Mechanisms background
Many experimental results in organic chemistry can be rationalized on the basis of the stepwise pathway for a reaction. This is referred to as the mechanism of the reaction and details the bond-making and bond-breaking steps leading from reactants to products.
The first step in a mechanism is often bond formation between an atom that is an electrophile and an atom that is a nucleophile.
:NH3
CH2=CH2
nucleophiles
H+
δ+H-Brδ–
electrophiles
An atom that is a nucleophile is electron rich due to
An atom that is an electrophile is electron deficient due to
Multistep reaction pathways involve species referred to as intermediates. Intermediates
The first step in a mechanism is often bond formation between an atom that is an electrophile and an atom that is a nucleophile.
:NH3
CH2=CH2
nucleophiles
H+
δ+H-Brδ–
electrophiles
An atom that is a nucleophile is electron rich due to
- being involved in a π (pi) bond or
- having a nonbonding pair
An atom that is an electrophile is electron deficient due to
- being positively charged or
- being the less electronegative atom in a polarized bond or
- having an incomplete octet of electrons
- are formed in one step and consumed in a subsequent step
Step 1:
reactants
intermediate
Step 2:
intermediate products
- are not in the overall balanced equation for the reaction.
reactants products