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What Is Imidazole?
Imidazole (CAS 288-32-4) is a heterocyclic base & buffer with the molecular formula C3H4N2 and molecular weight 68.08 g/mol. [001]
Physical and Chemical Properties
| Property | Value | Source |
|---|---|---|
| CAS Number | 288-32-4 | |
| Molecular Formula | C3H4N2 | |
| Molecular Weight | 68.08 g/mol |
How It Works
Imidazole functions as a Brønsted base, accepting a proton from acidic substrates (alcohols, amines, carboxylic acids, terminal alkynes, C-H acids) to generate the corresponding nucleophilic conjugate base. With a pKa of the conjugate acid (Et3NH+) of ~10.75, triethylamine is basic enough to deprotonate most O-H and N-H acids but not acidic enough to generate enolates from simple ketones (pKa ~19-20). The steric bulk of the three ethyl groups suppresses N-alkylation side reactions while providing sufficient basicity for acid scavenging. In acylation reactions, TEA neutralizes the HCl/HBr generated, driving the equilibrium toward product while preventing acid-catalyzed side reactions. In Sonogashira coupling, TEA serves dual roles — deprotonating the terminal alkyne to generate the copper acetylide intermediate AND neutralizing the HX byproduct from oxidative addition. In HPLC, TEA dynamically masks residual silanol groups on the C18 stationary phase via reversible proton transfer, reducing peak tailing for basic analytes without permanently modifying the column.
Key Applications
- Silylation Catalyst & Acid Scavenger: Imidazole is the standard catalyst/base for TBSCl, TIPSCl, and TBDPSCl protection of primary and secondary alcohols in DMF. Imidazole captures HCl as imidazolium chloride — the insoluble salt drives silylation to completion. Typical: 1.5 eq TBSCl + 2.5 eq imidazole in DMF, rt, 2-12 h. Primary alcohols react selectively over secondary at 0C. [004]
- Pharmaceutical Building Block (Azole Antifungals): Imidazole is the core of the azole antifungal drug class: ketoconazole, miconazole, clotrimazole, econazole. The imidazole N3 coordinates the heme iron of fungal CYP51, inhibiting ergosterol biosynthesis. Topical imidazoles are among the most-prescribed dermatological antifungals worldwide. [004]
- Carbonyldiimidazole (CDI) Precursor: Imidazole + phosgene (or triphosgene) -> CDI. CDI is the standard reagent for amide bond formation and carbonyl transfer in pharmaceutical synthesis. Imidazole is also the leaving group in CDI-mediated couplings, making it both the precursor and the byproduct of these reactions. [005]
- Biochemical Buffer & Metal Chelator: Imidazole (pKa 6.95) is an excellent biochemical buffer near physiological pH. 20-500 mM imidazole is universally used for eluting His-tagged proteins from Ni-NTA affinity columns in IMAC purification. Imidazole competes with the polyhistidine tag for Ni2+ coordination, enabling selective protein release. [005]
Handling and Storage
- GHS Hazard: H225: Highly flammable liquid and vapor, H302: Harmful if swallowed, H311+H331: Toxic in contact with skin or if inhaled, H314: Causes severe skin burns and eye damage, H335: May cause respiratory irritation
- Signal Word: Danger
- Pictograms: GHS02, GHS05, GHS06, GHS07
- Storage: Store at 2-8 °C or as recommended on the Certificate of Analysis. Keep container tightly closed in a cool, dry, well-ventilated area. Protect from moisture and incompatible materials (strong oxidizing agents, acids, bases). For long-term storage, keep under inert gas (N2 or Ar) if the compound is hygroscopic or oxygen-sensitive. Always consult the supplier's Safety Data Sheet (SDS) for lot-specific storage recommendations and shelf-life information.
- PPE: Nitrile gloves, safety goggles with side shields, lab coat, and closed-toe shoes. Work in a well-ventilated fume hood. Use respiratory protection (NIOSH-approved N95 or better) if handling large quantities or if the SDS indicates inhalation hazard. [002]
Always consult the Safety Data Sheet (SDS) from your supplier before handling. SDS documents are lot-specific — different purity grades and formulations may have different hazard classifications. For bulk handling, consult your institution's chemical hygiene plan and perform a job hazard analysis (JHA) before beginning work. Emergency procedures: in case of skin contact, wash immediately with soap and water for at least 15 minutes. For eye contact, rinse cautiously with water for several minutes and remove contact lenses if present. If inhaled, move to fresh air. Seek medical attention if symptoms persist.
