divide vs disunite

divide is a noun but disunite is not a noun.

Word	Noun	Adjective	Verb	Adverb
divide	Yes	No	Yes	No
disunite	No	No	Yes	No

As verbs, divide and disunite are synonyms defined as:

Other synonyms of divide include part, separate.

divide (noun)	disunite (noun)
a ridge of land that separates two adjacent river systems
a serious disagreement between two groups of people (typically producing tension or hostility)

divide (verb)	disunite (verb)
perform a division	force, take, or pull apart
move or break apart	part; cease or break association with
force, take, or pull apart
make a division or separation
separate into parts or portions
act as a barrier between; stand between