be said that there is a variety of solvents that can be used. Solvents used in separation of a mixture by extraction may be organic solvents which are denser than water; for example dichloromethane, chloroform and carbon tetrachloride. On the other hand they may also be organic solvents which are less dense than water; for example diethyl ether, toluene, hexane. In this experiment ether was used and this is very frequently used because ether is very immiscible with water, it has very powerful solvent properties for non-polar solvents, it has very low boiling point (35 ÌÅ C) hence it can be evaporated easily after the extraction. However special care must be taken when handling this solvent since it is extremely volatile and flammable. In particular, all naked flames in the immediate vicinity should be extinguished.

A solvent is very important in the extraction process. A solvent is actually a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature.

In this experiment liquid-liquid extraction was carried out. This is also known as solvent extraction and partitioning and this method was used in order to separate compounds based on their relative solubilities in two different immiscible liquids, which are water and an organic solvent. It is an extraction of a substance from one liquid 1"phase into another liquid phase. Liquid-liquid extraction is a basic technique in chemical laboratories, where it is performed using a separatory funnel.

In other words, liquid-liquid extraction is the separation of a substance from a mixture by dissolving that substance in a suitable solvent. By this process a soluble compound is usually separated from an insoluble compound.

One should say that solvent extraction is used in nuclear reprocessing, ore processing, the production of fine organic compounds, the processing of perfumes, and other industries.

While solvent extraction is often done on a small scale by laboratory chemists using a separatory funnel, it is normally done on the industrial scale using machines that bring the two liquid phases into contact with each other. Just for the sake of mentioning them such machines include 1"centrifugal contactors, thin layer extractors, 1"spray columns, pulsed columns, and mixer-settlers.

This brings us to the importance of using a separating funnel by which an extraction separation process can be carried out. A separating funnel is a pear-shaped laboratory apparatus which is used to separate two immiscible liquids that are usually very difficult to separate, for instance ether and water. It is very useful because the layers of the two liquids could be seen very easily, with the naked eye, separated from the side of the funnel. The separating funnel usually has a short stem and is fitted with a ground glass interchangeable stopper. The size of the separating funnel must always be about twice the volume to be extracted. It is usually very useful and convenient to have the separating funnel mounted in a ring on a stand with a firm base.

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Discussing the results obtained it was noted that the percentage yield calculated was quite low. Hence much of the product was lost and a reference to this was mentioned as one of the sources of error, where some product was not taken into account since it passed through the filter paper into the Buchner flask and the recystallisation process was not repeated. This might occurred due to the filter paper used, not being of the appropriate size.

In order to conclude one could discuss a modification which could be done to the above protocol for the separation of a mixture of benzoic acid and 4-nitrophenol. As mentioned in the introduction and further on with it in the procedure, the steps carried in the laboratory during the experiment were different from the ones below.

Initially acid anhydride is added and the 4-nitrophenol becomes 4-nitrophenyl ethanoate which is an ester that is soluble in ether. Then sodium bicarbonate is added which is not alkaline enough in order to convert the ester into alcohol but is alkaline enough in order to convert the benzoic acid into benzoate, which is soluble in water. Then extraction is done and NaOH is added to the ester and 4-nitophenol is obtained again. Concentrated hydrochloric acid is then added to the benzoate until crystallisation of benzoic acid occurs. Hence the individual compenents are obtained and in a pure form once the recrystallisation process is carried out.

5. Conclusion:

It as concluded that the benzoic acid / 4-nitrotoluene mixture was separated by means of extraction. Hence the individual components of the mixture were obtained separately and in a purified form by recrystallisation processes. The melting point of the purified crystals was also found, confirming the purity of the substances.