SCHEDULED MAINTENANCE
Hyperconjugative interactions in halogen-substituted carbonyls: ultraviolet photoelectron spectroscopy of ω-halogenoacetophenones
Abstract
The HeI and HeII photoelectron spectra of the para-substituted ω-halogenoacetophenones Y-C6H4COCH2X [Y = NO2, CN, H, OCH3, N(CH3)2; X = H, Cl, Br, I] are assigned on the basis of the composite-molecule approach, substituent effects, and intensity variations observed on changing the wavelenght of the ionizing radiation. Ab initio minimal basis set calculations using the pseudo-potential method have been used to calculate the most stable conformation of acetophenone and its ω-bromo and ω-iodo derivatives. The first band of the iodine derivatives shows peculiar energy and intensity variations on changing the para-substituent. These findings have been ascribed to an easier interaction of the iodine lone-pair orbitals with the substrate owing to their lower ionization energy values and larger size with respect to the other halogens.
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