Sciencemadness Discussion Board

Allophanic acid

bnull - 15-1-2024 at 08:14

Hello, everyone. Does anyone know anything about allophanic acid?

I'm very curious about it because the only mentions of it (that I could find) occur in an old book (Wöhler & Liebig, iirc) and some papers about polymers and enzymes. Another source is a 1987 paper in the Zhurnal Organicheskoi Khimii, which is almost impossible to find, whether online or at the college library. I searched the forum and the only time it was mentioned was in connection with a chlorate-based explosive.

Any suggestion is appreciated.

Sir_Gawain - 15-1-2024 at 08:54

It has the formula H2NC(O)NHCO2H. It can be prepared by reacting urea (carbonyl diamide) with sodium bicarbonate.

EF2000 - 15-1-2024 at 09:26

Quote: Originally posted by Sir_Gawain  
It can be prepared by reacting urea (carbonyl diamide) with sodium bicarbonate.

It can't. Allophanic acid is known only in the derivatives. Biuret is its amide. Esters are stable. And inorganic allophanates just hydrolyze back to carbonates, urea and CO2. See for example, this paper: https://doi.org/10.1021/ja00153a022 (full text).

bnull - 15-1-2024 at 09:33

Those were about the only things I knew about the acid, apart from the melting point. But thanks anyway.

I suppose I must be more specific. I'm going to prepare today a small quantity (about 2 g) of allophanic acid. I want to try some reactions with it and, if all goes well (or not particularly tarry), prepare ethyl allophanate. Maybe even thioallophanic acid derivatives. It's more for curiosity than practical uses (which I suppose are non-existent).

I thought of two routes: (1) add sodium bicarbonate to molten urea; (2) add a concentrated solution of sodium bicarbonate dropwise to urea in ethanol. Also, I'm not interested in carcinogens or gaseous cyanides as by-products for obvious reasons.

Now you see where I am.

Note: I should have guessed it would decompose. In a preliminar test, I tried to prepare it in solution and put a drop of phenolphthalein just to see how things would turn out. It went from slightly pinkish to pink in a couple of days.

[Edited on 15-1-2024 by bnull]

clearly_not_atara - 15-1-2024 at 14:10

I guess you might get somewhere the same way they make carbamate salts, by forming the anion of urea and reacting this with CO2.

bnull - 16-1-2024 at 04:22

Quote: Originally posted by EF2000  
Esters are stable. And inorganic allophanates just hydrolyze back to carbonates, urea and CO2.


I suppose quaternary ammonium salts are just as unstable.

bnull - 2-4-2024 at 02:51

Quote: Originally posted by bnull  
Another source is a 1987 paper in the Zhurnal Organicheskoi Khimii, which is almost impossible to find, whether online or at the college library.

I finally found a copy of the paper. It’s the original Russian version published in the Zhurnal Organicheskoi Khimii. The paper was Google-translated because I can barely read Cyrillic. The result was not particularly bad and I’ll share the preparations exactly as translated anyway.

Interaction of urea with alkali metal carbonates
  1. A mixture of 63.6 g of anhydrous soda (sodium carbonate) and 36 g of urea was heated to 120 °C and kept with stirring until the release of ammonia stopped. The reaction mass was washed with hot water (3 x 80 mL), dried and 7.2 g of sodium allophanate was obtained. IR spectrum (cm-1): 3360, 3200 (NH), 1714, 1660 (CONH), 1330 (CNC, 1120, 1090, 800, 765, 640, 540, 473, 454, 306. % found: C 18.79, 19.07; H 2.18, 2.38; N 21.81, 22.21. C2H2N2NaO3. Calculated %: C 19.05, H 2.38, N 22.22.
  2. A mixture of 69.1 g of anhydrous potassium [carbonate] and 30 g of urea was heated to 120 °C and kept with stirring until the evolution of ammonia stopped. The reaction mass was washed with hot water (3 x 50 mL) and dried. We received [obtained] 15.4 g of potassium allophanate. IR spectrum (cm-1): 3360, 3210 (NH), 1725, 1670 (CONH), 1305 (CNC), 1110, 1092, 772, 635, 555, 480, 460, 314. Found %: C 16.78, 16.92; H 2.10, 2.16; N 19.57, 19.77. C2H3KN2O3. Calculated %: C 16.90, H 2.11, N 19.72.


