Question

Total number of isomeric compounds (including stereoisomers) formed by monochlorination of 2-methylbutane is________.

Answer 1

Correct Answer: 6

Analysis of 2-Methylbutane Monochlorination:
2-Methylbutane (C$_5$H$_{12}$), a branched alkane, has the structure:
\[\text{CH}_3 - \text{CH(CH}_3\text{)} - \text{CH}_2 - \text{CH}_3\]
Monochlorination, the substitution of a hydrogen atom with chlorine, can occur at different positions. Identifying these unique sites determines the number of isomeric products.
Unique Monochlorination Positions:
1. Terminal primary carbon (CH$_3$) attached to carbon 1.
2. Secondary carbon at position 2 (a chiral center).
3. Secondary carbon at position 3.
4. Terminal primary carbon (CH$_3$) attached to carbon 4.
Resulting Isomeric Products:
1-chloro-2-methylbutane: Result of chlorination at the terminal CH$_3$ on carbon 1.
2-chloro-2-methylbutane: Chlorination at the chiral center (carbon 2) yields two stereoisomers (R and S configurations).
3-chloro-2-methylbutane: Result of chlorination at carbon 3.
4-chloro-2-methylbutane: Result of chlorination at the terminal CH$_3$ on carbon 4.
Total Number of Isomers:
\[1 \text{ (from carbon 1)} + 2 \text{ (stereoisomers from carbon 2)} + 1 \text{ (from carbon 3)} + 1 \text{ (from carbon 4)} = 6 \text{ isomers}\]
Conclusion: Monochlorination of 2-methylbutane produces a total of 6 isomers, including stereoisomers.