6-membered vs six-membered

6-membered and six-membered both are adjectives.

Word	Noun	Adjective	Verb	Adverb
6-membered	No	Yes	No	No
six-membered	No	Yes	No	No

As adjectives, 6-membered and six-membered are synonyms defined as:

6-membered and six-membered: of a chemical compound having a ring with six members

6-membered (adjective)	six-membered (adjective)
of a chemical compound having a ring with six members	of a chemical compound having a ring with six members