Difference between revisions of "Imidazole"

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{{chembox
 
|  Name = Imidazole
 
|  Name = Imidazole
 
|  ImageFile = Imidazole_chemical_structure.png
 
|  ImageFile = Imidazole_chemical_structure.png
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|  ImageSize = 345px
 
|  ImageName = Chemical structure of imidazole
 
|  ImageName = Chemical structure of imidazole
 
|  IUPACName = 1,3-diazole
 
|  IUPACName = 1,3-diazole
 
|  OtherNames = Imidazole<br />1,3-diazacyclopenta-2,4-diene
 
|  OtherNames = Imidazole<br />1,3-diazacyclopenta-2,4-diene
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|  SMILES = n1c[nH]cc1
 
 
| Section1 = {{Chembox Identifiers
 
| Section1 = {{Chembox Identifiers
 
|  CASNo = 288-32-4
 
|  CASNo = 288-32-4
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|  ChemSpiderID = 773
 
|  RTECS = N13325 1985-86
 
|  RTECS = N13325 1985-86
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|  SMILES = n1c[nH]cc1
 
   }}
 
   }}
 
| Section2 = {{Chembox Properties
 
| Section2 = {{Chembox Properties
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|  MeltingPt = 89-91 °C (362-364 K)
 
|  MeltingPt = 89-91 °C (362-364 K)
 
|  BoilingPt = 256 °C (529 K)
 
|  BoilingPt = 256 °C (529 K)
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|  pKa = pK<sub>a</sub>=6.993
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|  pKa= pK<sub>a</sub>=14.5, pK<sub>BH<sup>+</sup></sub>=6.993
 
   }}
 
   }}
 
| Section3 = {{Chembox Structure
 
| Section3 = {{Chembox Structure
 
|  Coordination = planar 5-membered ring
 
|  Coordination = planar 5-membered ring
 
|  CrystalStruct = [[monoclinic]]
 
|  CrystalStruct = [[monoclinic]]
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|  Dipole = 12.8 Cm*10<sup>30</sup>
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|  Dipole = 3.61[[Debye|D]]
 
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   }}
 
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| Section7 = {{Chembox Hazards
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'''Imidazole''' is a [[heterocyclic]] [[aromatic]] [[organic compound]]. It is further classified as an [[alkaloid]].  Imidazole refers to the parent compound C<sub>3</sub>H<sub>4</sub>N<sub>2</sub>, whereas imidazoles are a class of heterocycles with similar ring structure but varying substituents.  This ring system is present in important biological building blocks such as [[histidine]], and the related hormone [[histamine]]. Imidazole can act as a [[base (chemistry)|base]] and as a weak [[acid]]. Imidazole exists in two [[tautomer]]ic forms with the [[hydrogen]] [[atom]] moving between the two [[nitrogen]]s.  Many drugs contain an imidazole ring, such as [[antifungal drug]]s and [[nitroimidazole]].<ref>Katritzky; Rees. ''Comprehensive Heterocyclic Chemistry.'' Vol. 5, p.469-498, ('''1984''').</ref><ref>Grimmett, M. Ross. ''Imidazole and Benzimidazole Synthesis.'' Academic Press, ('''1997''').</ref><ref>Brown, E.G. ''Ring Nitrogen and Key Biomolecules.'' Kluwer Academic Press, ('''1998''').</ref><ref>Pozharskii, A.F, et.al. ''Heterocycles in Life and Society.'' John Wiley & Sons, ('''1997''').</ref><ref>Heterocyclic Chemistry TL Gilchrist, The Bath press 1985 ISBN 0-582-01421-2</ref>
+
'''Imidazole''' is an [[organic compound]] with the formula C<sub>3</sub>H<sub>4</sub>N<sub>2</sub>.  This [[aromatic]] [[heterocyclic]] is classified as an [[alkaloid]].  Imidazole refers to the parent compound  whereas imidazoles are a class of heterocycles with similar ring structure but varying substituents.  This ring system is present in important biological building blocks such as [[histidine]], and the related hormone [[histamine]]. Imidazole can serve as a [[base (chemistry)|base]] and as a weak [[acid]]. Many drugs contain an imidazole ring, such as [[antifungal drug]]s and [[nitroimidazole]].<ref>[[Alan R. Katritzky]]; Rees. ''Comprehensive Heterocyclic Chemistry.'' Vol. 5, p.469-498, ('''1984''').</ref><ref>Grimmett, M. Ross. ''Imidazole and Benzimidazole Synthesis.'' Academic Press, ('''1997''').</ref><ref>Brown, E.G. ''Ring Nitrogen and Key Biomolecules.'' Kluwer Academic Press, ('''1998''').</ref><ref>Pozharskii, A.F, et al. ''Heterocycles in Life and Society.'' John Wiley & Sons, ('''1997''').</ref><ref>Heterocyclic Chemistry TL Gilchrist, The Bath press 1985 ISBN 0-582-01421-2</ref>
  
