of the essence vs essential

of the essence is not a noun while essential is a noun.

Word	Noun	Adjective	Verb	Adverb
of the essence	No	Yes	No	No
essential	Yes	Yes	No	No

As adjectives, of the essence and essential are synonyms defined as:

Other synonyms of of the essence include all-important, all important, crucial.

of the essence (noun)	essential (noun)
	anything indispensable

of the essence (adjective)	essential (adjective)
of the greatest importance	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