soporific vs uninteresting

soporific is a noun but uninteresting is not a noun.

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

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

soporific (adjective)	uninteresting (adjective)
sleep inducing	arousing no interest or attention or curiosity or excitement
inducing mental lethargy	characteristic or suggestive of an institution especially in being uniform or dull or unimaginative