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Cyanamide

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Not to be confused with cyanogen or American Cyanamid.
Cyanamide
Full skeletal formulas of cyanamide, both tautomers
Space-filling model of the cyanamide molecule, nitrile tautomer
Space-filling model of the cyanamide molecule, diimide tautomer
Names
IUPAC name
Cyanamide
Other names
Amidocyanogen, carbamonitrile, carbimide, carbodiimide, cyanoamine, cyanoazane, N-cyanoamine, cyanogenamide, cyanogen amide, cyanogen nitride, diiminomethane, hydrogen cyanamide, methanediimine
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.006.358 Edit this at Wikidata
EC Number
  • 206-992-3
784
KEGG
RTECS number
  • GS5950000
UNII
UN number 2811
  • InChI=1S/CH2N2/c2-1-3/h2H2 checkY
    Key: XZMCDFZZKTWFGF-UHFFFAOYSA-N checkY
  • InChI=1/CH2N2/c2-1-3/h2H2
    Key: XZMCDFZZKTWFGF-UHFFFAOYAW
Properties
CH2N2
Molar mass 42.040 g/mol
Appearance Crystalline solid
Density 1.28 g/cm3
Melting point 44 °C (111 °F; 317 K)
Boiling point 260 °C (500 °F; 533 K) (decomposes)
83 °C at 6.7 Pa
140 °C at 2.5 kPa
85 g/100 ml (25 °C)
Solubility in organic solvents soluble
log P -0.82
Acidity (pKa) 10.3[1]
Hazards
GHS labelling:
GHS05: CorrosiveGHS06: ToxicGHS07: Exclamation markGHS08: Health hazard
Danger
H301, H311, H314, H317, H351, H361, H373, H412
P201, P202, P260, P261, P264, P270, P272, P273, P280, P281, P301+P310, P301+P330+P331, P302+P352, P303+P361+P353, P304+P340, P305+P351+P338, P308+P313, P310, P312, P314, P321, P322, P330, P333+P313, P361, P363, P405, P501
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g. white phosphorusSpecial hazards (white): no code
2
1
2
Flash point 141 °C (286 °F; 414 K)
NIOSH (US health exposure limits):
PEL (Permissible)
 none[2]
REL (Recommended)
 TWA 2 mg/m3
IDLH (Immediate danger)
 N.D.[2]
Safety data sheet (SDS) ICSC 0424
Related compounds
Related compounds
 Calcium cyanamide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

Cyanamide is an organic compound with the formula CN2H2. This white solid is widely used in agriculture and the production of pharmaceuticals and other organic compounds. It is also used as an alcohol-deterrent drug. The molecule features a nitrile group attached to an amino group. Derivatives of this compound are also referred to as cyanamides, the most common being calcium cyanamide (CaCN2).[3]

Tautomers and self-condensations

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Containing both a nucleophilic and electrophilic site within the same molecule, cyanamide undergoes various reactions with itself. Cyanamide exists as two tautomers, one with the connectivity N≡C–NH2 and the other with the formula HN=C=NH ("carbodiimide" tautomer). The N≡C–NH2 form dominates, but in a few reactions (e.g. silylation) the diimide form appears to be important.[3]

Cyanamide dimerizes to give 2-cyanoguanidine (dicyandiamide). This dimerization is hindered or reversed by acids and is inhibited by low temperatures. The cyclic trimer is called melamine.[3]

Production

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Cyanamide is produced by hydrolysis of calcium cyanamide, which in turn is prepared from calcium carbide via the Frank-Caro process.[4]

CaCN2 + H2O + CO2 → CaCO3 + H2NCN

The conversion is conducted on slurries.

