Org. Synth. 1927, 7, 46
DOI: 10.15227/orgsyn.007.0046
GUANIDINE NITRATE
Submitted by Tenney L. Davis
Checked by H. T. Clarke and Ross Phillips.
1. Procedure
It is strongly recommended that this procedure not be used to prepare guanidine nitrate. Mixtures of ammonium nitrate and organic materials not much different from the mixture in the procedure are now used extensively as commercial explosives. The aqueous mixture of (Note 10) is similar to some aqueous mixtures used in sizable quantities for rock blasting; a confined mixture of this sort is especially hazardous. Only a few laboratories devoted to explosives research have the barricades and remote control devices needed to run this preparation of guanidine nitrate without risk.
Guanidine nitrate can be bought from Eastman Organic Chemicals and other suppliers.
In a 1-l. round-bottomed flask is placed an intimate mixture of 210 g. of dicyanodiamide (2.5 moles) and 440 g. of ammonium nitrate (5.5 moles) (Note 1) and (Note 10). The flask is introduced into an oil bath at 110–120°, and the temperature of the oil is raised during about one-half hour to 160°. The bath is then held at this temperature (Note 2) and (Note 10) for three hours. During the first hour the mass melts to a clear liquid which begins to deposit crystals and finally sets to a solid cake (Note 3). At the end of three hours the flask is removed from the bath; the product is allowed to cool and is extracted on the steam bath with successive quantities of water (about 2 l. is necessary to bring all soluble material into solution) (Note 4). The solution is filtered to remove white amorphous insoluble material (ammeline and ammelide) (Note 5).
The filtrate contains guanidine nitrate along with a small amount of ammonium nitrate and very small amounts of dicyanodiamide and biguanide nitrate (Note 6). The solution is concentrated to about 1 l., and the guanidine nitrate which crystallizes on cooling is filtered off. A second crop is obtained by concentrating to 250 cc. (Note 7). The combined yield of crude guanidine nitrate is 520–560 g. (85–92 per cent of the theoretical amount). The product may be purified by recrystallization from 1 l. of water (Note 8), a second crop being taken after the mother liquor has been concentrated to 250 cc. The yield of recrystallized guanidine nitrate melting at 213–214° amounts to 500–520 g. (Note 9).
2. Notes
1.
A
10 per cent excess of ammonium nitrate is used because the
biguanide mononitrate which is formed as an intermediate is strongly basic and tends to attack the unreacted
ammonium nitrate, as is evidenced by the liberation of
ammonia during the heating. The excess of
ammonium nitrate can be easily separated from the
guanidine nitrate by the crystallization from water, and it does not interfere with the conversion of
guanidine nitrate into
nitroguanidine by the action of strong
sulfuric acid.
2.
When the molten mass reaches 160° its temperature begins to rise above that of the bath, generally reaching 200° during the course of five or six minutes. The mass should not be stirred at any time, especially before the mixture has completely melted; otherwise, the temperature may run somewhat higher.
3.
The
guanidine nitrate begins to crystallize soon after the temperature of the mixture begins to fall.
4.
The hard cake goes into solution slowly, and sufficient time must be given for each portion of water to become saturated before it is decanted.
5.
When the hot filtrate cools, it will deposit flocks of
ammelide along with the crystals of
guanidine nitrate. water may conveniently be added until the crystals dissolve, and the cold solution again filtered for the removal of
ammelide.
6.
This filtrate on evaporation to dryness and baking at 100° leaves a residue of
650 g., which is suitable for the preparation of
nitroguanidine (p. 399).
7.
At this point the mother liquor (about 200 cc.) may be discarded as it contains mainly
ammonium nitrate.
8.
Alcohol is a satisfactory solvent for
guanidine nitrate but appears to have no advantage over water. A saturated solution of
guanidine nitrate in water contains about
10 per cent at
15°.
9.
The second mother liquor may advantageously be worked up with a subsequent run.
10.
The submitter has prepared
guanidine nitrate in batches of about 1 kg. by heating
dicyanodiamide and
ammonium nitrate in
2-l. flasks in oil baths heated to 160°. If the oil bath is kept at 160° the temperature of the reacting materials rises at times considerably above that point, but apparently the temperature does not mount dangerously high with such sized runs.
It is suggested that the best way to carry out the preparation, particularly on a large scale, is to heat the reagents in an autoclave, with a convenient amount of water, at 160° for two to three hours. The autoclave is emptied while still warm. The liquid is filtered hot for the removal of white insoluble material, and the guanidine nitrate crystallizes out as the liquid cools. (T. L. Davis, private communication.)
3. Discussion
Guanidine salts can be prepared by heating
ammonium thiocyanate;
1 by hydrolysis of
dicyanodiamide by
acids2 (whereby one molecule of the
guanidine salt is produced); and by the action of
ammonium salts on
dicyanodiamide,
3 from which two molecules of
guanidine salt result. The
nitrate can be prepared from the
thiocyanate by the action of
nitric acid4 or by conversion to the
sulfate and treatment with
calcium nitrate.
5 The
nitrate is also obtained by heating
ammonium nitrate and
calcium cyanamide.
6 A detailed study has been made of the preparation of
guanidine nitrate in improved yields from
dicyanodiamide and
ammonium nitrate.
7
This preparation is referenced from:
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
calcium cyanamide
dicyanodiamide
Guanidine salts
acids
guanidine salt
ammonium salts
alcohol (64-17-5)
sulfuric acid (7664-93-9)
ammonia (7664-41-7)
ammonium thiocyanate (1762-95-4)
nitric acid (7697-37-2)
sulfate (14808-79-8)
ammonium nitrate
Guanidine nitrate (506-93-4)
ammelide (645-93-2)
biguanide nitrate,
biguanide mononitrate
Nitroguanidine (556-88-7)
nitrate
thiocyanate
calcium nitrate (10124-37-5)
Copyright © 1921-, Organic Syntheses, Inc. All Rights Reserved