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
✍ Scribed by Roderick Hai-Ying He; Xi-Kui Jiang
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 120 KB
- Volume
- 12
- Category
- Article
- ISSN
- 0894-3230
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✦ Synopsis
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 ! max values of their UV spectra were measured. Correlation analysis of the # max values by a dual-parameter equation shows that the # max values of these compounds are affected, albeit to different degrees, by both the polar (s x ) and spin-delocalization effects (s Á ) 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.