Aspirin and measure its boiling point

The purpose of this experiment was to prepare a sample of Aspirin and measure its boiling point. Reacting salicylic acid with acetic anhydride in excess with the presence of a catalyst sulphuric acid. Through a sequence of heating, filtering and recrystallizing the end product of making aspirin was positive and the measuring of its boiling point was successful. The sample was purified and the percentage yield was calculated to be 61. 2% and to measure the purity of the sample the melting point was considered which came to be 122°c.

Introduction

The chemical name for Aspirin is Acetylsalicylic acid. Aspirin is known to relieve pain and is an over the counter drug. Salicylic acid was first found in the bark of the willow tree, which used to be used for treating fever and a variety of illnesses. However scientists soon began to realise that the acid used to thin the stomach lining and burn throats. (Ling, 1994) Not long after a German scientist, Felix Hoffman, derived a pain reliever that did not produce the same side effects as salicylic acid, and is credited for the finding of Aspirin.

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(Ling, 1994)

Uses of Aspirin

Another use of aspirin is people having to take it to thin the blood, which reduces the chance of unnecessary blood clots to form; therefore in the long term taking an aspirin everyday will prevent heart attacks and strokes in high risk patients. There is a less chance of blocked arteries causing the amount of blood flowing to decrease and thus causing cardiac arrest.

(Ling, 1994) Aspirin has been becoming increasingly popular with patients that have experienced a heart attack to avoid any recurrence taking place or tissue death surrounding the cardiac muscle.

Aspirin can also be defined as a non-steroidal anti-inflammatory drug and Aspirin being one of the first to be classed as one. (Greenlaw, 2005) These are medications with analgesics that reduce fever and have anti-inflammatory effects. Aspirin, ibuprofen and naproxen are the more common NSAIDs mainly because they can be bought over the counter and no prescription is required. Physical Properties Aspirin appears to be generally white although at times a colourless powder.

Aspirin.

In addition to aspirins physical properties, it has no odour or toxic smell, however when it does come in to contact with any type of moisture it releases a smell of acetic acid (RSoC, 2014). In cold water Aspirin is insoluble but as the water heats up the solute starts to dissolve. Melting and boiling point The experiment melting point is approximately 135°C. (Haynes 2013) Preparing Aspirin by reacting salicylic acid and acetic anhydride, and recording its melting point was the aim of this experiment.

A sample of the salicylic acid was weighed and then a measured amount of acetic anhydride and a minimal amount of sulphuric acid was also added. The reason as to why the reaction is heated is because salicylic acid is solid at room temperature but also to form acetyl salicylic acid and acetic acid. (chemlatech) In addition heat is used to initiate a reaction, provide energy for molecules to react with another. The water is added to purify the sample and wash away any excess acetic anhydride. Using vacuum filtration the sample is filtered and weighed.

Balance symbol equation: C7H6O3+C4H6O3>C9H8O4+ C2H4O2 Diagram 1 shows the skeletal formula of the changes in shape that takes place in the molecules. The limiting reactant, structure of salicylic acid contains a benzene ring and a carboxylic group. It shows the addition of water allows the excess acetic anhydride to become hydrated break in to two molecules, one of which is added to the salicylic acid to produce the aspirin, forming an ester.

For the breaking of bonds heat is required which is how the reaction is initiated under gentle heating. The H+ is obtained either from concentrated H2SO4 or H3PO4 and is used to catalyse the reaction. There are numerous amounts of equipment that would help produce Aspirin in a lab, however suction filtration is a common way to filtrate and the draining of the water works by a creating a vacuum and isolating the substance. The heating mantle is a much more efficient way to heat the round bottom flask, as the mantle encloses the flask and circulates heat within it.

Also the temperature of the heating mantle can be controlled more closely as there are numbers used to adjust the heat. To find the melting point a small cylinder was inserted into the beaker full of Aspirin. This was then inserted in to a larger cylinder which then applied heat on to the small tube and became even hotter recording the temperature. Method All reactions were completed in a fume cupboard for safety. The first step was to add 50g of salicylic acid with 80ml of acetic anhydride in a round bottom flask.

As it is very tricky to get exactly 50g of the acid exactly the sample used was 50. 07g, as close as possible to the preferred amount. In addition to these two reactants a maximum of 0. 5ml of concentrated sulphuric acid was added to the flask. During the heating process the temperature was to be maintained between 60-70°c. If the temperature had exceeded 70°C the acid would have been burnt and effect the final product. To heat the flask a heating mantle was used.

After that to guarantee the sulphuric acid was dispersed throughout the product, loosening the round bottom flask from the clamp and swirling it around helped ensure this. The sample should have been gently heated for a period of 30 minutes to ensure a better quality product and then cooled to 50°c. 750ml of cold water should be added to the acid after the heating process and mixed it. To help filter and recrystallize the product, the Buchner funnel was used which helps sucks the remaining water from the product. Lastly measure the yield and the melting point of the crystals.