Experiment 8: Acetylsalicylic Acid Experiment

Melting Point Data Table Compound Aspirin Caffeine Salicylamide Actual MP (ºC) 93 - 98 260 - 262 96 - 102 Expected MP (ºC) 135 236 140 Percent Error (%) ~30% ~12% ~30%

Moisten filter paper with a few drops of solvent and turn on water vacuum to fullest extent

The product was placed in a Craig tube and several drops of hot (100°C) solvent (50% water, 50% methanol, by volume) was added and heated until all of the crystals dissolved. The Craig tube was plugged and set in an Erlenmeyer flask to cool. Crystallization was induced once the mixture was at room temperature by scratching the inner wall of the tube. It was then placed into an ice bath for ten minutes until crystallization was complete. The tube was then

Aspirin was synthesized by reacting salicylic acid with acetic anhydride in the presence of phosphoric acid, H3PO4, as a catalyst:

The product was then suspended in 2 ml of water with a stir rod in a 50 ml Erlenmeyer flask and heated to boiling. Water was added in one milliliter increments until all the product was dissolved (18 ml added total). The saturated solution was allowed to slowly cool, and gradual white crystal formation was observed. Recrystallized product was collected once more by suction filtration with the Hirsch funnel once crystallization ceased. Collected product dried on a watch glass for a week, weighed 0.14 g (1.2 mmol), and the melting point was 139°-141°

16) Heat some of the hexane to boiling and place the solid to be crystallized into an Erlenmeyer flask.

The aspirin crystals were washed by pouring 10 mL of water over them through the funnel.

Materials: Solutions of crystal violet and sodium hydroxide were available in the laboratory which were previously prepared of concentrations 2.00 E-5 and 2.00 E-2 respectively. Deionized water was used

The pipet was put into the top of the condenser and leaving no open spaces. The vacuum served to get rid of the nitrogen oxide gases that were formed during the oxidation reaction. The solution was heated for 30 minutes, beginning the time when the first sign of nitrogen oxide fumes were observed. After the 30 minutes, the solution was removed and cooled for a few minutes. The solution turned was a brownish-yellow color and all the crystal were dissolved, leaving a liquid. The solution was then transferred, using a Pasteur pipet, to 3 mL of water in a beaker. The reaction flask was rinsed to remove the remainder of the solution. The solution was stirred with a glass rod until room temperature of the solution was achieved. A yellow solid was to form, but instead the solution remained aqueous in the case of the specific experiment explained here. With additional scraping of the solution with a glass rod, no crystals formed at all. The next procedure, if the crystals had formed was to crush the solid with the glass rod and filter the solid until the crystals were dry. The mass would then be weighed and the crystals were to be recrystallized with 95% ethanol. The crystals were to be cooled in ice water to get full crystallization and then the crystals were to be filtered and air dried, then weighed.

Salicylic acid can by synthesized into acetylsalicylic acid through a process known as esterification. Esterification occurs when a carboxylic acid

8. Crush crystals into powder with a stirring rod and use a melting point device to determine the melting point of your active ingredient.

The purpose of this experiment was to determine which temperature (hot, cold or room temperature) affects the growth of crystals the most.

Acetylsalicylic acid is the active pharmaceutical ingredient that is found in aspirin and is used to treat inflammation, pain and fever. It is created by an esterification reaction of salicylic acid with acetic anhydride in the presence of an acid catalyst. At the end of the reaction, a product and unreacted salicylic acid and acid catalyst was created. The product contains impurities, such as acetic anhydride and salicylic acid, which needs to be removed. Crystallization, a technique used to purify substances, produces crystals and the impurities get filtered under the vacuum. Adding water after the crystals are made but before the crystals are vacuumed helps to purify the crystals and get rid of some impurities. Melting the crystals can determine the purity of the product that was made. When performing the experiment, salicylic acid will be in a flask and in a water bath. It is important that it sits in the water bath for at least eight minutes but no more than ten minutes. If it is in the water bath for more than ten minutes, the salicylic acid could decompose. The purpose of this experiment was to determine the presence of salicylic acid and starch in acetylsalicylic acid. The presence of salicylic acid can be determined by performing a ferric chloride test. The presence of starch can be determined by performing an iodine test. In order to find the percent yield, the following formula was used:

The weight of crude aspirin obtained from 4g of Salicylic Acid was 4.74g. After recrystallization, approximately 2.9g of recrystallized aspirin was obtained. After calculating the molar mass of Salicylic Acid and aspirin, the theoretically obtainable weight of aspirin was 5.217g. The percentage of theoretical crude aspirin obtained was 90.85%. The percentage of theoretical recrystallized aspirin obtained was 55.58%. During the Salicylic Acid testing, the crude aspirin tested positive by changing to dark purple color, which occurs due to the Salicylic Acid reacting with methanol and iron(III) chloride. After recrystallizing the crude aspirin, the aspirin was tested negative by changing to light yellow color. There is a possibility that these results are not entirely accurate due to human error. A few of the steps that require the use of a few drops of an chemical substance. However, there was no exact way to measure a few drops. As a result, it was possible to place too much or too little of the chemical substance, which can affect product of the reaction.

The melting point determination consists of five major steps: obtain the sample and make sure it is grinded, fill 2-3 capillary tubes with the sample, ensure that the sample is tightly packed, insert the tubes into the Melting Point Apparatus to run a fast and a slow ramp, and finally record the data.3 Grinding the sample could be done by several methods. A large stainless steel spatula could be used to directly crush the tiny crystals into fine powder, or the sample could be first placed within a folded piece of filter paper and then pressed with the spatula.2 A mortar and pestle are also an appropriate instrument to grind the sample.4 Next, the adequate amount of sample, which is 1-2mm, should be collected with each capillary tube.2 If less sample is collected, it is much harder to see when the first and last droplets form, making it difficult for the chemist to record melting range temperatures.6 If the capillary tubes are filled with larger sample, this could cause uneven heating during the fast and slow ramps and could also provide inaccurate melting range that is