Preparation of Procaine and Procaine Monohydrochloride from Amino Benzoic Acid:

1. Synthesis of Procaine:

Step 1: Esterification of amino benzoic acid

Amino benzoic acid (p-aminobenzoic acid) is reacted with 2-diethylaminoethanol in the presence of a suitable catalyst (e.g., dicyclohexylcarbodiimide, DCC) to form procaine.

Equation:

```

p-H₂NC₆H₄COOH + HOCH₂CH₂N(C₂H₅)₂ → p-H₂NC₆H₄COOCH₂CH₂N(C₂H₅)₂ + H₂O

```

2. Synthesis of Procaine Monohydrochloride:

Step 2: Salt formation with hydrochloric acid

Procaine is then treated with hydrochloric acid (HCl) to form procaine monohydrochloride.

Equation:

```

p-H₂NC₆H₄COOCH₂CH₂N(C₂H₅)₂ + HCl → p-H₂NC₆H₄COOCH₂CH₂N(C₂H₅)₂·HCl

```

Overall Reaction:

The overall reaction can be summarized as:

```

p-H₂NC₆H₄COOH + HOCH₂CH₂N(C₂H₅)₂ + HCl → p-H₂NC₆H₄COOCH₂CH₂N(C₂H₅)₂·HCl + H₂O

```

Note:

* The above equations represent the simplified reactions. In reality, the synthesis involves multiple steps and purification procedures.

* Procaine monohydrochloride is the commonly used form of procaine due to its better stability and solubility.

* Procaine is a local anesthetic and is used mainly for infiltration anesthesia and nerve blocks.