1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide


1-Ethyl-3-carbodiimide is a water-soluble carbodiimide usually handled as the hydrochloride, which is a white solid.
It is typically employed in the 4.0-6.0 pH range. It is generally used as a carboxyl activating agent for the coupling of primary amines to yield amide bonds. While other carbodiimides like dicyclohexylcarbodiimide or diisopropylcarbodiimide are also employed for this purpose, EDC has the advantage that the urea byproduct formed can be washed away from the amide product using dilute acid. Additionally, EDC can also be used to activate phosphate groups in order to form phosphomonoesters and phosphodiesters. Common uses for this carbodiimide include peptide synthesis, protein crosslinking to nucleic acids, but also in the preparation of immunoconjugates. EDC is often used in combination with N-hydroxysuccinimide for the immobilisation of large biomolecules. Recent work has also used EDC to assess the structure state of uracil nucleobases in RNA.

Preparation

EDC is commercially available. It may be prepared by coupling ethyl isocyanate to N,''N''-dimethylpropane-1,3-diamine to give a urea, followed by a dehydration reaction mediated by TsCl and TEA:

Mechanism

EDC couples primary amines, and other nucleophiles, to carboxylic acids by creating an activated ester leaving group. First, the carbonyl of the acid attacks the carbodiimide of EDC, and there is a subsequent proton transfer. The primary amine then attacks the carbonyl carbon of the acid which forms a tetrahedral intermediate before collapsing and discharging the urea byproduct. The desired amide is obtained.

Safety

In vivo dermal sensitization studies according to OECD 429 confirmed EDC is a strong skin sensitizer, showing a response at <0.01 wt% in the Local Lymph Node Assay placing it in Globally Harmonized System of Classification and Labelling of Chemicals Dermal Sensitization Category 1A. Thermal hazard analysis by differential scanning calorimetry shows EDC poses minimal explosion risks.