Alkanes do not react with copper(I) chloride, but ethyne and terminal alkynes do react.
When ethyne is passed through an ammoniacal solution of copper(I) chloride, a red-brown precipitate of copper(I) acetylide is produced.
Terminal alkynes also react to form a red-brown precipitate. Thus.
Non-terminal alkynes like but-2-yne,
You can, therefore, use this reaction to distinguish between terminal and non-terminal alkynes.