Hydrolysis of Acetylsalicylic Acid


The purpose of this experiment is to explore the hydrolysis of esters and create a sympathetic ink. In addition, it is to become acquainted with the identification of ester, carboxylic acid and alcohol useful teams, to understand that formation and chemical reaction of esters equilibrium processes, to understand however organic compound chemical reaction yields acid and alcohol merchandise, and to understand what a sympathetic ink is and the way such inks envisioned.


1. Crush two 325 mg aspirin tablets into powder.

Place the powder in a 50 or 100 mL beaker. Add 2grams of sodium carbonate. Then measure and add 20 mL of water.

2. Stir the mixture occasionally. Cover it with plastic wrap or similar and allow it to stand overnight in a safe place where it will not be disturbed. This will hydrolyze the aspirin to salicylic acid.

3. Prepare a developing solution by dissolving 1 gram of iron (II) sulfate heptahydrate into 60 mL of white vinegar. Stir until fully dissolved; a cloudy green solution will result.

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4. To the developing solution, add 2-3 mL of household bleach solution. Stir. The solution will turn dark orange. If the solution is not dark enough, add another couple of drops of bleach.

Experimental and Analysis

On normal, one ibuprofen tablet contains approximately 325 mg of ibuprofen. One headache medicine tablet was broken down in 7 mL of ethanol. The tablet did not totally break up. This is often thought to be due to pollutions within the tablet that hold it together. Then, 0.1 mL of this arrangement was weakened with ethanol to form 5 mL and spared for an afterward step within the test.

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Since the base-catalyzed hydrolysis produces acidic corrosive, a buffer arrangement was made to anticipate the pH of the response arrangement from changing. In case the pH is as well moo, at that point the response would not continue through a based-catalyzed handle. This seem influence the rate of response. To create the buffer arrangement, 0.0060 g of H3BO3 was measured out on the electronic adjust. This parcel was added to a container, together with 10 mL of deionized water. This made a 9.70 mM arrangement of H3BO3. Another, 0.040 g of NaOH was measured on the electronic adjust. This test was at that point included to 10 mL of deionized water. This made a 100.0 mM arrangement of NaOH. The pH meter was incapable to be standardized. It would either work at the lower calibration buffer and not the higher one, or the pH meter would work at the higher calibration buffer and not the lower one. In the long run it was chosen that the pH meter was calibrated near sufficient to the higher calibration some time recently to continue with the explore. A little sum of the 100 mM NaOH solution was slowly pipetted to the 9.70 mM H2BO3 solution until the pH was between 9.9 and 10.2. The addition was halted at a pH of 10.07. This buffer solution was used to keep the pH constant throughout the reaction.

The base-catalyzed hydrolysis was too carried out at a consistent temperature of 65°C. The Peltier cooler/heater was utilized to hold the temperature of the cuvette at 65°C whereas within the Cary 50. The Peltier cooler/heater capacities by exchanging warm between the cuvette and water that circulating through the cell holder (found within the Cary 50). The water stream was provided by a little aquarium pump inundated in a container of water. The pump kept a consistent stream of water whereas the Peltier gadget was on so that the gadget would not be harmed. The water pumped was turned, taken after by the Peltier gadget. The required temperature on the show of the Peltier gadget was changed to 65°C. The gadget was at that point permitted to warm.

Another the Cary 50 UV/vis spectrophotometer was set up for the explore. The wavelength at which retention would take put was set to 298 nm. This is often the wavelength in which both salicylic corrosive and the salicylate particle have the same absorbance. This absorbance is known as the isosbestic points-the molar absorptivity's are indistinguishable. Normal time (time each information point was measured) was set to 4 seconds (s). Following the X mode was set in seconds. The collection timing was set to simple, and the cycle was set to require a estimation each 60 s. Information was taken for ~ 70 min.

This response takes after first-order energy. To calculate the rate steady for the base-catalyzed hydrolysis, the absorbance of the reactant is required, not the item, for which the absorbance in this explore was measured. There was a 1:1 stoichiometric proportion between headache medicine and salicylic acid/salicylate. The sum of headache medicine also the sum of salicylate is consistent. This gives the relationship: [aspirin]t=0=[salicylate]t=?=[aspirin]t+[salicylate]t. Another relationship between the two concentrations is [aspirin]t=[salicylate]t=? - [salicylate]t. Since this response as it were depends on the concentration of one reactant (headache medicine), it complies first-order energy, [salicylate]t can be fit with the taking after condition within the slightest square's fitter:

a exp(-b t) + c

To begin with, the Agui program was utilized to construct a demonstrate of headache medicine. It was critical to keep in mind when developing the ibuprofen particle that it was in a essential arrangement, so the hydrogen connected to the carboxylic corrosive would be separated. The modeled looked just like the following:

Next, the same process was used to determine the bond lengths, angles, and conformations of the intermediate. The structure of the intermediate was as follows:

These calculations were used to determine the bond lengths and hybridization of the products. The two products are salicylate and acetate respectively as follows:

Results / Conclusion:

The Acetylsalicylic corrosive was hydrolyzed with a base to salicylic corrosive and acidic corrosive. The colorless salicylic corrosive was at that point complexed with Fe3+ to deliver a purple thoughtful ink. The other hydrolysis item, acidic corrosive, was famous to have an odor like vinegar.

Lab Questions

1. Identify the functional groups in methylsalycylate, acetylsalicylic acid and salicylic acid:





Figure 1:


A. Ester, Alcohol, and Phenyl

B. Carboxylic acid, Ester, Phenyl

C. Carboxylic acid, Alcohol, and Phenyl

2. How may the position of this equilibrium be shifted to favor the products?

Answer: By increasing pressure, decreasing volume or providing excess of CO2 one can shift the reaction in a forward direction.

3. The bleach in this exercise was used to convert the Fe2 in FeSO4*7H2O to Fe3+. Is this oxidation or reduction?

Answer: Oxidation

4. Look up sympathetic inks on the internet. Give some examples of other substances that can be used for these inks.


Lemon juice, vinegar, cerium oxalate, clear soda, apple juice, milk, and soapy water can be used for sympathetic inks.

Updated: May 19, 2021
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Hydrolysis of Acetylsalicylic Acid. (2019, Dec 19). Retrieved from https://studymoose.com/hydrolysis-of-acetylsalicylic-acid-essay

Hydrolysis of Acetylsalicylic Acid essay
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