Ammonium carbamate

Structural formula
General
Surname	Ammonium carbamate
other names	Ammonium carbamate Ammonium carbamate
Molecular formula	H 2 NCOONH 4
Brief description	white solid with an ammonia-like odor
External identifiers / databases
CAS number 1111-78-0 EC number 214-185-2 ECHA InfoCard 100,012,896 PubChem 12550248 ChemSpider 451267 Wikidata Q337285
properties
Molar mass	78.07 g mol −1
Physical state	firmly
density	1.6 g cm −3
Melting point	152 ° C (in closed ampoule)
boiling point	Decomposition from 35 ° C
Vapor pressure	117.70 h Pa (25 ° C) (decomposition)
solubility	good in water (790 g l −1 at 20 ° C)
safety instructions
GHS labeling of hazardous substances danger H and P phrases H: 302-315-318 P: 280-302 + 352-305 + 351 + 338-313
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Ammonium carbamate , formerly also called ammonium carbamate , is the ammonium salt of carbamic acid , which is not known in the free state. It is a minor ingredient in staghorn salt .

properties

Ammonium carbamate forms a colorless crystal powder that dissolves well in water (at 790 g / l). The solubility is increased by adding ammonia gas . In aqueous solution, ammonium carbamate partially hydrolyzes above 35 ° C, and above 60 ° C completely, with the formation of ammonium carbonate , which in turn can break down into ammonia and carbon dioxide .

${\displaystyle \mathrm {H_{2}NCOONH_{4}+H_{2}O\rightleftharpoons (NH_{4})_{2}CO_{3}} }$

${\displaystyle \mathrm {(NH_{4})_{2}CO_{3}\rightleftharpoons 2NH_{3}+CO_{2}+H_{2}O} }$

The decay can be quantified via the corresponding dissociation pressures.

Dissociation pressure of ammonium carbamate
temperature	in ° C	10.03	14.92	17.86	21.25	24.91	26.77	30.91	35.91	39.89	44.86
pressure	in kPa	3.89	5.66	7.03	9.08	11.77	13.37	17.85	24.89	32.33	44.21

When heated in a closed system, decomposition into urea and water can be observed at temperatures around room temperature . The rate of conversion increases sharply with increasing temperature, with the water formed having a catalytic effect.

${\displaystyle \mathrm {H_{2}NCOONH_{4}\rightleftharpoons H_{2}NCONH_{2}+H_{2}O} }$

synthesis

Ammonium carbamate is produced by the direct reaction of ammonia gas and CO ₂ in a volume ratio of 2: 1 with the exclusion of water .

${\displaystyle \mathrm {2\ NH_{3}+CO_{2}\rightleftharpoons H_{2}NCOONH_{4}} }$

use

Ammonium carbamate is used in the cosmetics industry and in the manufacture of pesticides. It is also an important intermediate in the production of urea . It is also used as a cleaning, pickling and neutralizing agent, as well as in the deer horn salt mentioned above for baking. In Germany, the direct production of ammonium carbamate is only around 1000 t / a due to the low demand. The automotive industry is investigating ammonium carbamate as an alternative to the AUS 32 urea solution in SCR catalysts.

Individual evidence

1. ↑ ^{a b c d e f g} Entry on ammonium carbamate in the GESTIS substance database of the IFA , accessed on February 1, 2016(JavaScript required) .
2. ↑ K.-H. Zapp, K.-H. Wostbrock, M. Schäfer, K. Sato, H. Seiter, W. Zwick, R. Creutziger, H. Head: Ammonium Componds. In: Ullmann's Encyclopedia of Industrial Chemistry . Wiley-VCH Verlag, Weinheim 2005, doi : 10.1002 / 14356007.a02_243 .
3. ↑ ^{a b c} T. R. Briggs, V. Migrdishian: The Ammoniumn Carbamate Equilibrium. In: J. Phys. Chem. 28, 1923, pp. 1121-1135, doi: 10.1021 / j150245a001 .