IGNOU BCHET 147 2026 - Explain the Feiser and Scott rules for predicting π − &

Question

Explain the Feiser and Scott rules for predicting π − π absorption in $\alpha, \beta$ -unsaturated ketones (enones) and aldehydes.

10 Jan 2026

Answer :

Word Count : 235

The Feiser and Scott rules are empirical guidelines used to predict the wavelength of π − π* electronic transitions in conjugated carbonyl compounds, such as α,β-unsaturated ketones (enones) and aldehydes. These rules are particularly useful in UV spectroscopy for interpreting absorption maxima in polyenic and conjugated systems, including organometallic complexes with conjugated ligands. According to Feiser and Scott, the base absorption of a

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