DCC

Definition

DCC, or dicyclohexylcarbodiimide, is a coupling agent commonly used in organic chemistry for the activation and coupling of carboxylic acids and alcohols, as well as in peptide synthesis and the preparation of acid anhydrides. It plays a crucial role in various reactions by facilitating the formation of new carbon-carbon or carbon-heteroatom bonds.

5 Must Know Facts For Your Next Test

1. DCC is commonly used in the esterification of alcohols with carboxylic acids, forming new carbon-oxygen bonds.
2. In the synthesis of acid anhydrides, DCC promotes the dehydration of two carboxylic acid groups, forming a new carbon-oxygen bond.
3. DCC is a key reagent in the Merrifield solid-phase method of automated peptide synthesis, enabling the formation of amide bonds between amino acids.
4. The by-product of DCC coupling reactions is dicyclohexylurea (DCU), which can be removed by filtration or recrystallization.
5. DCC is often used in combination with a nucleophilic catalyst, such as 4-dimethylaminopyridine (DMAP), to enhance the efficiency of the coupling reaction.

Review Questions

• Explain how DCC is used in the esterification of alcohols with carboxylic acids.
  • In the esterification of alcohols with carboxylic acids, DCC acts as a coupling agent, activating the carboxylic acid by forming an O-acylisourea intermediate. This intermediate then reacts with the alcohol, forming the desired ester product and releasing dicyclohexylurea (DCU) as a byproduct. The use of DCC facilitates the formation of new carbon-oxygen bonds, allowing for the synthesis of various esters.
• Describe the role of DCC in the synthesis of acid anhydrides.
  • DCC is employed in the synthesis of acid anhydrides, where it promotes the dehydration of two carboxylic acid groups. The carboxylic acids first react with DCC to form an O-acylisourea intermediate, which then undergoes intramolecular attack by the other carboxylic acid group, resulting in the formation of the acid anhydride. The DCC coupling enables the creation of new carbon-oxygen bonds, leading to the formation of the desired acid anhydride product.
• Discuss the importance of DCC in the Merrifield solid-phase method of automated peptide synthesis.
  • In the Merrifield solid-phase method of automated peptide synthesis, DCC is a crucial reagent for the formation of amide bonds between amino acids. DCC activates the carboxylic acid group of the incoming amino acid, allowing it to react with the free amino group of the growing peptide chain, which is attached to a solid support. This DCC-mediated coupling facilitates the stepwise assembly of the peptide, enabling the automated synthesis of complex peptide structures.

Related terms

Carbodiimide: A functional group containing a carbon-nitrogen double bond flanked by two nitrogen atoms, often used as a coupling agent in organic synthesis.

Acid Anhydride: A compound containing two acyl groups bonded to a single oxygen atom, formed by the dehydration of two carboxylic acid groups.

Peptide Synthesis: The process of assembling amino acids into peptide chains, often facilitated by coupling agents like DCC.