How many structural isomers are there of trichloropropane, C3H5Cl3 ? A. 3 B. 4 C. 5 D. 6
The Correct Answer and Explanation is:
The correct answer is C. 5.
Explanation:
Trichloropropane (C₃H₅Cl₃) is a molecule where three chlorine atoms are attached to a propane backbone (C₃H₈). When considering structural isomers, we focus on how the chlorines can be positioned on the carbon chain in distinct ways.
There are five possible structural isomers of trichloropropane, and they can be derived by varying the positions of the chlorine atoms along the propane chain. Here’s a breakdown of the five possible isomers:
- 1,1,1-Trichloropropane: The chlorines are attached to the first carbon atom (the one at the end of the chain). This is a simple case where all three chlorines are on the same carbon.
- 1,1,2-Trichloropropane: In this structure, two chlorines are on the first carbon and one chlorine is on the second carbon.
- 1,2,2-Trichloropropane: One chlorine is on the first carbon and two chlorines are on the second carbon.
- 1,2,3-Trichloropropane: Here, one chlorine is attached to each of the three carbon atoms. This results in a linear structure where the chlorines are distributed across the chain.
- 2,2,3-Trichloropropane: In this structure, two chlorines are attached to the second carbon and one chlorine is attached to the third carbon.
Why not more than 5?
The number of isomers is limited by the available positions for the chlorine atoms on the carbon backbone. Since there are only three carbon atoms, and considering the symmetry of the molecule, the possible distinct arrangements are capped at five.
This is why the correct answer is C. 5.
