b. Addition Reaction : These reactions occur by the formation of rapid formation of rapid chains and no elimination of small molecules occur. Such reactions generally occur among double or triple-bonded molecules, or oxo-ring compounds.

Addition reactions can be further of three types—

 

• i.  Step Reactions

ii.  Chain Reactions

iii.  Ionic Reations

i .Step Reactions : In step reactions, a π bond is broken and two new σ bonds are formed. The substrate of an electrophilic addition reaction must have a double bond or triple bond .

ii .Chain Reactions : In chain addition reactions, the polymer is formed in a single step and within the fraction of a second. The chain kinetics occur in 4 steps – Initiation, Propagation, Transfer and Termination.

 

Variations of Chain Addition Reaction :

If we consider ‘M' and ‘N' be two monomeric species, then the chain addition reaction can be of the following types –

Homopolymerization

If only M and N are present,

 

Copolymerization

If M and N are present together,

 

Random type

 

• MM MN NNN MM N M MM N N……

 

Alternating type

 

• M N M N M N M N M ………