Addition Reaction
A reaction in which the substrate and the reagent are added up to form a single molecule is called addition reaction. The reaction occurs at the site of unsaturation in a molecule. Thus, compounds having multiple bonds such as alkenes, alkynes, aldehydes, and ketones undergo addition reactions. The reactivity of these compounds is due to the more exposed and easily available π electrons to the electron-seeking (electrophilic) reagent.
Types of Addition Reactions
Addition reactions are basically classified into two types, they are:
1. Polar Addition Reaction
2. Non-Polar Addition Reaction
Polar Addition Reactions
In polar addition reaction, an electrophile or nucleophile adds to multiple bonds to form an adduct. Polar addition reaction are further divided into two types-
1. Electrophilic Addition Reactions
2. Nucleophilic Addition Reactions
Electrophilic Addition Reactions
Involves the addition of an electrophile to a multiple bond. Addition of bromine to alkene in CCl4 or water is an example of electrophilic addition reaction.
Nucleophilic Addition Reactions
Involves the addition of a nucleophile to a multiple bond. Addition of HCN to carbonyl compounds (aldehydes or ketones) in acidic or basic medium is an example of nucleophilic addition reaction.
Non-Polar Addition Reactions
In nonpolar addition reactions, nonpolar molecules or nonpolar functional groups combines with unsaturated compounds in the absence of a polar solvent or catalyst. Non-polar addition reaction are further divided into two types, they are:
1. Free Radical Addition Reactions
2. Cycloaddition Reactions
Free Radical Addition Reactions
Involves the addition of a free radical to a multiple bond. Addition of HBr to alkene in the presence of free radical initiator like peroxide or light etc. is an example of free radical addition reaction.
Cycloaddition Reactions
Involves the addition of two or more unsaturated molecules to form a cyclic product. Diels-Alder reaction is an example of a cycloaddition reaction in which a conjugated diene reacts with a dienophile to form a cyclic compound. An example of this reaction is the reaction of 1,3-butadiene with ethene to form cyclohexene.
