of import vs essential

of import is not a noun while essential is a noun.

Word	Noun	Adjective	Verb	Adverb
of import	No	Yes	No	No
essential	Yes	Yes	No	No

of import (noun)	essential (noun)
	anything indispensable

of import (adjective)	essential (adjective)
of great significance or value	basic and fundamental
	defining rights and duties as opposed to giving the rules by which rights and duties are established
	being or relating to or containing the essence of a plant etc
	of the greatest importance
	absolutely necessary; vitally necessary