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Home> Encyclopedia >Heterocyclic compounds>Pharmaceutical Intermediates>Organic Intermediate
Imidazole structure
Imidazole structure


Iupac Name:1H-imidazole
CAS No.: 288-32-4
Molecular Weight:68.079
Modify Date.: 2022-11-06 06:47
Introduction: Imidazole is a planar 5-membered ring. Imidazole is a highly polar compound. Imidazole has been used extensively as a corrosion inhibitor.Imidazole is incorporated into many important biological molecules. The most pervasive is the amino acid histidine, which has an imidazole side-chain. Imidazole is useful as a buffer in the pH range of 6.2-7.8 One of the applications of imidazole is in the purification of His-tagged proteins in immobilised metal affinity chromatography(IMAC). Imidazole View more+
1. Names and Identifiers
1.1 Name
1.2 Synonyms

1,3-DIAZA-2,4-CYCLOPENTADIENE 1,3-Diaza-2,4-cyclopentadiene,Glyoxaline 1,3-DIAZOLE 1,3-imidazole 1H-IMIDAZOLE 1-imidazole Clotrimazole Impurity 4 EINECS 206-019-2 glioksal GLYOXALIN IMD Imidazoie Imidazol IMIDAZOLE BUFFER IMINAZOLE Imutex LABOTEST-BB LTBB001344 LMIDAZOLE MFCD00005183 Miazole

1.3 CAS No.
1.4 CID
1.6 Molecular Formula
C3H4N2 (isomer)
1.7 Inchi
1.8 InChkey
1.9 Canonical Smiles
1.10 Isomers Smiles
2. Properties
2.1 Density
2.1 Melting point
2.1 Boiling point
90.5 °C
2.1 Refractive index
2.1 Flash Point
145°C c.c.
2.2 Precise Quality
2.2 PSA
2.2 logP
2.2 Solubility
633 g/L (20 oC)
2.3 Viscosity
Viscosity is a measure of a fluid's resistance to flow. It describes the internal friction of a moving fluid.
2.4 VaporDensity
Relative vapor density (air = 1): 2.35
2.5 Appearance
white to yellow crystals or powder,with an amine odour
2.6 Atmospheric OH Rate Constant
3.59e-11 cm3/molecule*sec
2.7 AutoIgnition
2.8 Storage
Hygroscopic. Store under Nitrogen. Ambient temperatures.
2.9 Autoignition Temperature
480 deg C
2.10 Chemical Properties
Imidazole is a heterocyclic compound with a five-membered planar ring. It is amphoteric and highly polar.The pharmacophore of imidazole exists in bioactive compounds including amino acids, plant growth regulators and therapeutic agents.
2.11 Color/Form
2.12 Decomposition
Hazardous decomposition products formed under fire conditions - Carbon oxides, nitrogen oxides (NOx), hydrogen cyanide (hydrocyanic acid).
2.13 Odor
Amine-like odor
2.14 PH
pH 10.5 for 38 g/L at 20 deg C
2.15 Physical
2.16 pKa
6.953(at 25℃)
2.17 Water Solubility
633 g/L (20 oC)
2.18 Stability
Stable. Incompatible with acids, strong oxidizing agents. Protect from moisture.
2.19 StorageTemp
3. Use and Manufacturing
3.1 Definition
ChEBI: An imidazole tautomer which has the migrating hydrogen at position 1.
3.2 GHS Classification
Signal: Danger
GHS Hazard Statements
H302: Harmful if swallowed [Warning Acute toxicity, oral]
H314: Causes severe skin burns and eye damage [Danger Skin corrosion/irritation]
H360D: May damage the unborn child [Danger Reproductive toxicity]

Precautionary Statement Codes
P201, P202, P260, P264, P270, P280, P281, P301+P312, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P308+P313, P310, P321, P330, P363, P405, and P501
3.3 Purification Methods
Crystallise imidazole from *benzene, CCl4, CH2Cl2, EtOH, pet ether, acetone/pet ether and distilled de-ionized water. Dry it at 40o under vacuum over P2O5. Distil it at low pressure. It is also purified by sublimation or by zone melting. [Snyder et al. Org Synth Coll Vol III 471 1955, Bredereck et al. Chem Ber 97 827 1964, Caswell & Spiro J Am Chem Soc 108 6470 1986.] 15N-imidazole crystallises from *benzene [Scholes et al. J Am Chem Soc 108 1660 1986]. [Beilstein 23 II 34, 23 III/IV 564, 23/4 V 191.] Imidazole Preparation Products And Raw materials Raw materials
3.4 Usage
Excellent for buffers in the range of pH 6.2-7.8
4. Safety and Handling
4.1 Symbol
4.1 Hazard Codes
4.1 Signal Word
4.1 Risk Statements
4.1 Safety Statements
4.1 Packing Group
4.1 Fire Hazard
Noncombustible solid.
4.2 Hazard Class
4.2 Hazard Declaration
H302; H314; H360D
UN 1759
4.2 Caution Statement
P201-P260-P280-P303 + P361 + P353-P305 + P351 + P338-P308 + P313
4.2 WGK Germany
4.2 Safety

