Preperation of Antifebrin

In this experiment, I am going to prepare the organic compound of antifebrin from readily available chemical reagents.

Antifebrin is an odourless solid chemical of white flake-like appearance. Chemically, antifebrin is the amide phenylethanamide CH3ONHC6H5. It’s slightly soluble in water. It does have the ability to self-ignite if it reaches the temperatures of 545�c but otherwise it’s a stable compound. The pure crystals of antifebrin are plate shaped and white in colour.

The antifebrin in this experiment is prepared from the reaction between phenylammonium chloride (C6H5NH3Cl) and ethanoic anhydride[ (CH3CO)2O ].

Chemical Equation for the Reaction:

C6H5NH3+ Cl- + (CH3CO)2O CH3ONHC6H5 + CH3OOH + HCl

Procedure & Observations:

Procedure

Observation

Dissolve 1.0g of phenylammonium chloride in 30cm3 of water in a conical flask.

Phenylammonium chloride is a greyish-green crystal like product. Adding water to it gives a solution pale grey with green tinge. After dissolving the solutions turns clear with a green-grey colour and no precipitate.

Prepare a solution of 6.0g of sodium ethanoate in 25cm3 of water in a conical flask.

Sodium ethanoate is a white powder. It dissolves completely in water to give a colourless solution.

Carefully add 2cm3 of ethanoic anhydride to the solution of phenylammonium chloride,and stir vigorously until all the ethanoic anhydride is dissolved.

Ethanoic Anhydride smells of vinegar. Adding it to the phenylammonium chloride gives a solution with oily blobs with a sweet fruity smell. Vigorous stirring results in the oily blobs to dissolve completely leaving a clear greenish-grey solution.

Then add the sodium ethanoate solution and continue to stir for a few minutes.

Adding sodium ethanoate solution gives crystals precipitate in the off-white solution which is no longer clear. After stirring the solution doesn’t change but it now smells of vinegar.

Collect the precipitate by filtering under reduced pressure.

Filtering under reduced pressure leaves a wet sample of white crystal precipitate.

Recrystallise the whole product from the minimum volume of hot water.

As it boils the crystals dissolve but the impure black blobs appear. Adding little more water and boiling dissolves these impurities and leaves a colourless solution.

Then allow the mixture to cool and when crystallisation, it would give a compound of pure product, more pure and larger precipitate is formed. Filter off the pure product again under reduce pressure.

This results in another wet sample but it is purer and has bigger and whiter wet crystals.

After filtering, dry the bulk of the product in air and small portion between filter paper

After drying, the final products are dry sparkling white sharp needle like crystals.

Measurements and Results:

Mass of phenylammonium chloride used = 1.000g

Mass of sodium ethanoate used = 6.012g

Melting Points:

Rough

1st Accurate

2nd Accurate

3rd Accurate

Mean Melting Point

112�c

114�c

114�c

113�c

114�c

Yield:

C6H5NH3+ Cl- + (CH3CO)2O CH3ONHC6H5 + CH3OOH + HCl

Mr of phenylammonium chloride = 129.5

Mass of phenylammonium chloride = 1.010g

Moles of phenylammonium chloride = 1.010 � 129.5 = 101/12950 moles

If 1 mole of phenylammonium chloride gives 1 mole of antifebrin, then 101/12950 moles of phenylammonium chloride will give 101/12950 moles.

Mr of antifebrin = 135

Moles of antifebrin = 101/12950 moles

Theoretical Mass of antifebrin = 135 � 101/12950 = 1.053g

Actual yield of antifebrin = 0.022g

Percentage Yield = (0.022 � 1.053) � 100 = 2.09%

I have listed all the safety precautions and risks involved in this experiment below:

* Wear safety goggles at all time to avoid contact with any harmful chemicals.

* Wear gloves when handling ethanoic anhydride and use it in the fume cupboard.

* Handle Bunsen burner with care. If you have long hair then tie them back to avoid contact with the flames. If you burn your skin, call for medical help immediately.

* Keep work place tidy and stools under the desk to avoid any accidents and take other people’s safety into consideration too.

* Always keep the bottles of chemicals closed with tops if not being used.

* Phenylammonium chloride is harmful if absorbed through the skin and maybe harmful if inhaled or swallowed.

* Sodium ethanoate maybe harmful if large amount is swallowed. If there’s an eye or skin contact, rinse immediately with water and if irritation persists, ask for medical help.

* Ethanoic anhydride is strongly corrosive and can cause serious burns. It is poisonous and will cause serious damage if swallowed or inhaled. Do not allow the pure liquid or a solution containing it to come into contact with your skin. Ensure that you work only in an area with good ventilation – do not breathe the fumes. If there’s an eye contact, immediately rinse your eyes with water for 10 minutes and call for medical help. If there’s a skin contact, wash the skin with plenty of water, remove any contaminating clothing and call for medical help. If swallowed, immediately seek medical help.