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Imidazole is a five -membered aromatic heterocyclic compound containing molecular structure between the two nitrogen atoms of the imidazole ring 1 - unshared electron pair involved in cyclic conjugated nitrogen atom , the electron density of the nitrogen atom is reduced , so that the nitrogen a hydrogen atom in the form of hydrogen ions easily leaving . Thus imidazole with a weak acid, can form salts with alkali .
Imidazole ring 3 - position nitrogen atom unshared electron pair is not involved in conjugation , and occupy sp2 hybrid orbitals that can accept a proton to form salts with strong acids . Imidazole alkaline slightly stronger than the pyrazole and pyridine.
The presence of tautomerism imidazole ring. 1 - hydrogen on the nitrogen atom can be transferred to a 3 - position to the nitrogen atom , so that , respectively, in 4 - position and 5 - positions with the same imidazole substituents are tautomers .
Imidazole acid stability, oxidation resistance. Imidazole derivatives are widely found in nature . Such as histamine , histidine , benzimidazole and the like.
Acyl imidazole compound has some interesting reagent . Such as 1 - acetyl imidazole acylating agent is a stable . With pyrrole to produce 1 - acetyl pyrrole. In addition usually 1 - acetylimidazole and reducing the use of Grignard reagents to generate ketones and aldehydes. N, N'- carbonyldiimidazole is reacted with a carboxyl group , an acyl imidazole produce useful reagents . The relationship between the imidazole and natural compounds extremely close . E.g., the condensation of the pyrimidine ring , a purine derivative obtained , in addition as a 6 - diaminopurine , guanine bases of nucleic acids , but also in the presence of uric acid in the organism , caffeine and theophylline . Imidazole catalyst, such as accelerated enzymatic hydrolysis , are being studied. Cause allergic skin , similar to its toxicity and diamine . Rat oral LD501880mg/kg.
Imidazole derivatives exist in nature only , without the free imidazole. By precipitation from benzene monoclinic prismatic colorless crystals. Ammonia odor. Relative molecular mass of 68.08 . The relative density of 1.0303 (101/4 ℃). Melting point 89 ~ 91 ℃, boiling point 257 ℃, 165 ℃ ~ 168 ℃ (2.67 × 103Pa), 138.2 ℃ (1.60 × 103Pa). Fp 145 ℃. Refractive index of 1.4801 (101 ℃). Viscosity 2.696mPa · s (100 ℃). Slightly soluble in benzene , petroleum ether , soluble in ether , acetone , chloroform , pyridine, soluble in water ( room temperature 70 ) , ethanol. Significant alkaline. Because the formation of a hydrogen bond between the -NH- bond and the -N = bond of 3 , so the higher the boiling point , when one hydrogen is substituted , it can not form hydrogen bonds , the boiling point drops. The thermal stability, hardly below 250 ℃ decomposition ( decomposition temperature 590 ℃). The reducing and oxidizing agents are also very stable, but the stability of the inorganic acid salt is formed . With some aromatic nature , in the catalyst can halogenation, nitration , sulfonation and hydroxymethyl . And may be in the 2 and coupling the diazonium salt . Further, since the = NH group ( 1 ) connected to two double bonds , but also some "acid " may be substituted with the metal to form a salt . Three nitrogen atoms on the coordination role of metal ions can form chelates. Although it is difficult to be restored , but can be added together to generate a proton resonance of cationic structure and to form a stable form. Easily change between tautomers of the imidazole ring , so four isomers 5 and difficult to distinguish .
The above information is edited by the Chemicalbook of Andy .
The main purpose
Imidazole epoxy resin curing agent can be used , products can improve the bending , stretching, compression and other mechanical properties, improved electrical insulating properties and improve resistance to chemicals and chemical properties, are widely used in computers, appliances ;
As copper and rust inhibitor for printed circuit boards and integrated circuits ;
Used as pharmaceutical raw materials for the manufacture of antifungal , anti-mold agents , hypoglycemia treatment drugs, artificial plasma , trichomoniasis treatment drug treatment of bronchial asthma drugs, anti- rash , etc. ;
Used as a pesticide raw materials for the preparation of boric acid synergist , preparation of insecticides and fungicides ;
Additionally , urea-formaldehyde resins are also used as an imidazole curing agent, photographic drugs , adhesives , paints, rubber vulcanizing agent, an antistatic agent of raw materials ; organic synthesis intermediates.
Glyoxal as raw material, formaldehyde and ammonium sulfate ( or ammonia ) reaction at 85 ~ 90 ℃, imidazole sulfates obtained first , and then neutralized with calcium hydroxide , available imidazole crude product was filtered, washed with water combined filtrate and washings were concentrated by evaporation under reduced pressure , crystallization, can be obtained. If the direct use of ammonia sulfate no processing steps, prepared in one step . Either with ammonia or ammonium sulfate , this method is low yield , approximately 45% .
With o-phenylenediamine and formic acid as raw materials, cyclization, benzimidazole, re-oxidation in sulfuric acid solution to produce two carboxyl imidazole , and finally in the role of copper oxide in 100 ~ 150 ℃ under decarboxylation can be obtained crude in benzene solution and then recrystallized to obtain the imidazole product.
With D- tartaric acid as raw materials in sulfuric acid , and nitrated with nitric acid , to obtain 2,3 - dinitro- tartaric acid and then reacted with ammonia in formaldehyde , a carboxyl group can be prepared by two imidazole, and then decarboxylation , can be obtained.