Benzocaine

Structure

• Benzocaine Chemical Structure – C9H11NO2

Mode of action

• The neuronal membrane is reversibly stabilised by benzocaine, which lowers its permeability to sodium ions. The initiation and conduction of nerve impulses are prevented by inhibiting neuronal membrane depolarization.

Structure-Activity Relationship (SAR) of Benzocaine

• Benzocaine is a local anesthetic commonly used for pain relief in minor surgical procedures.

Its SAR characteristics are:

1. Ester Linkage:

• Benzocaine is an ester local anesthetic. The ester linkage in its structure is crucial for its local anesthetic activity.

• Esters are generally associated with a lower incidence of allergic reactions compared to amide local anesthetics.

2. Aromatic Ring:

• The presence of an aromatic ring (benzene) is essential for local anesthetic activity.

• This part of the molecule is lipophilic, which helps in penetrating membranes to reach the site of action.

3. Para-Aminobenzoic Acid Derivative:

• Benzocaine is a derivative of para-aminobenzoic acid (PABA).

• The PABA structure is associated with local anesthetic properties.

4. Ethanamine Group:

• The ethanamine (ethylamine) side chain attached to the aromatic ring is important for the activity.

• The length and nature of this side chain can influence potency and duration of action.

Here is the mind map illustrating the Structure-Activity Relationship (SAR) of Benzocaine:

Synthesis of Benzocaine

• The synthesis of Benzocaine is a straightforward esterification reaction and can be represented by the following chemical equation:

• Esterification Reaction: 

• C7​H7​NO2​ + C2​H5​OH → C9​H1​1NO2 ​+ H2​O

  • In this reaction, para-aminobenzoic acid (C7H7NO2) is esterified with ethanol (C2H5OH) to form Benzocaine (C9H11NO2) along with the production of water (H2O).

  • This reaction typically involves the use of an acid catalyst like sulfuric acid or hydrochloric acid to facilitate the esterification process.

  • The synthesis of Benzocaine is a classic example of Fischer esterification, a fundamental reaction in organic chemistry.

Uses

• It is used to reduce the pain of piles, rectal irritation, virginal irritation and tooth pain.