Question

Acetic anhydride is prepared in the laboratory by heating sodium acetate with:
A.Ethyl chloride
B.Acetyl chloride
C.Conc.$H_{2}S{O}_4$
D.Zinc dust

Answer 1

Hint:Acetic anhydride is the simplest isolable anhydride of carboxylic acid and has the formula $(C{H}_{3}CO{)}_{2}O$. This is also known as ethanoic anhydride. It is widely used as a reagent in organic chemistry.

Complete step by step answer:
In the laboratory, acetic anhydride is prepared by treating the acetyl chloride with the sodium salt of carboxylic acids. The chemical reaction for the preparation of acetic anhydride from acetyl chloride is given as below:

Hence the correct answer is option B.

Additional information: There are some other methods for the preparation of acetic anhydride and they are discussed below:
1.We can prepare acetic anhydride by heating the two molecules of carboxylic acid in the presence of a strong dehydrating agent such as phosphorus pentoxide or concentrated sulphuric acid by the elimination of a molecule of water. The chemical reaction for above is written as :

2.Acetic anhydride can also be obtained by treating acid chlorides with a carboxylic acid in the presence of pyridine as a base as given below:

Note:
Acetic anhydride is a clear liquid and it smells like vinegar. It is used as the raw material for the cellulose acetate fiber and plastic also. It is also used as a reagent in a number of chemical syntheses. It is also used in the preparation of aspirin and other pharmaceutical manufacturing. But it is highly corrosive and irritates, burns the skin and eye with possible eye damage. In high concentrations, it can cause lung damage with shortness of breath.