Step 1: Understanding the Concept:
Antipsychotics (neuroleptics) are classified based on their heterocyclic ring structures. Chlorpromazine was the first "typical" antipsychotic discovered.
Step 2: Detailed Explanation:
1. Structure: Chlorpromazine consists of a tricyclic phenothiazine nucleus (a sulfur and nitrogen-containing ring system) with a side chain.
2. Sub-classification: It is specifically an aliphatic side-chain phenothiazine.
3. Others: Haloperidol is a Butyrophenone. Diazepam is a Benzodiazepine. Thiothixene is a Thioxanthene.
Step 3: Final Answer:
Chlorpromazine is the prototype drug of the phenothiazine chemical class.