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W. Olczyk


An attempt to explain themechanism of the reactions of urethanes synthesis catalyzed by dibenzyltin compounds


Polimery 1982, No 2, 55



DOI: dx.doi.org/10.14314/polimery.1982.055

Summary

A hypothesis concerning the mechanism of the reaction of urethanes (polyurethanes) formation catalyzed by dibenzyl tin compounds has been presented. This reaction takes place through the stage of formation of spatial three– and five-membered complexes, in which both substrates: isocyanate and polyol are coordinated with the tin atom of the catalyst as the central atom. Then, urethane is formed by shifts of charges with in the complex, these charges being larger than in other tin compounds, such as e.g. in dibutyltin compounds. Thus, the reaction of urethane format ion is are action of the intramolecular type, its rate being controlled by the spatial structure of the complex and by the steric hindrance effects making more difficult the contacts among the complexed functional groups of the substrates.


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