Spectroscopy
UV-Visible spectroscopy is useful for detecting:
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About This Question
- Subject
- chemistry
- Chapter
- purification and characterisation of organic compounds
- Topic
- spectroscopy
- Difficulty
- Easy
- Year
- 2025
Solution
Correct Answer:
Compounds with conjugated double bonds
UV-Visible Spectroscopy studies the electronic transitions within a molecule.
- Detection: It is extremely useful for identifying chromophores - groups that absorb light. Specifically, it detects conjugated π systems (like in polyenes or aromatic rings) and carbonyl groups.
- Requirement: Saturated compounds (like alkanes) only show σ→σ∗ transitions, which occur in the vacuum-UV region (<200 nm) and are typically not measurable with standard instruments. Conjugated systems lower the energy required for excitation, shifting the absorption into the measurable UV or visible range.
This easy difficulty chemistry question is from the chapter purification and characterisation of organic compounds, covering the topic of spectroscopy. It appeared in the 2025 exam.
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