NaOCN from urea and sodium carbonate
(Rated as: excellent)
Production of Sodium Cyanate from Urea and Sodium Carbonate
Various members of the hive have previously theorized and experimented with production of the alkali cyanates. Alkali cyanates are useful compounds. They can be used for interesting reactions. For example, one would find its utility in the production of 4-MAR Post 354295 (Bandil: "trans-4-MAR synth w/o cyanogenbromide writeup!", Methods Discourse) and if one really wants to, they can even be reduced further to the significantly more toxic cyanides Post 385632 (Rhodium: "Yes. Alkali metal cyanide plus bromine gives ...", Stimulants)Post 378904 (Polverone: "I can top that", Chemicals & Equipment).
Potassium cyanate can be prepared through the oxidation of potassium ferro-cyanide by fusing it with lead or manganese dioxide Post 383277 (Aurelius: "Urea", Chemistry Discourse). In addition, the alkali cyanates can also be prepared by heating alkali carbonates in a mixture with powdered cyanuric acid Post 340082 (Polverone: "Encouraging results", Chemistry Discourse). Perhaps an even more OTC method for the production of cyanates was explored by Polverone whereby sodium cyanate was produced from sodium bicarbonate and urea. Sodium carbonate was formed by direct heating of the bicarbonate and then combined with urea to generate sodium cyanate Post 378904 (Polverone: "I can top that", Chemicals & Equipment). Experimentally, it was reported that direct heating of urea and sodium carbonate at 150°C produced an effervescing mixture that evolved large quantities of ammonia. Sodium cyanate was thereafter reduced to sodium cyanide when heated further in the presence of charcoal.
Another hive member suggested that sodium cyanate could be best formed through melting the urea first, then adding the carbonate, followed by recrystallization of the product Post 379016 (Wraith: "Just an alternative", Chemicals & Equipment). However, others indicated that this should be avoided as alkali cyanates hydrolyze easily and the conversion of the carbonate to the cyanate can be ensured through the addition of excess urea Post 379434 (Polverone: "First-hand experience", Chemicals & Equipment).
That distinctive and skillful Foxy2, complied a set of patent abstracts which pertained directly to the synthesis of alkali cyanates from sodium carbonate and urea with good yields ranging from 95%-99% Post 214057 (foxy2: "NaOCN and KOCN Production", Novel Discourse). In addition, these abstracts contained vital information about the starting reagent molar ratios, reaction conditions, yields, and purity of product. A strong similiarity among these abstracts was evident. All the authors seem to agree that the production of high quality NaOCN proceeds from the addition of urea to the carbonate at molar ratio of (2.0-2.2):1 with stirring and gradually in 3 equal portions, giving each portion to time to react. Furthermore, Schunk et al. (1) noted that the reaction progresses through 3 stages: Na allophanate and Na cyanate are formed in the 1st stage at 100-120°C, water is evaporated in the 2nd stage at 130-140°C, and Na allophanate is converted into Na cyanate in the 3rd stage at 140-180°C. During the entire course, the reaction gases are simultaneously being removed in all stages. Dragalov et al.(2)recommended, that after the addition of the entire amount of urea, it is important calcine the resulting NaOCN is at 180-300°C until the gasification of impurities ceases. To calcine means to heat (a substance) to a high temperature but below the melting or fusing point, causing loss of moisture, reduction or oxidation, and the decomposition of carbonates and other compounds.
Taken together, these data suggest that the total reaction can be described by the following chemical equation:
Na2CO3 + 2CH4N2O + heat ---> 2NaOCN + H2O + 2NH3 + CO2
The following experimental method for the production of sodium cyanate from the direct heating of sodium carbonate and urea emphasized a 1:2.2 molar ratio of sodium carbonate to urea. The slight excess of urea was used to ensure total conversion of the carbonate. As well, urea was added in 3 equal portions and with good stirring. This means babysitting it so make sure you have some reading to do as well! The final process of calcine is very important in that unwanted contaminants are vapourized leaving a more pure product.