Reactions and uses

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Cyanamide can be regarded as a functional single carbon fragment which can react as an electrophile or nucleophile. The main reaction exhibited by cyanamide involves additions of compounds containing an acidic proton. Water, hydrogen sulfide, and hydrogen selenide react with cyanamide to give urea, thiourea, and selenourea, respectively:

H2NCN + H2E → H2NC(E)NH2 (E = O, S, Se)

In this way, cyanamide behaves as a dehydration agent and thus can induce condensation reactions. Alcohols, thiols, and amines react analogously to give alkylisoureas, isothioureas, and guanidines. The anti-ulcer drug cimetidine is generated using such reactivity. Related reactions exploit the bifunctionality of cyanamide to give heterocycles, and this latter reactivity is the basis of several pharmaceutical syntheses such as the aminopyrimidine imatinib, and agrichemicals Amitrol and hexazinone. The hair-loss treatment minoxidil and the anthelmintics albendazole, flubendazole, and mebendazole feature 2-aminoimidazole substructures derived from cyanamide.[3] Cyanamide is also used in the synthesis of other pharmaceutical drugs including tirapazamine, etravirine, revaprazan, and dasantafil.

The cyanamide anion has the character of a pseudo chalcogen, cyanamide can therefore be regarded as analogue to water or hydrogen sulfide.

A convenient method for the preparation of secondary amines which are not contaminated with primary or tertiary amines is the reaction of cyanamide with alkyl halides to N,N-dialkylcyanamides which can easily be hydrolyzed to dialkylamines and then decarboxylated.[5] Cyanamide adds itself in the presence of N-bromosuccinimide to olefinic double bonds. The addition product is converted by bases to N-Cyanaziridine,[6] cyclized in the presence of acids to imidazolines, which can be further reacted to vicinal diamines by alkaline cleavage.[7]

Cyanamide is also a versatile synthetic building block for heterocycles: it forms 2-aminobenzimidazole with 1,2-diaminobenzene[8] and it forms with the readily available cyclic enamine 4-(1-cyclohexenyl)morpholine[9] and with elemental sulfur a 2-aminothiazole in good yields.[10]

Sodium dicyanamide is available in good yield and high purity from cyanamid and cyanogen chloride,[11][12] which is suitable as an intermediate for the synthesis of active pharmaceutical ingredients.[13] A guanidino group is introduced by reaction of cyanamide with sarcosine In the industrial synthesis of creatine:.[14]

reaction equation
reaction equation

This synthesis route mostly avoids problematic impurities like chloroacetic acid, iminodiacetic acid, or dihydrotriazine that occur in other routes. The physiological precursor guanidinoacetic is obtained analogously by reacting cyanamide with glycine.

Methods to stabilize cyanamide make it available on an industrial scale. Due to the strong affinity towards self-condensation in alkaline media (see above) solutions of cyanamide are stabilized by the addition of 0.5 wt% of monosodium phosphate as buffer. Solid cyanamide is produced by careful evaporation of the solvent and subsequent addition of a hydrolysis-labile ester of formic acid. The ester absorbs traces of moisture (suppression of urea formation), neutralizes alkalinity (ammonia) and continually releases small amounts of formic acid.[15]

Agricultural use

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Cyanamide, under the trade name Dormex, is a common agricultural rest-breaking agent applied in spring to stimulate uniform opening of buds, early foliation and bloom. Cyanamide can effectively compensate for the moderate lack of chilling units accumulated in the previous autumn and save the harvest that would otherwise be lost. It is particularly effective for woody plants such as blueberries, grapes, apples, peaches and kiwifruit. Most recently the product was approved for use on almonds and pistachios in the USA. Overdosage, high concentration and error in timing of application can damage the buds (especially of peach trees).[16] Growers may avoid damage by applying 30 days prior to bud break according to the label.