 
==Discovery==
 
==Discovery==
−
Imidazole was first synthesized by H. Debus in 1858, but various imidazole derivatives had been discovered as early as the 1840s. His synthesis, as shown below, used [[glyoxal]] and [[formaldehyde]] in [[ammonia]] to form imidazole.  This synthesis, while producing relatively low yields, is still used for creating C-substituted imidazoles.
+
Imidazole was first synthesized by Heinrich Debus in 1858, but various imidazole derivatives had been discovered as early as the 1840s. His synthesis, as shown below, used [[glyoxal]] and [[formaldehyde]] in [[ammonia]] to form imidazole.<ref>{{cite journal
−
:[[Image:Debusmethod.gif|Debus method]]
+
| title = Ueber die Einwirkung des Ammoniaks auf Glyoxal 
 +
| author = Heinrich Debus
 +
| journal = [[Annalen der Chemie und Pharmacie]]
 +
  | volume = 107
 +
| issue = 2
 +
| pages = 199 &ndash; 208
 +
| year = 1858
 +
| url = 
 +
| doi = 10.1002/jlac.18581070209}}</ref> This synthesis, while producing relatively low yields, is still used for creating C-substituted imidazoles.
 +
:[[Image:DiketRouteHIm.png|300px]]
 
In one [[microwave chemistry|microwave]] modification the reactants are [[benzil]], [[formaldehyde]] and [[ammonia]] in [[glacial acetic acid]] forming ''2,4,5-triphenylimidazole'' (Lophine).<ref>''Microwave-Mediated Synthesis of Lophine: Developing a Mechanism To Explain a Product'' Crouch, R. David; Howard, Jessica L.; Zile, Jennifer L.; Barker, Kathryn H. J. Chem. Educ. '''2006''' 83 1658</ref>
 
In one [[microwave chemistry|microwave]] modification the reactants are [[benzil]], [[formaldehyde]] and [[ammonia]] in [[glacial acetic acid]] forming ''2,4,5-triphenylimidazole'' (Lophine).<ref>''Microwave-Mediated Synthesis of Lophine: Developing a Mechanism To Explain a Product'' Crouch, R. David; Howard, Jessica L.; Zile, Jennifer L.; Barker, Kathryn H. J. Chem. Educ. '''2006''' 83 1658</ref>
 +
 +
==Structure and properties==
 +
Imidazole is a 5-membered planar ring, which is soluble in water and other [[Chemical polarity|polar]] solvents. It exists in two equivalent [[tautomer]]ic forms because the [[hydrogen]] [[atom]] can be located on either of the two [[nitrogen]] atoms.  Imidazole is a highly polar compound, as evidenced by a calculated dipole of 3.61[[debye|D]], and is entirely soluble in water. The compound is classified as [[aromaticity|aromatic]] due to the presence of a sextet of [[pi bond|π-electron]]s, consisting of a pair of electrons from the protonated nitrogen atom and one from each of the remaining four atoms of the ring.
 +
 +
Some resonance structures of imidazole are shown below:
 +
<center>[[Image:Resonance-imidazole.png|550px]]</center>
 +
 +
===Amphotericity===
 +
Imidiazole is [[amphoteric]], ''i.e.'' it can function as both an acid and as a base. As an acid, the p''K''<sub>a</sub> of imidazole is 14.5, making it less acidic than carboxylic acids, phenols, and imides, but slightly more acidic than alcohols. The acidic proton is located on N-1. As a base, the p''K''<sub>a</sub> of the conjugate acid (cited above as p''K''<sub>BH<sup>+</sup></sub> to avoid confusion between the two) is approximately 7, making imidazole approximately sixty times more basic than [[pyridine]]. The basic site is N-3.
  
