Molecule is related to Sun. Sun is related to Evening. Evening is related to Time. 
Purchase is the opposite of Sale. Sale is related to Retail. Retail is related to Republic. 
Molecule <--RelatedTo--> Sun <--RelatedTo--> Evening <--RelatedTo--> Time 
Purchase <--Antonym--> Sale <--RelatedTo--> Retail <--RelatedTo--> Republic 