Question

Procaine (its hydrochloride is marketed as Novocain) was one of the first local anesthetics for infiltration and regional anesthesia. See "Chemical Connections: From Cocaine to Procaine and Beyond." According to the following retrosynthetic scheme, procaine can be synthesized from 4 -aminobenzoic acid, ethylene oxide, and diethylamine as sources of carbon atoms.

Short answer

Briefly explain the purpose of each reactant. Answer: The synthesis of procaine involves two main steps. In the first step, 4-aminobenzoic acid reacts with ethylene oxide, resulting in the formation of a 2-(4-aminobenzoyloxy)ethanol intermediate. The purpose of ethylene oxide in this step is to open its epoxide ring and allow the amine group of 4-aminobenzoic acid to attack and form a new C-N bond. In the second step, the intermediate 2-(4-aminobenzoyloxy)ethanol reacts with diethylamine, replacing the hydroxyl group through a nucleophilic substitution reaction, forming a new C-N bond and yielding the final product - procaine. The purpose of diethylamine in this step is to participate in the nucleophilic substitution reaction and lead to the formation of procaine.

Step-by-step solution

Identify the starting materials and target molecule

In this synthesis, procaine must be formed by reacting 4-aminobenzoic acid, ethylene oxide, and diethylamine. The target molecule is procaine, a local anesthetic compound. Step 2: Break down the synthesis reaction

Reaction of 4-aminobenzoic acid and ethylene oxide

First, the 4-aminobenzoic acid reacts with ethylene oxide. The ethylene oxide will open its epoxide ring and the amine group of 4-aminobenzoic acid will attack the carbon atom bearing the oxygen, forming a new C-N bond. The end product of this reaction is a 2-(4-aminobenzoyloxy)ethanol intermediate. Step 3: Reaction with diethylamine

Formation of procaine

Next, the intermediate 2-(4-aminobenzoyloxy)ethanol reacts with diethylamine. The amine group of diethylamine will replace the hydroxyl group in the intermediate, via a nucleophilic substitution reaction. This forms a new C-N bond, and the final product is procaine. In summary, procaine can be synthesized from 4-aminobenzoic acid, ethylene oxide, and diethylamine in two main steps. The starting materials react to form an intermediate, which then reacts with diethylamine to yield the target molecule - procaine.