Extraction Laboratory Report
Title
Extraction of sucrose, acetylsalicylic acid, and acetanilide from Phensuprin using acid/base extraction process.
Dates the Experiment Was Done
17 September 2015 and 24 September 2015
Objective
The experiment aimed to separate components of Phensuprin, which are acetylsalicylic acid, acetanilide, and sucrose, using acid/base extraction process.
Physical properties
-
- Acetylsalicylic acid (“Chemical Book: Product Chemical Properties” par. 1)
Form: White crystals
Molecular formula: C9H8O4
Molecular weight: 180.16
Melting point: 134-1360C
Boiling point: 1400C
Water solubility at 200C: 3.3g/L
Hazards: poisonous, irritant, and combustible - Acetanilide (“Chemical Book: Product Chemical Properties” par. 2)
Form: Grey or White powder
Molecular formula: C8H9NO
Molecular weight: 135.16
Melting point: 113-1150C
Boiling point: 3040C
Water solubility at 200C: 5g/L
Hazard: Harmful, toxic, and irritant - Sucrose (“Chemical Book: Product Chemical Properties” par. 1)
Form: White crystalline powder
Molecular formula: C12H22O11
Molecular weight: 342.3
Melting point: 185-1870C
Boiling point: decomposes
Water solubility at 200C: 1970g/L
Hazard: Irritant - Dichloromethane (“Chemical Book: Product Chemical Properties” par. 1)
Form: Colorless liquid
Molecular formula: CH2Cl2
Molecular weight: 84.93
Melting point: -970C
Boiling point: 39.8-400C
Water solubility at 200C: 20g/L
Hazards: Harmful, toxic, highly flammable, carcinogenic, and corrosive - Sodium bicarbonate (“Chemical Book: Product Chemical Properties” par. 2)
Form: White crystals or powder
Molecular formula: CHNaO3
Molecular weight: 84.01
Melting point: 3000C
Boiling point: 8510C
Water solubility at 200C: 90g/L
Hazards: Harmful and irritant - Sodium sulfate (“Chemical Book: Product Chemical Properties” par. 3)
Form: White crystals or powder
Molecular formula: Na2O4S
Molecular weight: 142.02
Melting point: 8840C
Boiling point: 17000C
Water solubility at 200C: 18.5mg/L
Hazard: Irritant - Hydrochloric acid (“Chemical Book: Product Chemical Properties” par. 2)
Form: Fuming liquid
Molecular formula: ClH
Molecular weight: 36.46
Melting point: -350C
Boiling point: 570C
Water solubility at 200C: Miscible
Hazards: Extremely flammable, harmful, irritant, toxic, and corrosive
- Acetylsalicylic acid (“Chemical Book: Product Chemical Properties” par. 1)
Procedure
To commence the experiment, 2g of the Phensuprin sample was weighed precisely using a weighing balance and put into a 125ml Erlenmeyer flask. Subsequently, 50ml of dichloromethane was added to the Phensuprin sample in the 125ml Erlenmeyer flask and then stirred briskly until all soluble solids dissolved. The brisk process of stirring ensured that all the clumps of the Phensuprin sample were broken and dissolved in dichloromethane. To measure the amount of solids, a filter paper was weighed, and the mass was noted in the laboratory notebook for further analysis. Then, the pre-weighed filter paper was used to filter the mixture through a process of gravity filtration to separate solids from the mixture. The collected solids in the filter paper, which are sucrose, were washed with 5ml of dichloromethane to remove residues of other components of the Phensuprin. The collected sucrose in the filter paper was then dried for a week at room temperature by placing them in a beaker. After a week, the sucrose and filter paper were completely dry and were weighed to determine the mass of sucrose in the 2g Phensuprin sample. The weight of the sucrose was obtained, and its percent composition was calculated and then recorded in the laboratory notebook.
As the filtrate was a mixture that comprised acetylsalicylic acid and acetanilide, extraction process was used to separate the two compounds. Acetylsalicylic acid in the filtrate, which is dichloromethane solution, was put in a separatory funnel and extracted twice using double portions of 5% sodium carbonate solution. To perform the first extraction of acetylsalicylic acid, one portion of 5% sodium carbonate solution (25ml) was added to the dichloromethane solution in the separatory funnel. The funnel containing the mixture was then stoppered and shaken slightly for two minutes. The cork was intermittently opened to release pressure before the funnel was finally fixed in a clamp to allow separation of layers to occur. The lower layer containing dichloromethane was drained and collected in a 125ml Erlenmeyer flask. The top layer containing aqueous compounds was poured into a 400ml beaker from the funnel. The separated dichloromethane in the Erlenmeyer flask was poured into the separatory funnel to be extracted for the second time using the second 25ml portion of 5% sodium carbonate. The dichloromethane phase was kept while the two aqueous phases were mixed for further extraction.
