Sucrose does not dissolve in a non-polar organic solvent, dichloromethane because it cannot create hydrogen bonds with the dichloromethane.
It was noted that sucrose could not dissolve in dichloromethane because it cannot form hydrogen bonds with the reactant. Hence, the gravity filtration was used to separate it from the solution. It is noted that filtration is a physical process that is used to separate solid particles from a liquid content by sieving or applying a membrane that only allows liquid to pass through while limiting soli particles. Sucrose particles were separated from dichloromethane solution using a filter paper because the filter paper only allowed the liquid to pass but not solid particles.
The filtered sucrose was further cleaned by washing using dichloromethane to eliminate traces of acetanilide and acetylsalicylic acid, which could have possibly made the particles impure. Cleaning is a critical process after filtration that eliminates all impure traces that could be present in collected residues. Hence, traces of acetylsalicylic acid and acetanilide would still be present in the sucrose without washing.
The reaction between acid and base was used to control the solubility of acetylsalicylic acid and acetanilide. While both acetylsalicylic acid and acetanilide are soluble in dichloromethane, sodium carbonate is used to alter the solubility of acetylsalicylic acid. Sodium carbonate reacted with acetylsalicylic acid to form sodium acetylsalicylate. In this reaction, sodium bicarbonate was used to provide the basic condition while the acetylsalicylic acid created acidity for the reaction to occur. Acetanilide does not react with sodium carbonate because of its low strength as a basic substance. Thus, acetanilide remained in the solution of dichloromethane. Additional of 25 ml drops of sodium carbonate was required to change all acetylsalicylic acid to sodium acetylsalicylate – a soluble salt. This reaction results in the creation of immiscible solutions of dichloromethane solution and sodium acetylsalicylate solution, which are organic and inorganic solutions respectively. The separating funnel is effective for separating two immiscible solutions due to its accuracy and efficacy. These solutions also have different density. As such, dichloromethane solution settled at the bottom while sodium acetylsalicylate solution formed the upper layer. The solution containing acetanilide was first drained and 25 ml of 5% sodium carbonate was added to remove all the retained acetylsalicylic acid.
Hydrochloric acid was used to extract acetylsalicylic acid from the aqueous solution. Hydrochloric acid was used to extract acetylsalicylic in a solid state, which was insoluble in water. The reaction involved hydrochloric acid, sodium elements, and acetylsalicylate to produce acetylsalicylic. Acetylsalicylic was precipitated using ice from the solution and then separated using filtration. The pH of 2 was ideal for sodium acetylsalicylate re-protonation, leading to its precipitation in the ice. Sodium carbonate used specifically to reduce the pH of the solution and make it stable.
Acetanilide was separated from the dichloromethane solution using anhydrous sodium sulfate. Anhydrous sodium sulfate was used a drying agent in order to get dry acetanilide. Anhydrous sodium sulfate has ability to absorb water from other substances. Dichloromethane was separated from acetanilide solution using a rotary evaporator because it was an inorganic solvent.
This extraction experiment was progressive based on solubility of the three compounds found in the sample. Sucrose was initially extracted using gravity filtration, which depends on gravity for particle filtration. On the contrary, vacuum filtration was preferred for acetylsalicylic acid separation because it is faster, acts as a drying agent, and can tolerate high boiling points. It was faster relative to gravity filtration because of vacuum pressure applied in the pressure.
Different masses of the three compounds were obtained. Sucrose was 0.52 g, acetylsalicylic acid was 0.5 g while acetanilide was 0.4 g. The percentages of extracted sucrose, acetylsalicylic acid, and acetanilide were 36.6%, 35.2%, and 28.1% respectively. These percentages represented the most abundant component of Phensuprin. Sucrose was the most abundant, followed by acetylsalicylic acid, and finally acetanilide of the recovered Phensuprin. The total mass of the separated components was 1.42 g from the original sample of 2.0 g, representing 71% recovery rate of Phesuprin.
The pure form of sucrose was recovered because it had a similar melting point as indicated in literature. On the contrary, it was noted that the melting point of acetylsalicylic acid was 1230 C while acetanilide was 960 C. These melting points were lower than the melting points indicated in literature. Hence, these two substances contained traces impurities. Impurities lower melting points of substances. Unfortunately, the presence of impurities showed chemical extraction was not always completely efficient. As such, it was nearly impossible to separate all original substances contained in Phensuprin as pure single components. In addition, each constituent of Phensuprin was most likely to have traces of one or more of the extracted compounds. To extract pure compounds, recrystalization was needed by following recommended laboratory procedures.
Notably, experimental processes could have led to some errors. For instance, sucrose was washed, aqueous solutions were separated using various reactants and stored for one week. Ineffective processes could have contributed to errors and presence of impurities in other extracted substances. The pH of the aqueous solution was also controlled to ensure that acetylsalicylic acid could be obtained. However, improper processes could have led to poor solubility of the contents.
Lide, David R. CRC Handbook of Chemistry and Physics. 79th ed. 1999. Boca Raton, FL: CRC Press, Inc,. Print.
National Center for Biotechnology Information. Compound Summary – Acetanilide. 2016. Web.
—. Compound Summary – Acetylsalicylic Acid. 2016. Web.
—. Compound Summary – Hydrochloric Acid. 2016. Web.
—. Compound Summary – Sodium Bicarbonate. 2016. Web.
—. Compound Summary – Sodium sulfate. 2016. Web.
—. Compound Summary – Sucrose. 2016. Web.
O’Neil, Maryadele J. The Merck Index – An Encyclopedia of Chemicals, Drugs, and Biologicals. 14th ed. 2006. Whitehouse Station, NJ: Merck and Co., Inc,. Print.
Zubrick, James W. The Organic Chem Lab Survival Manual. 5th ed. 2001. New York: John Wiley & Sons, Inc,. Print.
- 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?
The organic layer had dichloromethane and acetanilide while the aqueous layer had acetylsalicylic acid.
- 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.
The density of water, which is 1.0 g/mL, is comparatively higher than the density of diethyl ether, 0.71 g/mL and, thus, diethyl ether can be found on 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.)
The solubility challenge will occur since the solution would be homogenous. Methanol, a polar solvent, is not considered as an extraction solvent in this case because it is miscible with water and, thus, will not form a different layer. Instead, the resultant mixture will be a homogenous mixture of acetylsalicylic acid and acetanilide. Thus, no formation of layers would occur to enhance the separation of acetylsalicylic acid and acetanilide.
- 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.
Used substances, such as sodium carbonate, acetylsalicylic acid, and anhydrous sodium sulfate, are most likely impurities that can affect melting. These impurities are observed, as shown by low boiling points, because the separation process is not absolutely perfect and, therefore, traces of substances used or contained in the samples and reactants can be detected.
- National Center for Biotechnology Information. Sucrose. 2016. Web.
- National Center for Biotechnology Information, Acetylsalicylic Acid. 2016. Web.
- O’Neil, Maryadele J, The Merck Index – An Encyclopedia of Chemicals, Drugs, and Biologicals, 14th ed, Whitehouse Station, NJ: Merck and Co., Inc, 2006, p. 140.
- National Center for Biotechnology Information, Acetanilide. 2016. Web.
- National Center for Biotechnology Information.Sodium Sulfate. 2016. Web.
- National Center for Biotechnology Information.Sodium Bicarbonate. 2016. Web.
- National Center for Biotechnology Information.Hydrochloric Acid. 2016. Web.
- Zubrick, James W, The Organic Chem Lab Survival Manual. 5th ed. 2001. New York: John Wiley & Sons, Inc,. p 110-122.