1.

Which of the following reagents can distinguish between propene and propyne? (i) `Na` (in hexane) (ii) `Na^(+)NH_2` (in liquid `NH_3`) (iii) `Ag(NH_3)_2^(+)OH^(-)` (iv) `Cu(NH_3)_2^(+)OH^(-)`A. (i),(ii),(iii),(iv)B. (i),(ii)C. (iii),(iv)D. (ii),(iii),(iv)

Answer» Correct Answer - A
All these tests are based on the acidity of the terminal H of a terminal alkyne.
`2CH_3C-=CH+2Natounderset("sodium propynide")(2CH_3C-=C)`:` .^(-)Na^(+)+H_2uarr`
`CH_3C-=CH+NaNH_2overset("liq.NH_3")toCH_3C-=C`:` .^(-)Na^(+)+NH_3uarr`
`CH_3C-=CHunderset("ammoniacal silver nitrate")(+Ag(NH_3)_2^(+)OH^(-))toCH_3C-=CAg(s)+2NH_3+H_2O`
`CH_3C-=CH+underset("Ammoniacal cuprous chloride")(AG(NH_3)_2^(+)OH^(-))toCH_3C-=CAg(s)+2NH_3+H_2O`
Similar chemical tests can be used to distinguish propane from propyne.


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