Monochlorination of propane yields two constitutional isomers, and dichlorination yields four. Trichlorination yields five constitutional isomers. Draw all five trichloropropane isomers (C3H7Cl).
The Correct Answer and Explanation is:
The trichlorination of propane (C₃H₇Cl) results in five distinct constitutional isomers. To identify them, let’s break down the process step by step.
- Propane Structure: Propane has the molecular formula C₃H₈, with the structure CH₃-CH₂-CH₃, where each carbon is bonded to hydrogen atoms, and the middle carbon is also bonded to two hydrogens.
- Trichlorination Reaction: When chlorine (Cl₂) is added to propane, three hydrogen atoms are replaced by chlorine atoms. The position of the chlorines in the molecule will create different isomers based on which carbon atoms they are attached to.
Trichloropropane Isomers:
- 1,1,2-Trichloropropane: In this isomer, the chlorines are attached to the first and second carbons. The first carbon holds two chlorines, and the second carbon holds one.
- 1,2,2-Trichloropropane: This isomer has one chlorine on the first carbon and two chlorines on the second carbon.
- 1,3,3-Trichloropropane: Here, the chlorines are positioned on the first and third carbons. The first carbon gets one chlorine, and the third carbon holds two chlorines.
- 2,2,3-Trichloropropane: The second carbon carries two chlorines, while the third carbon carries one chlorine.
- 2,3,3-Trichloropropane: The second carbon holds one chlorine, while the third carbon has two chlorines attached.
These are the five possible constitutional isomers of trichloropropane (C₃H₇Cl), and each one differs in the position of the chlorines on the carbon chain. The different placements result in distinct molecules despite having the same molecular formula.
This is an example of positional isomerism, where the connectivity of atoms remains the same, but their positions within the molecule differ.
