Number of possible position isomers for dichlorobenzene is:

• A. Two.
• B. Three.
• C. Four.
• D. Five.

To determine the number of possible position isomers for dichlorobenzene, we first need to understand what is meant by position isomers. Position isomers are compounds that have the same molecular formula but differ in the position of substituents on the benzene ring. In the case of dichlorobenzene, we have a benzene ring with two chlorine atoms attached.

Understanding Dichlorobenzene

The molecular formula for dichlorobenzene is C6H4Cl2. This indicates that there are six carbon atoms, four hydrogen atoms, and two chlorine atoms in the molecule. The challenge lies in determining how the two chlorine atoms can be arranged on the benzene ring.

Possible Arrangements

When considering the placement of the two chlorine atoms, we can visualize the benzene ring as having six positions where substituents can be attached. However, due to the symmetry of the benzene ring, not all arrangements will yield unique isomers. The key positions to consider are:

• 1,2-Dichlorobenzene (ortho)
• 1,3-Dichlorobenzene (meta)
• 1,4-Dichlorobenzene (para)

Analyzing the Isomers

Let's break down these isomers:

• 1,2-Dichlorobenzene: The chlorine atoms are adjacent to each other on the benzene ring.
• 1,3-Dichlorobenzene: The chlorine atoms are separated by one carbon atom.
• 1,4-Dichlorobenzene: The chlorine atoms are opposite each other on the benzene ring.

These three arrangements represent all the unique ways to position the two chlorine atoms on the benzene ring without repeating any configurations. Other combinations, such as placing both chlorines on the same carbon or in positions that would lead to the same isomer, do not count as distinct isomers.

Final Count of Isomers

Therefore, the total number of unique position isomers for dichlorobenzene is three. This leads us to the correct answer:

B. Three

In summary, when dealing with dichlorobenzene, the distinct arrangements of the chlorine atoms yield three unique position isomers: ortho, meta, and para. Understanding the symmetry and structure of the benzene ring is crucial in determining these isomers accurately.