Hydrocarbons - Result Question 42
25. Propyne and propene can be distinguished by their reactions with bromine water
(2000)
(a) conc. $H_2SO_4$
(b) $Br _2$ in $CCl _4$
(c) dil. $KMnO_4$
(d) $AgNO _3$ in ammonia
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Answer:
Correct Answer: 25. (d)
Solution:
Terminal alkynes form silver salt with Tollen’s reagent while alkene does not react with Tollen’s reagent.
$CH _3-C \equiv C-H+AgNO _3 \stackrel{NH _3(a q)}{\longrightarrow} CH _3 \underset{\text { white ppt. }}{C \equiv CAg \downarrow}$
Therefore, Tollen’s reagent can be used to distinguish a terminal alkyne like propyne from alkenes as well as from internal alkynes.
BETA
