What reagent is used to distinguish terminal alkynes (containing a -C#C-H group) from non-terminal alkynes via formation of a reddish-brown precipitate?
Answer and explanation
Correct answer: B. Ammoniacal copper(I) chloride solution
Terminal alkynes react with ammoniacal copper(I) chloride to precipitate reddish-brown copper(I) acetylide (or with ammoniacal silver nitrate to form silver acetylide), demonstrating the acidic nature of the terminal acetylenic hydrogen. Internal alkynes do not react.
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