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Acetamidine hydrochloride

Chemical compound From Wikipedia, the free encyclopedia

Acetamidine hydrochloride or acetamidinium chloride is an organic compound with the formula [CH3C(NH2)2]+Cl−, used in the synthesis of many nitrogen-bearing compounds. It is the hydrochloride of acetamidine, one of the simplest amidines.

Quick facts Names, Identifiers ...
Acetamidine hydrochloride
2-D skeletal version of acetamidine hydrochlordie
Names
IUPAC name
Ethanimidamide hydrochloride
Other names
  • Acetamidinium chloride
  • Ethanimidamide monohydrochloride
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.004.274 Edit this at Wikidata
EC Number
  • 204-700-9
UNII
  • InChI=1S/C2H6N2.ClH/c1-2(3)4;/h1H3,(H3,3,4);1H
    Key: WCQOBLXWLRDEQA-UHFFFAOYSA-N
  • Cl.N=C(N)C
Properties
C2H7ClN2
Molar mass 94.54 g·mol−1
Appearance colourless monoclinic crystals
Structure
Monoclinic
C2/c
a = 11.673, b = 9.862, c = 9.601
α = 90°, β = 111.71°, γ = 90°[1]
Hazards[2]
GHS labelling:
GHS07: Exclamation mark
Warning
H315, H319, H335
P261, P264, P271, P280, P302+P352, P304+P340, P305+P351+P338, P312, P362+P364, P403+P233, 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 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
2
0
0
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Properties

Acetamidine hydrochloride is a hygroscopic solid which forms colourless monoclinic crystals.[1] It is soluble in water and alcohol.

It releases ammonium chloride upon heating. Dry acetamidine hydrochloride releases acetonitrile, while in aqueous solution, it instead undergoes hydrolysis to acetic acid and ammonia.[3]

[CH3C(NH2)2]Cl → CH3CN + [NH4]Cl
[CH3C(NH2)2]Cl + 2 H2O → CH3COOH + NH3 + [NH4]Cl

As free base amidines are strong Lewis bases, acetamidine hydrochloride is a weak Lewis acid. Treatment with strong base gives free base acetamidine:

[CH3C(NH2)2]Cl + KOH → CH3C(NH)NH2 + KCl + H2O

Synthesis

Acetamidine hydrochloride is synthesised in a two-step process that begins with a solution of acetonitrile in ethanol at close to 0 °C.[4] First, the mixture is treated with anhydrous hydrogen chloride in a Pinner reaction, producing crystals of ethyl acetimidate hydrochloride:

H3C−C≡N + C2H5OH + HCl → H3C−C(=NH+2Cl−)−OC2H5

This imino ether salt is then treated with an excess of ammonia in dry ethanol, converting it to the amidine:

H3C−C(=NH+2Cl−)−OC2H5 + NH3 → [H3C−C(NH2)2]+Cl− + C2H5OH

All reagents must be thoroughly dried using a strong desiccant such as phosphorus pentoxide, as the intermediate imino ether is susceptible to hydrolysis, yielding ammonium chloride and ethyl formate. Layers of ammonium chloride can form on the imino ether salt, limiting the formation of amidine.[4]

Applications

As a source of amidine, acetamidine hydrochloride is a precursor to the industrial and laboratory synthesis of many nitrogen compounds. It reacts with β-dicarbonyls to produce substituted pyrimidines,[5] with acetaldehydes to form substituted imidazoles,[6] and with imidates to form substituted triazines.[7]

In particular, its reaction with a dicarbonyl intermediate is an early step in the synthesis of thiamine (vitamin B1) and many of its derivatives.[8]

References

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