Question

Which of the following is ‘ambient nucleophile’?
(This question has multiple answers)
A. $\text{N}{{\text{O}}_{\text{2}}}^{-}$
B. $\text{C}{{\text{N}}^{-}}$
C. $\text{O}{{\text{H}}^{-}}$
D. $\text{B}{{\text{r}}^{-}}$

Answer 1

Hint: To know which among the following options are the examples of ambient nucleophile, we need to know the meaning of it. So, the answer to this question, must begin with the definition of ambient nucleophile. Then we can write about the ways to identify an ambient nucleophile, then categorizing the options.

Complete step-by-step answer:
Let us begin the answer by defining the nucleophile.
A nucleophile is a chemical species that donates an electron pair to form a chemical bond in relation to a reaction. All molecules or ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate the electrons, they are defined as Lewis Bases.
Now, let us understand what does ambient nucleophile mean. A nucleophile that can form new bonds at two or more spots in its structure, usually due to resonance contributors, is known as an ambient nucleophile.
To identify ambient nucleophiles, we need to look for two nucleophilic centres. Now, moving on to the options. This means the compound should be having more than one lone pair donors.
In option A, we have $\text{N}{{\text{O}}_{\text{2}}}^{-}$.
$\text{N}{{\text{O}}_{\text{2}}}^{-}$ consists of two elements which are N and O. Both the elements N and O consist of lone pairs. When N donates the lone pair, the compound becomes nitrate and when O donates, then the compound is called nitrite. This means that the compound has two lone pair donors. This makes $\text{N}{{\text{O}}_{\text{2}}}^{-}$ an ambient nucleophile.
In option B, we have $\text{C}{{\text{N}}^{-}}$.
$\text{C}{{\text{N}}^{-}}$ consists of two elements which are C and N. Both the elements C and N consist of lone pairs. When an alkyl group is attached to C it is known as cyanide, that is R – CN. But when the alkyl group is attached with N, then it is known as isocyanide, that is R – NC. So the compound has two lone pair donors. This makes $\text{C}{{\text{N}}^{-}}$ an ambient nucleophile.
In option C, we have $\text{O}{{\text{H}}^{-}}$
$\text{O}{{\text{H}}^{-}}$ consists of one lone pair donor. This is the reason why $\text{O}{{\text{H}}^{\text{-}}}$ is not an ambient nucleophile.
In option D, we have $\text{B}{{\text{r}}^{-}}$.
$\text{B}{{\text{r}}^{-}}$ consists of one lone pair donor. This is the reason why $\text{B}{{\text{r}}^{-}}$is not an ambient nucleophile.
Therefore, the correct answers to the question are Option A and Option B.

Note: The other way of defining an ambient nucleophile is that it is an anionic nucleophile. But the negative charge that it will possess, will be delocalized by resonance over two like but not equivalent atoms. The most common ambient nucleophiles are enolate ions.