A 50% aqueous solution of cyanamide is also used as a biocide (disinfectant) particularly in pig farming, because it effectively kills salmonella and shigella and fights flies in all stages of development.[17]

Environmental aspects

[edit]

Cyanamide degrades via hydrolysis to urea, an excellent fertilizer. Fungi, like Myrothecium verrucaria, accelerate this process utilizing the enzyme cyanamide hydratase.[18]

Cyanamide functional group

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Cyanamide is the name for a functional group with the formula R1R2N−C≡N where R1 and R2 can be a variety of groups. These compounds are called cyanamides. One example is naphthylcyanamide, C10H7N(CH3)CN, which has been produced by the von Braun reaction,[19] a general method for the conversion of tertiary amines to cyanamides using cyanogen bromide as reagent.[20] Alternatively, secondary amines can attack an aryl cyanate to give a carbamimidate; heating then eliminates the arenol to give a cyanamide. A similar reaction occurs with sulfonyl cyanides, but thiocyanates require a thiophilic metal to induce elimination.[21]: 1389 

Some cyanamides where R1 and R2 are identical alkyl groups are prepared directly by alkylation of a salt of the parent cyanamide.[11] Likewise, acyl cyanamides can be formed from an acyl chloride and cyanamide, often with a base.[21]: 1388 

Alternatively, dehydration of ureas or dehydrosulfurization of thioureas can produce cyanamides, sometimes with rearrangement.[21]: 1390–1392  Isonitrile dichlorides react with ammonia to give cyanamides.[21]: 1392  As a stabler valence isomer of carbodiimides, cyanamides form when carbodiimides are heated or undergo electrophilic substitution.[21]: 1393 

Secondary cyanamides are stable, but primary cyanamides trimerize to the corresponding triazine.[21]: 1398 

Cyanamides are more acidic and less basic than alkylamines, protonating at the terminal nitrogen. However, nickel(0) complexes are known in which nickel coordinates to both nitrogen atoms. When protonated, the central carbon is very electrophilic, and will add a variety of nucleophiles.[21]: 1393–1395, 1399 

Cyanamide in space

[edit]

Due to its high permanent dipole moment (i.e., 4.32 ± 0.08 D),[22] cyanamide was detected in spectral emissions coming from the Sgr B2 molecular cloud (T < 100 K) through its microwave transitions as the first known interstellar molecule containing the NCN frame.[23]

Safety

[edit]

It is used as an alcohol-deterrent drug in Canada, Europe, and Japan.[3]

Cyanamide has a modest toxicity in humans.[24] Workplace exposure to hydrogen cyanamide sprays or exposure in people living in the vicinity of spraying have been reported as causing respiratory irritation, contact dermatitis, headache, and gastrointestinal symptoms of nausea, vomiting, or diarrhea.[24]

