Concept:A chromophore is an unsaturated functional group containing delocalized \(\pi\)-electrons that absorbs electromagnetic radiation in the visible region (\(400\text{--}700\text{ nm}\)), thereby imparting color to a molecule.
Formula / Reaction:$$-\text{N}=\text{N}- \quad (\text{Azo Chromophore})$$
Solution:- The azo group (\(-\text{N}=\text{N}-\)) contains a double bond with a conjugated \(\pi\)-system capable of \(\pi \rightarrow \pi^*\) transitions in the visible spectrum.
- Azo compounds constitute the largest class of synthetic organic dyes.
Why other options are incorrect:- Amino Group (\(-\text{NH}_2\)): An auxochrome that intensifies color and shifts absorption wavelength, but cannot impart color on its own.
- Hydroxyl Group (\(-\text{OH}\)): An auxochrome containing lone pairs that enhance the chromophore's absorption.
- Sulfonic Acid Group (\(-\text{SO}_3\text{H}\)): A solubilizing group used to render dye molecules water-soluble.
Quality & Fidelity Assurance:
Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.