Question

The unshared pair of electrons on a cyanide ion can acts as
A. Isocyanide centre
B. Amido centre
C. Cationic centre
D. Nucleophilic centre

Answer 1

Hint: Cyanide is a functional group possessing the formula of CN. There is a triple bond between carbon and the nitrogen atom. The acidic hydrolysis of cyanide gives carboxylic acid. Cyanide is an ambident nucleophile.

Complete Step by Step Solution:
 The structure of the cyanide ion is,

Image: Cyanide ion

Now, let's look at the resonance of the cyanide ion.

Image: Resonance of cyanide ion

As we can see, the cyanide ion has lone pair of electrons. So, it can attract positive charges. Therefore, cyanide ion acts as a ca cationic centre.Hence, option C is right.
Additional information/b>
Let's understand the nucleophilic characteristics of the cyanide ion. From the end of Carbon, the behavior of Cyanide ion (-CN-) as a nucleophile is stronger because it will result in the formation of C-C bond whose stability is more than the C-N bond.

Image: Reaction of an alkyl halide with cyanide ion

Cyanide ion is an ambident nucleophile and reacts either through Carbon or Nitrogen atom. An ambident nucleophile is one in which either can happen through two sites of the same atom. For example, in the cyanide ion, the reaction happens through either C or N atom.

Note: It is to be noted both cyanide and isocyanide are two different functional groups. In cyanide, the reaction happens at the C atom, that is, bond formation takes place like (-CN). In isocyanide, the reaction happens at the N atom, that is, bond formation occurs as (R-NC).