This ring system is present in important biological building blocks, such as histidine and the related hormone histamine. Many drugs contain an imidazole ring, such as certain antifungal drugs , the nitroimidazole series of antibiotics , and the sedative midazolam.
Imidazole and Its Derivatives, Part 1
When fused to a pyrimidine ring, it forms a purine , which is the most widely occurring nitrogen-containing heterocycle in nature. The name "imidazole" was coined in by the German chemist Arthur Rudolf Hantzsch — Imidazole is a planar 5-membered ring. It exists in two equivalent tautomeric forms, because hydrogen can be bound to one or the other nitrogen atom.
Imidazole is a highly polar compound, as evidenced by its electric dipole moment of 3. Some resonance structures of imidazole are shown below:. Imidazole is amphoteric. That is, it can function as both an acid and as a base. As an acid, the p K a of imidazole is The acidic proton is the one bound to nitrogen. Deprotonation gives the imidazole anion, which is symmetrical.
The basic site is the nitrogen with the lone pair and not bound to hydrogen. Protonation gives the imidazolium cation, which is symmetrical. Imidazole was first reported in by the German-British chemist Heinrich Debus , although various imidazole derivatives had been discovered as early as the s. It was shown that glyoxal , formaldehyde , and ammonia condense to form imidazole glyoxaline, as it was originally named.
In one microwave modification, the reactants are benzil , benzaldehyde and ammonia in glacial acetic acid , forming 2,4,5-triphenylimidazole "lophine". Imidazole can be synthesized by numerous methods besides the Debus method. Many of these syntheses can also be applied to substituted imidazoles by varying the functional groups on the reactants. These methods are commonly categorized by the number of reacting components.
The 1,2 and 2,3 bonds can be formed by treating a 1,2-diamino alkane , at high temperatures, with an alcohol , aldehyde , or carboxylic acid. A dehydrogenating catalyst, such as platinum on alumina , is required. The yield of this reaction is moderate, but it seems to be the most effective method of making the 1,4 substitution.
This method proceeds in good yields for substituted imidazoles. An adaptation of the Debus method, it is called the Debus-Radziszewski imidazole synthesis.
The starting materials are substituted glyoxal, aldehyde, amine, and ammonia or an ammonium salt. Imidazole can be synthesized by the photolysis of 1-vinyltetrazole. This reaction will give substantial yields only if the 1-vinyltetrazole is made efficiently from an organotin compound , such as 2-tributylstannyltetrazole. Imidazole can also be formed in a vapor-phase reaction. This forms a very pure imidazole product. The reaction has later been expanded to a two-step synthesis in which the aldimine is generated in situ: the Van Leusen Three-Component Reaction vL-3CR.
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.
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Imidazole-based histidine compounds play a very important role in intracellular buffering. Histamine can cause urticaria hives when it is produced during allergic reaction. The relationship between histidine and histamine is shown below:. 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 nickel ions attached to the surface of beads in the chromatography column. With usual stamps and markings, In fair condition, suitable as a study copy. More information about this seller Contact this seller 4.
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Published by Pergamon Press About this Item: Pergamon Press, Condition: Very Good Condition. Seller Inventory B More information about this seller Contact this seller 6. Published by Wiley-Interscience About this Item: Wiley-Interscience, Condition: Used: Good. More information about this seller Contact this seller 7. Ex-library, With usual stamps and markings, In fair condition, suitable as a study copy.
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More information about this seller Contact this seller 8. Condition: Very Good. No Jacket. Has all standard Library markings, pocket, labels, stamps, wear and soil to covers. Thank you for your purchase from Sunset Books! In stock, Ships from Ohio. Will not fit in Flat Rate Priority Mail envelope. Size: 8vo. The Imidazolecarboxylic and Sulfonic Acids A. Imidazolecarhoxylic Acids B. Imidazolesulfonic Acids VII. Nomenclature B. Imidazolidines VIII. Synthetic Procedures D. The 1-Acylbenzimidazoles and tire Bamberger Reaction E. Imidazoles A. Halogenoimidazoles E. Nitroimidazoles F.
Arylazoimidazoles G. Aminoimidazoles H. Cyano- and Isocyanatoimidazolcs I. Tinidazolcearboxylic Acids J. Imidnzolcsulftnic and Sulfonic Acids K. Imidazole Arscnicals L. Isoimidazolcs M. Imidazolines A. Imidazolidines A. Alkyl- and Arylimidazolidines B. Benzimidazoles A.