Exer 2 Postlab Discussion
Exer 2 Postlab Discussion IV. Data (revised) Table 2.1. Observations on the isolation of crude piperine. Reagent/Action Observations black peppercorn black coarse solid with a pungent odor addition of 95% ethanol dark green mixture with black solids at the bottom after reflux formation of two layers (brown-black solution at the top and black solids at the bottom) after filtration A filtrate A brown-black solution with a pungent odor residue A black coarse solid with a pungent odor after distillation distillate clear solution with a pungent odor residue dark brown solution after cooling to room temperature addition of 10 % ethanolic KOH solution after mixing thoroughly for 5 minutes after filtration B filtrate B dark brown solution residue B fine black powdery solid with a pungent smell addition of 100 mL of NaCl solution coffee-like mixture and formation of and 100 mL distilled H2O precipitates after standing for 10 minutes formation of two layers (light brown solution at the top and brown precipitates at the bottom) after filtration C filtrate C light brown solution residue C light brown powdery solid Table 2.2. Observations on the purification of crude piperine. Reagent/Action Observations crude piperine light brown solid after dissolution with acetone yellowish-brown mixture with few precipitate at the bottom
after heating after filtration filtrate residue after cooling
yellow-brown solution yellow solution light brown solid yellow-brown solid
Table 2.3. Solubility of aspirin in different solvents at varying temperatures. Aspirin + Reagent/Action Aspirin + H2O Aspirin + CH2Cl2 Methanol At room clear mixture light yellow clear temperature Mixture with presence of homogenous homogenous description white precipitate solution solution at the bottom + + Solution (+/-) With hot solvent Mixture white turbid ------description mixture Solution (+/-) + Resulting crystal Size medium-sized fine fine Color white white light yellow Crystal form irregular-shaped flake-like irregular-shaped * Benzoic acid was used instead of aspirin and ethanol was used to replace methanol. Table 2.4. Observations on the recrystallization process of aspirin. Reagent/Action Observations crude aspirin white tablet after dissolution with hot solvent white turbid mixture (H2O) after reheating white mixture with few white precipitates at the bottom filtration A filtrate A dull white mixture residue A white powder after cooling to room temperature dull white mixture after crystallizing dull white mixture with white precipitate at the bottom filtration B filtrate B dull white solution
residue B white powder *Aspirin tablet was used instead of crude aspirin. Table 2.5. Melting point determination of piperine using oil-bath method and Fisher-Johns melting point apparatus. Parameter Melting Point Observed oil-bath method temperature when melting starts (⁰C) temperature when melting completes (⁰C) melting point range (⁰C) observations while heating Fisher-Johns melting point apparatus temperature when melting starts (⁰C) 106 ⁰C temperature when melting 110 ⁰C 4 ⁰C completes (⁰C) melting point range (⁰C) observations while heating Table 2.6. Reaction of crude piperine to concentrated acids. Sample Observations crude piperine + HCl yellowish solution crude piperine + HNO3 yellowish solution crude piperine + H2SO4 reddish black solution Table 2.7. Mass (g) black peppercorns container + sample empty container sample crude piperine container + sample empty container sample purified piperine container + sample empty container sample crude aspirin container + sample empty container sample purified aspirin
19.102 4.103 14.999 3.56% 0.258 2.12%
50.199 49.998 0.201
container + sample empty container sample
1.493 1.380 g 0.113 g
VI. Discussion Piperine, piperanine, and piperettine are common alkaloids that make up 5-9% of ground black pepper. These alkaloids, which are naturally occurring chemical compounds, can be extracted from black pepper in the presence of ethanol and KOH (Epstein, 1993). Black pepper is composed of moisture, protein, sugar, amylose, and ash. It is one of the many peppers that aid in digestion, help balance a diet, and act as natural painkillers. Peppers also activate taste receptors associated with appetite. Piperine is an alcohol-soluble alkaloid responsible for monoclinic needles and the pungency of black pepper. It is composed of lignans, alkaloids, and oils. It has a variety of important biological properties, such as anti-antigenic and anti-cancerous properties, which prevent the formation of blood vessels that can potentially feed oxygen to cancerous tissue. Piperine also has anti-depression like activity, and exhibits cognitive enhancement in some cases. Lastly, piperine is been shown to stimulate anti-inflammatory responses, as well as skin pigmentation (Raman, 2002).