The aqueous phase in the beaker was put in an ice bath to cool, and 10 ml of concentrated hydrochloric acid was added slowly using transfer pipette while stirring. The beaker was swirled periodically during the addition of hydrochloric acid because foaming transpired. When the addition of hydrochloric acid was complete, the pH was tested using a pH paper. A glass rod was used periodically to transfer a drop of the solution from the beaker into the pH paper until the pH became less than 2. To obtain acetylsalicylic acid, the acidified aqueous phase was continued to be cooled in the ice bath pending the formation of solid acetylsalicylic acid. Vacuum filtration was done to collect the formed solid and washed with 5ml of cold water. The vacuum pump was run for a couple of minutes subsequent to the filtration process to enhance drying of the collected solid. The collected solid was allowed to dry for a week at room temperature in an uncapped sample vial. After one week, the solid dried, its mass was weighed, and the percent composition was determined.
To extract acetanilide, the dichloromethane solution was dried over anhydrous sodium sulfate. A scoopful of anhydrous sodium sulfate was placed on the dichloromethane solution while swirling to mix. Sodium sulfate was added gradually in small portions and allowed to clump together until when an excess of it started to remain free. The mixture was swirled for a few minutes and filtered into a pre-weighed 100ml round-bottom flask. The solvent, methylene chloride, was evaporated using a rotary evaporator leaving acetanilide component as a solid. The collected solid was kept in the unstoppered round bottom flask to be used during the subsequent lab period. The solid was then weighed, and its percent composition by mass was determined and recorded.
The purity of three compounds, namely, sucrose, acetylsalicylic acid, and acetanilide was determined using their melting points and then compared to ones in the literature.
Results
Calculation of percent composition of the three compounds
Mass of the Phensuprin: 2.0g
Mass of the filter paper used to separate the sucrose: 0.94g
Mass of the filter paper+ sucrose: 1.06g
Mass of sucrose obtained: 0.12g
Mass of acetanilide obtained: 0.74g
Mass of the round bottom flask: 61.00g
Mass of acetylsalicylic obtained: 0.58g
Total mass: 0.12 + 0.74 + 0.58 = 1.44g
Total percent recover: [1.44g/2.0] x 100 = 72%
Percent composition of sucrose: [0.12/1.44] x 100 = 8.3%
Percent composition of acetanilide: [0.74/1.44] x 100 = 51.4%
Percent composition of acetylsalicylic: [0.58/1.44] x 100 = 40.3%
Synopsis of Results
The extraction of the compounds in Phensuprin was successful because out 2g of the sample, the total masses of compounds recovered were 1.44, which is 72% recovery. The remaining 0.66g, which represents 28%, was not recovered due to some errors in the extraction process. The masses of sucrose, acetylsalicylic acid, and acetanilide obtained were 0.12g, 0.85g, and 0.74g respectively. Sucrose comprised 8.3%, acetylsalicylic acid constituted 40.3%, and acetanilide composed 51.4% of the total mass of Phensuprin recovered. Sucrose was pure because its melting point was the same as the one in the literature, which is 185-1870C. The melting point of acetylsalicylic acid was 122 °C, which is significantly lower than the one in the literature of 134-136 °C. The melting point of acetanilide was 920C, which is lower than the li melting point of 113-1150C in the literature.
Discussion
The experiment aimed to separate components of Phensuprin using acid/base extraction process. The separation of these components entailed extraction of solid and liquid phases based on their solubility in organic and inorganic solvents. Phensuprin is an analgesic, which contains sucrose, acetylsalicylic acid, and acetanilide. The first process of extraction involved separation of sucrose from acetylsalicylic acid and acetanilide. Sucrose is soluble in an inorganic solvent while acetylsalicylic acid and acetanilide are soluble in an organic solvent. In this case, Phensuprin sample was mixed with dichloromethane, an inorganic solvent, to dissolve acetylsalicylic acid and acetanilide while leaving sucrose as an insoluble solid. Given that sucrose does not dissolve in dichloromethane, it was separated from the solution using gravity filtration. According to Zubrick, filtration is a physical process of separating solids from the liquids using a sieve or a membrane that allows liquid to pass through and restricts the passage of solids (95). A filter paper was used in the separation of sucrose from dichloromethane solution because of its porosity to allow passage of solution while retaining particles.
The sucrose collected as a residue by filtration was washed with dichloromethane to remove acetylsalicylic acid and acetanilide, which are potential impurities of sucrose. Zubrick states that washing is an important step in the filtration process because it removes unwanted soluble materials from a residue collected (112). Without washing, the sucrose residue would be impure because it would retain acetylsalicylic acid and acetanilide. Acid/base reaction was used in manipulating the solubility of acetylsalicylic acid and acetanilide. Although these two components of Phesuprin are soluble in dichloromethane, the addition of sodium carbonate changes their solubility. Essentially, sodium carbonate deprotonates acetylsalicylic acid to form a soluble salt called sodium acetylsalicylate. However, sodium carbonate does not react with acetanilide because it is a weak base. Therefore, the addition of sodium carbonate makes acetylsalicylic acid insoluble in dichloromethane and acetanilide to remain in dichloromethane solution. The addition of the double 25ml portion of sodium carbonate solution ensured that all the acetylsalicylic acid was converted into sodium acetylsalicylate, which is a soluble salt.
