Extraction Lab - Lab Report

Experiment 3: Extraction Introduction: Extraction is a widely used method by scientists for the separation of a substance from a mixture. It is frequently used to isolate a specific desired compound from a mixture or from its impurities. Solubility characteristics of organic substances in the solvents used play a large role in solvent extraction methods. The phrase “like dissolves like” is a principal that extraction follows, along with concepts such as polarity and the intermolecular forces present in the compounds that are intended to dissolve. There are two major types of extractions used in the organic laboratory being, liquid-liquid and solid-liquid extractions. The process of a solid-liquid extraction occurs when a compound is extracted from a solid material into a liquid, and when the transfer occurs from one liquid into another, it is called a liquid-liquid extraction. An acid-base extraction is a type of liquid-liquid extraction involving an organic solvent, being ethanol in this experiment. Acid-base extractions are based on solvents of different pH levels to separate acids, bases, and neutral compounds from each other, and when adding an acid or base, the compounds become more protonated, which also makes them more soluble in water. The purpose of this experiment is to use technique of extraction to separate the three compounds 4-cholroanilline, benzoic acid, and 1,4- dibromobenzene. In this lab, NaOH, a base, is added to the acids, and HCl, an acid, is added to the base. Through this, an aqueous solution is formed which is then removed by a separator flask. Once the aqueous solution is removed, an acid is added to the compound if it is an acid after protonation, and if the compound is a base, a base will be added. These compounds are them fried through heating and vacuum filtration. Heating the compound allows the organic solvents to evaporate, leaving behind the desired compound. Vacuum filtration is used in order to filter the water from the leftover salt in this experiment. Chemicals Table: Name 4-chloroaniline Structure Melting Point Density Molecular Weight 232 °C 1.43 g/cm3 127.57 g/mol Benzoic Acid 122.3°C 1.27 g/cm3 122.12 g/mol 1,4 Dibromo benzene 87°C 1.84 g/cm3 235.9 g/mol Ether -116.3°C 713 kg/cm3 72.12 g/mol Glassware/Setup: Setup Acid-base reactions and arrow pushing mechanism: Procedure: Procedures: 1. Place 0.5g of the mixture in a flask and create a solution with diethyl ether as the solvent. 2. Using HCl, dilute the solution to allow protonation. Use a separator funnel to separate the aqueous acidic salt from the organic layer. 3. Shake the funnel and open the stopcock to vent the gas until there is no longer a sound. 4. Drain the aqueous layer into another flask, and was the organic layer with HCl and water to drain all of the aqueous extract. The flask being drained should then be labeled aniline salt. Add aqueous sodium bicarbonate to the remaining organic layer to form another aqueous layer. Observations: 1. A solution of the mixture and diethyl ether is created. 2. When HCl is added, two layers appear. 3. An organic and aqueous layer are formed. 4. Due to the HCl added and water, the product is completely drained. 5. Sodium bicarbonate reacts with benzoic acid. 6. Dibromobenzene composes the entire organic layer. 7. Ether evaporates when heated, as it is a volatile substance. 8. Each of the solids have successfully been extracted. 5. Repeat the steps to collect the aqueous extract in another flask and label benzoate salt. After repeating, place the organic layer in a separate flask along with a sodium sulfate. 6. Weigh the flask and then filter the dibromobenzene into another flask. Gently heat the dibromobenzene to get rid of the ether. 7. In the flask labeled aniline, add NaOH and then immerse into an ice bath. Test the pH for confirmation and collect the solution through vacuum filtration. 8. In the flask with benzoic acid, add HCl, and repeat the above step by testing the pH and performing vacuum filtration to collect the solution. Data/Calculations: Mass collected of 4-chloroaniline: 0.35g/mol Mass of collected of Benzoic acid: 0.42 g/m Mass collected of 1,4 dibromobenzene: 0.38 g/mol Percent Recovery= (Final Compound Mass/ Starting Compound Mass)*100 Percent recovery of 4-chloroaniline: (0.35/0.5)*100= 70% Percent recovery of Benzoic acid: (0.42/0.5)*100= 84% Percent recovery of 1,4 dibromobenzene: (0.38/0.5)= 76% Conclusion: The purpose of this experiment was to use the technique of extraction to separate three compounds, 4-chloroanaline, Benzoic acid, and 1,4-dibromobenzene. Hydrochloric acid was used to create an aniline salt, and through this 4-chloroanaline was separated from the other two compounds. Once the salt was removed from the other two organic compounds, NaOH was used to react with Benzoic acid, which was then removed from the separator. In order to obtain purified 1,4-dibromobenzene, the remaining solution was mixed with the sodium sulfate. After completing these extractions the percent recovery for 4-chloroanaline, Benzoic acid, and 1,4- dibromobenzene was found to be 70%, 84%, and 76%, respectively. There were many errors that could have taken place during this experiment, one main one being that all of the product may not have been collected if the flask was not rinsed properly with water and HCl during the collection of the aniline salt. Q&A: 1. During an extraction, if you become uncertain about which layer is the organic layer, how could you determine it experimentally? During separation if unsure of the organic layer vs aqueous later, we can take a few millimeters of one of the layers and add water to it in a test tube, through this we can determine if it is organic, as it would be miscible with added water, and if it was aqueous it would form two separate layers in the test tube. 2. Propose a method (Tree diagram) to separate Phenol (Weakly acidic) Benzoic acid (Strongly acidic), Naphthalene (Neutral) and P-nitroaniline (Basic). 3. What is the purpose of adding anhydrous magnesium sulfate or anhydrous calcium to organic layer at the end of the extraction? The purpose of adding anhydrous magnesium sulfate or anhydrous calcium to the organic layer at the end of the extraction is to collect any water that may be leftover. 4. Label which solvent will be on top and which solvent will be on the bottom for the following solvent mixtures in extraction. a. Ether- Top, Water-Bottom b. Dichloromethane- Bottom, Water- Top c. Chloroform- Bottom, Water- Top 5. A student prepares compound A in organic lab. This compound is known to contain impurity, compound B. Propose a method (by using extraction) to separate these compounds. Use a diagram or flow chart to explain.