In which of the following molecules are all atoms coplanar?

Q: What is NEET?

NEET is a competitive examination conducted in India. This question is from the 2016 NEET Chemistry paper.

Q: How can I prepare for NEET Chemistry?

To prepare for NEET Chemistry, practice previous year questions (PYQs), understand concepts thoroughly, and solve mock tests regularly. This 2016 question covers Hydrocarbons topic.

Q: What is the difficulty level of this question?

This NEET 2016 Chemistry question has a medium difficulty level.

Q: Where can I find more NEET previous year questions?

You can find more NEET previous year questions on AspirantMitraa. Browse by subject, topic, year, and difficulty level to practice effectively.

Question

In which of the following molecules are all atoms coplanar?

Accepted Answer

Correct Answer: C — NaphthaleneStep-by-step Solution:Naphthalene (C₁₀H₈) is a fused bicyclic aromatic hydrocarbon consisting of two benzene rings sharing one C–C bond. All 10 carbon atoms are sp² hybridised. Each sp² carbon has a planar arrangement of bonds (bond angles ≈ 120°), and all the p-orbitals are perpendicular to this plane to form the delocalised π system. As a result, all 10 C atoms and all 8 H atoms lie in a single plane — the molecule is completely planar.Why other options are incorrect:Option A: A substituted alkene (e.g., with CN and CH₃ groups): the alkene carbon framework is planar (sp²), but substituents like CH₃ have sp³ H atoms that extend out of the plane of the double bond. Not all atoms are coplanar.Option B: Biphenyl consists of two phenyl rings connected by a single bond. Due to steric repulsion between the ortho hydrogen atoms of the two rings, biphenyl adopts a twisted conformation in the gas phase (dihedral angle ≈ 45°). The two rings are not coplanar; hence not all atoms lie in one plane.Option D: Cyclohexane consists entirely of sp³ carbons. It adopts a non-planar chair conformation to relieve ring strain and torsional strain. No arrangement of cyclohexane has all atoms coplanar.Key Concept: All atoms in a molecule are coplanar when the entire carbon skeleton consists of sp² hybridised atoms that form a rigid, conjugated framework with no rotational flexibility around single bonds. Fused aromatic systems such as naphthalene, anthracene, and benzene are inherently planar.

In which of the following molecules are all atoms coplanar?

Master NEET with Our Test Series

Frequently Asked Questions

In which of the following molecules are all atoms coplanar?

Master NEET with Our Test Series

Frequently Asked Questions