Interaction of urea with alkali metal bicarbonates
  1. A mixture of 4.2 g of sodium bicarbonate and 6 g of urea in a sealed reactor was heated to 110 °C and kept for 3 hours. The resulting reaction mass was washed with hot absolute ethanol, dried and 6.2 g of sodium allophanate was obtained, the yield was 98%. The IR spectrum is identical to the spectrum of sodium allophanate obtained by the method described above. Found %: C 18.88, 19.18; H 2.31, 2.39; N 22.20, 22,50. C2H2N2NaO3. Calculated %: C 19.05, H 2.38, N 22.22
  2. The interaction of 5 g of potassium bicarbonate and 6 g of urea was carried out under the conditions of method A. We obtained 7.1 g of potassium allophanate, yield 99%. The IR spectrum is identical to the spectrum of potassium allophanate obtained by the method described above. Found %: C 16.79, 17.15; H 1.99, 2.13; N 19.57, 19.75. C2H3KN2O3. Calculated %: C 16.90, H 2.11, N 19.72.


Karachinskii, S. V.; Dragalov, V. V.; Chimishkyan, A. L.; Tsvetkov, V. Yu. (1987). "Reaction of urea with alkali metal carbonates". Zhurnal Organicheskoi Khimii. 23: 93–6. The attached file is the original Russian.

Attachment: Karachinskii et al. (344kB)
This file has been downloaded 138 times

[Edited on 2-4-2024 by bnull]

kmno4 - 7-4-2024 at 14:50

Nice paper, it shades more light on the cyanates formation from urea+carbonate - multistep and complex reaction, which always amazed me.
Russian bandits from chemport.ru are sometimes useful for obtaining such papers, as in this case :P

BTW. This russian journal has its english translation, but both ones are not available online. I used to talk with a man from Springer about it and he said that " there is no chance for online access to it" but he did not explain why.... pity.

bnull - 7-4-2024 at 16:06

It's quite beautiful even in that broken english.
Quote: Originally posted by kmno4  
Russian bandits from chemport.ru are sometimes useful for obtaining such papers, as in this case :P

I saw some titles of what they have there. If I weren't so lazy to learn new languages...
Quote: Originally posted by kmno4  
BTW. This russian journal has its english translation, but both ones are not available online. I used to talk with a man from Springer about it and he said that " there is no chance for online access to it" but he did not explain why.... pity.

It has. And it's practically impossible to find a physical copy. My alma mater has none. It's sad.

kmno4 - 8-4-2024 at 02:35


Even the best, largest and richest libraries have not all important literature on given subject. Even legendary Berichte, published at Wiley's site has missing issues (I wonder if they know it).
The total lack of available online archives of important and interesting russian (translated or original) journals: organic, inorganic and applied chemistry, is one of the most frustrating (me) things.
"HathiTrust Digital Library – Millions of books online" has all these russian journal scanned. But for who, if copyright is 100 years ? It makes no sense. However, recently (COVID) they made some exception and granted temporary access to these journal to some univ's.

The Japanese made the best thing : they published their journals' archives online, for free, from the 1st volumes !.
Give me fast scanner and paper input - I will do the same in 1-2 years :D

This is all bout it.
-------------------------
In attachment - slightly OCR-improved version of the russian paper.




[Edited on 8-4-2024 by kmno4]

Attachment: Karachinskii et al_3.pdf (117kB)
This file has been downloaded 117 times

bnull - 8-4-2024 at 05:47

Quote: Originally posted by kmno4  

Even the best, largest and richest libraries have not all important literature on given subject. Even legendary Berichte, published at Wiley's site has missing issues (I wonder if they know it).

Chances are those who would be interested in the missing issues would choose to search somewhere else rather than send a complaint to Wiley.

Thanks.