charge that attracts to the positively charged hydrogen. A more stable structure is formed when the charge on the oxygen moves from being a lone pair to forming a double bond and the ether substituents are removed. In the presence of Hydronium, the negatively charged oxygen shares electrons with a hydrogen from the reagents. This mechanism allows for the formation of Salicylic Acid.
When Acetic Anhydride is used as a reagent, the double bond on the ketone is transferred as a charge to the oxygen causing the opposite charges to attract. Once again, the electrophilic oxygen takes the lone pairs between the O-H bonds to form the final product of Aspirin and acetic acid. These mechanisms for this experiment can be seen in Scheme 1. Aspirin is classified as a Non-Steroidal Anti-Inflammatory Drug that is indicated for heart attack, pain, and fever.
Procedures Part A: Ten milliliters of 6M Sodium Hydroxide was added to two milliliters of methyl salicylate in a test tube. A white, crystal-like precipitate was immediately formed. Even upon shaking, the solution held its structure. The test tube was placed in a water bath containing boiling chips for while swirling the contents occasionally. The test tube was removed after 20 minutes. The precipitate no longer remained; the solution was now a pink liquid. The contents of the test tube were poured into a beaker to cool for approximately five minutes. Once cooled, 25 milliliters of 6M Hydrochloric Acid were slowly poured into the beaker.
Precipitation occurred leaving a white powder-like substance in the beaker. This beaker was placed in an ice bath until a clear separation of layers was clearly seen. Upon removal of the beaker from the ice bath, a pH strip was hovered above the solution were the strip changed color to a red-shade which indicated a pH of approximately two. Vacuum filtration was assembled in order to isolate the white precipitant”Salicyclic Acid. Cold, deionized water was used to ensure that all of the visible precipitant was transferred from the beaker to the filter paper. The substance underwent vacuum filtration for five minutes then placed onto a paper towel in order to dry.
The precipitate weighed 3.90 grams. A capillary tube was used to collect a small sample of the powder. The sample was used to determine a crude melting point of 145 °C. The specimen was placed in a desiccant jar and allowed tofurther dry for 72 hours. Part B: Once dried, the specimen was measured as 1.83 grams. One gram was isolated for further testing and placed into a test tube. Two milliliters of Acetate Anhydride and five drops of concentrated Sulfuric Acid was added to the test tube and shaken vigorously. Only a small amount of the powder remained; the addition dissolved the specimen; a pink liquid was formed.
The test tube was placed in a warm water bath (51°C) until no powder could be observed. After nineteen minutes, the test tube was removed. The solution was transferred to twenty milliliters of cold, deionized water which resulted in the precipitation of a white substance”Aspirin after six minutes of cooling. The contents of the beaker underwent vacuum filtration in order isolate the precipitant. Once the vacuum crudely dried the powder, the filter paper and contents of the Buchner Funnel where placed on a paper towel to further removal of water while the aqueous layer within the filter flash was discarded in the liquid waste container.
A small sample was captured in a capillary tube to determine an approximate melting point. When the melting point was deterred as 79°C, further purification of the substance was 2 required. The specimen was returned to a test tube with deionized water and placed in a boiling water bath. Once the powder was no longer visible, the test tube was transferred to an ice water bath where the crystals reformed. Once again, the specimen was filtered with vacuum system, dried on a paper towel, and tested to determine a crude melting point. The synthesized Aspirin was determined to have a crude melting point of 132°C. Calculations and Results Formula1 shows the conversion of milliliters of methyl salcyclate into grams of methyl salcyclate.