In modern organic synthesis, few reagents are as versatile and valuable as 1,1′-Carbonyldiimidazole (CDI). Known by its CAS number 530-62-1, CDI is a widely used coupling agent that simplifies the formation of amides, esters, peptides, and other key chemical bonds. Its efficiency, mild reaction conditions, and broad compatibility make it indispensable in both academic research and industrial applications.
This article provides a complete guide to 1,1′-Carbonyldiimidazole—covering its structure, properties, synthesis, applications, and safe handling practices.
1,1′-Carbonyldiimidazole is an organic reagent used to activate carboxylic acids for nucleophilic substitution. It serves as a milder and safer alternative to traditional coupling reagents such as phosgene, carbodiimides (DCC, EDC), and acid chlorides.
Chemical Name: 1,1′-Carbonyldiimidazole
CAS Number: 530-62-1
Molecular Formula: C₇H₆N₄O
Molecular Weight: 162.15 g/mol
Appearance: White to off-white crystalline solid
Formula Representation: (C₃H₃N₂)₂CO
CDI was first introduced in the 1950s as a safer phosgene substitute, and it has since become a go-to reagent for amide and peptide bond formation.
The molecule contains two imidazole rings connected through a central carbonyl (CO) group. This configuration allows CDI to act as a carbonyl transfer reagent, forming reactive intermediates that can easily react with amines, alcohols, or acids.
Property |
Value |
|---|---|
Molecular Formula |
C₇H₆N₄O |
Molecular Weight |
162.15 g/mol |
Melting Point |
117–122 °C |
Solubility |
Soluble in THF, DCM, DMF, acetonitrile; reacts slowly with water |
Stability |
Stable under dry, inert conditions; moisture-sensitive |
Odor |
Mild to none |
CDI’s reactivity stems from the electrophilic carbonyl carbon, which readily undergoes nucleophilic attack—making it ideal for bond-forming reactions.
When CDI reacts with a carboxylic acid, it forms an acyl imidazole intermediate—a highly reactive species. This intermediate can then be attacked by an amine or alcohol to form amides or esters, respectively.
Reaction sequence:
Carboxylic acid + CDI → Acyl imidazole
Acyl imidazole + Nucleophile (amine/alcohol) → Amide or ester + CO₂ + imidazole
This mechanism eliminates the need for strong acids or bases, reducing side reactions and improving yields.
Commercial CDI is typically synthesized through phosgene-free methods to ensure safety and environmental compliance.
General Synthesis Route:
Starting materials: Imidazole and phosgene or its safer equivalent (e.g., triphosgene).
Reaction:
2C3H4N2+COCl2→(C3H3N2)2CO+2HClThe product is purified via recrystallization or vacuum distillation to yield high-purity CDI.
In modern manufacturing, green chemistry approaches are increasingly being adopted, replacing phosgene with carbonyl diimidazole intermediates derived from CO₂ or urea.
CDI is widely used for amide coupling in peptide synthesis and pharmaceutical chemistry. Its ability to activate carboxylic acids makes it essential for creating biologically active molecules.
CDI converts alcohols and acids into esters, carbamates, and carbonates under mild conditions, often yielding cleaner products compared to acid chloride methods.
In biochemistry, CDI facilitates the preparation of nucleoside derivatives and protected peptides, avoiding the harsh conditions that can degrade sensitive molecules.
CDI is used to functionalize polymers, introducing reactive sites for further modification. It also plays a role in crosslinking agents and surface coatings where controlled reactivity is required.
Owing to its phosgene-free reactivity and low toxicity, CDI aligns well with green chemistry principles, reducing hazardous waste generation and simplifying purification.
Mild Reaction Conditions: Works efficiently at room temperature.
High Yields: Produces minimal by-products.
Phosgene-Free: Safer than traditional acylating agents.
Versatile Solvent Compatibility: Works in DMF, THF, DCM, and acetonitrile.
Environmentally Friendly: Generates imidazole as a benign by-product.
Although CDI is safer than many other reagents, it should still be handled with care:
Avoid contact with water: CDI reacts with moisture, releasing CO₂ and imidazole.
Protective equipment: Use gloves, goggles, and work in a fume hood.
Storage: Keep in tightly sealed containers under inert gas (nitrogen or argon).
Disposal: Dispose of in accordance with local chemical waste regulations.
Hazards: May cause skin or respiratory irritation. Always refer to the manufacturer’s Safety Data Sheet (SDS) before handling.
1,1′-Carbonyldiimidazole is a high-demand reagent in the pharmaceutical, biochemical, and fine chemical industries.
Key applications include:
Drug development (e.g., peptide therapeutics)
Bioconjugation reactions
Specialty polymers and coatings
Manufacturers often offer CDI with purity ≥99%, ensuring consistent performance in critical synthesis processes.
With the global shift toward sustainable chemistry, CDI’s role is expanding. Researchers are developing phosgene-free and CO₂-based synthesis routes to make CDI production even more eco-friendly. Its continued use in bioconjugation, peptide engineering, and advanced materials underscores its growing relevance in 2025 and beyond.
1,1′-Carbonyldiimidazole (CAS No. 530-62-1) stands out as a safe, efficient, and versatile reagent in organic and biochemical synthesis. From laboratory-scale peptide formation to large-scale pharmaceutical manufacturing, CDI enables countless reactions under mild, environmentally responsible conditions.
Its blend of reactivity, safety, and sustainability ensures that CDI will remain a cornerstone reagent in synthetic chemistry for years to come.
