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Dual‐parameter correlation analysis of UV spectral data for 1‐methyl‐2‐formyl‐5‐Y‐substituted pyrroles and their hydrazones. First observation of a dominant polar effect
Author(s) -
HaiYing He Roderick,
Jiang XiKui
Publication year - 1999
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/(sici)1099-1395(199905)12:5<392::aid-poc139>3.0.co;2-7
Subject(s) - chemistry , pyrrole , substituent , delocalized electron , polar , molecule , polarization (electrochemistry) , stereochemistry , medicinal chemistry , computational chemistry , organic chemistry , physics , astronomy
By using 1‐methyl‐2‐formyl‐5‐Y‐substituted pyrroles ( 1‐Ys ), 1‐methyl‐2‐formyl‐5‐Y‐substituted pyrrole phenylhydrazones ( 2‐Ys ) and 1‐methyl‐2‐formyl‐5‐Y‐substituted pyrrole (4‐nitrophenyl)hydrazones ( 3‐Ys ) as models for nitrogen‐containing heterocyclic aromatic compounds, the K ‐band λ max values of their UV spectra were measured. Correlation analysis of the ν max values by a dual‐parameter equation shows that the ν max values of these compounds are affected, albeit to different degrees, by both the polar (σ x ) and spin‐delocalization effects (σ · ) of the substituents. Interestingly, the UV spectra of 3‐Ys are mainly affected by the polar effects. The correlation results are in accord with a previous speculation that a higher degree of polarization of the substrate molecule would demand a higher degree of polar assistance from the substituent at the transition states. Copyright © 1999 John Wiley & Sons, Ltd.