Page |1Myeeka Hammond May 24,2017 Extraction Purpose: The most significant purpose of this experiment is to learn one of the techniques for the separation of complex mixtures into individual components and further understanding how to purify a mixture of compounds. Introduction: Extraction is the selective transfer of any solute or impurity from one phase into another. In any organic lab, the most common form of extraction is liquid to liquid extraction, where a solute is transferred from one solvent, the liquid phase, into another solvent, another liquid phase. This is the most useful technique for separating a solute or an impurity from components in a mixture. A term that is commonly used when talking about extractions distribution coefficient, Kd. This simply refers to the ratio of the concentration of the solute in each solvent, which is at equilibrium, at a specified temperature. Their two types of extraction (1) batch extraction and (2) one time extraction. Of the two, batch extraction is the better because multiple small extractions generate multiple equilibrium stages of mass transfer of solute and are more efficient than a onetime extraction which involves a single equilibrium stag of mass transfer of solute. Since the partition coefficient of solute between the two solvents is independent of the quantity of solvent being used for the extraction a large volume of solvent in a onetime extraction is just adding cost without any value addition. The main thing when doing an extraction experiment is knowing which layer is the organic phase and which layer is the aqueous phase. In order to check the identity of one of the layers, one must place a few drops of the layer into a test tube containing water. If the layer is aqueous then the mixture should be homogenous but if the layer is organic, two layers will form. Materials: 1. One gram dimethoxybenze/benzoic acid mixture 2. A small Erlenmeyer flask 3. 45mL of diethyl ether 4. Ice bath 5. 10mL of 0.5 N sodium hydroxide 6. 125mL Erlenmeyer flask 7. 10mL of deionized water 8. One gram of anhydrous sodium sulfate to dissolve the mixture and then transferred the mixture into a separatory funnel. which was added to a small Erlenmeyer flask. we extracted the ether layer with 10mL of cooled deionized water and add it to the rest of the aqueous extracts in the Erlenmeyer flask. swirling the solution and stoppering the flask until ready for use later. The ether layer was then poured out from the top of the separatory funnel in to a 250mL Erlenmeyer flask and dried by adding anhydrous sodium sulfate. and repeated the adding of the sodium hydroxide and releasing the aqueous phase process two more times.Hot water bath 15. stoppered the flask . One main thing that was different was what we used to dry the substance. and about 45mL of dimethyl ether. which was cooled in an ice bath for about 5-10 minutes.Capillary tubes Procedure: The first thing that was done was weighing out one gram of a dimethoxybenzene/benzoic acid mixture. Once we were done shaking for about fifteen to thirty seconds we drew off the aqueous phase into a 125mL Erlenmeyer flask.30mL methylene chloride 12. After using the rest of the cooled ether to rinse the Erlenmeyer flask we added 10mL of cooled 0. in small amounts. To assure that all traces of the base were gone.250mL Erlenmeyer flask 13. Litmus paper 10. this time we used anhydrous magnesium sulfate. Page |2 Myeeka Hammond May 24. We are now dealing with the aqueous phase again by pouring it back into the separatory funnel along with 5mL of cooled 3M hydro-chloric acid.Thermometer 18.2017 Extraction 9. We then followed rh same procedure before to let off one of the phases through the funnel by adding three 10mL portions of methylene chloride into a 250 mL Erlenmeyer flask.Separatory funnel 16.5 N sodium hydroxide solution to the separatory funnel and shake the mixture in a back and forth manner. We then used the cooled dimethyl ether. To check the acidity of this solution we used a litmus paper and the glass rod to make sure that the solution was acidic.Mel-Temp apparatus 17.5mL of hydro-chloric acid 11.Two 50mL Erlenmeyer flask 14. which was the upper layer. 