antiknock vs antiknocking

antiknock is a noun but antiknocking is not a noun.

Word	Noun	Adjective	Verb	Adverb
antiknock	Yes	Yes	No	No
antiknocking	No	Yes	No	No

As adjectives, antiknock and antiknocking are synonyms defined as:

antiknock and antiknocking: suppressing or eliminating engine knock in combustion engines

antiknock (noun)	antiknocking (noun)
any of various compounds that are added to gasoline to reduce engine knocking

antiknock (adjective)	antiknocking (adjective)
suppressing or eliminating engine knock in combustion engines	suppressing or eliminating engine knock in combustion engines