 
==Preparation==
 
==Preparation==
 +
[[Image:Imidazole-ball-and-stick.png|right|thumb|150px|A ball-and-stick model of imidazole, showing carbon-carbon and a carbon-nitrogen double bonds.]]
 
Imidazole can be synthesized by numerous methods besides the Debus method. Many of these syntheses can also be applied to different substituted imidazoles and imidazole derivatives simply by varying the [[functional groups]] on the reactants. In literature, these methods are commonly categorized by which and how many bonds form to make the imidazole rings. For example, the Debus method forms the (1,2), (3,4), and (1,5) bonds in imidazole, using each reactant as a fragment of the ring, and thus this method would be a three-bond-forming synthesis. A small sampling of these methods is presented below.
 
Imidazole can be synthesized by numerous methods besides the Debus method. Many of these syntheses can also be applied to different substituted imidazoles and imidazole derivatives simply by varying the [[functional groups]] on the reactants. In literature, these methods are commonly categorized by which and how many bonds form to make the imidazole rings. For example, the Debus method forms the (1,2), (3,4), and (1,5) bonds in imidazole, using each reactant as a fragment of the ring, and thus this method would be a three-bond-forming synthesis. A small sampling of these methods is presented below.
  
−
;Formation of One Bond
+
;Formation of one bond
−
The (1,5) or (3,4) bond can be formed by the reaction of an immediate and an α-aminoaldehyde or α-aminoacetal, resulting in the cyclization of an [[amidine]] to imidazole. The example below applies to imidazole when R=R<sub>1</sub>=Hydrogen.
+
The (1,5) or (3,4) bond can be formed by the reaction of an [[imidate]] and an α-aminoaldehyde or α-aminoacetal, resulting in the cyclization of an [[amidine]] to imidazole. The example below applies to imidazole when R=R<sub>1</sub>=Hydrogen.
  
 
:[[Image:Onebondmethod.gif|Formation of one bond]]
 
:[[Image:Onebondmethod.gif|Formation of one bond]]
  
 
;Formation of Two Bonds
 
;Formation of Two Bonds
−
The (1,2) and (2,3) bonds can be formed by treating a 1,2-diaminoalkane, at high temperatures, with an [[alcohol]], [[aldehyde]], or [[carboxylic acid]]. A dehydrogenating agent, such as [[platinum]] with [[alumina]], must be present in the reaction for the imidazole to form. The example below applies to imidazole when R=Hydrogen.
+
The (1,2) and (2,3) bonds can be formed by treating a 1,2-diaminoalkane, at high temperatures, with an [[alcohol]], [[aldehyde]], or [[carboxylic acid]]. A dehydrogenating catalyst, such as [[platinum]] on [[alumina]], is required.
  
−
:[[Image:Twobondmethod.gif|Formation of two bonds]]
+
:[[Image:RCO2HrouteImH.png|Formation of two bonds|300px]]
 
The (1,2) and (3,4) bonds can also be formed from N-substituted α-aminoketones and [[formamide]] and heat. The product will be a 1,4-disubstituted imidazole, but here since R=R<sub>1</sub>=Hydrogen, imidazole itself is the product. The yield of this reaction is moderate, but it seems to be the most effective method of making the 1,4 substitution.
 
The (1,2) and (3,4) bonds can also be formed from N-substituted α-aminoketones and [[formamide]] and heat. The product will be a 1,4-disubstituted imidazole, but here since R=R<sub>1</sub>=Hydrogen, imidazole itself is the product. The yield of this reaction is moderate, but it seems to be the most effective method of making the 1,4 substitution.
  
