Indicate whether or not the following molecules are chiral

Indicate whether or not the following molecules are chiral.

3,3-dimethylheptane
2,3-dimethylheptane
2-methylheptane
3-methylheptane
4-methylheptane

The correct answer and explanation is :

Chirality of the Given Molecules

1. 3,3-Dimethylheptane → Not Chiral
2. 2,3-Dimethylheptane → Chiral
3. 2-Methylheptane → Chiral
4. 3-Methylheptane → Not Chiral
5. 4-Methylheptane → Not Chiral

Explanation

A molecule is chiral if it lacks a plane of symmetry and contains at least one chiral center (a carbon atom bonded to four different groups). Let’s analyze each molecule in detail.

1. 3,3-Dimethylheptane (Not Chiral)

The presence of two identical methyl groups (-CH₃) at the same carbon (C3) makes it impossible for this molecule to have a chiral center. Since no carbon is attached to four different groups, the molecule is achiral.

2. 2,3-Dimethylheptane (Chiral)

The carbon at position C2 is attached to four different groups: a hydrogen (-H), a methyl (-CH₃), an ethyl (-C₂H₅), and the rest of the heptane chain. This asymmetry makes the molecule chiral.

3. 2-Methylheptane (Chiral)

The C2 carbon is bonded to four different groups: hydrogen (-H), methyl (-CH₃), ethyl (-C₂H₅), and the remaining hydrocarbon chain. Since there is no internal symmetry, it is chiral.

4. 3-Methylheptane (Not Chiral)

At C3, there is a methyl group, but the two other groups on the carbon are the same type of alkyl chains, making it not chiral.

5. 4-Methylheptane (Not Chiral)

The C4 carbon is bonded to two identical ethyl-like chains, which prevents it from being a chiral center. Hence, the molecule is achiral.

Thus, 2,3-Dimethylheptane and 2-Methylheptane are chiral, while the others are not.