54°C. the lower layer. we obtained a melting point range of 103. Once we obtained the crystals we weighed them and used the Mel-temp apparatus to find the melting point of each compound.2017 Extraction and set it aside with the other organic phase.5%. with deionized water. the bottom layer. Page |3 Myeeka Hammond May 24. For benzoic acid. which might be the reason our percent recovery was lower than what is normally recovered. Compared to the literature value. Another time that this layer formed was when we were washing the ether layer.8- 54. Then we added them to the hot bathe and we watched until all the solution was evaporated and then we put the two flasks into a ice bath to cool down and aid in the formation of the crystals. is denser than the other. we decanted the two organic phases into two separate 50mL Erlenmeyer flasks. I think we got this one to be more accurate.41°C.9°C. To me that vapor looked like a matrix movie when a gun was shot it the show the bullet moving in slow-motion.8-105°C. Another calculation that had to be made was the melting point of each compound. Data and observations: This lab was fun and cool to do. while we were doing this part of the experiment some of the solution spilled out of the funnel. . Once the we shook to the funnel and started to let out the vapor we realized that you not only hear when the vapor is released. This layer formed because the compounds mixed and one layer. the very first thing that was noticeable to my group members and I was the layer that formed when we added the 10mL of 0. For p-Dimethoxybenzene the melting point average was 49. Unfortunately. The only thing I can think of that would affect the melting point for this compound is heating it too fast or it wasn’t packed tightly. The only thing wrong is that it is not a sharp melting point which can mean that the substance was not as pure as it needed to be to get a sharp melting point. So. I believe that the extremely low recovery for the second compound was due to the fact that when one of my partners was putting the solution to heat in the hot bath he dropped it in the bath and some of the water might have gotten into beaker and compromised the solution. but you can also see the vapor go into the air. Our percent revered for the benzoic acid was 25.7% and for p-Dimethoxybenzene we recovered 1. While waiting for the hot bathe to start boiling.5 N of sodium hydroxide. which is low compared to the literature values 122. 3. Sodium sulfate. Page |4 Myeeka Hammond May 24. But we did get enough of the compounds to get the calculations that we needed. One thing I think would help the lab go a little more smoothly is a procedure that was a little easier to understand. Why would ethyl alcohol not be a good solvent to use with water in an extraction? Ethyl alcohol would not be a good solvent because ethyl alcohol is soluble in water. Post lab questions: 1. and we were a little confused on the procedure and had to constantly ask the professor for help to further understand.2017 Extraction Conclusion: If I was to say that I think we conquered the main concept of this lab. some of the steps were more confusing than others. That was my biggest flaw with this experiment. How does the extraction procedure differ when the organic phase is (a) less dense than water and (b) denser than water? What differences did you observe between the two drying agents that you used in today’s extraction process? If the organic phase is denser than water. then we collect the bottom phase and aqueous phase will be on top. I think that the recovery was low because we lost some of our solution while separating and it could also be because of the amount of time we left the substances to dry for. however. Our percentage recovered was very low. I think I would be lying. Magnesium sulfate is fluffier than sodium sulfate and tends to remain suspended in solutions for longer periods of time. has the higher water capacity. If the organic phase is less dense. What is the purpose of venting the separatory funnel by occasionally opening the stopcock during the shaking process? Why is there a buildup of pressure even when no gas is being produced by a chemical reaction? . The substance that was left drying for a longer period of time recovered more of the pure compound than the one that was drying for a lesser amount of time. we collect the top phase and the aqueous phase is on the bottom. 2. thus can be separated. Why is it necessary to remove the stopper from the separatory funnel when the liquid is being drained from it through the stopcock? To release any possible buildup of pressure and to help the flow of liquid through the small opening in the stopcock. p-dichlorobenzene forms percipitate and settles down. What is the biggest safety hazard in this experiment? The biggest safety hazard in this experiment is evaporating any solvent into the laboratory airspace shared by all. When hot water is added into the mixture. It can thus be skimmed and filtered. 6. P-chloroaniline dissolved completely in water. That is the reason the separating funnel stopcock needs to be occasionally opened. . 4. Describe a procedure that might be used to separate p-dichlorobenzene (a neutral compound) from p-chloroaniline ( a basic compound) by extraction.2017 Extraction The buildup of pressure will take place due to the formation of the ether of organic solvent vapor produced by the heat of the hands. Page |5 Myeeka Hammond May 24. They can be separated by using hot water. 5.