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;Formation of Four Bonds
 
;Formation of Four Bonds
−
This is a general method which is able to give good yields for substituted imidazoles. The starting materials are substituted glyoxal, aldehyde, amine, and ammonia or an ammonium salt.<ref>{{US patent reference|number=6,177,575|y=2001|m=01|d=23|inventor=[[Anthony J. Arduengo, III]]|title=Process for Manufacture of Imidazoles}}
+
This is a general method which is able to give good yields for substituted imidazoles. It is essentially an adaptation of the Debus method called the [[Debus-Radziszewski imidazole synthesis]]. The starting materials are substituted glyoxal, aldehyde, amine, and ammonia or an ammonium salt.<ref>{{US patent reference|number=6,177,575|y=2001|m=01|d=23|inventor=[[Anthony J. Arduengo, III]]|title=Process for Manufacture of Imidazoles}}
 
</ref>
 
</ref>
  
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[[Image:Ringformation.gif]]
 
[[Image:Ringformation.gif]]
  
−
Imidazole can also be formed in a vapor phase reaction. The reaction occurs with [[formamide]], [[ethylenediamine]], and hydrogen over [[platinum on alumina]], and it must take place between 340 and 480 &deg;C. This forms a very pure imidazole product.
+
Imidazole can also be formed in a vapor phase reaction. The reaction occurs with [[formamide]], [[ethylenediamine]], and hydrogen over [[platinum on alumina]], and it must take place between 340 and 480 °C. This forms a very pure imidazole product.
  
−
==Structure and properties==
+
==Biological significance and applications==
−
Imidazole is a 5-membered planar ring, which is soluble in water and [[Chemical polarity|polar]] solvents.  The compound has an [[aromatic]] sextet, which consists of one π electron from the =N- [[atom]] and one from each carbon atom, and two from the NH nitrogen.  Some [[resonance]] structures of imidazole are shown below.
+
Imidazole is incorporated into many important biological molecules.  The most pervasive is the [[amino acid]] [[histidine]], which has an imidazole [[side chain]]. Histidine is present in many [[proteins]] and [[enzymes]] and plays a vital part in the structure and binding functions of [[hemoglobin]]. Histidine can be [[carboxyl|decarboxylated]] to [[histamine]], which is also a common biological compound. It is a component of the [[toxin]] that causes [[urticaria]], which is another name for [[allergy|allergic]] hives.  The relationship between histidine and histamine are shown below:
−
[[Image:Imidazoleresonace.gif]]
 
  
−
Imidazole is a base and an excellent [[nucleophile]].  It reacts at the NH nitrogen, attacking alkylating and acylating compounds.  It is not particularly susceptible to [[electrophilic]] attacks at the carbon atoms, and most of these reactions are substitutions that keep the aromaticity intact.  One can see from the resonance structure that the carbon-2 is the carbon most likely to have a nucleophile attack it, but in general nucleophilic substitutions are difficult with imidazole.
+
<center>[[Image:Histidine decarboxylase.svg]]</center>
−
 
 
−
==Biological significance and applications==
 
−
Imidazole is incorporated into many important biological molecules.  The most obvious is the [[amino acid]] [[histidine]], which has an imidazole [[side chain]]. Histidine is present in many [[proteins]] and [[enzymes]] and plays a vital part in the structure and binding functions of [[hemoglobin]]. Histidine can be [[carboxyl|decarboxylated]] to [[histamine]], which is also a common biological compound. It is a component of the [[toxin]] that causes [[urticaria]], which is basically an [[allergy|allergic]] reaction.  The structures of both histidine and histamine are:
 
−
[[Image:Histidine-histamine.gif]]
 
  
 
One of the applications of imidazole is in the purification of [[His-tag]]ged [[protein]]s in [[Chromatography#Immobilized metal ion affinity chromatography|immobilised metal affinity chromatography]](IMAC). Imidazole is used to elute tagged proteins bound to [[nickel|Ni]] [[ion]]s attached to the surface of beads in the chromatography column. An excess of imidazole is passed through the column, which displaces the His-tag from nickel co-ordination, freeing the His-tagged proteins.
 