Naturally extracted drugs are often used in both pharmaceuticals and medicine. Extracted products that contain healing agents tend to be found in natural sources such as microbes and plants. Scientists have found abundant evidence that nature is a potential source for extraction of a large range of therapeutic agents. Using techniques such a chromatographic fractionation, the active therapeutic component in natural extractions can be identified (Hong-Fang, 2009). One common natural extraction is isolation of piperine from black pepper. During this isolation, ground black pepper was refluxed
with 50 mL of ethanol in the presence of heat. After vacuum filtration, the liquid filtrate was evaporated with a nitrogen stream and the oil residue was dissolved in 12.5 mL of 10 % KOH in ethanol. 100 mL of water was slowly added to the warm solution until a yellow precipitate began to form. After vacuum filtration isolated the yellow crystals, recrystallization yielded pure piperine product (Raman, 2002). Isolation of Crude Piperine The isolation of crude piperine by solid-liquid extraction was carried out in a reflux setup consisting of a round bottom flask connected to a condenser; 14.999 grams of freshly ground peppercorns were transferred into a round-bottom flask. Freshly ground peppercorns were used to yield consistent and accurate results for the final product of piperine. Boiling chips was also added beforehand to promote bubbling and keep the liquid from superheating and flying out of the flask (bumping) (Zubrick, 2011). Then, 150 mL of 10% of 95% ethanol was used as the extracting solvent for the extraction of piperine when undergoing a reflux. 95% of ethanol, a good extracting solvent for piperine, was used because piperine is as polar as ethanol, and it is soluble in ethanol at its boiling point. Also, ethanol does not react with piperine and it boils at 78.7⁰C which is high enough to cause the desired reaction of the ethnol and peppercorns (piperine). This reflux served to pull the piperine from the pepper grounds into solution. Many other components of black pepper, such as the lignans and flavonoids are less polar then piperine and do not move into the ethanol solution. Following reflux, these less polar compounds were removed by distillation. Reflux allows the solution to be boiled and the vapors to condense that enable the return of the condensate to the reaction flask. Upon increase of temperature, the organic compound of piperine was dissolved in the organic solvent ethanol. During reflux, the loss of solvent containing those organic compounds was minimized. One can see the upper limit traveled by the vapors as sort of a "mirage," called the reflux ring, and caused by a difference in the index of refraction for air versus the ethanol’s vapor (Straus,
2002). The flask was not more than half-filled to allow for enough room during expansion and/or boiling (Straus, 2012). During the reflux, the stopper was not put at the tip of the reflux condenser and the water inside it was maintained to cool temperature. The inlet of the water was on the lower end of the condenser, the outlet at the upper end independent if the condenser was used for reflux or distillation. In this way, a low flow rate of the water will be sufficient for the cooling because the outer jacket of the condenser will fill up with water first before it reaches the outlet (Straus, 2012). After the reflux for two hours, there were two layers formed inside the round-bottom flask, a brown-black solution at the top and black solids at the bottom. The mixture was cooled to room temperature and filtered through suction filtration to remove the unnecessary peppercorns which will not be used in further distillation. peppercorns + ethanol The filtrate from the reaction mixture from reflux undergone distillation for further purification. Unlike reflux, in distillation, a liquid is heated until it is boiling. The vapor which is produced is condensed and collected in a separate flask. In reflux, the liquid is boiled, but the vapor is allowed to condense and flow back into the original flask. Collecting the condensed vapor in a second flask allows separating out the individual components of the mixture by distillation (Zubrick, 2011). Allowing the condensed vapor to flow back into the original reaction flask, allow dissolving hard the undissolved compounds by reflux. This continual recycling of the solvent helps drive the reaction to completion. Distillation was done to separate the concentrated mixture of piperine, chavicine, and other components to the solvent, ethanol (Gaikar, 2010). Also, the precipitation of piperine in the further process will be fastened. product -> piperine + chavicine + other components Raoult’s law applies to the concept of simple distillation. This law states in an ideal solution, the partial vapor pressure of a component in a mixture is equal to the vapor pressure of the pure component at that temperature multiplied by its mole fraction in the mixture (Clark, 2014).
