Question

Match the compounds/ions in Column I with their properties/reactions in Column II

$\begin{array}{cc}ColumnI& ColumnII\\ 1.\text{Benzaldehyde}& \text{p. gives precipitate with 2,4-dinitrophenylhydrazine}\\ 2.\text{Propyne}& \text{q. gives precipitate with}AgN{O}_3\\ 3.C{N}^{-}& \text{r. is a nucleophile}\\ 4.I^{-}& \text{s. is involved in cyanohydrin formation}\end{array}$

• A. 1. - p, q, r, s; 2 - q, r, s; 3 - r, s; 4 - r
• B. 1. - p, q, s; 2 - q,r; 3 - q, r, s; 4 - q, r
• C. 1. - p, q; 2 - q; 3 - r, s; 4 - r
• D. 1. - p, r, s; 2 - q, r; 3 - q, r, s; 4 - r

Answer 1

The correct option is B

1. - p, q, s; 2 - q,r; 3 - q, r, s; 4 - q, r

Carbonyls like aldehydes and ketones do form a yellow-orange precipitate with DNP.
So it is no surprise that benzaldehyde - an aldehyde - gives a precipitate with 2,4-dinitrophenylhydrazine.
Also, as an aldehyde, it can sure form a cyanohydrin with $C{N}^{-}$. Benzaldehyde gives positive
Tollen's test.

Propyne does not react with 2,4-DNPH or 2,4-dinitrophenylhydrazine.
But it does decolourize bromine water or add to bromine (which is an excellent electrophile).
Hence, we can make a case for propyne to be a nucleophile. Propyne does give a white precipitate
with $AgN{O}_3$. It is not involved in cyanohydrin formation.

$C{N}^{-}$ gives a precipitate with $AgN{O}_3$. It is also a nucleophile;
Further, it can form a cyanohydrin with carbonyls.

$I^{-}$ gives a precipitate with $AgN{O}_3$. It is also a nucleophile;
Unlike $C{N}^{-}$, iodide does not form a cyanohydrin with carbonyls.