Urea nitrates, dehydration

Davis studied the dehydration of urea nitrates as a route to iV-nitroureas. The nitrate salt of iV-methylurea undergoes dehydration-rearrangement on treatment with concentrated sulfuric acid to give Af-nitro-A -methylurea in 42 % yield. In this compound the nitro and methyl groups are attached to the same nitrogen and so its hydrolysis can provide a route to methylnitramine. In contrast, the nitrate salts of ethyl, n-propyl, n-butyl and n-amyl ureas, give iV-nitro-A -ethylurea (49 %), A -nitro-A -propylurea (60 %), iV-nitro-iV -butylurea (67 %) and iV-nitro-A -amylurea (67 %), respectively, on treatment with concentrated sulfuric acid. 

Finally, urea nitrate can be taken one step further chemically. Through the process of dehydration (chemical removal of water), urea nitrate can be transformed into nitrourea (NH2CONH-NO2). Typically UNi is added to concentrated sulfuric acid to facilitate this reaction. In theory, the loss of water should make nitrourea more powerful than UNi. There is not a great deal of experimental data available about this material. It was theorized that the group that bombed the World Trade Center may have planned to conduct this reaction. No conclusive evidence exists to prove this speculation. To date, nitrourea has not been seen in any terrorist bombs. 

NNH2,CH3N303 mw 105.06 N 39.98% OB to C02 —7.61% colorl platelets (from ethanol plus eth) mp 158.4—.8° (decompn). Freely sol in acet, acetic acid and ethanol sol in hot w (forms cyanic acid and nitroamide) si sol in benz, chlf and petr eth. CA Registry No [556-89-8]. Prepn is by dehydration of Urea Nitrate with coned sulfuric acid. The compd can be detonated but is not sensitive to percussion or heating (Ref 7)... 

It is synthesized by dehydration of urea nitrate with sulfuric acid. 

A further synthesis method is self-propagating combustion synthesis [33, 36, 37], In this alternative approach, nitrate starting powders are dissolved in H20 and urea (CH4N20) is added. When this mixture is boiled, dehydrated, and dried, it forms a hygroscopic precursor to calcium aluminates, which can be crystallized by heating in dry air between 250 and 1,050°C. The gaseous decomposition products of the precursor mixture are NH4 and HCNO, which ignite at 500°C, locally the temperature in the dried foam increases to 1,300°C, which promotes crystallization of the CAC phase. 

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