Terminal alkynes such as ethyne react with ammoniacal silver nitrate to give a precipitate because
Correct answer: B. the hydrogen attached to the triply bonded carbon is weakly acidic and is replaced by silver
- A. the triple bond adds silver
- B. the hydrogen attached to the triply bonded carbon is weakly acidic and is replaced by silver
- C. silver catalyses polymerisation
- D. alkynes are strong bases
Explanation
The sp hybridised carbon holds its bonding electrons closer, so the attached hydrogen is slightly acidic and can be replaced by a metal to form an acetylide precipitate, which is the standard test distinguishing a terminal alkyne from an internal one. Alkenes and alkanes give no such reaction. The dry precipitates are explosive and must be destroyed with acid.
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About Alkynes
Alkynes are unsaturated hydrocarbons containing a carbon-carbon triple bond, with sp-hybridised carbon atoms and a linear arrangement around the bond. The content includes nomenclature, preparation, acidity of terminal alkynes, and addition reactions with hydrogen, halogens, hydrogen halides and water, as well as oxidation.
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