Therefore, for two liquids at the same temperature; the one with the higher vapor pressure, 95% ethanol, is the one with the lower boiling point. Simple distillation will be used to separate 95% ethanol (boiling below 150°C at 78.3 °C at 1 atm) from the remaining nonvolatile impurities of piperine and the other 5% water that boils at least 25°C higher than ethanol (at 100 °C) (Zubrick, 2011). PT = PA + PB = XAPoA + XBPoB A reflux setup includes a round bottom flask connected directly to a condenser, whereas in a distillation, the round bottom flask is connected to a y-adapter. The round bottom flask should be 50-75% full to prevent losing the product when it is 33% full and throwing up of undistilled material into the condenser if it is more than 75% full (Zubrick, 2011). Boiling chips was added. The side arm of the y-adapter connects to the condenser. The condenser connects to a receiving flask through a vacuum adapter. The receiving flask will be placed under an ice water bath. Vapor passing through the plastic tubing will condense immediately when it comes into contact with the cooler air of the receiving flask (Gaikar, 2010). Lastly, the thermometer bulb is placed below the side arm of the three-way adapter (about 5 mm) to obtain the correct vapor temperature while distilling. If not, then there will a chance that the determined vapor temperature is higher (lower than 5 mm) or lower (higher than 5 mm). About 1 to 2 drops of distillate per second was maintained to sustain the separation process (Epstein, 1993).The distillation was stopped when the volume of the mixture is reduced to about 5 to 10 mL. The distillate was then transferred into a bottle labeled as “recovered ethanol”. st The crude extract obtained by heating black pepper in ethanol also contains some acidic, resinous materials that must not be allowed to precipitate with and therefore contaminate the piperine. In order to prevent co-precipitation of piperine and the resin acids, dilute ethanolic potassium hydroxide is added to the concentrated extract to keep acidic materials in
solution as their potassium salts (Clark, 2014). This treatment would yield piperic acid and piperidine. The mixture was stirred and filtered the warm mixture to remove any insoluble materials. 250 mL of water and 100 mL of NaCl solution was added into the filtrate to precipitate out crude piperine from the solution (Epstein, 1993). This will displace the ethanolic KOH solution from being a solvent because ethanolic KOH is more soluble in water while piperine is not. This will yield a metallic yellow precipitate identified as crude piperine. The mixture was stand for 10 minutes, was filtered, and was dried under the fumehood to acquire to crude piperine which will be used for recrystallization.
Recrystallization of Piperine Recrystallization is used in solids for purification to ensure that the product is free from contaminants. The crude piperine is dissolved in minimum amounts of acetone for recrystallization. Piperic acid would react with acetone, yielding purified piperine as the final product. The final product was flaky yellow crystals which is consistent with the literature for this experiment. It could also be concluded that piperidine may have been removed by the addition of acetone because of the lesser peppery odor of the purified piperine (Gaikar, 2010). Black peppercorns contain piperine (3-9%), volatile oil (1-2.5%), pungent resin (6%), piperidine and starch (30%). The percentage yield of crude piperine is 4.56%. On the other hand, the purified piperine has a percentage yield of 3.12%. Crude piperine has a higher percentage yield than purified piperine due to the contaminants (excess products or solvents) present in it unlike the purified piperine which undergone the purification process.
