Post by Anders Hoveland on Mar 2, 2011 15:25:12 GMT -8
Several different methods of preparing hydrazine exist, including one that uses urea instead of ammonia. The advantage to using urea is much higher yields.
There should be between 0.8 to 1 mole of hypochlorite for each mole of urea.
For the one mole ratio of NaOCl, the yields were 50% with respect to urea, and 50% with respect to NaOCl. For the 0.8 mole ratio, the yields were 48.5% with respect to urea, and 60% with respect to NaOCl. For best yields, the hypochlorite solution should contain at least 3 moles of sodium hydroxide for every 0.8 moles of sodium hypochlorite. Solutions of sodium hypochlorite and urea were first both cooled to 4degC, then mixed.
Hydrazine
A glue solution was added, 0.5g of glue for each mole of sodium hypochlorite. The mixture was heated to 90degC, then allowed to cool. This exact temperature is very important for good yields from the reaction. Sulfuric acid was added into the solution so that the concentration of acid in the solution reached 20%. Hydrazine sulfate precipitated and was filtered out, then washed with alcohol and dried at 100degC. Note that the reaction cannot be done in a steel pot, as this catalyzes the decomposition of hydrazine.
Hydrazodicarbonamide
This compound is similar to semicarbazide.
A 12.9% solution (0.3 moles) of Biuret NH2CONHCONH2 was placed in a 2L glass at 5degC with hypochlorite solution (0.3 moles). The reaction temperature was kept at 5degC. This formed NH2CON(Cl)CONH(-) Na+ in 98% yield.
The whole product was added to a 2L glass and the temperature was raised to 100C. Liquid ammonia (8.8 moles) was added, and the temperature maintained at 100degC for 30min.
The unreacted ammonia was removed, and the remaining product filtered. The resulting hydrazodicarbonamide NH2CONHNHCONH2 was obtained in 95% yield. Supposedly hydrazodicarbonamide is almost insoluble in methanol, whereas semicarbazide is soluble.
The hydrochloride of semicarbazide precipitates out of methanol, however.
Biuret can be prepared by heating urea above its melting point. Further heating, however, will only produce cyanuric acid.
2 CO(NH2)2 --> H2N-CO-NH-CO-NH2 + NH3 (gas)
There should be between 0.8 to 1 mole of hypochlorite for each mole of urea.
For the one mole ratio of NaOCl, the yields were 50% with respect to urea, and 50% with respect to NaOCl. For the 0.8 mole ratio, the yields were 48.5% with respect to urea, and 60% with respect to NaOCl. For best yields, the hypochlorite solution should contain at least 3 moles of sodium hydroxide for every 0.8 moles of sodium hypochlorite. Solutions of sodium hypochlorite and urea were first both cooled to 4degC, then mixed.
Hydrazine
A glue solution was added, 0.5g of glue for each mole of sodium hypochlorite. The mixture was heated to 90degC, then allowed to cool. This exact temperature is very important for good yields from the reaction. Sulfuric acid was added into the solution so that the concentration of acid in the solution reached 20%. Hydrazine sulfate precipitated and was filtered out, then washed with alcohol and dried at 100degC. Note that the reaction cannot be done in a steel pot, as this catalyzes the decomposition of hydrazine.
Hydrazodicarbonamide
This compound is similar to semicarbazide.
A 12.9% solution (0.3 moles) of Biuret NH2CONHCONH2 was placed in a 2L glass at 5degC with hypochlorite solution (0.3 moles). The reaction temperature was kept at 5degC. This formed NH2CON(Cl)CONH(-) Na+ in 98% yield.
The whole product was added to a 2L glass and the temperature was raised to 100C. Liquid ammonia (8.8 moles) was added, and the temperature maintained at 100degC for 30min.
The unreacted ammonia was removed, and the remaining product filtered. The resulting hydrazodicarbonamide NH2CONHNHCONH2 was obtained in 95% yield. Supposedly hydrazodicarbonamide is almost insoluble in methanol, whereas semicarbazide is soluble.
The hydrochloride of semicarbazide precipitates out of methanol, however.
Biuret can be prepared by heating urea above its melting point. Further heating, however, will only produce cyanuric acid.
2 CO(NH2)2 --> H2N-CO-NH-CO-NH2 + NH3 (gas)