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| Names | |||
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| IUPAC name Cyanamide | |||
| Other names Amidocyanogen, carbamonitrile, carbimide, carbodiimide, cyanoamine, cyanoazane, N-cyanoamine, cyanogenamide, cyanogen amide, cyanogen nitride, diiminomethane, hydrogen cyanamide, methanediimine | |||
| Identifiers | |||
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3D model (JSmol) | |||
| ChEBI | |||
| ChEMBL | |||
| ChemSpider |
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| DrugBank |
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| ECHA InfoCard | 100.006.358 | ||
| EC Number |
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| 784 | |||
| KEGG |
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| RTECS number |
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| UNII | |||
| UN number | 2811 | ||
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| 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 | ||
| logP | −0.82 | ||
| Acidity (pKa) | 10.3[1] | ||
| Hazards | |||
| GHS labelling: | |||
    | |||
| 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) | |||
| 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). | |||
Cyanamide is anorganic compound with 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 anitrile group attached to anamino group. Derivatives of this compound are also referred to as cyanamides, the most common beingcalcium cyanamide (CaCN2).[3]
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–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 give2-cyanoguanidine (dicyandiamide). This dimerization is hindered or reversed by acids and is inhibited by low temperatures. The cyclictrimer is calledmelamine.[3]
Cyanamide is produced by hydrolysis ofcalcium cyanamide, which in turn is prepared fromcalcium carbide via theFrank–Caro process.[4]
The conversion is conducted on slurries.
Cyanamide can be regarded as a functional single carbon fragment which can react as anelectrophile ornucleophile. 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:
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 drugcimetidine is 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 agrichemicalsAmitrol andhexazinone. The hair-loss treatmentminoxidil and theanthelminticsalbendazole,flubendazole, andmebendazole feature 2-aminoimidazole substructures derived from cyanamide.[3] Cyanamide is also used in the synthesis of other pharmaceutical drugs includingtirapazamine,etravirine,revaprazan, and dasantafil.
The cyanamideanion has the character of a pseudochalcogen, cyanamide can therefore be regarded as analogue towater orhydrogen 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 cyclicenamine 4-(1-cyclohexenyl)morpholine[9] and with elementalsulfur a 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 anintermediate for the synthesis of active pharmaceutical ingredients.[13] A guanidino group is introduced by reaction of cyanamide withsarcosine In the industrial synthesis ofcreatine:.[14]
This synthesis route mostly avoids problematic impurities likechloroacetic acid,iminodiacetic acid, ordihydrotriazine that occur in other routes. The physiological precursorguanidinoacetic is obtained analogously by reacting cyanamide withglycine.
Methods tostabilize 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% ofmonosodium phosphate as buffer. Solid cyanamide is produced by careful evaporation of the solvent and subsequent addition of a hydrolysis-labileester offormic acid. The ester absorbs traces of moisture (suppression of urea formation), neutralizes alkalinity (ammonia) and continually releases small amounts of formic acid.[15]
Cyanamide, under the trade name Dormex, is a common agriculturalrest-breaking agent applied in spring to stimulate uniform opening ofbuds, early foliation and bloom. Cyanamide can effectively compensate for the moderate lack ofchilling 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 ofpeach 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 abiocide (disinfectant) particularly inpig farming, because it effectively kills salmonella and shigella and fightsflies in all stages of development.[17]
Cyanamide degrades via hydrolysis to urea, an excellent fertilizer.Fungi, likeMyrothecium verrucaria, accelerate this process utilizing the enzymecyanamide hydratase.[18]
Cyanamide is the name for a functional group with the formulaR1R2N−C≡N where R1 and R2 can 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 amines to cyanamides usingcyanogen bromide as reagent.[20] Alternatively, secondary amines can attack an arylcyanate 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 byalkylation of asalt of the parent cyanamide.[11] Likewise,acyl cyanamides can be formed from anacyl chloride and cyanamide, often with a base.[21]: 1388
Alternatively, dehydration ofureas or dehydrosulfurization of thioureas can produce cyanamides, sometimes with rearrangement.[21]: 1390–1392 Isonitrile dichlorides react withammonia to 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 corresponding1,3,5-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
Due to its high permanent dipole moment (i.e., 4.32 ± 0.08 D),[22] cyanamide was detected inspectral emissions coming from theSgr B2molecular cloud (T < 100 K) through its microwave transitions as the first known interstellar molecule containing the NCN frame.[23]
It is used as analcohol-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 causingrespiratory irritation,contact dermatitis,headache, andgastrointestinal symptoms of nausea,vomiting, ordiarrhea.[24]
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