Aspirin is most widely sold over-the-counter drug. It has the ability to reduce fever (an antipyretic), to reduce pain (an analgesic), and to reduce swelling, soreness, and redness (an anti-inflammatory agent) (Los Angeles City College, 2005). Aspirin, known chemically as acetylsalicylic acid, is a white solid derived from salicylic acid which occurs naturally in the bark of willow trees. Salicylic acid contains two acidic functional groups, a carboxylic acid and an a phenol group.
Recrystallization of Aspirin Selection of a solvent for recrystallization The choice of solvent is perhaps the most critical step in the process of recrystallization since the correct solvent must be selected to form a product of high purity and in good recovery or yield. The recrystallization of aspirin has begun with the selection of an appropriate solvent for recrystallization. First, a clear homogenous solution was formed upon mixing 0.5 mL methanol to a spatula tip of aspirin. Next, aspirin and dichloromethane yielded a light
yellow homogenous solution. Aspirin is an organic acid; therefore, it is soluble in an organic solvent (dichloromethane), but will react with a basic reagent such as methanol to produce the conjugate base of the acid. The conjugate base is a salt and is water soluble; therefore, it is removed from the organic solvent layer. Re-acidification of this basic aqueous layer will regenerate the organic acid, which will precipitate from the aqueous solution due to the acid's limited solubility in water. aspirin + meoh aspirin + CH2CL2 A clear mixture with presence of white precipitate at the bottom was formed upon addition of 0.5 mL water to a spatula-tip of aspirin. Aspirin is only slightly soluble in water because it contains polar functional groups which can form hydrogen bonds with polar water molecules. When aspirin ages, it gradually reacts with absorbed moisture from the air and partially reverts back to salicylic acid and acetic acid. In general, it's the above reaction run backwards (NST, 2011). It is the acetic acid that smells like vinegar. However, after the aspirin and water was boiled to test its solubility, aspirin did completely dissolve in water, forming white crystals when all the water molecules evaporate. For some time, some hydrolysis will occur more rapidly and it will partly decompose to salicylic acid and acetic (ethanol) acid again. That is why most modern-day aspirin tablets are coated with a substance that keeps moisture away from the active ingredient (NST, 2011). As a result, they last a long time. The synthesis reaction of aspirin is shown below: aspirin (acetylsalicylic acid)
+ water →
acetic acid (ethanoic acid)
Therefore, water is considered as a good recrystallizing solvent because it dissolves the aspirin at elevated temperature and only sparingly soluble in the solvent at room temperature. This difference in solubility at hot versus cold temperatures is essential for the recrystallization process. If the compound is very soluble in the solvent at room temperature, then getting the compound to crystallize in pure form from solution is difficult. Second, the unwanted impurities should be either very soluble in the solvent like water at room temperature or insoluble in the hot solvent. This way, after the impure solid is dissolved in the hot solvent, any undissolved impurities can be removed by filtration. After the solution cools and the desired compound crystallizes out, any remaining soluble impurities will remain dissolved in the solvent. The boiling point of water is less than the melting point of aspirin. If it is not, oil would be obtained rather than crystals. Next, water does not react with the aspirin being purified. Aspirin may be lost during recrystallization if the water reacts with the compound. Lastly, water was volatile enough to be easily removed after aspirin has crystallized. This allows for easy and rapid drying of the solid aspirin compound after it has been isolated from the solution (https://www.erowid.org/archive/rhodium/chemistry/equipment/recrystallizati on.html). Recrystallization Process Commercial aspirin (substitute to crude aspirin) was dissolved in minimum amount of hot water, the selected solvent for recrystallization. As water is cooled, the impurities must stay soluble while the compound of interest precipitates. It is important that minimum amount of hot solvent will be used that will just dissolve the compound of interest to prevent its lower recovery and degree of unsaturation (Sneling, 2004). A small amount of decolorizing carbon was added if the resulting solution is highly colored. Decolorizing carbon, also called activated charcoal, is finely divided carbon often used to decolorize a solution. The small particles of decolorizing carbon provide a large surface area to which large colored molecules may
