This question involves determining the number of isomers formed upon monochlorination of a given alkane. The compound shown is 2,3-dimethylbutane. Monochlorination means replacing one hydrogen atom with a chlorine atom. Isomers include both structural isomers (different carbon positions) and stereoisomers (different spatial arrangements).

Step 1: Identify the Structure
The compound is 2,3-dimethylbutane. Its structure is:
${\mathrm{CH}}_3-CH\left({\mathrm{CH}}_3\right)-CH\left({\mathrm{CH}}_3\right)-{\mathrm{CH}}_3$
It has a chain of 4 carbons with methyl groups on carbons 2 and 3.

Step 2: Identify Types of Hydrogens
Different hydrogens lead to different products upon substitution. Classify hydrogens based on their environment:

• Primary (1°): Hydrogens on carbon attached to one carbon.
• Secondary (2°): Hydrogens on carbon attached to two carbons.
• Tertiary (3°): Hydrogens on carbon attached to three carbons.

In 2,3-dimethylbutane:

• Carbon 1 and 4: Each has 3 equivalent 1° hydrogens.
• Carbon 2 and 3: Each is a chiral carbon with one hydrogen (these are equivalent and are 2° hydrogens).

So, there are two types of hydrogens: 1° and 2°.

Step 3: Determine Structural Isomers
Chlorination at different carbon types gives structural isomers:

• Chlorination at a 1° carbon (C1 or C4): 1-chloro-2,3-dimethylbutane
• Chlorination at a 2° carbon (C2 or C3): 2-chloro-2,3-dimethylbutane

So, 2 structural isomers.

Step 4: Consider Stereoisomers
For the product from 2° carbon chlorination (2-chloro-2,3-dimethylbutane):
The molecule has two chiral centers (C2 and C3). Each can have R or S configuration, leading to stereoisomers:

• RR, SS, RS, SR
• But RS and SR are enantiomers, and RR and SS are enantiomers. Also, meso form exists if the molecule is symmetric.

In this case, the molecule is symmetric. The chlorination product has a plane of symmetry, making it a meso compound. So, only one stereoisomer (meso) for this structural isomer.

The 1° chlorination product has no chiral center, so no stereoisomers.

Step 5: Total Isomers
- Structural isomer from 1° carbon: 1 (no stereoisomers)
- Structural isomer from 2° carbon: 1 (meso compound)
Total isomers = 2.

Final Answer: 2 isomers are possible.

Related Topics

Structural Isomerism: Compounds with the same molecular formula but different connectivity of atoms. In monochlorination, different carbon positions yield structural isomers.

Stereoisomerism: Compounds with the same structural formula but different spatial arrangement. Includes enantiomers (mirror images) and diastereomers. Meso compounds are symmetric and achiral despite having chiral centers.

Chirality: A carbon is chiral if it has four different groups attached. Molecules with chiral centers can exhibit optical activity unless they are meso.

Formulae

Number of stereoisomers for a molecule with n chiral centers: up to 2ⁿ, but reduced by symmetry and meso forms.

For a symmetric molecule with two equivalent chiral centers, the number of stereoisomers is 3 (a pair of enantiomers and one meso form) if no additional symmetry, but in this case, the meso form is the only one.