Im ehemaligem VC Forum hat mal einer einen Syntheseweg aus Kalkstickstoff Dünger beschrieben:
(VC-backup > Chemie_1 > Anorganische Chemie > ab Seite 2222 )
Erfolgreich darstellen konnte ich jedoch mittlerweile Dicyandiamid/2-Cyanoguanidin und dies sogar mit recht simplen Mitteln. Hält man
die Temperatur beim Einleiten des CO2s in die Calciumcyanamid Lösung konstant auf Temperaturen von 65-70°C geht das entstehende
Cyanamid direkt in Dicyandiamid über und fällt beim Abkühlen der Lösung als weiße Nadeln aus. Die Ausbeute ist recht nah am
theoretisch möglichen Wert, jedoch geht aufgrund der auch darin vorhandenen unbekannten Flüssigkeit ein Teil verloren, da man diese
(Am besten mit Eiswasser) auswaschen muss. Da Dicyandiamid schlecht löslich ist, bleibt aber selbst bei sorgfältigem Waschen am
Ende etwa 70% der theoretischen Menge erhalten, welche nach dem Trocknen nahezu rein ist.
Weiß jemand, um was für eine Flüssigkeit es sich in dem Dünger handeln könnte? Alles was mir bekannt ist, sind diverse Öle die bei
der Herstellung der Düngerpellets verwendet werden könnten, allerdings ist die Flüssigkeit vollständig mit Wasser mischbar und lässt
sich nicht daraus trennen, auch nach dem kochen ist diese noch vorhanden. Es kann auch sein, dass diese erst während der Synthese
des Cyanamids entsteht, allerdings habe ich keine Idee, welcher Stoff dort mit solchen Eigenschaften entstehen könnte.
Sollte Interesse an einer ausführlichen Synthese von Dicyandiamid/2-Cyanoguanidin bestehen, mache ich gerne beim nächsten Mal
Fotos vom Vorgang und stelle diese zusammen.
Im habe im Buch "Inorganic Synthesis - Volume 3 von 1939" noch folgenden detailierten Syntheseweg von Dicyandiamid über Cyanamid , ausgehend von Calciumcyanamid gefunden:
(
https://ia800804.us.archive.org/4/items/InorganicSynthesesVolume3/InorganicSynthesesVolume3_text.pdf )
Seite 39 bis 44
CYANAMIDE
References
1. Gustavson: Ann., 172, 173 (1874).
2. Moissan: Compt. rend., 113, 19 (1891).
3. Lantenois: ibid., 166, 1385 (1913).
4. Walker: J. Chem. Soc, 85, 1090 (1904).
5. Moissan: Bull. soc. chim., [3] 7, 746 (1892).
9. CYANAMIDE
2CaCN 2 + 2H 2 0-> Ca(HCN 2 ) 2 + Ca(OH) 2
Ca(HCN 2 ) 2 + H 2 S0 4 -> 2H 2 NCN + CaS0 4
Submitted by L. A. Pinck* and J. M. Salisbury!
Checked by H. A. DeWalt, Jr., J A. B. Herrick,}: and K. B. Mohk(
Cyanamide, H 2 NCN, has been prepared by (1) desul-
furizing thiourea with mercury (II) oxide, 1,6 lead acetate, 2
or bromine, 3 (2) passing gaseous cyanogen chloride into
ammonia dissolved in anhydrous ether, 4 and (3) oxidiz-
ing thiourea with alkaline permanganate. 5 The method
described below is an adaptation for laboratory use of &
commercial procedure 8 that uses calcium cyanamide as a
starting material.
Procedure
A. AQUEOUS SOLUTION OF CYANAMIDE
A slurry made by mixing 600 g. of crude calcium cyana-
mide containing 62.3 per cent calcium cyanamide § with
600 ml. of water|| is poured into a 10-in. Buchner funnel.^
* U.S. Department of Agriculture, Bureau of Plant Industry, Soils and
Agricultural Engineering, Beltsville, Md
f American Cyanamid Company, Stamford Laboratories, Stamford,
Conn.
{ University of Illinois, Urbana, 111.
§ Aero Cyanamid, Minimum Hydrate, contains 60 to 63 per cent calcium
cyanamide but on storage in a humid atmosphere the calcium cyanamide
content will decrease. Samples containing as low as 56.9 per cent calcium
cyanamide have been used successfully.
|| In order to obtain the most efficient extraction, it is necessary to have
the crude calcium cyanamide finely ground so that 65 per cent will pass
through a 200-mesh sieve.
f The best results are obtained with a filter cake approximately J^ in.
thick.
The outlet of the funnel is connected to a glass spiral con-
denser, which leads into a filter flask connected to a water
pump. Ice water is circulated through the jacket of the
condenser to cool the filtrate. The filter cake is extracted
with 3.6 1. of water at 60° at such a rate that there is gen-
erally only a thin aqueous layer above the cake. The
extraction requires about 25 minutes.* The hot water is
allowed to remain in contact with the slurry for only a very
short time; the resultant solution of calcium hydrogen
cyanamide must be cooled immediately to below 20°.