One of the applications of imidazole is in the purification of [[His-tag]]ged [[protein]]s in [[Chromatography#Immobilized metal ion affinity chromatography|immobilised metal affinity chromatography]](IMAC). Imidazole is used to elute tagged proteins bound to [[nickel|Ni]] [[ion]]s attached to the surface of beads in the chromatography column. An excess of imidazole is passed through the column, which displaces the His-tag from nickel co-ordination, freeing the His-tagged proteins.
Line 87: Line 103:
 
Imidazole has been used extensively as a corrosion inhibitor on certain transition metals, such as copper. Preventing copper corrosion is important, especially in aqueous systems, where the conductivity of the copper decreases due to corrosion.
 
Imidazole has been used extensively as a corrosion inhibitor on certain transition metals, such as copper. Preventing copper corrosion is important, especially in aqueous systems, where the conductivity of the copper decreases due to corrosion.
  
−
Many compounds of industrial and technological importance contain imidazole.  The thermostable polybenzimidazole PBI contains imidazole fused to a [[benzene]] ring and linked to a benzene, and acts as a fire retardant.  Imidazole can also be found in various compounds which are used for photography and electronics.
+
Many compounds of industrial and technological importance contain imidazole derivatives.  The thermostable polybenzimidazole PBI contains imidazole fused to a [[benzene]] ring and linked to a benzene, and acts as a fire retardant.  Imidazole can also be found in various compounds which are used for photography and electronics.
  
 
==Salts of imidazole==
 
==Salts of imidazole==
 
[[Image:Imidazolium salt.png|left|60px|Simple imidazolium cation]]
 
[[Image:Imidazolium salt.png|left|60px|Simple imidazolium cation]]
−
Salts of imidazole where the imidazole ring is in the [[cation]] are known as imidazolium salts (for example, imidazolium chloride). These salts are formed from the [[protonation]] or substitution at [[nitrogen]] of imidazole. These salts have been used as [[ionic liquids]] and precursors to [[stable carbene]]s.
+
Salts of imidazole where the imidazole ring is in the [[cation]] are known as imidazolium salts (for example, imidazolium chloride). These salts are formed from the [[protonation]] or substitution at [[nitrogen]] of imidazole. These salts have been used as [[ionic liquids]] and precursors to [[stable carbene]]s. Salts where a deprotonated imidazole is an [[anion]] are also possible; these salts are known as '''imidazolide salts''' (for example, sodium imidazolide).
−
Salts where a deprotanated imidazole is an [[anion]] are also possible; these salts are known as '''imidazolide salts''' (for example, sodium imidazolide).
 
  
 
==Related heterocycles==
 
==Related heterocycles==
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==References==
 
==References==
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<references/>
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{{reflist}}
 +
 
 +
{{Antifungals}}
  
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==Suppliers==
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[[Category:Imidazoles|*]]
−
*[https://www1.fishersci.com/Coupon?cid=1334&gid=148084 Fisher Scientific]
 
−
*[http://www.sigmaaldrich.com/catalog/search/ProductDetail/SIAL/I2399 Sigma-Aldrich]
 
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*[http://www.basf.com/specialtyintermediates/imidazoles.html BASF]
 
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*[http://www.rdchemicals.com/chemicals.php?mode=searchname&searchtext=imidazole&page=0 Substituted Imidazoles]
 
  
−
[[Category:Imidazoles| ]]
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{{Imported from Wikipedia|name=Imidazole|id=296636458}}

Revision as of 19:12, 9 August 2009

Imidazole
Chemical structure of imidazole
IUPAC name 1,3-diazole
Other names Imidazole
1,3-diazacyclopenta-2,4-diene
Identifiers
CAS number [288-32-4]
RTECS N13325 1985-86
ChemSpider 773
SMILES
Properties
Chemical formula C3H4N2
Molar mass 68.08 g/mol
Appearance white or pale yellow solid
Density 1.23 g/cm3, solid
Melting point

89-91 °C (362-364 K)

