How to make salicylic acid from willow bark

Simple Synthesis of Aspirin Lab

By Alaysia Fox

CHM 304

January 23, 2020

Abstract

Aspirin is an over the counter, nonsteroidal anti- inflammatory drug that can temporarily relieve symptoms such as migraines, aches, and pain. It can also prevent blood clots or reduce the risks of having a heart attack. In this experiment we used willow bark, ethanol, iron chloride, acetylsalicylic acid, salicylic acid, acetic acid, and an aspirin tablet in order to synthesize aspirin. Salicylic acid had the pH of 5 with lower acidity. Salicylic acid, is less acidic which means its less harmful to the stomach when compared to aspirin tablets because the tablet have higher acidity (pH 3) which can cause damage to the stomach lining if too acidic.

Introduction

With an estimated world-wide consumption of 40[thin space (1/6-em)]000 metric tons per year, aspirin (acetylsalicylic acid) which was discovered in 1853, is still one of the most prominent and widely used medicines with an incredible spectrum of properties. 1 Apart from its exceptional analgesic, anti-pyretic, and anti-inflammatory properties, it is commonly used in the primary and secondary prevention of cardiovascular diseases. 2

Aspirin is typically administered via the oral route, but unfortunately possesses a number of undesired side effects in long-term use that are mainly related to its acidity and low bioavailability. Aspirin is only sparingly soluble in water (0.33 g in 100 mL) or in the acidic environment of the stomach, resulting in undissolved particles adhering to the gastrointestinal mucosea and causing topical irritation and gastric distress. 3 Once absorbed in the small intestine, acetylsalicylic acid is rapidly metabolized to its main metabolite salicylic acid , thereby irreversibly acetylating and inhibiting COX-1 oxygenase. 4 Like aspirin , salicylic acid itself is also part of the non-steroidal anti-inflammatory drug (NSAID) family and is frequently found in a wide range of medical and cosmetic formulations such as skin-care products or sunscreens. 5 Apart from problems related to the poor solubility of aspirin , the bitter taste of acetylsalicylic acid is another major drawback, with the required dosage of aspirin leading to tablets that are notoriously hard to swallow.

Procedure

The experiment was completed in triplicate meaning steps done in well A1, were also done in B1 and C1. The materials used were a 24- well plate, pipettes, willow bark, litmus paper, ethanol, iron chloride, acetylsalicylic acid, salicylic acid, acetic acid and an aspirin tablet. In part 1 the procedure, consisted of the extraction of salicylic acid. In the first step of Part 1, A1 on the 24-well plate was half-filled with willow bark then the pipette was used to cover the bark with ethanol. A timer was set to 15 minutes to allow the bark to soak. In Part 2 of the experiment 0.5g of acetylsalicylic acid was added to well A2 on the 24-well plate. 50 drops of the ethanol was added with a pipette using the end of the pipette to stir after the ethanol was placed in all three wells. Thereafter each solution was then tested with litmus paper. In part 3 of the experiment, using a pipette one drop of iron chloride solution was added to the acetylsalicylic acid along with the salicylic acid mixtures in wells A2 and A3. In part 4 of the experiment a pipette was used to extract the ethanol from the willow bark in A1 once the 15 minutes were up. 5 drops of ethanol was added to well A4, then the ph was tested with the result of 5. Lastly 1 drop of iron chloride was added to well A1. In part 5 of the experiment using a pipette 5 drops of the willow bark ethanol was added to well A4 following 1drop of iron chloride and 15 drops of acetic acid then stirred with the end of the pipette. The observation was a strong vinegar like smell and brown color to the solution. In part 6 of the experiment an aspirin was crushed and weighed (2.24g). 0.25g of crushed aspirin was poured into well A6, and 50 drops of ethanol was added and stirred into well A6. The pH of the mixture was tested and resulted in pH4. Lastly one drop of iron chloride was added to the well changing the mixtures color from white to light yellow.

Results

The results for part 2 pH determination, acetylsalicylic acid in well A2 was 3. The pH of salicylic acid in well A3 was 3. The weight of acetylsalicylic acid in wells A1 was .53735 g, B2 was .5005 and C3 was .5020.The weight of salicylic acid in well A3 was .5049, well B3 WAS .5013, and well C3 was .5020. For part 3 the iron chloride test, the color of the acetylsalicylic acid solution was yellow in well A2 and the salicylic acid solution was dark purple in well A3.

For part 4 salicylic acid determination the pH of well A4 was 5. After 1 drop of iron chloride was added into the wells the solution turned from white clear to a light yellow color. For part 5 the synthesis of aspirin a strong smell of vinegar was produced after the acetic acid was added into well A5 cause a color change of brown. For part 6 comparison of aspirin tablets the pH of the mixture in well A6 was 4 and after 1 drop of iron chloride was added it turned into a yellowish white color.

Conclusion questions

Triplicate is having 3 copies of , experiments are done in triplicate so that if there is an error in the experiment all samples won’t be ruined and they are more likely to be correct with less room for error. Salicylic acid proved to be more irritating to the stomach due to the higher pH compared to the weak pH of the aspirin. The chemical structure of salicylic acid is (CH6O3) and acetylsalicylic acid is (C9H8O4). The salicylic acid and the salicylic acid that was extracted from the willow bark differ in acidity because of the extraction method used to get the salicylic acid from the willow bark. The salicylic acid had the pH of 3 and the willow bark had a pH of 6. The aspirin synthesis was successful because the color change and odor indicated a chemical reaction. The synthesized aspirin compares to the aspirin tablet because they both contain salicylic acid. In conclusion salicylic acid is and active ingredient in willow bark and aspirin but the willow bark solution had a pH of 6 making it the least acidic compared the aspirin tablet which had a pH of 4.

Figures/ Tables

Image result for aspirin chemical equation

References

Bica, Katharina, et al. "In search of pure liquid salt forms of aspirin: ionic liquid approaches with acetylsalicylic acid and salicylic acid." Physical Chemistry Chemical Physics 12.8 (2010): 2011-2017.

“Simple Synthesis of Aspirin Lab Handout”