Hazard Codes:?CorrosiveC,IrritantXi
Risk Statements: 36/38-63-34-22-20/21/22?
R20/21/22:Harmful by inhalation, in contact with skin and if swallowed.?
R22:Harmful if swallowed.?
R34:Causes burns.?
R36/38:Irritating to eyes and skin.?
R63:Possible risk of harm to the unborn child.
Safety Statements: 26-36/37/39-45-22-36-27
S22:Do not breathe dust.?
S26: In case of contact with eyes, rinse immediately with plenty of water and seek medical advice.?
S27:Take off immediately all contaminated clothing.?
S36:Wear suitable protective clothing.?
S36/37/39:Wear suitable protective clothing, gloves and eye/face protection.?
S45:In case of accident or if you feel unwell, seek medical advice immediately (show the label whenever possible.)

4.3 Specification

?Imidazole , its cas register number is 288-32-4. It also can be called 1,3-Diazole ; 1H-Imidazole ; and Glyoxaline . It is hazardous, so the first aid measures and others should be known. Such as: When on the skin: first, should flush skin with plenty of water immediately for at least 15 minutes while removing contaminated clothing. Secondly, get medical aid. Or in the eyes: Flush eyes with plenty of water for at least 15 minutes, occasionally lifting the upper and lower eyelids. Then get medical aid soon. While, it's inhaled: Remove from exposure and move to fresh air immediately. Give artificial respiration while not breathing. When breathing is difficult, give oxygen. And as soon as to get medical aid. Then you have the ingesting of the product:?Do not induce vomiting. If victim is conscious and alert, give 2-4 cupfuls of milk or water. Get medical aid immediately. Notes to physician: Treat supportively and symptomatically.
In addition, Imidazole (CAS NO.288-32-4) could be stable under normal temperatures and pressures. It is not compatible with strong oxidizing agents, acids, acid chlorides, and you must not take it with incompatible materials, dust generation. And also prevent it to broken down into hazardous decomposition products:?hydrogen cyanide, nitrogen oxides, carbon monoxide, carbon dioxide, ammonia.

4.4 Toxicity

Organism Test Type Route Reported Dose (Normalized Dose) Effect Source
cat LDLo subcutaneous 125mg/kg (125mg/kg) BEHAVIORAL: FOOD INTAKE (ANIMAL)
Archiv fuer Experimentelle Pathologie und Pharmakologie. Vol. 84, Pg. 155, 1918.
dog LD50 subcutaneous 28mg/kg (28mg/kg) ? Przeglad Epidemiologiczny. Vol. 67, Pg. 295, 1993.
guinea pig LD50 oral 760mg/kg (760mg/kg) ? Przeglad Epidemiologiczny. Vol. 67, Pg. 295, 1993.
mammal (species unspecified) LD50 oral 1gm/kg (1000mg/kg) ? Pesticide Chemicals Official Compendium, Association of the American Pesticide Control Officials, Inc., 1966. Vol. -, Pg. 608, 1966.
mouse LD50 intraperitoneal 300mg/kg (300mg/kg) ? National Technical Information Service. Vol. AD277-689,
mouse LD50 intravenous 475mg/kg (475mg/kg) BEHAVIORAL: CONVULSIONS OR EFFECT ON SEIZURE THRESHOLD Arzneimittel-Forschung. Drug Research. Vol. 33, Pg. 716, 1983.
mouse LD50 oral 880mg/kg (880mg/kg) ? German Offenlegungsschrift Patent Document. Vol. #3046325,
mouse LD50 subcutaneous 817mg/kg (817mg/kg) ? Journal of Pharmacology and Experimental Therapeutics. Vol. 119, Pg. 444, 1957.
rat LD50 oral 220mg/kg (220mg/kg) ? Przeglad Epidemiologiczny. Vol. 67, Pg. 295, 1993.
rat LD50 subcutaneous 626mg/kg (626mg/kg) ? Journal of Pharmacology and Experimental Therapeutics. Vol. 119, Pg. 444, 1957.