Approximately 3.8 kg. of filtratef is obtained. The filtrate
is immediately cooled to 10° and then -treated with 20 per
cent aqueous sulfuric add to precipitate the calcium and
to lower the pH to 5.1. | Approximately 1 kg. of acid will
be needed.
The mixture is filtered. Using specified quantities, the
filtrate will weigh about 4.1 kg., and will contain about 80
per cent of the cyanamide present in tiie original calcium
cyanamide as a 3.5 per cent solution.
The filtrate may be concentrated with respect to cyana-
mide by vacuum distillation § at 40 mm. through a 12-in.
* This operation should be done as quickly as possible, but some lag must
be allowed to give time for the water to extract the cyanamide. The recom-
mended leaching system is one in which advantage is taken of the higher
rate of solution and hydrolysis of calcium cyanamide in hot water, at the
same time avoiding the formation of dicyanodiamido in objectionable
amounts.
t Analysis of the filtrate from a typical preparation showed 2.81 per cent
cyanamide nitrogen, indicating that 89.2 per cent of the original cyanamide
had been extracted.
X The pll of the free cyanamide solution should be kept at about 5.0.
Previous work at the Stamford Research Laboratories of the American
Cyanamid Company, indicates that at a pll of 6 or higher free cyanamide
may polymerize violently to dicyanodiamido during the concentration.
At a pH of about 3, cyanamide decomposes to urea.
§ The solution must be stirred during concentration to expedite removal
of water and to prevent bumping. A simple and convenient stirring device
that will operate efficiently for use in systems under reduced pressure is
depicted in Fig. 12. A piece of rubber tubing A serves as the seal between
the shaft of the stirrer B and the glass bearing guide C. A few drops of
glycerol are applied at B to lubricate the glass-rubber interface and to permit
CYANAMIDE
column 1 in. o.d. packed with }{-in. Raschig rings to remove
the water. There is a strong tendency for the cyanamide
to be carried over into the distillate, and it is therefore
necessary to use a column to
minimize such losses. Distillation
should be carried out behind a safety
screen. Aqueous solutions of cyan-
amide of any desired concentration
up to 20 to 25 per cent can be pre-
pared easily in this manner. Such
solutions are often employed for
synthetic purposes (syntheses 10 and
11) rather than the solid material.
B. CRYSTALLINE CYANAMIDE
If crystalline cyanamide is de-
sired, the concentration of the solu-
tion prepared in A is continued
until the temperature in the pot
reaches 70°.*
The warm solution is filtered to remove the small amount
of calcium sulfate that crystallizes during the evaporation.
The filtrate is then cooled to 10° to effect crystallization of
cyanamide which is separated by filtration and dried in an
evacuated desiccator over phosphorus (V) oxide. The crys-
talline mass should be broken up at intervals in order to
easy rotation. The tube C is conveniently sealed to a male taper joint and
can thus be fitted readily to the all-glass distillation apparatus recommended
for the concentration operation.
* Toward the end of the concentration process, the pot temperature will
rise rapidly from approximately 40 to 70°. A good yield of cyanamide can
be obtained if a pressure no higher than 10 mm. and a maximum temperature
of 40° are employed, but poor yields are obtained if distillation is attempted
at 40 mm. at this same temperature, Bimply because insufficient water is
thus removed. The temperature of the residue in the flask should be kept as
low as possible to minimize formation of dicyanodiamide and should never
exceed 70". Evaporation of cyanamide solutions to dryness is hazardous
due to the tendency of cyanamide to polymerize with explosive violence
when heated in the presence of too little water.
facilitate complete desiccation. The yields of cyanamide,
with a purity of 93.5 per cent as determined by analysis,
will vary between 110 and 130 g. and average about 120 g.
or about 65 per cent of theory based on the calcium cyana-
mide content of the starting material. Additional cyana-
mide of lesser purity can be obtained by cooling the filtrate
to 0°. It is inadvisable to effect further concentration,
however, since explosive polymerizations are very prone to
occur at this concentration.
