soporific vs hypnogogic

soporific is a noun but hypnogogic is not a noun.

Word	Noun	Adjective	Verb	Adverb
soporific	Yes	Yes	No	No
hypnogogic	No	Yes	No	No

As adjectives, soporific and hypnogogic are synonyms defined as:

Other synonyms of soporific include hypnagogic, somniferous, somnific, soporiferous.

soporific (noun)	hypnogogic (noun)
a drug that induces sleep

soporific (adjective)	hypnogogic (adjective)
sleep inducing	sleep inducing
inducing mental lethargy