The IUPAC name of C6H5COCl is:

(a) Benzoyl chloride

(b) Benzene chloro ketone

(c) Oxochloro benzene

(d) Chlorophenyl ketone

The compound ${{C}_{6}}{{H}_{5}}COCl$ is known as benzoyl chloride. This is the correct IUPAC name, making option (a) the right choice. Let’s break down why this is the case and clarify the structure and naming conventions involved.

Understanding the Structure

The molecular formula ${{C}_{6}}{{H}_{5}}COCl$ can be dissected into two parts: the phenyl group ($C_6H_5$) and the acyl chloride functional group ($COCl$). The phenyl group is derived from benzene, which is a six-carbon aromatic ring. The acyl chloride part indicates that we have a carbonyl group (C=O) attached to a chlorine atom.

Breaking Down the Components

• Phenyl Group: This is the $C_6H_5$ part, which is simply a benzene ring minus one hydrogen atom.
• Carbonyl Group: The $CO$ indicates a carbon atom double-bonded to an oxygen atom.
• Chlorine Atom: The $Cl$ signifies that a chlorine atom is attached to the carbon of the carbonyl group.

Nomenclature Rules

According to IUPAC naming conventions, the presence of the acyl chloride functional group is key in determining the name. The compound is classified as an acyl chloride because it contains the carbonyl group directly bonded to a chlorine atom. The phenyl group attached to the carbonyl carbon indicates that this is a benzoyl derivative.

Why Other Options Are Incorrect

Let’s briefly consider why the other options do not fit:

• Benzene chloro ketone: This name suggests a ketone with a chlorine atom on a benzene ring, which is misleading since the carbonyl is part of an acyl chloride, not a ketone.
• Oxochloro benzene: This name implies a chlorinated benzene with a carbonyl group, which does not accurately describe the structure of benzoyl chloride.
• Chlorophenyl ketone: Similar to the previous options, this suggests a ketone structure that does not align with the acyl chloride nature of the compound.

Conclusion

In summary, the correct IUPAC name for ${{C}_{6}}{{H}_{5}}COCl$ is benzoyl chloride. This name accurately reflects the structure and functional groups present in the compound, distinguishing it from other similar compounds. Understanding these naming conventions is crucial for accurately identifying and communicating about chemical substances.