Properties
Cyanamide is a crystalline solid melting at 46°C. and is
exceedingly soluble in water, alcohol, and ether. Cyana-
mide is easily recrystallized from a solution of two parts
of benzene and one part of ether. In the presence of acid
or strong alkali it hydrolyzes readily to urea, whereas under
mild alkaline conditions it polymerizes exothermally to
dicyanodiamide (synthesis 10). Cyanamide combines with
hydrogen chloride 9 to form a dihydrochloride and forms
salts with metals. 7 ' 10 It reacts with hydrogen sulfide 11 or
mercaptans 12 to form thiourea or substituted isothioureas
and reacts with alcohols 13 in the presence of acid to form
substituted isoureas. With formaldehyde 14 cyanamide
forms methylol compounds; with amines 16 it forms sub-
stituted guanidines. Cyanamide can be acylated with
acylating agents, 10,18 or alkylated with alkylating agents. 10
When fused with potassium hydroxide, 17 cyanamide forms
potassium cyanate. When treated with hydrazine salts, 18
it forms aminoguanidonium salts. Cyanamide is toxic to
the skin and readily attacks iron, steel, copper, lead, and,
to a slight extent, Duriron. Glass and enamelware are
found to be most resistant. 19
References
1. Volhard: J. prakt. Chem., [2] 9, 6 (1874).
2. Walther: J. prakt. Chem., [2] 64, 510 (1896).
3. Rathke: Ber., 12, 776 (1879).
4. CloEz and Cannizzaro: Compt. rend., 32, 62 (1851).
DICYANODIAMIDE
5. Werner: J. Chem. Soc, 116, 1168 (1919).
6. Hantzsch and Wolvekamp: Ann., 331, 282 (1904).
7. Franklin: "The Nitrogen System of Compounds," A.C.S. Monograph,
pp. 93-97, Reinhold Publishing Corporation, New York, 1935.
8. Hetherington and Pinck: U.S. patent 1673820 (1928); cf. Chem.
Abstracts, 22, 2816 (1928).
9. Pinck and Hetherinoton : Ind. Eng. Chem., 18, 629 (1926).
10. Drechsel: J. prakt. Chem., [2] 11, 284 (1875).
11. Heuser: U.S. patent 1991852 (1935); cf. Chem. Abstracts, 29, 2180
(1935).
12. Arndt: Ber., 54, 2236 (1921).
13. Stieglitz and McKee: Ber. 33, 1517 (1900).
14. Griffith: U.S. patent 2019490 (1935); cf. Chem. Abstracts, 30, 538
(1936).
15. Bischoff: J. Biol. Chem., 80, 345 (1928).
16. Mertens: J. prakt. Chem., [2] 17, 1 (1878).
17. Emich: Monatsh., 10, 321 (1889).
18. Fantl and Silbermann: Ann., 467, 274 (1928).
19. Unpublished work of the U.S. Department of Agriculture.
10. DICYANODIAMIDE
(Cyanoguanidine)
2H 2 NCN -+ H 2 NC(=NH)NHCN
Submitted by L. A. Pinck*
Checked by R. L. PHELPsf
Methods for preparation of dicyanodiamide involve
polymerization of cyanamide under controlled conditions
in aqueous solutions in the presence of metallic hydroxides
or ammonia. 1 Dicyanodiamide is an important chemical
intermediate and is used for the preparation of guanidonium
nitrate, 2 biguanide, 3 and numerous other derivatives of the
ammonocarbonic acids. 4 The present method is easily
adaptable to preparation of laboratory quantities.
Procedure
A neutral aqueous solution of cyanamide (synthesis 9),
or a solution made very slightly alkaline with ammonia, is
* U.S. Department of Agriculture, Bureau of Plant Industry, Soils and
Agricultural Engineering, Beltsville, Md.
f American Cyanamid Company, Stamford, Conn.
concentrated by evaporation under reduced pressure at a
temperature of 40° or less until the residual solution con-
tains approximately 20 to 25 per cent cyanamide.
One kilogram of the concentrated solution is transferred
to an evaporating dish and while still warm (about 40°) is
treated with 70 to 80 g. of concentrated aqueous ammonia
to bring the concentration of the latter to about 2 per cent. *
The temperature of the solution is then raised as rapidly as
possible on a steam bath. Heating is continued for 15 to
20 minutes until the cyanamide has been converted com-
pletely into dicyanodiamide, as shown by the nonformation
of the characteristic yellow precipitate of silver cyanamide
when an ammoniacal silver nitrate solution is added to a
test portion. 5 The solution is cooled and the solid product
separated by filtration and dried at 100°. In a typical
experiment there was obtained from 1 kg. of a 25 per cent
solution 260 g. of dicyanodiamide (m.p. 206 to 208°) con-
taining 0.4G per cent water by analysis. The yield is prac-
tically quantitative.
Properties
Dicyanodiamide melts at 209.5° (corr.) and can be crys-
tallized in the form of rhombic plates from water, alcohol,
or a mixture of the two. It is only slightly soluble in water,
moderately soluble in alcohol and in liquid ammonia.
Aqueous solutions are neutral, but liquid ammonia solutions
are acidic in character, and react with metallic oxides and
amides to form well-defined salts. 6
References
1. Pinck and Hetherington: Ind. Eng. Chem., 27, 834 (1935); Grubb and
Nitsche: Z. angew. Chem. 27, 3G8 (1914).
2. Smith: Inorganic Syntheses, 1, 96 (1939).
3. Davis: /. Am. Chem. Soc, 43, 2234 (1921).
4. Franklin: "Nitrogen System of Compounds," chaps. X and XI, Rein-
hold Publishing Corporation, New York, 1935.
* Maximum, conversion of cyanamide is achieved in solutions containing
at least 20 per cent HjNCN and 2 per cent NH,.
Thema: Dicyandiamid (Gelesen 5152 mal)