Regulatory & Compliance
Chemical Inventories: Imidazole (CAS 288-32-4) is listed on major chemical inventories including the TSCA (Toxic Substances Control Act) inventory in the United States, EINECS (European Inventory of Existing Commercial Chemical Substances) in the EU, and similar inventories in Japan (ENCS), China (IECSC), Korea (KECL), and Australia (AICS). The specific regulatory status of CAS 288-32-4 should be verified with the appropriate national authority before importing into any jurisdiction, as inventory listing status can change with regulatory updates and new chemical assessments.
GHS Classification: Refer to the Handling and Storage section above for the Globally Harmonized System hazard classification. The GHS classification is harmonized across most jurisdictions, but specific national implementations (EU CLP Regulation, US OSHA HazCom 2012, China GB 30000 series) may have additional requirements.
Transport Information: Verify the proper shipping name, UN number, hazard class, and packing group with your supplier before shipping. Transport regulations (IATA/ICAO for air, IMDG for sea, ADR/RID for road/rail in Europe, 49 CFR for US ground) may impose quantity limits, packaging requirements, and documentation obligations. Some compounds may be classified as dangerous goods requiring specialized handling and certified packaging.
Export Control: Imidazole is a standard research and industrial chemical. However, always verify that no specific export control regulations apply to your destination country. Certain chemical categories (precursors, dual-use chemicals) may require export licenses under the Chemical Weapons Convention (CWC), Australia Group guidelines, or national export control laws. Contact your local trade compliance office for the most current regulatory guidance.
[004] [002]
Frequently Asked Questions
What is the CAS number of Imidazole?
The CAS Registry Number is 288-32-4. Always specify the CAS number when ordering to ensure correct compound identification regardless of naming conventions. [001]
What is the molecular weight of Imidazole?
The molecular weight is 68.08 g/mol based on the molecular formula C3H4N2. Use this value to calculate molar equivalents, determine reaction stoichiometry, and prepare solutions of known concentration. [001]
What is Imidazole used for?
Imidazole is used for: Silylation Catalyst & Acid Scavenger (Imidazole is the standard catalyst/base for TBSCl, TIPSCl, and TBDPSCl protectio...); Pharmaceutical Building Block (Azole Antifungals) (Imidazole is the core of the azole antifungal drug class: ketoconazole, miconazo...); Carbonyldiimidazole (CDI) Precursor (Imidazole + phosgene (or triphosgene) -> CDI. CDI is the standard reagent for am...). For detailed protocols, see the Key Applications section above. [002]
How should Imidazole be stored?
Store at 2-8 °C or as recommended on the Certificate of Analysis. Keep container tightly closed in a cool, dry, well-ventilated area. Protect from moisture and incompatible materials (strong oxidizing agents, acids, bases). For long-term storage, keep under inert gas (N2 or Ar) if the compound is hygroscopic or oxygen-sensitive. Always consult the supplier's Safety Data Sheet (SDS) for lot-specific storage recommendations and shelf-life information.. Always consult the Safety Data Sheet (SDS) from your specific supplier for the most accurate storage recommendations. [002]
Where can I buy Imidazole?
Imidazole (CAS 288-32-4) may be sourced through CoreyChem. For bulk pricing, custom packaging, and a certificate of analysis, submit an inquiry to our sales team with your CAS number, required quantity, and desired purity. [002]
Where to Buy
Imidazole (CAS 288-32-4) is not currently listed in the CoreyChem catalog. Contact [email protected] for sourcing assistance. [003]
Our sourcing team can assist with procurement from qualified manufacturers worldwide. Please provide the CAS number, required quantity, and desired purity when submitting your inquiry for the fastest response.
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References & Sources
https://www.tcichemicals.com/US/en/search/?text=288-32-4
https://pubchem.ncbi.nlm.nih.gov/compound/288-32-4
https://pubchem.ncbi.nlm.nih.gov/compound/288-32-4#section=Use-and-Manufacturing
