Polar Addition Reactions

A polar addition reaction is a chemical reaction where an electrophile or nucleophile adds to multiple bonds to form an adduct. Polar addition reaction are further divided into two types which are:

• Electrophilic Addition Reactions: Involves the addition of an electrophile to a double bond.
• Nucleophilic Addition Reactions: Involves the addition of a nucleophile to a double bond.

Electrophilic Addition Reaction

In an electrophilic addition reaction, a reactant with a double bond is attacked by an electrophile, which adds the electrophile to the double bond. The mechanism of electrophilic addition can be illustrated using the example of adding hydrogen halide to an alkene, such as adding HCl to propene.

Step 1: The pi bond of the alkene acts as a nucleophile and attacks the hydrogen of the hydrogen halide, forming a carbocation intermediate and a halide ion.

CH₃CH=CH₂ + HCl → CH₃CH₂⁺+ Cl ^–

Step 2: The carbocation intermediate then reacts with the halide ion, forming the addition product.

CH₃CH⁺+ Cl ^– → CH₃CH₂Cl

Nucleophilic Addition Reaction

In a Nucleophilic Addition Reaction, a chemical compound with a double bond reacts with a nucleophile, adding the nucleophile to the double bond. The mechanism of nucleophilic addition can be illustrated using the example of adding a nucleophile to a carbonyl compound, such as adding a Grignard reagent to a ketone.

Step 1: The nucleophile, such as a Grignard reagent, attacks the carbonyl carbon, leading to the formation of an alkoxide intermediate.

R₂C=O + R’MgX → R₂C(OMgX)R’

Step 2: The alkoxide intermediate then picks up a proton from the solvent, forming the addition product.

R₂C(OMgX)R’ + H₂O → R₂C(OR’)R’ + MgXOH

Addition reaction is a chemical process in which two or more molecules combine to form a single molecule. They are typical of unsaturated organic compounds such as alkenes, alkynes, aldehydes, and ketones.

In this article, we will look into what addition reaction is, types of addition reaction, its examples, applications, and the difference between addition and substitution reaction.