dissociate vs split up

dissociate is not a noun while split up is a noun.

Word	Noun	Adjective	Verb	Adverb
dissociate	No	No	Yes	No
split up	Yes	No	Yes	No

As verbs, split up is a hypernym of dissociate; that is, split up is a word with a broader meaning than dissociate:

Other hypernyms of dissociate include break, break up, part, separate, split.

dissociate (noun)	split up (noun)
	an increase in the number of outstanding shares of a corporation without changing the shareholders' equity

dissociate (verb)	split up (verb)
to undergo a reversible or temporary breakdown of a molecule into simpler molecules or atoms	become separated into pieces or fragments
regard as unconnected	get a divorce; formally terminate a marriage
part; cease or break association with	discontinue an association or relation; go different ways
	separate into parts or portions