Nucleophiles and electrophiles

Many of the steps in polar reaction mechanisms involve bond formation between a species known as the electrophile (from Greek:  electron lover) and a species known as the nucleophile (from Greek: nucleus lover).

A nucleophile (or nucleophilic reagent) forms a bond to its reaction partner (the electrophile) by donating both bonding electrons.

An electrophile (or electrophilic reagent) forms a bond to its reaction partner (the nucleophile) by accepting both bonding electrons from that reaction partner.  

How do I recognize a nucleophile?
Nucleophiles are electron-rich due to having a π (pi) bond or an atom bearing a nonbonding electron pair. 

As shown below, nucleophiles
may be negatively charged
may have no charge.
 
Common nucleophiles:

alkenes R2C=CR2
alkynes RC≡CR
in ethers (ROR) 
in  alcohols (ROH)

 
in C=O compounds
in amines RNH2
or amides RCONH2		halide ions


hydroxide ions

How do I recognize electrophiles?
Electrophiles have an electron deficient atom due
this atom having a positive charge
metal cations and the proton (H+)

this atom being in a covalent bond to a more electronegative atom.
The H in HX is an electrophile for X equals halogen.
The C in C-X is an electrophile for X equals halogen or oxygen.
The C in C=O is an electrophile.
Dr Sheila Woodgate
© The University of Auckland 2002