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Cyanamide

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Not to be confused withcyanogenorAmerican 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)
3DMet
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.006.358Edit this at Wikidata
EC Number
  • 206-992-3
784
KEGG
RTECS number
  • GS5950000
UNII
UN number 2811
  • InChI=1S/CH2N2/c2-1-3/h2H2checkY
    Key: XZMCDFZZKTWFGF-UHFFFAOYSA-NcheckY
  • 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)
Solubilityin organic solvents soluble
logP -0.82
Acidity(pKa) 10.3[1]
Hazards
GHSlabelling:
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 theirstandard state(at 25 °C [77 °F], 100 kPa).

Cyanamideis anorganic compoundwith theformulaCN2H2.This white solid is widely used in agriculture and the production of pharmaceuticals and other organic compounds. It is also used as analcohol-deterrent drug.The molecule features anitrilegroup attached to anaminogroup. Derivatives of this compound are also referred to as cyanamides, the most common beingcalcium 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 twotautomers,one with the connectivity N≡C–NH2and the other with the formula HN=C=NH ( "carbodiimide"tautomer). The N≡C–NH2form dominates, but in a few reactions (e.g.silylation) the diimide form appears to be important.[3]

Cyanamide dimerizes to give2-cyanoguanidine(dicyandiamide). This dimerization is hindered or reversed by acids and is inhibited by low temperatures. The cyclictrimeris calledmelamine.[3]

Production

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Cyanamide is produced by hydrolysis ofcalcium cyanamide,which in turn is prepared fromcalcium carbidevia theFrank-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 anelectrophileornucleophile.The main reaction exhibited by cyanamide involves additions of compounds containing an acidic proton. Water, hydrogen sulfide, and hydrogen selenide react with cyanamide to giveurea,thiourea,andselenourea,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, andguanidines.The anti-ulcer drugcimetidineis generated using such reactivity. Related reactions exploit the bifunctionality of cyanamide to giveheterocycles,and this latter reactivity is the basis of several pharmaceutical syntheses such as the aminopyrimidineimatinib,and agrichemicalsAmitrolandhexazinone.The hair-loss treatmentminoxidiland theanthelminticsalbendazole,flubendazole,andmebendazolefeature 2-aminoimidazole substructures derived from cyanamide.[3]Cyanamide is also used in the synthesis of other pharmaceutical drugs includingtirapazamine,etravirine,revaprazan,and dasantafil.

The cyanamideanionhas the character of a pseudochalcogen,cyanamide can therefore be regarded as analogue towaterorhydrogen 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 toN,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 forheterocycles:it forms 2-aminobenzimidazole with1,2-diaminobenzene[8]and it forms with the readily available cyclicenamine4-(1-cyclohexenyl)morpholine[9]and with elementalsulfura 2-aminothiazole in good yields.[10]

Sodium dicyanamide is available in good yield and high purity from cyanamid andcyanogen chloride,[11][12]which is suitable as anintermediatefor the synthesis of active pharmaceutical ingredients.[13]A guanidino group is introduced by reaction of cyanamide withsarcosineIn the industrial synthesis ofcreatine:.[14]

reaction equation
reaction equation

This synthesis route mostly avoids problematic impurities likechloroacetic acid,iminodiacetic acid,ordihydrotriazinethat occur in other routes. The physiological precursorguanidinoaceticis obtained analogously by reacting cyanamide withglycine.

Methods tostabilizecyanamide 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% ofmonosodium phosphateas buffer. Solid cyanamide is produced by careful evaporation of the solvent and subsequent addition of a hydrolysis-labileesterofformic 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 agriculturalrest-breaking agentapplied in spring to stimulate uniform opening ofbuds,early foliation and bloom. Cyanamide can effectively compensate for the moderate lack ofchilling unitsaccumulated 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 ofpeachtrees).[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 abiocide(disinfectant) particularly inpig farming,because it effectively kills salmonella and shigella and fightsfliesin all stages of development.[17]

Environmental aspects

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Cyanamide degrades via hydrolysis to urea, an excellent fertilizer.Fungi,likeMyrothecium verrucaria,accelerate this process utilizing the enzymecyanamide hydratase.[18]

Cyanamide functional group

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Cyanamide is the name for a functional group with the formulaR1R2N−C≡Nwhere R1and R2can be a variety of groups. These compounds are calledcyanamides.One example is naphthylcyanamide, C10H7N(CH3)CN, which has been produced by thevon Braun reaction,[19]a general method for the conversion oftertiary aminesto cyanamides usingcyanogen bromideas reagent.[20]Alternatively, secondary amines can attack an arylcyanateto 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 R1and R2are identical alkyl groups are prepared directly byalkylationof asaltof the parent cyanamide.[11]Likewise,acylcyanamides can be formed from anacyl chlorideand cyanamide, often with a base.[21]: 1388 

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

Secondary cyanamides are stable, but primary cyanamides trimerize to the correspondingtriazine.[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

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Due to its high permanent dipole moment (i.e., 4.32 ± 0.08 D),[22]cyanamide was detected inspectral emissionscoming from theSgr B2molecular 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 analcohol-deterrent drugin 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 causingrespiratoryirritation,contact dermatitis,headache,andgastrointestinal symptomsof nausea,vomiting,ordiarrhea.[24]

References

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  1. ^"Cyanamide_msds".
  2. ^abNIOSH Pocket Guide to Chemical Hazards."#0160".National Institute for Occupational Safety and Health(NIOSH).
  3. ^abcdeThomas Güthner; Bernd Mertschenk (2006). "Cyanamides".Ullmann's Encyclopedia of Industrial Chemistry.Weinheim: Wiley-VCH.doi:10.1002/14356007.a08_139.pub2.ISBN3527306730.
  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.PMID5439242.
  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. ^abE. 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.Archived fromthe originalon 2013-05-23.Retrieved2019-07-01.
  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.ISSN0304-3894.PMID19505756.
  16. ^Powell, A. (1999)."Action Program for Dormex Application on Peaches".Auburn University. Archived fromthe originalon 2018-06-20.
  17. ^"ALZOGUR®".AlzChem(in German).Retrieved2019-07-01.
  18. ^Stransky H, Amberger A (1973). "Isolierung und eigenschaften einer Cyanamid-hydratase (E.C.-Gruppe 4. 2.1.) ausMyrothecium verrucariaAlb. u. Schw "[Isolation and properties of a cyanamide hydratase (EC 4.2.1) fromMyrothecium 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,ISBN0-471-60180-2
  21. ^abcdefgNekrasov, 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. ^abSchep 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.PMID18951270.S2CID6961576.
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