Cyanamide : definição de Cyanamide e sinónimos de Cyanamide (inglês)

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definição - Cyanamide

cyanamide (n.)

1.a compound used as a fertilizer and as a source of nitrogen compounds

2.a weak soluble dibasic acid (the parent acid of cyanamide salts)

Cyanamide (n.)

1.(MeSH)A cyanide compound which has been used as a fertilizer, defoliant and in many manufacturing processes. It often occurs as the calcium salt, sometimes also referred to as cyanamide. The citrated calcium salt is used in the treatment of alcoholism.

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Cyanamide

                   
Cyanamide
Identifiers
CAS number 420-04-2 YesY
PubChem 9864
ChemSpider 9480 YesY
UNII 21CP7826LC YesY
EC number 206-992-3
UN number 2811
DrugBank DB02679
KEGG D00123 YesY
ChEBI CHEBI:16698 YesY
ChEMBL CHEMBL56279 YesY
RTECS number GS5950000
Jmol-3D images Image 1
Properties
Molecular formula CH2N2
Molar mass 42.040 g/mol
Appearance Crystalline solid
Density 1.28 g/cm3
Melting point

44 °C

Boiling point

260 °C (decomp.)
83 °C at 6.7 Pa
140 °C at 2.5 kPa

Solubility in water 85 g/100 ml (25 °C)
Solubility in organic solvents soluble
Hazards
MSDS ICSC 0424
EU Index 615-013-00-2
EU classification Toxic (T)
R-phrases R21, R25, R36/38, R43
S-phrases (S1/2), S3, S22, S36/37, S45
NFPA 704
NFPA 704.svg
1
4
3
Flash point 141 °C
Related compounds
Related compounds Calcium cyanamide
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

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 in Canada, Europe and Japan. The molecule features a nitrile group attached to an amino group. Although it is similar in structure to hydrogen cyanide, it is not as toxic. Derivatives of this compound are also referred to as cyanamides, the most common being calcium cyanamide (CaCN2).

Contents

  Tautomers and self-condensations

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 NCNH2 and the other with the formula HNCNH ("diimide" tautomer). The NCNH2 form dominates, but in a few reactions (e.g. silylation) the diimide form appears to be important.

Cyanamide dimerizes to give 2-cyanoguanidine (dicyandiamide). This decomposition process is disfavored by acids and is inhibited by low temperatures. The trimer is called melamine.

  Production, reactions, uses

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

CaCN2 + H2O + CO2 → CaCO3 + H2NCN

The conversion is conducted on slurries, consequently most commercial cyanamide is sold as an aqueous solution.

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, "pseudothioureas," 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 (3-Amino-1,2,4-triazole) and Hexazinone. The hair-loss treatment Minoxidil and the anthelmintic (worm-killing) drugs Albendazole, Flubendazole, and Mebendazole feature 2-aminoimidazole substructures derived from cyanamide.[1]

Cyanamide 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. Overdosage, high concentration and error in timing of application can damage the buds (especially of peach trees).[2]

  Environmental aspects

Cyanamide degrades via hydrolysis to urea, an excellent fertilizer. Microorganisms, e.g. the bacterium Myrothecium verrucaria, accelerate this process utilizing the enzyme cyanamide hydratase.

  Safety

Cyanamide has a modest toxicity in humans.[3] 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.[3]

  See also

  References

  1. ^ Thomas Güthner; Bernd Mertschenk (2006). "Cyanamides". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a08_139.pub2. 
  2. ^ Powell, A. (1999). Action Program for Dormex Application on Peaches. Auburn University. Retrieved 2010-05-24.
  3. ^ 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 (Philadelphia, PA) 472 (1): 58–60. doi:10.1080/15563650802459254. PMID 18951270. 

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