course vs of course

course is a noun but of course is not a noun.

Word	Noun	Adjective	Verb	Adverb
course	Yes	No	Yes	Yes
of course	No	No	No	Yes

As adverbs, course and of course are synonyms defined as:

Other synonyms of course include naturally.

course (noun)	of course (noun)
a mode of action
education imparted in a series of lessons or meetings
facility consisting of a circumscribed area of land or water laid out for a sport
(construction) a layer of masonry
part of a meal served at one time
a connected series of events or actions or developments
a body of students who are taught together
general line of orientation
a line or route along which something travels or moves

course (adverb)	of course (adverb)
as might be expected	as might be expected