What is an ambident nucleophile?

1 Answer
May 3, 2015


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


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).