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Lab Report Acid Base Extraction, Lab Reports of Organic Chemistry

Universiti Teknologi MaraOrganic Chemistry

Organic Chemistry,Lab Report Acid Base Extraction

Typology: Lab Reports

2022/2023

Available from 08/26/2023

baizatul-emylia
baizatul-emylia ๐Ÿ‡ฒ๐Ÿ‡พ

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Objective
1) To separate a mixture of benzoic acid and a neutral compound into its
individual components.
2) To determine the yields and melting points for both products .
Introduction / Theory
Extraction is a process of transferring a solute from one solvent to another
Extraction is frequently used to separate one or more components from a mixture. In
this respect, extraction is like distillation and recrystallization. However, extraction,
unlike recrystallization or distillation, rarely gives a pure product. Recrystallization or
distillation may be needed to purify a crude product extracted from a mixture.
Suppose, for example a reaction is carried out in aqueous solution and the
desired product is an organic compound. The reaction mixture is then shaken with a
small amount of an organic solvent, such as ether (diethyl ether) whereupon the
organic solute, being more soluble in the organic solvent than in water transfers
primarily to the organic layer. Then the undesired aqueous layer is drawn off and
discarded resulting organic solution is shaken with a small amount of distilled water to
"wash" the organic solution (remove inorganic impurities). The new aqueous layer
containing inorganic impurities is then drawn off and discarded. The organic solution
that remains is now ready for further treatment to isolate the desired product.
If two solutes are both soluble in an organic solvent but insoluble in water, they
can still be separated by extraction if one of the solutes can be converted to a water-
soluble salt. For example, a mixture of benzoic acid and napthalene (neutral
hydrocarbon) can be separated as follows. Dissolve the mixture in a small amount of
ether (or other water-immiscible solvent). Pour the mixture into a separatory funnel.
Add a small amount of dilute NaHCO; solution (the NaHCO3 is assumed to be
dissolved in water). The NaHCO3 (a base) reacts with the benzoic acid to form a water-
soluble salt. The napthalene, being neutral, remains in the ether. Then the aqueous
layer can be separated from the ether layer by opening the separatory funnel's
stopcock and draining the aqueous solution into a separate container.
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Objective

  1. To separate a mixture of benzoic acid and a neutral compound into its individual components.
  2. To determine the yields and melting points for both products. Introduction / Theory Extraction is a process of transferring a solute from one solvent to another Extraction is frequently used to separate one or more components from a mixture. In this respect, extraction is like distillation and recrystallization. However, extraction, unlike recrystallization or distillation, rarely gives a pure product. Recrystallization or distillation may be needed to purify a crude product extracted from a mixture. Suppose, for example a reaction is carried out in aqueous solution and the desired product is an organic compound. The reaction mixture is then shaken with a small amount of an organic solvent, such as ether (diethyl ether) whereupon the organic solute, being more soluble in the organic solvent than in water transfers primarily to the organic layer. Then the undesired aqueous layer is drawn off and discarded resulting organic solution is shaken with a small amount of distilled water to "wash" the organic solution (remove inorganic impurities). The new aqueous layer containing inorganic impurities is then drawn off and discarded. The organic solution that remains is now ready for further treatment to isolate the desired product. If two solutes are both soluble in an organic solvent but insoluble in water, they can still be separated by extraction if one of the solutes can be converted to a water- soluble salt. For example, a mixture of benzoic acid and napthalene (neutral hydrocarbon) can be separated as follows. Dissolve the mixture in a small amount of ether (or other water-immiscible solvent). Pour the mixture into a separatory funnel. Add a small amount of dilute NaHCO; solution (the NaHCO 3 is assumed to be dissolved in water). The NaHCO 3 (a base) reacts with the benzoic acid to form a water- soluble salt. The napthalene, being neutral, remains in the ether. Then the aqueous layer can be separated from the ether layer by opening the separatory funnel's stopcock and draining the aqueous solution into a separate container.

