Acetic anhydride is obtained from acetyl chloride by the reaction of
A.\[{{\rm{P}}_{\rm{2}}}{{\rm{O}}_{\rm{5}}}\]
B. \[{{\rm{H}}_{\rm{2}}}{\rm{S}}{{\rm{O}}_{\rm{4}}}\]
C. \[{\rm{C}}{{\rm{H}}_{\rm{3}}}{\rm{COONa}}\]
D. \[{\rm{C}}{{\rm{H}}_{\rm{3}}}{\rm{COOH}}\]

Hint: Acetic anhydride also called ethanoic anhydride is a chemical species possessing the formula of \[{\left( {{\rm{C}}{{\rm{H}}_{\rm{3}}}{\rm{CO}}} \right)_{\rm{2}}}{\rm{O}}\] . The common abbreviation of this compound is \[{\rm{A}}{{\rm{c}}_{\rm{2}}}{\rm{O}}\]. In the synthesis of many organic compounds, it is widely used as a reagent.

Complete Step by Step Solution:
Let’s understand what acetyl chloride is. Acetyl chloride belongs to the class of acyl chloride that we get from acetic acid. Acetyl chloride also belongs to the group of acid halides. It has no colour. It is a liquid of volatile nature. And it is a corrosive substance.

The structure of acetyl chloride is,

Image: Acetyl chloride

The structure of acetic anhydride is,

Image: Acetic anhydride
Now, we have to understand the conversion of acetyl chloride to acetic anhydride. When sodium acetate undergoes a reaction with acetyl chloride, the formation of acetic anhydride takes place. In this reaction, a molecule of Sodium chloride (NaCl) is extracted. The chemical reaction is as follows:

Image: Formation of acetic anhydride due to the reaction of sodium acetate and acetyl chloride
Hence, option C is right.

Additional Information: Acyl chlorides are the organic species derived from carboxylic acid. In acyl chlorides, the OH group of the carboxylic acid is replaced by an atom of chloride.

Image: Acyl chloride

Note: Grignard reagent is one of the important compounds in organic chemistry. It is beneficial for the preparation of various organic compounds such as acetals, amides, amino compounds, etc. It is used for the manufacture of many compounds that are useful in the pharmaceutical field.