Conjugate addition general information

For the chemical classification we attempted to work solely with the TT-electron calculations, which cover the conjugated radicals. Basic information on calculations and experimental data is given in the preceding sections for additional details, see the original publications. Before presenting a confrontation of theoretical and experimental data, we note some general features in the nature of electronic spectra of radicals. 

Mass spectrometry, infrared spectroscopy, and nuclear magnetic resonance spectroscopy are techniques of structure determination applicable to all organic molecules. In addition to these three generally useful methods, there s a fourth—ultraviolet (UV) spectroscopy—that is applicable only to conjugated systems. UV is less commonly used than the other three spectroscopic techniques because of the specialized information it gives, so we ll mention it only briefly. 

The addition of acylcobalt carbonyls to conjugated dienes is a very general reaction (14, 15). Some information on the reactivity of differently substituted double bonds in the diene system can be obtained from the structures of the l-acylmethyl-7r-allylcobalt tricarbonyls formed from them. The acyl group is reasonably assumed to add to the least-hindered and most reactive double bond. Isoprene reacts with methylcobalt tetracarbonyl to form l-acetylmethyl-2-methyl-7r-allylcobalt tricarbonyl. 

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