become adsorbed (Los Angeles City College, 2005). Adsorption is the binding of molecules or particles to a surface which must be distinguished from absorption, the filling of pores in a solid (Los Angeles City College, 2005). However, the amount of decolorizing carbon is maintained. If not, excessive loss of the desired product will happen. Gravity filtration is normally used to remove unwanted solids from a desired solution. In contrast, to collect a solid product, the usual choice is suction filtration (http://www.chemistry.sjsu.edu/straus/FILTRATION %20htms/GravFilt.htm). In both processes the solution passing through the filter is called the "filtrate." A fluted piece of filter paper was placed inside a stemless funnel. A short-stemmed or stemless glass funnel should be used to minimize crystallization in the funnel, and using fluted filter paper will minimize crystallization on the filter (Yoder, 2015). The set up hot must be kept hot to prevent crystals from forming prematurely. At these cooler temperatures, crystals are likely to form. If the funnel was properly heated before filtration, all of the solution will have passed through and no crystals will have formed on the paper or in the funnel. If crystals have formed, pouring a small amount of boiling solvent through the funnel will dissolve these (Yoder, 2015). Afterwards, the filtrate was cooled to room temperature to enable the recrystallization of aspirin. Gradual cooling is conducive to the formation of large, well-defined crystals. After a while, crystals should appear in the flask. However, no crystals have formed so a stirring rod was used to scratch the bottom of the flask. This will produce sites of nucleation. To maximize the yield, the flask was placed in an ice bath to finish the crystallization process. The crystals were finally collected using suction filtration. They were put in a watchglass and were allowed to air dry in the fumehood. After removing all the crystals from the filter paper, the filter paper was removed and was scraped to acquire any remaining crystals from the funnel. Spreading the crystals out in a beaker or a crystallizing dish will provide for the most efficient drying as the crystals will have a maximum of exposed surface area. After drying, percentage yield was obtained.
st Crystals will not form if there is a large excess of solvent. If no crystals form with the methods already discussed, a portion of the solvent may need to be removed. This can be accomplished by heating the solution for a period of time in order to evaporate some solvent. The new, concentrated solution should be cooled, and the previously mentioned methods to stimulate crystallization should again be attempted. Another potential problem in recrystallization is that the solute sometimes comes out of solution in the form of impure oil instead of forming purified crystals. This usually happens when the boiling point of the solvent is higher than the melting point of the compound, but this is not the only scenario in which this problem presents itself. If this begins to happen, cooling the solution will not stimulate crystallization, it will make the problem worse. If oil begins to form, heat the solution until the oil portion dissolves and let the whole solution cool. As the oil begins to form again, stir the solution vigorously to break up the oil. The tiny beads of oil that result from this shaking may act as the nuclei for new crystal formation. Characterization of Piperine Melting Point Determination A melting point is the temperature at which the first crystal just starts to melt until the temperature at which the last crystal just disappears (Zubrick, 2011). In this point, the solid and liquid phases coexist are in equilibrium at 1 atm. Thus the melting point (abbreviated mp) is actually a melting range. Even after a solid has been recrystallized, it may still not be pure. Thus, it is important to determine the purity of the sample, and one of the easiest methods to do this is by determining the melting point of the solid. Melting point determination defines the purity (less than 1⁰C), and serves as identification and characterization of the sample. When a sample is pure, the temperature remains constant during the whole process of solidification and it requires certain amount of heat to break its
intermolecular forces of attraction (Gaikar, 2010). The characterization of piperine involves the use of melting point determination. In oil bath method, few crystals of the compound are placed in a thinwalled capillary tube 10-15 cm long, about 3-5 mm inside diameter, and closed at one end. The capillary, which contains the sample, and a thermometer are then suspended so they can be heated slowly and evenly. The temperature range over which the sample is observed to melt is taken as the melting point. The thermometer and the sample must be at the same temperature while the sample melts, and so is the heating as the melting point is approached should be slow. If the approximate temperature at which the sample will melt is not known, a preliminary melting point determination is determined by allowing the temperature of the sample to rise quickly (Gaikar, 2010). Fisher-Johns melting point apparatus is a quick and easy method to determine the melting point of a solid wherein a small amount of crystal of the sample was heated between a pair of microscope cover glasses on an electrically heated metal block while observing the crystals with the aid of a magnifying glass. It is more