Question

What is an ambident nucleophile?

Answer 1

An ambident nucleophile is an anionic nucleophile in which the negative charge is delocalized over two unlike atoms.

Explanation:

A nucleophile is a chemical species that can donate an electron pair and form a bond to a carbon atom. For example,

The word ambident comes from two Latin words: ambi = "on both sides" + dens = "tooth".

So an ambident nucleophile has "teeth" on two sides.

It can attack from two different places and form two different products.

For example, the thiocyanate ion, `"SCN"^-`, is a resonance hybrid.

Both the `"S"` and the `"N"` atoms can act as nucleophiles.

So, the `"S"_"N"2` reaction of an alkyl halide with `"SCN"^−` often leads to a mixture of an alkyl thiocyanate and an alkyl isothiocyanate.

`"R-X" + "SCN"⁻ → "X"^(-) + underbrace("R-SCN")_color(red)("alkyl thiocyanate") + underbrace("R-NCS")_color(red)("alkyl isothiocyanate")`

A common ambident nucleophile in organic chemistry is the enolate ion.

For example, the resonance forms of acetone enolate are

Both the `"C"` and the `"O"` atoms can act as nucleophiles.

Thus, the reaction of the enolate with methyl iodide gives a mixture of a ketone (1) and an enol ether (2).