Since dichloromethane solution and sodium acetylsalicylate solution are organic and inorganic solutions respectively, they form two layers because they are immiscible. Zubrick asserts that separatory funnel separation is appropriate in separating immiscible liquids because of its accuracy and effectiveness (112). Given that dichloromethane solution is denser than the sodium acetylsalicylate solution, the former formed the upper layer while the latter formed the lower layer. Hence, the lower layer containing acetanilide was drained first and added 25 ml of 5% sodium carbonate to extract the remaining acetylsalicylic acid. To extract acetylsalicylic acid from the aqueous phase, hydrochloric acid was added. The function of the hydrochloric acid was to acidify sodium acetylsalicylate, and thus, converting it into acetylsalicylic acid, which is insoluble. Moreover, the pH of 2 ensured re-protonation of sodium acetylsalicylate, and hence, making it precipitates out of the solution when cooled in an ice bath. To extract acetanilide from the dichloromethane solution, anhydrous sodium sulfate was used. The purpose of anhydrous sodium sulfate was to dry acetanilide because it is a drying agent. Zubrick states that anhydrous salts are drying agents because they have the capacity to absorb water from diverse substances (64). The rotary evaporator was then used to remove dichloromethane from acetanilide solution because it is an inorganic solvent.
Separation of compounds occurred progressively, according to the solubility of each compound. Sucrose was the first compound, which was separated using gravity filtration. Gravity filtration is a form of filtration that relies on gravity as the force that determines the rate of filtration. In contrast, the second compound to be separated was acetylsalicylic acid. Vacuum filtration was used to separate acetylsalicylic acid because it is not only fast, but also act as a drying agent. Comparatively, vacuum filtration is faster than gravity filtration because it uses vacuum pressure in filtering and drying residues.
The masses of sucrose, acetylsalicylic acid, and acetanilide recovered are 0.12g, 0.58g, and 0.74g respectively. The recovered percentages for each compound are 8.3%, 40.3%, and 51.4% for sucrose, acetylsalicylic acid, and acetanilide respectively. The results indicate that acetanilide is a component that constitutes half of the recovered Phensuprin. Acetylsalicylic acid ranked the second in recovered percentage while the sucrose was the least in recovered percentage. The total mass recovered is 1.44g out of 2g, which means that 72% of Phesuprin was recovered. When compared to literature, the proportions of Phensuprin components are similar to that of Aspophen I, which contain 10% sucrose, 40% acetylsalicylic acid, and 50% acetaminophen. The comparison indicates that the recovered proportions of Phensuprin components are within the normal range of other analgesics that contain sucrose and acetylsalicylic acid as the main components. The melting point of sucrose was the same as that of literature indicating that it was pure. However, the melting point of acetylsalicylic acid was 1220C and that of acetanilide was 920C. Since these melting points were lower than the literature values, they indicate that acetylsalicylic acid and acetanilide recovered had impurities, which lowered melting points.
The probable sources of error in the experiment were washing sucrose residues, separating aqueous and organic layers, and changing of pH using sodium carbonate and hydrochloric acid. Improper washing of sucrose could have left some acetylsalicylic acid and acetanilide in sucrose. Since aqueous and organic layers have an interface, it introduces impurities into either layer. Manipulation of pH determines the solubility of acetylsalicylic acid; however, an inappropriate manipulation would ineffectively reduce the solubility of acetylsalicylic acid.
References
Chemical Book: Product Chemical Properties 2008. Web.
Zubrick, James. The organic chem. Lab survival manual: A student’s guide to techniques. New York: John Wiley & Sons, 2012. Print.
Questions
- The original organic solution was extracted two times with aqueous sodium bicarbonate. After the extraction, what compound(s) were in the organic layer? What compound(s) were in the aqueous layer?
Acetanilide remained in the organic layer whereas acetylsalicylic acid remained in aqueous layer. - Assume that both acetylsalicylic acid and acetanilide are soluble in diethyl ether, and that diethyl ether was used in place of the methylene chloride. Would the ether layer be the bottom layer in the separatory funnel or the top layer? Explain your answer.
Densities of water, methylene chloride, and diethyl ether are 1.0g/mL, 1.33g/mL, and 0.713g/mL respectively. In this case, the use of diethyl ether, which is less dense than water, implies that diethyl ether layer would be the top layer. - Assume that both acetylsalicylic acid and acetanilide are soluble in methanol, and that methanol was used in place of the methylene chloride. What problem(s) might occur during the extractions? (Careful, this is a trick question.)
Methanol is a polar solvent, which means that it would mix with water to form a homogenous mixture of acetylsalicylic acid and acetanilide. In essence, there would be no formation of layers that aid in the separate extraction of acetylsalicylic acid and acetanilide. Therefore, the problem is that both acetylsalicylic acid and acetanilide are in the same solution. - Historically, the solid residue that is left after the methylene chloride solution is evaporated has a lower melting point that its literature value, due to impurities. Explain what impurities are present and why.
The impurities found are sodium carbonate, acetylsalicylic acid, and anhydrous sodium sulfate. These impurities are present because extraction process is not perfect, and thus, leaving traces of chemicals added or contained in the previous mixture.