convenient because this method requires as little as a single crystal. The recovered sample in the Fisher-Johns method has a melting point range of 4⁰C. Although there should be a single temperature at which a pure solid and a liquid are in equilibrium, most samples appear to melt over a small temperature range. This happens because, with block melting points, the temperature of the block rises a little during the time it takes the sample to melt. The presence of impurities in the sample also caused the sample to melt over a range of temperatures. Lastly, the usage of filter paper prior the melting point determination caused contamination of the purified sample since it contains cellulose that may end up in the tube along with the sample and affects the melting point range of the piperine (Raman, 2002). Thus, a sharp melting point (actually, a melting range of less than about 1°C) is often taken as evidence that the sample is fairly pure, and a wide melting range is evidence that it is not pure.
Reaction with Concentrated Acids Crude piperine is a very weak base, and its salts are decomposed by water. Crude piperine reacts with concentrated hydrochloric acid forming a yellowish solution. The color of the formed solution is also the same with the addition of concentrated nitric acid in crude piperine. However, a reddish black solution is formed by the addition of concentrated sulfuric acid to crude piperine. Since piperine is known as a weak base, it reacts with concentrated strong acids like HCl and HNO3 to form water and salt. This shows that the acquired substance is piperine because it has reacted to these strong acids. C17H19NO3 + H+ -> H20 + C17H19NO3 + H+ -> H20 + VII. Summary and Conclusions Extraction from natural products is an important practice in chemistry because it is the source of many medicinal and pharmaceutical compounds. Black pepper itself has many important biological properties including analgesic effects and anti-cancer effects. To gain a better understanding of these effects, it is necessary to study the components which make up black pepper. Piperine can be obtained from two different sources, synthetic and natural. Isolating piperine from black pepper was done by reflux with 95%ethanol and precipitation with 10% ethanolic KOH. Reflux and distillation are two chemistry lab techniques which involve boiling and condensing of a solution. Reflux helps complete a reaction and distillation separates components of a mixture. In distillation, a liquid is heated until it is boiling. The vapor which is produced is condensed and collected in a separate flask. In reflux, the liquid is boiled, but the vapor is allowed to condense and flow back into the original flask. Raoult's law applies the conpect of simple distillation. This states that the vapor pressure of a solvent above a solution is equal to the vapor pressure of the pure solvent at the same temperature scaled by the mole fraction of the solvent present. Crude piperine has a higher percentage yield than purified piperine due to the contaminants
(excess products or solvents) present in it unlike the purified piperine which undergone the purification process. Piperine was purified by recrystallization using acetone. Recrystallization, also known as fractional crystallization, is a procedure for purifying an impure compound in a solvent. The method of purification is based on the principle that the solubility of most solids increases with increased temperature. The identity of the product is determined using melting point determination through oil-bath method and Fisher-Johns melting point apparatus. Melting point determination defines the purity (less than 1⁰C), and serves as identification and characterization of piperine. The melting point range of the purified piperine was compared to the literature value and it showed that the purified sample is logically “far” (4⁰C) to the literature value because of its wide range. Purified piperine was also reacted with concentrated acids such as HCl, H2SO4, and HNO3. Concentrated hydrochloric acid and nitric acid both yielded yellow solution. On the other hand, sulfuric acid with piperine formed a reddish black solution. This shows that the acquired substance is piperine because it has reacted to these strong acids. As an additional procedure aspirin was also recrystallized. Acetylsalicylic acid, also known as aspirin, is one of the most widely used medications to reduce fever and is also used as a pain killer. It is an acetyl derivative of salicylic acid. It is a white, crystalline, weakly acidic substance which melts at 140°C. First, water dichloromethane, and methanol were tested with crude aspirin to determine which the appropriate solvent for the recrystallization process. Water is the appropriate solvent for aspirin because its boiling point is lower than the melting point of aspirin, it has dissolved aspirin at an elevated temperature, it is volatile, and it did not reacted with aspirin. Recrystallization was done by hot gravity filtration. Gravity filtration is used to remove the unwanted solids from a desired solution. On the other hand, suction filtration is used to collect a solid product.
