Über Umsetzungen von Harnstoff mit Alkoholen

Abstract

Abstrakt Die Umsetzung von Harnstoff mit Alkoholen zu Urethanen findet in vielen Fällen, besonders bei mehrwertigen Alkoholen mit benachbarten Hydroxylgruppen, nicht statt. Dafür entstehen Derivate der Iminodicarbonsäure oder der Anhydro-(oxyalkyl-carbamid- säuren). Es wurden Katalysatoren gefunden, welche die Urethanbildung begünstigen, und solche, welche die Umsetzung nach der anderen Richtung lenken. Bei 3- und mehrwertigen Alkoholen mit benachbarten Hydroxylgruppen entstehen höhermolekulare, wasserlösliche Harze. Mehrwertige Alkohole mit nicht benachbarten Hydroxylgruppen gestatten Urethangewinnung. Spaltprodukte des 1.3-Butylen-diurethans: flüchtige Basen, Anhydro-{[4-oxy-butyl-(2) ] - carbamidsäure }und JV.iV'-[a-Methyl-trimethylen] -harnstoff. Verwendung als Weichmacher, Duftstoffe, kautschukartige Massen, Stabilisierungsmittel für Nitrobronzelacke und Zaponlacke, Futtermittel und als Textildruckerei-Hilfsmittel.

Esters of Carbamic Acid

“…Here the simplest method of preparation was the ester interchange of a diol with ethyl or methyl carbamate in the presence of aluminum isopropoxide with (65,147,148) or without a solvent (37), in yields of 80-90%. The reaction of diols (V) with urea in the presence of a catalyst had been reported by Paquin to form diol dicarbamates (VIII) in good yields (260). In an attempt to prepare meprobamate by treating the corresponding diol with urea following Paquin's directions, low melting material in poor yields was obtained.…”

“…Here matters stood until Paquin (260) in 1946 reported the catalytic effect of various metal salts upon the rate of reaction of an alcohol with urea. By using heavy metal salts of weak organic acids, or zinc and cobalt chlorides, alkyl carbamates were obtained in yields of 90% or better with much shorter heating cycles.…”

“…heat COOCA Pyrolysis of the dicarbamate of 1,3-butylene glycol (Villa) reportedly afforded an oxazolidone (XIII) and a cyclic urea (XHIa). No mechanism has yet been offered for this unusual reaction in which C-0 bonds are replaced by C-N bonds (260). Stability of Carbamates Heated in Acidic and Basic Solvents.…”

Cycling of waste fusel alcohols from sugar cane industries using supercritical carbon dioxide

“…The addition of triphenylphosphine as a co-catalyst yielded carbonates. 39 Isononyl alcohol is used to produce plasticizers of low cost with several applications. 40 It is also used as a fragrance ingredient in cosmetics, shampoos, household cleaners, among others.…”

Organic Carbonates

“…The reaction of urea with alcohols which leads to the formation of carbamates using metal salts like zinc acetate and lead acetate was discovered by Paquin. 38 Prolongation of the reaction or the addition of triphenylphosphine as a cocatalyst results in the formation of carbonate. Isocyanuric acid is a major byproduct of this reaction (eq 9).…”