Step 1: Concept
Anticonvulsants have diverse chemical structures, ranging from heterocyclic rings to simple fatty acids.
Step 2: Meaning
Pentanoic acid is a 5-carbon straight-chain carboxylic acid.
Step 3: Analysis
Valproic acid is 2-propylpentanoic acid. Phenytoin is a hydantoin, Gabapentin is a GABA analog, and Phenobarbitone is a barbiturate.
Step 4: Conclusion
Valproic acid is the only option that is a derivative of pentanoic acid.
Final Answer: (C)