-stainless steel cup
-small cooking pot
-stainless steel stir rod
-anhydrous sodium carbonate, Na2CO3, FW=106 g/mol
-urea, molecular biology grade, CH4N2O, FW=60 g/mol
Warning: Ammonia gas is formed in this reaction, so it is a good idea to work in a fume hood or outside where there is good ventilation.
1) A hotplate was rested on the base of a clampstand. A cooking pot containing peanut oil was placed on the hotplate stirrer.
2) Into the stainless steel cup there was placed 27g sodium carbonate. The cup was then placed into the oil and secured with clamps to the clamp stand. The end of the thermometer was placed in the oil and positioned as close to the cup as possible.
3) Though the sodium carbonate used here in was anhydrous, it was warmed to a temperature of 170°C for 10 minutes to remove any residual moisture. Throughout the reaction the temperature of the oil was kept at 170°C and stirring was done frequently.
4) 11.2 g of urea was added slowly, one scoop at a time and with good stirring. During this, ammonia was released and moisture (water) formed making the mixture damp. Over the course of 40 minutes the mixture gradually dried out and the amount of released gas lessened.
5) Another 11.2g of urea was added and allowed to react for 35 minutes.
6) The last 11.2g of urea was added and allowed to react for 30 minutes.
7) After adding the total amount of urea over 1h 45 min, the mixture was dry, contained white and off-white-to-yellow granules, and continued to release gas. The product was calcined at a temperature of 280°C directly on the hotplate for 4 hr or until gas evolution ceased. During this process the mixture was stirred every 15 minutes and off-white-to-yellow granules became more prominent and as white ones lessened. It is important to give the post reaction time to calcine. For example, after 2 hr into the calcine, the mixture was cooled and weighed 43g which is way over the theoretical yield of 33g. This means that contaminants or unconverted carbonates are still present. After heating the mix for another 2 hrs. The yield came down to 33g.
8) The NaOCN was allowed to cool and was weighed. Yield was 33g. Theoretical yield is 33g. It will be assumed that this product is 95-99% pure.
Taken together, this reaction felt like a success. The reaction indicators such as ammonia evolution and water formation were present. As well, the noted drop in yield of 43g to the more realistic 33g during the calcine process was a good indication that impurities and conversion were occuring. As well the product was considerably off-white-to-yellow in colour relative to the starting white carbonate. It would be nice to do a melting point determination on the product but 550°C seem a bit difficult to achieve. Perhaps the only way to know for sure is to try the this product in a reaction .
Any suggestions, advice or input is much appreciated.
Keep it easy
1 Sodium cyanate from urea and sodium carbonate. Schunk, Wolfgang; Hohn, Richard; Jasche, Klaus; Braumann, Dietrich; Schweizer, Heidrun. (VEB Agrochemie Piesteritz, Ger. Dem. Rep.). Ger. (East) (1985), 8 pp. CODEN: GEXXA8 DD 221449 A1 19850424 Patent written in German. Application: DD 84-260213 19840221. CAN 103:162702 AN 1985:562702 CAPLUS
2 Sodium cyanate. Dragalov, V. V.; Karachinskii, S. V.; Chimishkyan, A. L.; Izakson, G. Yu.; Shvets, P. K.; Kulygin, A. A.; Kulygina, A. F.; Turlanov, N. N. (Mendeleev, D. I., Chemical-Technological Institute, Moscow, USSR). U.S.S.R. (1984), CODEN: URXXAF SU 1074818 A1 19840223 Patent written in Russian. Application: SU 82-3513458 19820917. CAN 100:158962 AN 1984:158962 CAPLUS
It just seems to go faster...
(Stoni's sexual toy)
|Sounds good. Have you tried to recrystallize...||Bookmark|
Have you tried to recrystallize the sodium cyanate? Does anyone have solubility figures at higher temperatures?
I googled for it and found 110g/l at 20°C, MP 550°C
KOCN is 750g/l at 20°C, MP 315°C, thermal decomposition taking place >700°C
I'm not fat just horizontally disproportionate.
More cyanate info
(Rated as: excellent)
Here's the good bits from Ullmann 2002: