Conformational studies of α-substituted carbonyl compounds—V. Evidence for hyperconjugative interactions in 2-iodosubstituted carbonyl systems. ω-iodo-p-substituted acetophenones
✍ Scribed by P.R. Olivato; S.A. Guerrero; P.S. Santos
- Book ID
- 103906214
- Publisher
- Elsevier Science
- Year
- 1988
- Tongue
- English
- Weight
- 544 KB
- Volume
- 44
- Category
- Article
- ISSN
- 1386-1425
No coin nor oath required. For personal study only.
✦ Synopsis
The infrared carbonyl stretching (vco) frequencies as well as the carbon-iodine (vc_,) Raman and infrared frequencies for some w-iodo-p-substituted acetophenones are reported. Although in the title compounds the solvent effect on the carbonyl band does not indicate the existence of cis/gauche rotational isomerism, the comparison between the vco frequencies in the fundamental transition with those in the 1st overtone (in Ccl,) indicates the presence of the cis/gauche rotational isomerism. On going from electrondonating to electron-attracting substituents in the o-iodo-series, the progressive increase in the gauche carbonyl shifts (Av,) together with the progressive decrease in the vc_, frequencies suggest the increasing contribution of the hyperconjugative interaction between "co and ocml orbital& The U.V. spectra of the title compounds display the n+nro band which is bathochromically shifted in relation to the corresponding acetophenones, indicating the n&/d*c-, hyperconjugative interaction in the excited state. ['3C] NMR data for the methylene group of the w-iodoacetophenones in comparison with those of (IIbromoacetophenones [l] as well as with those for the methyl group of the unsubstituted acetophenones corroborates the existence of the ~c~/uc-~ hyperconjugation in the fundamental state of the title compounds.