Boiling point

256 °C (529 K)

Solubility in water miscible
Acidity (pKa) pKa=14.5, pKBH+=6.993
Structure
Crystal structure monoclinic
Coordination geometry planar 5-membered ring
Dipole moment 3.61D
Hazards
Material safety data sheet (MSDS) External MSDS
R-phrases Template:R20 Template:R22 Template:R34 Template:R41
S-phrases Template:S26 Template:S36 Template:S37 Template:S39 Template:S45
Flash point 146 °C
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)

Imidazole is an organic compound with the formula C3H4N2. This aromatic heterocyclic is classified as an alkaloid. Imidazole refers to the parent compound whereas imidazoles are a class of heterocycles with similar ring structure but varying substituents. This ring system is present in important biological building blocks such as histidine, and the related hormone histamine. Imidazole can serve as a base and as a weak acid. Many drugs contain an imidazole ring, such as antifungal drugs and nitroimidazole.[1][2][3][4][5]

Discovery

Imidazole was first synthesized by Heinrich Debus in 1858, but various imidazole derivatives had been discovered as early as the 1840s. His synthesis, as shown below, used glyoxal and formaldehyde in ammonia to form imidazole.[6] This synthesis, while producing relatively low yields, is still used for creating C-substituted imidazoles.

300px

In one microwave modification the reactants are benzil, formaldehyde and ammonia in glacial acetic acid forming 2,4,5-triphenylimidazole (Lophine).[7]

Structure and properties

Imidazole is a 5-membered planar ring, which is soluble in water and other polar solvents. It exists in two equivalent tautomeric forms because the hydrogen atom can be located on either of the two nitrogen atoms. Imidazole is a highly polar compound, as evidenced by a calculated dipole of 3.61D, and is entirely soluble in water. The compound is classified as aromatic due to the presence of a sextet of π-electrons, consisting of a pair of electrons from the protonated nitrogen atom and one from each of the remaining four atoms of the ring.

Some resonance structures of imidazole are shown below:

Resonance-imidazole.png

Amphotericity

Imidiazole is amphoteric, i.e. it can function as both an acid and as a base. As an acid, the pKa of imidazole is 14.5, making it less acidic than carboxylic acids, phenols, and imides, but slightly more acidic than alcohols. The acidic proton is located on N-1. As a base, the pKa of the conjugate acid (cited above as pKBH+ to avoid confusion between the two) is approximately 7, making imidazole approximately sixty times more basic than pyridine. The basic site is N-3.

Preparation

A ball-and-stick model of imidazole, showing carbon-carbon and a carbon-nitrogen double bonds.

Imidazole can be synthesized by numerous methods besides the Debus method. Many of these syntheses can also be applied to different substituted imidazoles and imidazole derivatives simply by varying the functional groups on the reactants. In literature, these methods are commonly categorized by which and how many bonds form to make the imidazole rings. For example, the Debus method forms the (1,2), (3,4), and (1,5) bonds in imidazole, using each reactant as a fragment of the ring, and thus this method would be a three-bond-forming synthesis. A small sampling of these methods is presented below.

Formation of one bond

The (1,5) or (3,4) bond can be formed by the reaction of an imidate and an α-aminoaldehyde or α-aminoacetal, resulting in the cyclization of an amidine to imidazole. The example below applies to imidazole when R=R1=Hydrogen.

Formation of one bond
Formation of Two Bonds

The (1,2) and (2,3) bonds can be formed by treating a 1,2-diaminoalkane, at high temperatures, with an alcohol, aldehyde, or carboxylic acid. A dehydrogenating catalyst, such as platinum on alumina, is required.

Formation of two bonds

The (1,2) and (3,4) bonds can also be formed from N-substituted α-aminoketones and formamide and heat. The product will be a 1,4-disubstituted imidazole, but here since R=R1=Hydrogen, imidazole itself is the product. The yield of this reaction is moderate, but it seems to be the most effective method of making the 1,4 substitution.