2.Hazard identification

2.1 Classification of the substance or mixture

Acute toxicity - Oral, Category 4

Skin corrosion, Category 1C

Serious eye damage, Category 1

Reproductive toxicity, Category 1B

2.2 GHS label elements, including precautionary statements

Signal word


Hazard statement(s)

H302 Harmful if swallowed

H314 Causes severe skin burns and eye damage

H360 May damage fertility or the unborn child

Precautionary statement(s)

P264 Wash ... thoroughly after handling.

P270 Do not eat, drink or smoke when using this product.

P260 Do not breathe dust/fume/gas/mist/vapours/spray.

P280 Wear protective gloves/protective clothing/eye protection/face protection.

P201 Obtain special instructions before use.

P202 Do not handle until all safety precautions have been read and understood.


P301+P312 IF SWALLOWED: Call a POISON CENTER/doctor/\u2026if you feel unwell.

P330 Rinse mouth.

P301+P330+P331 IF SWALLOWED: Rinse mouth. Do NOT induce vomiting.

P303+P361+P353 IF ON SKIN (or hair): Take off immediately all contaminated clothing. Rinse skin with water [or shower].

P363 Wash contaminated clothing before reuse.

P304+P340 IF INHALED: Remove person to fresh air and keep comfortable for breathing.

P310 Immediately call a POISON CENTER/doctor/\u2026

P321 Specific treatment (see ... on this label).

P305+P351+P338 IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing.

P308+P313 IF exposed or concerned: Get medical advice/ attention.


P405 Store locked up.


P501 Dispose of contents/container to ...

2.3 Other hazards which do not result in classification


9. Other Information
9.0 Usage
Imidazole is used as a buffer in the range of pH 6.2-7.8. It is also an histamine antagonist. It acts as a chelator and forms complexes with various divalent cations. It is used as a corrosion inhibitor on certain transition metals such as copper. Its derivatives, like polybenzimidazole (PBI), act as fire retardants. It finds application in photography and electronics. Imidazole salts are used as ionic liquids and precursors to stable carbenes. Imidazole derivatives like ketoconazole, miconazole and clotrimazole are involved in the treatment of various systemic fungal infections. It is a part of the theophylline molecule, present in tea leaves and coffee beans, which stimulates the central nervous system.
9.1 Usage
Imidazole is used as a chelator for the binding of various divalent cations, and is also used to elute tagged proteins bound to Ni ions attached to the surface of beads in the chromatography column.
9.2 Usage
Suitable for molecular biology applications
10. Computational chemical data
  • Molecular Weight: 68.079g/mol
  • Molecular Formula: C3H4N2
  • Compound Is Canonicalized: True
  • XLogP3-AA: null
  • Exact Mass: 68.037448136
  • Monoisotopic Mass: 68.037448136
  • Complexity: 28.1
  • Rotatable Bond Count: 0
  • Hydrogen Bond Donor Count: 1
  • Hydrogen Bond Acceptor Count: 1
  • Topological Polar Surface Area: 28.7
  • Heavy Atom Count: 5
  • Defined Atom Stereocenter Count: 0
  • Undefined Atom Stereocenter Count: 0
  • Defined Bond Stereocenter Count: 0
  • Undefined Bond Stereocenter Count: 0
  • Isotope Atom Count: 0
  • Covalently-Bonded Unit Count: 1
11. Question & Answer
  • 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, that stimulates the central nerv...
  • Why does imidazole have pKa = 7.1 according to the Henderson-Hasselbalch equation? It doesn’t. Because … The Henderson-Hasselbalch equation doesn’t have anything to say about the pKa of an acid. The reported pKa of imidazole is about 14. You may be referring to the pKa of imidazolium ion, which ...
  • Why imidazole is more basic than pyridine despite the fact that the former have more electronegativity in the ring than the latter? I have recently come across a statement in my organic chemistry manual that imidazole is more basic than pyridine. And the reason was given that since electron density...
  • I presume the role is to soak up the HI that is formed. Why not other bases such as triethylamine? Is this because the quaternary ammonium salt could be formed? Would other non-nucleophilic or inorganic bases work (for instance, k2co3 or DBU)?
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