Magnesium atoms, excited, reactions

An alternative route involves end-capping to produce a terminal hydroxyl followed by reaction with trichloroacetyl isocyanate (Equation 5.23). This new, reactive end group can be used to initiate the growth of a second block via the photoreduction method proposed by Bamford in which magnesium or ihenium carbonyls are excited by UV or visible radiation and extract a chloride atom from the terminal unit, thereby creating a radical site. As only one radical is formed, this is a much cleaner reaction compared with (1) however, block lengths are more difficult to control in both these radical reactions, and the exact structure of the product formed can depend on the mechanism of the termination reaction. 

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