Synthesis of Tylenol and Aspirin

Synthesis of Aspirin and Tylenol

Kyla Wykoff

Abstract

Aspirin and Tylenol were synthesized by means of crystallization, recrystallization, and melting point determination. Synthesis produced significantly high percent yields for aspirin, however, produced extremely low and impure percent yields for Tylenol. A second group was also used to compare results and errors, in which they too were also producing extremely low percent yields of Tylenol. Therefore, error was based on the specific protocol used.

Introduction

Aspirin, acetylsalicylic acid, was first synthesized by a German chemist, Gerhardt, in 1853, but his reports went largely ignored. However, forty years later, in 1893, Felix Hofmann, also German, reinvestigated Gerhardt's work and proved it to be true. Acetylsalicylic acid was found to be medically effective for both reducing fevers and relieving pain (Synthesis).

Today aspirin has many uses, which include; reducing fevers, reducing headache pain, relieve swelling and joint pain often associated with arthritis, enhances the elimination of uric acid. Acetylsalicylic acid, aspirin, is prepared by reacting salicylic acid with acetic anhydride:



Figure 1. Chemical Equation for Aspirin Synthesis (Aspirin)

Tylenol, acetaminophen, is also used both as a fever reducer and pain reliever. Acetaminophen is prepared by reacting ammonia with acetic acid:



Figure 2. Chemical Equation for Tylenol Synthesis (Acetaminophen)

The purity of an aspirin or Tylenol sample can be obtained by determining the melting point. The presence of impurities always lowers the melting point of any substance; the higher the concentration of impurities, the lower the melting point will be (Preparation).

Experimental

Synthesis of Aspirin

To synthesize aspirin, the following materials are needed: Salicylic acid, acetic anhydride, concentrated sulfuric acid, ethanol, dropper, 125mL Erlenmeyer flask, beakers (400mL, 100mL, 20mL), graduated cylinders (10mL, 25mL), hot plate, watch glass, stirring rod, vial to hold sample, ring stand, clamp, Buchner funnel, filter paper, vacuum filtration flask, ice, thermometer, melting point capillary tube, and melting point apparatus.

In a 125mL Erlenmeyer flask place 2.00 g of salicylic acid. Add 5mL of acetic anhydride, then swirl flask to wet the crystals. Add 5 drops of concentrated sulfuric acid, then heat flask in boiling water for about 10 minutes. Remove flask from water bath and add 10mL of distilled ice water. Chill the mixture in ice bath until crystals no longer form, stirring occasionally. If solid does not appear, reheat flask in hot water bath and cool again.

Set up vacuum filtration apparatus. Insert filter paper into funnel and turn on water aspirator. Decant the liquid onto the filter paper, being very careful to keep the transfer of any solid to a minimum. Add 15mL of cold water to flask, swirl, and chill again. Pour liquid and crystals onto filter paper. Repeat process until transfer of the crystals is complete. Wash crystals with 10mL of water, and utilize the vacuum to dry the crystals as best as possible. Determine and record the mass of the crude aspirin.

Recrystallization

Place crystals into 100mL beaker. Add 8mL of ethanol, and 25mL of water to beaker. Warm mixture in hot water bath until the aspirin has dissolved. Cover beaker with watch glass, remove from heat, and allow to cool slowly. Set beaker in ice bath, needle-like crystals will begin to form. Collect crystals by vacuum filtration. Wash crystals with two 10mL volumes of ice water, and utilize vacuum to dry crystals as best as possible. You may want to leave your crystals sit out overnight on a watch glass, in order for them to completely air dry. After drying, transfer crystals to a pre-weighed vial. Determine and record the mass of the aspirin crystals.

Melting Point Determination

Fill melting point capillary tube to a depth of 0.2cm with aspirin crystals. Place tube in melting point apparatus. Pure aspirin melts at 135 degrees Celsius. Determine the melting point of crystals, then calculate percent yield (Preparation).

Synthesis of Tylenol

To synthesize Tylenol, the following materials are needed: Acetic anhydride, p-aminophenol, concentrated phosphoric acid, ethanol, dropper, 125mL Erlenmeyer flask, beakers (400mL,