References

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  1. ^ "Cyanamide_msds".
  2. ^ a b NIOSH Pocket Guide to Chemical Hazards. "#0160". National Institute for Occupational Safety and Health (NIOSH).
  3. ^ a b c d e Thomas Güthner; Bernd Mertschenk (2006). "Cyanamides". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a08_139.pub2. ISBN 3527306730.
  4. ^ Kurzer, Frederick; Lawson, Alexander (1954). "Methylisourea Hydrochloride". Organic Syntheses. 34: 67. doi:10.15227/orgsyn.034.0067.
  5. ^ Jonczyk A, Ochal Z, Makosza M (1978). "Reactions of Organic Anions; LXXXV1. Catalytic Two-Phase Alkylation of Cyanamide". Synthesis. 1978 (12): 882–883. doi:10.1055/s-1978-24922.
  6. ^ Ponsold K, Ihn W (1970). "Die Addition von cyanamid und Halogen an Olefine ein neues Verfahren zur Darstellung von vic.-Halogencyanaminen und Aziridinen". Tetrahedron Lett. 11 (13): 1125–1128. doi:10.1016/S0040-4039(01)97925-0. PMID 5439242.
  7. ^ Kohn, Harold; Jung, Sang Hun (1983). "New stereoselective method for the preparation of vicinal diamines from olefins and cyanamide". Journal of the American Chemical Society. 105 (12): 4106–4108. doi:10.1021/ja00350a068..
  8. ^ Weiss, Stefan; Michaud, Horst; Prietzel, Horst; Krommer, Helmut (1973). "A New, Simple Synthesis of 2-Aminobenzimidazole". Angewandte Chemie International Edition in English. 12 (10): 841. doi:10.1002/anie.197308411..
  9. ^ S. Hünig, E. Lücke, and W. Brenninger (1961). "1-Morpholino-1-Cyclohexene". Organic Syntheses: 65. doi:10.15227/orgsyn.041.0065{{cite journal}}: CS1 maint: multiple names: authors list (link).
  10. ^ Gewald, K.; Spies, H.; Mayer, R. (1970). "Zur Reaktion von Enaminen mit Schwefel und Cyanamid" [On the Reaction of Enamines with Sulfur and Cyanamide]. Journal für Praktische Chemie. 312 (5): 776–779. doi:10.1002/prac.19703120507..
  11. ^ a b E. B. Vliet (1925). "Diallylcyanamide". Organic Syntheses. 5: 45. doi:10.15227/orgsyn.005.0045.
  12. ^ Verfahren zur Herstellung von Natrium-Dicyanamid, veröffentlicht am 10. August 2000, Anmelder: SKW Trostberg AG.
  13. ^ "Sodium dicyanamide (Na-dicyanamide)". lonza.com. Archived from the original on 2013-05-23. Retrieved 2019-07-01.
  14. ^ Deutsche Offenlegungsschrift DE-OS 10 2006 016 227 A1, Offenlegungsdatum: 11. Oktober 2007, Anmelder: Degussa GmbH
  15. ^ Wehrstedt, Klaus-Dieter; Wildner, Werner; Güthner, Thomas; Holzrichter, Klaus; Mertschenk, Bernd; Ulrich, Armin (2009-10-30). "Safe transport of cyanamide". Journal of Hazardous Materials. 170 (2–3): 829–835. doi:10.1016/j.jhazmat.2009.05.043. ISSN 0304-3894. PMID 19505756.
  16. ^ Powell, A. (1999). "Action Program for Dormex Application on Peaches". Auburn University. Archived from the original on 2018-06-20.
  17. ^ "ALZOGUR®". AlzChem (in German). Retrieved 2019-07-01.
  18. ^ Stransky H, Amberger A (1973). "Isolierung und eigenschaften einer Cyanamid-hydratase (E.C.-Gruppe 4. 2.1.) aus Myrothecium verrucaria Alb. u. Schw" [Isolation and properties of a cyanamide hydratase (EC 4.2.1) from Myrothecium verrucaria]. Z. Pflanzenphysiol. 70: 74–87. doi:10.1016/S0044-328X(73)80049-2.
  19. ^ Homer W. J. Cressman (1947). "N-Methyl-1-Naphthylcyanamide". Organic Syntheses. 27: 56. doi:10.15227/orgsyn.027.0056.
  20. ^ March, Jerry (1992). Advanced Organic Chemistry: Reactions, Mechanisms, and Structure (4th ed.). New York: Wiley. p. 436–7. ISBN 0-471-60180-2.
  21. ^ a b c d e f g Nekrasov, D. D. (2004) [24 July 2003]. "Synthesis and chemical transformations of mono- and disubstituted cyanamides". Russian Journal of Organic Chemistry (Zhurnal Organicheskoi Khimii). 40 (10). [[Nauka (publisher)|]]. doi:10.1007/s11178-005-0030-4.
  22. ^ Tyler, J.K.; Sheridan, J.; Costain, C.C. (August 1972). "The microwave spectra of cyanamide". Journal of Molecular Spectroscopy. 43 (2): 248–261. doi:10.1016/0022-2852(72)90021-5.
  23. ^ Turner, B. E.; Liszt, H. S.; Kaifu, N.; Kisliakov, A. G. (November 1975). "Microwave detection of interstellar cyanamide". The Astrophysical Journal. 201: L149. Bibcode:1975ApJ...201L.149T. doi:10.1086/181963.
  24. ^ a b Schep L, Temple W, Beasley M (January 2009). "The adverse effects of hydrogen cyanamide on human health: an evaluation of inquiries to the New Zealand National Poisons Centre". Clinical Toxicology. 47 (1). Philadelphia, PA: 58–60. doi:10.1080/15563650802459254. PMID 18951270. S2CID 6961576.
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