In conclusion, piperine was unsuccessfully isolated with high purity. There were no crystals formed after cooling the crude piperine so the oil bath method was not executed. This may be due to the pressure buildup during distillation (with more than 2-3 drops of distillate per second) since this will poorly separate the residue and distillate. Also, during the recrystallization of crude piperine, some of the purified piperine may be lost due to inadequate washing of the residue. The sources of error in the recrystallization of aspirin were the large excess of solvent which will result to no formation of crystals or erroneous hot gravity filtration where the crystals may be left on the filter paper.
VIII. References Archive, C. (w.p.). Proper purification of crystalline solids. Retrieved on September 12, 2015, from Recrystallization technique: https://www.erowid.org/archive/rhodium/chemistry/equipment/recrystal lization.html Clark, J. (2014). Ideal mixtures. Retrieved on September 12, 2015, from Raoult's law and ideal mixture of liquids: http://www.chemguide.co.uk/physical/phaseeqia/idealpd.html Epstein, W. (1993). Isolation of piperine from black pepper. American chemical society, 598-599. Gaikar, V. (2010). Separation science and technology. Extraction of Piperine, 3097-3099. Hong-Fang, J. (February 20, 2009). Natural products and drug discovery. Retrieved on September 12, 2015, from NCBI: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2658564/ Los Angeles city college, 2. (2005). Synthesis and analysis of aspirin. Retrieved on September 12, 2015, from Chemistry 51: Experiment 11: http://www.csun.edu/~alchemy/Chem51-LACC/Labs/C51F07L12.pdf
NST. (2011). Aspirin. Retrieved on September 12, 2015, from Material measurement laboratory: http://webbook.nst.gov/cgi/cbook.cgi? ID=C50782&Type=THZ-IR-SPEC&Index=0 Raman, G. (April 17, 2002). Microwave-assisted extraction of piperine from Piper nigrum. Retrieved on 12 September, 2015, from Industrial & engineering chemistry research: http://pubs.acs.org/doi/abs/10.1021/ie010359b?journalCode=iecred Sneling, C. (June 6, 2004). Recrystallization. Retrieved on September 12, 2015, from http://www2.volstate.edu/chem/2010/labs/recrystallization.html Straus, D. (2002). Reflux. Retrieved on September 12, 2015, from http://www.chemistry.sjsu.edu/straus/FAQ/Technique %20FAQ/RefluxFAQ.htm Yoder, C. (w.p.). Recrystallization. Retrieved on September 12, 2015, from Wired chemist: http://www.wiredchemist.com/chemistry/instructional/laboratorytutorials/recrystallization Zubrick, J. (2011). The organic chem lab survival manual: A student’s guide to techniques 8th edition. John Wiley & sons, Inc.
IX. Remarks A possible improvement could be made to the experiment to improve the percentage recovery of the piperine is by increasing the time the black pepper is refluxed to more precisely distill the mixture. Also, each substance must be carefully quantitatively transferred to another container to prevent the loss of important components in the mixture. Lastly, concentrated H3PO4 may be used to characterize piperine because allows direct determination of piperine from pepper (Sneling, 2004).