Acid-Base extraction of organic compound
Acid-base extraction is the process of purifying of an organic acid and an organic base of an organic mixture. It is the procedure using sequential liquid-liquid extraction to purify the acid and the base from the mixture based on their chemical properties and solubility of the molecular and ionic forms. Acid- base extraction is commonly performed during the work-up of a chemical reaction. The acid-base extraction procedure can also be used to separate very-weak acids from stronger acids and very-weak bases from stronger bases as long as the difference of their pKa (or pKb) constants is large enough.
The major limitation of this reaction is that it is not possible to separate chemically similar acids or similar base with a large different form of ions solubility between their charged and their uncharged form.
The main purposes of this experiment are as follows:
i. To extract benzoic acid, 4-nitroaniline and biphenyl from organic compound or from the mixture in order to purify them. ii. To develop the TLC plate and visualize the obtained TLC plate. iii. Learn to use a separatory funnel properly in lab while doing any other similar or different experiments. iv. Learn to use and see how vacuum filtration and rotory evaporation/vacuum works.
4nitroaniline hydrochloride (salt of PNA)
Remains unchanged in the
CH3 C O CH2 CH3
Obtained tube with labeled as sample#7 of 2.12gm of a dry mixture containing benzoic acid, 4-nitroaniline and biphenyl place it into the 100ml beaker, 30ml of ethyl acetate were measured and poured into the same beaker and stirred until all solids were dissolved. A small amount (1-2) drops of this mixture was separated into a separate test tube, covered and label it a “M” as a mixture and set aside to use for next day experiment.
The mixture that remains is poured into a separatory funnel, and set it to the ring stand. 10ml of 1M of HCL were added to separatory funnel which is tightly secured. The separatory funnel was taken to the hood where it was shook gently for about a minute and, allows the gas to escape that build up from reaction. Vent after 5 seconds, then vent again every 10 seconds. After ~1 minute of shaking, allow the two layers to separate. Collect the aqueous layer in 50ml Erlenmeyer flask. Label this flask as A for “Acid Extract”. Repeat this process in same manner by adding another 10ml of 1 M of HCL again. And collect the aqueous layer again in same flask. (20ml total)
Add 10ml of 1M NaOH to the remaining organic layer of separatory funnel. With the stopper firmly secured take funnel back to hood and shake it gently for ~ 1 Minute and then allow the gas to escape in hood. Vent after about 5 second, then vent again every 10 second. After gently shaking allow the two layers to separate and collect the aqueous layer into separate 50ml Erlenmeyer flask. Label this flask as B for “Base Extract”. Repeat the same process in a same manner one more time by adding 10ml of 1M NaOH. And collect the aqueous layer in same flask by combining the extract.
Poured the organic layer into another 50ml Erlenmeyer flask and add 1 or 2 spatulas of anhydrous Na2SO4 to the flask. Swirl gently and, stir for 5 minutes. Add 10ml of ethyl acetate to the mixture. Filter it into a 100ml of round bottom flask. Ethyl acetate is then removed under a vacuum with a rotary evaporator.
The beakers with aqueous acid “A” and Aqueous base “B” are cooled by placing them in an ice bath. Add 5-10ml of 6 M NaOH to the flask “A” and add 5-10ml of 6 M HCL to the “B”. Allow the flasks to sit in ice bath for around 5 minute to complete the crystallization. Isolate that crystal by using vacuum filtration using a...
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