Formation of three bonds
Formation of Four Bonds

This is a general method which is able to give good yields for substituted imidazoles. It is essentially an adaptation of the Debus method called the Debus-Radziszewski imidazole synthesis. The starting materials are substituted glyoxal, aldehyde, amine, and ammonia or an ammonium salt.[8]

Arduengo imidazoles
Formation from other Heterocycles

Imidazole can be synthesized by the photolysis of 1-vinyltetrazole. This reaction will only give substantial yields if the 1-vinyltetrazole is made efficiently from an organotin compound such as 2-tributylstannyltetrazole. The reaction, shown below, produces imidazole when R=R1=R2=Hydrogen.

File:Ringformation.gif

Imidazole can also be formed in a vapor phase reaction. The reaction occurs with formamide, ethylenediamine, and hydrogen over platinum on alumina, and it must take place between 340 and 480 °C. This forms a very pure imidazole product.

Biological significance and applications

Imidazole is incorporated into many important biological molecules. The most pervasive is the amino acid histidine, which has an imidazole side chain. Histidine is present in many proteins and enzymes and plays a vital part in the structure and binding functions of hemoglobin. Histidine can be decarboxylated to histamine, which is also a common biological compound. It is a component of the toxin that causes urticaria, which is another name for allergic hives. The relationship between histidine and histamine are shown below:

Histidine decarboxylase.svg

One of the applications of imidazole is in the purification of His-tagged proteins in immobilised metal affinity chromatography(IMAC). Imidazole is used to elute tagged proteins bound to Ni ions attached to the surface of beads in the chromatography column. An excess of imidazole is passed through the column, which displaces the His-tag from nickel co-ordination, freeing the His-tagged proteins.

Imidazole has become an important part of many pharmaceuticals. Synthetic imidazoles are present in many fungicides and antifungal, antiprotozoal, and antihypertensive medications. Imidazole is part of the theophylline molecule, found in tea leaves and coffee beans, which stimulates the central nervous system. It is present in the anticancer medication mercaptopurine, which combats leukemia by interfering with DNA activities.

Industrial applications

Imidazole has been used extensively as a corrosion inhibitor on certain transition metals, such as copper. Preventing copper corrosion is important, especially in aqueous systems, where the conductivity of the copper decreases due to corrosion.

Many compounds of industrial and technological importance contain imidazole derivatives. The thermostable polybenzimidazole PBI contains imidazole fused to a benzene ring and linked to a benzene, and acts as a fire retardant. Imidazole can also be found in various compounds which are used for photography and electronics.

Salts of imidazole

Simple imidazolium cation

Salts of imidazole where the imidazole ring is in the cation are known as imidazolium salts (for example, imidazolium chloride). These salts are formed from the protonation or substitution at nitrogen of imidazole. These salts have been used as ionic liquids and precursors to stable carbenes. Salts where a deprotonated imidazole is an anion are also possible; these salts are known as imidazolide salts (for example, sodium imidazolide).

Related heterocycles

References

  1. ↑ Alan R. Katritzky; Rees. Comprehensive Heterocyclic Chemistry. Vol. 5, p.469-498, (1984).
  2. ↑ Grimmett, M. Ross. Imidazole and Benzimidazole Synthesis. Academic Press, (1997).
  3. ↑ Brown, E.G. Ring Nitrogen and Key Biomolecules. Kluwer Academic Press, (1998).
  4. ↑ Pozharskii, A.F, et al. Heterocycles in Life and Society. John Wiley & Sons, (1997).
  5. ↑ Heterocyclic Chemistry TL Gilchrist, The Bath press 1985 ISBN 0-582-01421-2
  6. ↑ Heinrich Debus (1858). "Ueber die Einwirkung des Ammoniaks auf Glyoxal". Annalen der Chemie und Pharmacie 107 (2): 199 – 208. doi:10.1002/jlac.18581070209. 
  7. ↑ Microwave-Mediated Synthesis of Lophine: Developing a Mechanism To Explain a Product Crouch, R. David; Howard, Jessica L.; Zile, Jennifer L.; Barker, Kathryn H. J. Chem. Educ. 2006 83 1658
  8. ↑ Template:US patent reference

Template:Antifungals

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