N,N',N"-Triethyl phosphoratriamide and ethyl,N,N'diethyl phosphoradiamidate are not able to phosphorylate cellulose even at 160°C. The increased efficacy of these reagents as flame retardants for cotton has been proposed due to the formation of intermediates containing -P=N grouping by loss of an amine molecule from these compounds at an elevated temperature (> 200°C) in the first step. In the subsequent step, cellulose may add across the P=N bond of this intermediate to give phosphoryl cellulose. An appreciable amount of phosphorus has been incorporated in cellulose by reaction at ≃200°C with compounds formed on thermolysis of phosphoratriamides.
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