Post Lab Discussion

Experiment 17

Prelaboratory Assignment 1. Draw the structure of the following

compounds: Acetyl chloride Acetic anhydride Acetamide

Acetyl salicylic acid Salicylic acid

Acetyl chloride

Acetic anhydride

Acetamide

Prelaboratory Assignment 1. Draw the structure of the following

compounds: Acetyl chloride Acetic anhydride Acetamide

Acetyl salicylic acid Salicylic acid

Acetyl salicylic acid (ASA)

Salicylic acid

Prelaboratory Assignment 2. What is the purpose of adding ferric

chloride to the filtrate of acetyl salicylic acid?

Ferric chloride is added as an indicator which detects the presence of salicylic acid in the products.

When FeCl3 ionizes, Iron(III) forms complexes with phenolic compounds, such as salicylic acid. The color of these complexes range from red to purple.

Prelaboratory Assignment 3. How would you test for ammonia vapor in

the basic hydrolysis of amides?

Since it is the vapor that is being tested, the most reliable method available would be to suspend a damp piece of red litmus paper at the mouth of the test tube.

Ammonia vapor is basic and would thus turn the red litmus paper blue upon exposure.

Results

Experiment 17

Results

Observation

Acid Hydrolysis of Acetyl Salicylic Acid

Minimal amounts of ASA dissolved. When cooled crystals, removed through filtering formed. Solution turned purple after addition of FeCl3.

Esterification Separation of layers after heating. Strong scent of bananas.

Hydrolysis of Acetic Chloride

Reactions of Esters

Observation

Acetyl chlorideIt became slightly warmer after 2 drops of Acetyl chloride. It turned to a cloudy white solution after adding AgNO3

Acetic anhydride

•No temperature change•No change on the appearance of solution after adding AgNO3

ResultsReaction of Amides

Observation

Acetamide + HClThe vapor of the solution changed the blue

litmus paper to red. Smelled like vinegar

Acetamide + NaOH

The red litmus paper turned blue. Pungent odor

Hydrolysis of Acetic Chloride

Experiment 17

OBSERVATIONS

Acetyl chlorideIt became slightly warmer after 2 drops of Acetyl chlorideIt turned to a cloudy white solution after adding AgNO3

Acetic anhydride•No temperature change•No change on the appearance of solution after adding AgNO3

Acetyl Chloride

or ethanoyl chloride :

or acyl chloride

The Equation:

Reaction of an Acyl Chloride with water

The Mechanism

1st

2nd

Acetic Acid and hydrogen chloride gas is produced - the hydrogen coming from the -OH group, and the chlorine from the Acetyl chloride.

Adding an acyl chloride to water produces the corresponding carboxylic acid together with steamy acidic fumes of hydrogen chloride.

The reaction is usually extremely vigorous at room temperature.

Addition with AgNO3 produced a cloudy solution. The precipitate formed is from the reaction between AgNO3 and HCl, forming AgCl3.

This is done to indicate that a halide ion is present, in this case Cl

THE REACTION OF ACID ANHYDRIDES WITH WATER

Acetic anhydride

or ethanoic anhydride :

Equation:

Acetic acid is formed as the second product rather than hydrogen chloride gas.

The reactions are slower. Acid anhydrides aren't so violently reactive as acyl chlorides

Ethanoic anhydride can’t be said to dissolve in water. When Ethanoic anhydride reacts with water, it would give Acetic acid.

The only difference is that Ethanoic acid (Acetic acid) is produced as the second product of the reaction rather than Hydrogen chloride

Reactions of Esters

Experiment 17

Results

Observation

Acid Hydrolysis of Acetyl Salicylic Acid

Minimal amounts of ASA dissolved. When cooled crystals, removed through filtering formed. Solution turned purple after addition of FeCl3.

Esterification Separation of layers. Strong scent of bananas.

Acid Hydrolysis of Acetyl Salicylic Acid

Acid Hydrolysis of Acetyl Salicylic Acid

The reaction can proceed either way depending in the conditions.

At equilibrium, this reaction favors a high concentration of SA and a very small one of ASA.

Acetyl Salicylic

Acid

Salicylic Acid

Acetic Acid and Water

Acid Hydrolysis of Acetyl Salicylic Acid

Hydrolysis of acetylsalicylic acid is an equilibrium reaction catalyzed by acid (as in this case) or by base.

Normally the hydrolysis is driven to the right by low pH, as well as by losses of HOAc to the air.

Acetyl Salicylic

Acid

Salicylic Acid

Acetic Acid and Water

Acid Hydrolysis of Acetyl Salicylic Acid Addition of ferric chloride is done in order to

detect the presence of a phenolic group.

The purple coloration results fro the formation of ferric salicylate complexes.

Esterification

The aroma of bananas is due to the synthesis of isoamyl acetate from isopentyl alcohol and acetic acid.

Isopentyl alcohol Acetic acid Isoamyl acetate

Water

Reaction of Amides

Observations

Acetamide + HCl• The vapor of the

solution changed the blue litmus paper to red

• Smelled like vinegar

Acetamide + NaOH

• The red litmus paper turned blue

• Pungent odor

Acetamide with HCl

Acetamide with NaOH

Basic Hydrolysis Acetamide

If Acetamide is heated with NaOH, ammonia gas is given off and left with a solution containing sodium ethanoate

Ammonia evolved

Acid Hydrolysis Acetamide is heated with a dilute HCl ethanoic

acid is formed together with ammonium ions. The final solution would contain ammonium chloride and ethanoic acid.

Ammonia did not evolve, ammonium chloride was present

With the addition of HCl on acetamide, it smelled like vinegar since acetic acid was formed. The color of the blue litmus paper turned red due to the acetic acid.

With the addition of NaOH, the color of the red litmus paper turned blue indicating the basicity of the substance since ammonia was formed.