H3C N 3=O N CH3 O=C \N- CH3 C=C C-H Caffeine C-N
The Correct Answer and Explanation is:
Correct Lewis Structure of Caffeine
The molecular formula of caffeine is C₈H₁₀N₄O₂. Its structure includes:
- A purine ring system: fused imidazole and pyrimidine rings.
- Two amide-like carbonyl groups (=O).
- Three methyl groups (-CH₃) attached to nitrogen atoms.
- Multiple C-N, C=C, and C=O bonds.
Below is a simplified version of its skeletal structure:
mathematicaCopyEdit O=C1N(c2ncn(c2C)C)C(=O)N(C1)C
This translates to:
- A six-membered ring fused to a five-membered ring.
- Methyl groups attached to two nitrogen atoms in the ring and one carbon.
- Two carbonyl groups (=O) bonded to nitrogen.
Hybridization of Atoms in Caffeine
Each atom’s hybridization in caffeine is based on its bonding and lone pairs:
- sp² hybridized atoms:
- All carbon atoms in double bonds (C=C)
- Carbonyl carbon atoms (=O)
- Ring nitrogen atoms involved in aromatic delocalization
- Carbon atoms in aromatic rings (conjugated system)
- sp³ hybridized atoms:
- Methyl carbon atoms (-CH₃)
- Nitrogen atoms bonded to three atoms and one lone pair (if not conjugated)
- sp hybridized atoms:
- None in caffeine, as there are no triple bonds or linear geometries.
Functional Groups in Caffeine
Caffeine contains several key functional groups:
- Amide-like carbonyls (C=O adjacent to nitrogen)
- Tertiary amines (nitrogen atoms bonded to three carbons)
- Alkene-like C=C (within aromatic purine ring)
- Methyl groups (-CH₃)
Conclusion
Caffeine is an aromatic, heterocyclic compound with multiple nitrogen atoms and carbonyl groups that contribute to its chemical reactivity and biological activity. The molecule is predominantly sp² hybridized, supporting its planar structure and ability to participate in hydrogen bonding and π–π interactions, which explain its biological effects as a central nervous system stimulant.