Procedure

  1. ) 0.24 g of Triphenylmethanol and 0.12 g of benzoic acid were weighed and placed in a test tube. 10 ml ether was added to the mixture and the test tube was shaken to dissolve the mixture.
  2. The solution was transferred to the separatory funnel and 5 mL of 1M NaOH was added, tightly capped and the layers were mixed by swirling and shaking gently for 30 seconds.
  3. Pressure was vented by titling the funnel and opening the stop cork. The stop cork was closed, shook and vented again.
  4. The mixture left let stood to allow the layers to separate. The top layer was ether layer and the bottom was the aqueous layer.
  5. The aqueous layer was drained into an Erlenmeyer flask and labelled as the first extraction of NaOH.
  6. Another 5 ml of the 1M NaOH solution was added to the ether layer in the funnel and step 1 to 4 were repeated for the second extraction step. The aqueous solution was transferred to another Erlenmeyer flask and labelled as second extraction NaOH.
  7. Flask has been taken to the hood, and slowly stirred (glass rod), 6M HCI is added into each Erlenmeyer flask until the solution is acidic using blue litmus paper.
  8. 5 mL of saturated solution of sodium chloride is added to the ether layer in separatory funnel (to remove any trace of NaOH solution). Cap, mix, vent, and the layers separate as before.
  9. The aqueous layer has been discarded. The ether layer is transferred into an Erlenmeyer flask and 1 g of anhydrous sodium sulphate (drying agent) is added to remove the moisture (water) it contains. The flask is closed, swirled, and let stand for 10 minutes.

Data Actual mass of benzoic acid (g) 0. Actual mass of unknown sample (g) 0. Mass of Erlenmeyer flask (g) 50. Mass of unknown sample + Erlenmeyer flask

Mass of unknown sample recovered (g) 0. Melting point of unknown sample (ยฐC) 171. Identity of unknown sample Triphenylmethanol Results Actual mass of unknown substance 0.24 g Mass of unknown sample recovered ( 50.9153 โ€“ 50.8257 )g = 0.0896g Percent recovery of unknown sample 0.^0896 ๐‘”

  1. 2400 ๐‘” x 100% = 37.33 %

Discussion In this experiment, the objective was to separate a mixture of neutral compounds from acid impurities. We used 0.24g of the unknown sample mixed with 0.12g of benzoic acid to create an unknown mixture. To conduct the experiment, we mixed ether into the mixture. Next, NaOH was added and since benzoic acid is acidic, when NaOH was added, it will react with benzoic acid. It will create a layer at the bottom of the separatory funnel which is sodium benzoate. Hence, the top layer of the separatory funnel is the neutral compound. Our next objective is to identify the neutral compound by melting point comparison. This can be satisfied by separating the ether layer and swirling the Erlenmeyer flask. Next, we collected the drying agent and evaporated all the water left in a water bath. Next, we weigh the solid formed with the Erlenmeyer flask. Our results showed that the mass of the Erlenmeyer flask and the sample is 50.9153 g and the mass of the Erlenmeyer flask only was 50.8257 g. Hence, the mass of the unknown solution is 0.0896 g. To know the melting point, we melted down some of the samples using high heat and recorded the time when they turned from solid to liquid. The melting point is 171ยฐ C. Hence our second objective already be obtained. Conclusion In conclusion, our first objective which was to separate a mixture of benzoic acid and a neutral compound into its individual components was satisfied by doing the extraction mentioned before. Not only that, our second objective which was to determine the yields and melting points for both products was also satisfied by recording the melting point of the compound collected. That objectives were met. The Percent recovery of unknown sample is 37.33 %%. By comparing the melting point, we discovered that the compound is Triphenylmethanol

Questions

  1. List four water-immiscible liquids other than ether that could be used to extract Organic compounds from aqueous solution.
  • Carbon tetrachloride
  • Methyl chloride
  • Cyclohexane
  • Chloroform
  1. Why is it wrong to leave a bottle of anhydrous sodium sulphate or calcium chloride open?
  • When open the bottle of anhydrous, the air contains of water which is it expose the anhydrous to absorb the water particles in the air. This will affect the anhydrous effectiveness during the experiment.
  1. Draw the structure of the product when benzoic acid reacts with sodium hydroxide. Why is the product of this reaction easily extracted into H 2 O, while the original benzoic acid is not so easily extracted into H 2 O?
  • It is because the more OH-^ that remove a hydrogen H+^ to form a salt, the polar salt is soluble in aqueous solution, where both OH-^ and benzoate are bases, the stronger base takes the H+^ to form the weaker base.
  1. Why does benzoic acid precipitate out when the aqueous layer is acidified with HCl?
  • Because the benzoic ion is stronger than Cl-. So each one takes H+^ from HCI which means that the acid forms are not soluble in water so it will precipitate out from the solution.
  1. Develop a procedure for isolating a neutral compound from a mixture containing a basic impurity by drawing a flow chart as on page 20.