Optical Activity in Heptanol Isomers – Which of Heptan-1-ol, 2-ol, 3-ol and 4-ol are Chiral?

 Introduction

Optical activity is an important concept in organic chemistry and stereochemistry.
A compound shows optical activity when it contains a chiral (asymmetric) carbon atom
attached to four different groups. Such molecules rotate plane polarized light.

In this problem, we must determine which of the following heptanol isomers are optically active:

• Heptan-1-ol
• Heptan-2-ol
• Heptan-3-ol
• Heptan-4-ol

 Concept of Chirality

• Carbon must have four different substituents
• No plane of symmetry
• Molecule becomes optically active

 Step-by-Step Solution

1️⃣ Heptan-1-ol

Structure:
CH₃–(CH₂)₅–CH₂OH

The carbon containing –OH has two identical hydrogen atoms.

❌ Not four different groups → Achiral

Result: Optically inactive

2️⃣ Heptan-2-ol

Structure:
CH₃–CH(OH)–(CH₂)₄–CH₃

Carbon is attached to:

• H
• OH
• CH₃
• C₅H₁₁

✔ Four different groups → Chiral

Result: Optically active

3️⃣ Heptan-3-ol

Structure:
CH₃–CH₂–CH(OH)–(CH₂)₃–CH₃

Carbon is attached to:

• H
• OH
• C₂H₅
• C₄H₉

✔ Four different groups → Chiral

Result: Optically active

4️⃣ Heptan-4-ol

Structure:
CH₃–CH₂–CH₂–CH(OH)–CH₂–CH₂–CH₃

Two identical propyl groups are present on both sides of the carbon.

Identical substituents → Plane of symmetry → Achiral

Result: Optically inactive

 Final Answer

Optically active compounds: Heptan-2-ol and Heptan-3-ol

✔ Correct Option: (A)

 Quick Comparison Table

 Exam Tips

• Terminal alcohols are usually achiral
• Check for identical groups carefully
• Always verify four different substituents