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Sodium Reaction:
$$\text{R--C}\equiv\text{CH} + \text{Na} \to \text{R--C}\equiv\text{C}^-\text{Na}^+ + \frac{1}{2}\text{H}_2\uparrow$$
Tollen's Test (Ammoniacal Silver Nitrate):
$$\begin{aligned}\text{R--C}\equiv\text{CH} + [\text{Ag(NH}_3)_2]^+ + \text{OH}^- \to \text{R--C}\equiv\text{CAg}\downarrow \text{ (White Precipitate)} + \text{NH}_4^+ + \text{H}_2\text{O}\end{aligned}$$
Cuprous Chloride Test (Ammoniacal $$\text{Cu}_2\text{Cl}_2$$):
$$\begin{aligned}\text{R--C}\equiv\text{CH} + \text{Cu}_2\text{Cl}_2 + 2\text{NH}_4\text{OH} \to \text{R--C}\equiv\text{CCu}\downarrow \text{ (Red Precipitate)} + 2\text{NH}_4\text{Cl} + 2\text{H}_2\text{O}\end{aligned}$$
Notation & Key Points: Internal alkynes ($$\text{R--C}\equiv\text{C--R'}$$) lack an acidic hydrogen and give negative results for all three tests.
- The white ($$\text{Ag}$$) and red ($$\text{Cu}$$) precipitates decompose upon treatment with dilute mineral acids ($$\text{HNO}_3$$or$$\text{HCl}$$) to regenerate the original terminal alkyne.
