Aniline Will Be Reacted with Acetic Anhydride to Form Acetanilide and Acetic Acid

Acetanilide

Gerardo Lee Garza

University of Texas Rio Grande valley

Organic Chemistry 2123-19

October 11, 2017

Purpose:

Aniline will be reacted with acetic anhydride to form acetanilide and acetic acid. An amide can be formed when an amine is treated with acetic anhydride. The amine will be aniline and the amide will be acetanilide.

Introduction:

Acyl groups can be introduced to amines using a variety of methods. For this experiment acetic anhydride will be utilized. Some of the other methods to acylate amines are by using acetyl chloride or glacial acetic acid. The method regarding the use of glacial acetic acid is far more business favorable than acetyl chloride due to it being more economical. Although, this method does require a rather extensive amount of time heating. The use of acetyl chloride is unacceptable for several reasons. Mainly due to the high reactivity that it has, freeing HCl; this effect alters half of the amine to hydrochloric salt, making it inept of to take part in the reaction. Some of the reasons why acetic anhydride will be utilized instead of acetyl chloride or glacial acetic acid are because its rate of hydrolysis is at a level low enough to allow the acetylation of amines to be conducted. The technique gives a product of high purity and respectable yield but it is not appropriate for use with weak bases; neutralized amines.

The addition of an acyl group is utilized to protect a primary or a secondary amine group. Acylated amines are less volatile to aromatic substitution reactions, less prone to lose electrons, and less susceptible to to join in the reactions of free amines, because they are more acidic. The amino group can be restored easily by hydrolysis in either a base or acid.

Materials:

• Boiling chips
• 2 g Aniline
• 2.5 mL acetic anhydride
• Electric flask heater
• 125-mL Erlenmeyer flask, with stopper
• Glass stirring rod
• 10-mL graduated cylinder
• 50-mL graduated cylinder
• Pasteur pipet
• Distilled water
• 50 mL beaker
• Activated charcoal powder
• Filter paper
• Vacuum
• Buchner funnel
• Ice bath

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Experimental Procedure:

Reaction Mixture:

1. Weigh 2 g of Aniline. Record the mass of the aniline and transfer to a 125-mL Erlenmeyer flask using a Pasteur pipet. Add 15 mL of distilled water to the flask. Mix the contents gently while slowly adding 2.5 mL of acetic anhydride. Make note of any changes that occur.

Crystallization:

1. Add 50 mL of water with a boiling chip to the flask with the aniline and acetic anhydride. Place the flask on a hot plate and heat the mixture until all of the solid and oily products have dissolved. Carefully remove the Erlenmeyer flask from the hot plate and proceed to pour approximately 1 mL of solution into a small beaker and allow the substance to cool.

Decolorization:

1. Add about .5 g of activated charcoal to the flask containing the mixture. Place the flask on the hot plate and let the substance return to a boil. While boiling gently swirl the contents in the flask. Be sure to add the charcoal before placing on a hot plate due to the possibility of violent frothing.

Gravity Filtration:

1. While the solution is boiling, assemble an apparatus for gravity filtration, equipped with a funnel and filter paper in a 125 mL Erlenmeyer flask. Also prepare about 25 mL of boiling water. The water will be used in the next steps to wash the solvent
2.  Place a filter paper in the funnel. Filter the acetanilide-charcoal mixture rapidly, but in small portions, through the filter paper. Be sure to keep the solution warm on the hot plate until it is to be filtered through the funnel along with the collection flask. The reason for keeping both flasks warm on the hot plate is to allow the water vapor to warm the water stem and reduce the likelihood that crystal will form in the funnel. The products that remain should be charcoal on the filter paper and aqueous acetanilide in the collection flask. If crystal begin to form in the funnel add hot water to dissolve.

Crystallization and Vacuum Filtration

1. To complete the crystallization process, the flask must be placed in an ice water bath for about 15 minutes. Filter the solution by gathering the crystals by vacuum filtration and dry them as completely as possible by allowing air to be drawn through them while they remain on the funnel.
2.  Record the wright of the pure crystallized product and calculate the percentage yield

Results:

        In this experiment the technique, purification by recrystallization, was utilized because it allows for the purification of a crude material.  The potential loss in yield is made up by the high purity content.  2.446 g of crude acetanilide was recovered from a theoretical yield of 2.589 g.  This corresponds to a percent recovery of 94.48 %: The amount of pure product recover translated to .861 g. This divided by the amount of crude product which is 2.446 g produces a 35.20 % recovery.