Zinc oxide polymer oxidation catalyzed

Methyl ethyl ketone may also he produced hy the catalyzed dehydrogenation of sec-hutanol over zinc oxide or brass at about 500°C. The yield from this process is approximately 95%. MEK is used mainly as a solvent in vinyl and acrylic coatings, in nitrocellulose lacquers, and in adhesives. It is a selective solvent in dewaxing lubricating oils where it dissolves the oil and leaves out the wax. MEK is also used to synthesize various compounds such as methyl ethyl ketone peroxide, a polymerization catalyst used to form acrylic and polyester polymers and methyl pentynol by reacting with acetylene ... 

In the case of the esterification of the diacid, the reaction is self-catalyzed as the terephthalic acid acts as its own acid catalyst. The reverse reaction, the formation of TPA and EG from BHET is catalytic with regard to the usual metal oxides used to make PET, but is enhanced by either the presence of hydroxyl groups or protons. In the case of transesterification of dimethyl terephthalate with ethylene glycol, the reaction is catalytic, with a metal oxide needed to bring the reaction rate to commercial potential. The catalysts used to produce BHET are the same as those needed to depolymerize both the polymer to BHET and BHET to its simpler esters. Typically, titanium, manganese and zinc oxides are used for catalysts. 

An alternative method for generating enriched 1,2-diols from meso-epoxides consists of asymmetric copolymerization with carbon dioxide. Nozaki demonstrated that a zinc complex formed in situ from diethylzinc and diphenylprolinol catalyzed the copolymerization with cyclohexene oxide in high yield. Alkaline hydrolysis of the isotactic polymer then liberated the trans diol in 94% yield and 70% ee (Scheme 7.20) [40]. Coates later found that other zinc complexes such as 12 are also effective in forming isotactic polymers [41-42]. 

The first two steps in the synthesis of melanin are catalyzed by tyrosinase, a copper-containing oxidase, which converts tyrosine to dopaquinone. All subsequent reactions presumably occur through nonenzymatic auto-oxidation, in the presence of zinc, with formation of the black to brown pigment eumelanin. The yellow to reddish brown, high-molecular-weight polymer known as pheomelanin and the low-molecular-weight trichromes result from addition of cysteine to dopaquinone and further modification of the products. Pheome-lanins and trichromes are primarily present in hair and feathers. 

Isophthaloyl chloride has also been employed in block copolymer preparation. Poly(m-phenylene isophthalamide) and either poly-(ethylene oxide) or poly(dimethyl siloxane) block copol3miers have been prepared by terminating the former with isophthaloyl chloride and subsequently adding hydroxy terminated poly(ethylene oxide) or poly(dimethyl siloxane)(79). Block copolymers were also produced when a polyformal was capped with 1,6-hexandiol, and then heated in the presence of poly(tetramethylene terephthalate)(80). In another interesting application, polyesterpolyether block copolymers of poly-(ethylene terephthalate) and a number of polyglycols have been reported(Sl). Their synthesis involves esterification, catalyzed by zinc acetate/titanyl oxalate. ABA block polymer of 2-hydroxyethyl methacrylate and styrene was prepared by coupling -NH2 terminated PHEMA and isocyanate terminated polystyrene. The latter material was prepared by UV polymerization of styrene in the presence of bis(p-isocyanatophenyl)disulfide (82),... 

Sun, X.-K. Zhang, X.-H. Wei, R.-J. Du, B.-Y Wang, Q. Fan, Z.-Q. Qi, G.-R. Mechanistic Insight into Initiation and Chain Transfer Reaction of COj/Cyclohexene Oxide Copolymerization Catalyzed by Zinc-Cobalt Double Metal Cyanide Complex Catalysts. J. Polymer Sci. Part A Polymer Chem. 2012, 50,2924-2934. 

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