long chain vs chemical chain

long chain and chemical chain both are nouns.

Word	Noun	Adjective	Verb	Adverb
long chain	Yes	No	No	No
chemical chain	Yes	No	No	No

As nouns, chemical chain is a hypernym of long chain; that is, chemical chain is a word with a broader meaning than long chain:

long chain: (chemistry) a relatively long chain of atoms in a molecule
chemical chain: (chemistry) a series of linked atoms (generally in an organic molecule)

Other hypernyms of long chain include chain.

long chain (noun)	chemical chain (noun)
(chemistry) a relatively long chain of atoms in a molecule	(chemistry) a series of linked atoms (generally in an organic molecule)