Lactic acid in which a methyl group, a hydroxyl group, a carboxylic acid group and a hydrogen atom are attached to a central carbon atom, show optical isomerism due to the molecular geometry at the

Options

A. Central carbon atom
B. Carbon atom of the methyl group
C. Carbon atom of the carboxylic acid group
D. Oxygen of the hydroxyl groups

Answer

**Step-by-Step Solution:**

1. **Identify the Structure of Lactic Acid:**
Lactic acid is chemically known as 2-hydroxypropanoic acid. Its structure consists of three carbon atoms (C), where one carbon is part of the carboxylic acid (-COOH) group, another is a hydroxyl (-OH) group, and the third is a methyl (-CH3) group.

2. **Determine the Chiral Center:**
In lactic acid, the central carbon atom (the second carbon in the chain) is attached to four different groups: a methyl group (CH3), a hydroxyl group (OH), a carboxylic acid group (COOH), and a hydrogen atom (H). This carbon atom is referred to as a chiral center because it has four distinct substituents.

3. **Understand Optical Isomerism:**
Optical isomerism occurs when a compound can exist in two non-superimposable mirror images, known as enantiomers. The presence of a chiral center in lactic acid allows for this phenomenon. The two enantiomers will have identical physical properties except for the direction in which they rotate plane-polarized light.

4. **Draw the Enantiomers:**
The two enantiomers of lactic acid can be represented as follows:
- One enantiomer (R-lactic acid) has the hydroxyl group oriented in one direction.
- The other enantiomer (S-lactic acid) has the hydroxyl group oriented in the opposite direction.

5. **Conclusion:**
Therefore, lactic acid exhibits optical isomerism due to the presence of a chiral carbon atom that is bonded to four different groups, leading to the formation of two enantiomers.