Chain growth on zinc

Scheme 8 Chain growth on zinc by 5a/MAO and proposed mechanism for the process...

Britovsek GJP, Cohen SA, Gibson VC, Maddox PJ, van Meurs M (2002) Iron-catalyzed polyethylene chain growth on zinc linear a/pfia-olefins with a Poisson distribution. Angew Chem Int Ed 41(3) 489 91... 

Van Meurs, M., Britovsek, G. J.P., Gibson, V.C., and Cohen, S.A. (2005) Polyethylene chain growth on zinc catalyzed by olefin polymerization catalysts A comparative investigation of highly active catalyst systems across the transition series. Journal of the American Chemical Society, 127,9913-9923. 

Scheme 10 Chain growth on zinc cataiyzed by iron compiex 9/MAO and nickei-cataiyzed dispiacement of the resuiting zinc aikyis.

The reaction of diethyl zinc with water produces zinc oxide, and then zinc carbonate, as the alkaline reserve. These chemicals have antiseptic properties which may also prevent the growth of mold in paper. They may also improve the brightness of treated papers. However, it is also known that zine oxide is a photosensitizer (56) which may trigger photo-oxidation of treated papers to initiate a chemical chain reaction that will lead eventually to the formation of acidic products (57). Moreover, the interaction of zinc oxide and zinc carbonate with copper, iron and cobalt present in the paper and their subsequent effects on paper stability have not been studied. 

In contrast to zinc, the crucial role of Fe in the bioenergetics of carbon (C) and N metabolism is well recognized (e.g., Morel et al., 1991 Sunda, 1989). Substantial amounts of Fe are required in both photosynthetic and respiratory electron transport chains (e.g., Raven, 1988), the synthesis of chlorophyll (Chereskin and Castelfranco, 1982), and the assimilation ofNOj. Theoretical calculations based on Fe utilization efficiencies and cellular metabolic Fe demands, predict that phytoplankton growing on NOJ require 60% more Fe than those growing on NH (Raven, 1988, 1990), and greater cellular Fe requirements for NO growth have indeed been demonstrated for laboratory cultures of diatoms (Maldonado and Price, 1996). The extra Fe is needed to reduce NO to NH4 before it can be incorporated into amino acids. This process requires the assimilatory enzymes nitrate reductase (requires one... 

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