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Bifunktionelle Katalyse und Mechanismus der Monomethylol‐Bildung aus Harnstoff und Formaldehyd in Wasser
Author(s) -
Eugster P.,
Zollinger H.
Publication year - 1969
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19690520723
Subject(s) - chemistry , bifunctional , catalysis , formaldehyde , aqueous solution , reaction rate constant , inorganic chemistry , base (topology) , organic chemistry , kinetics , mathematical analysis , physics , mathematics , quantum mechanics
(1) The third‐order catalytic rate constants of the reaction of formaldehyde with urea with 5 general acid‐base catalysts in aqueous solution were measured polarographically in the temperature range 30–45°. (2) The catalytic constants obtained with hydrogencarbonate, primary and secondary phosphate are higher than expected on the basis of the B RÖNSTED relationship. The activation entropies for the reactions with these catalysts are 15 to 20 entropy units lower than those with the water molecule and the hydroxyl ion as catalysts. (3) These observations indicate a bifunctional catalysis with a cyclic rate‐determining transition state by the three firstmentioned catalysts. It is postulated that with mono‐ and bifunctional catalysts no termolecular collison step takes place, but first a hydrogen‐bonded complex of the general acid catalyst with formaldehyde or the general base with urea is formed.