Wittig Reaction

What is Wittig reaction?

Wittig reaction is a chemical reaction that converts primary or secondary aldehyde, ketone or alkyl halide using a Wittig reagent namely triphenylphosphine to provide triphenylphosphine oxide and alkane.

Wittig Reaction

It has its applications in organic synthesis that is required for the preparation of alkenes. One of the prime advantages of alkene synthesis is that the site of a double bond is precisely fixed in comparison to the mixtures that are repeatedly formed by alcohol dehydration.

Wittig Reagents

Preparation of phosphorus yield: Yields are defined as a compound consisting of opposite charges at adjoining atoms wherein both the atoms have complete octets. In the below illustration organophosphorus ylide is used as a Wittig reagent. Dipolar phosphorous compounds are stabilized by a p-bonding.

Wittig Reaction

The capacity of a phosphorous to hold 8 valence electrons leads to a resonance structure constituting a double bond structure.

Yield Formation

  1. SN2 reaction

    Wittig Reaction

  2. Deprotonation

    Wittig Reaction

Wittig Reaction Example

Wittig Reaction

Wittig Reaction

Scope:

Wittig reaction is one of the prominent methods that is used in the synthesis of an alkene from aldehydes and ketones. Wittig reagents comprise of functional groups namely aromatic nitro, OR, OH and ester groups.

Limitations:

Wittig reaction is barely used to prepare tetrasubstituted alkenes as triphenylphosphine with most secondary halides is inefficient.


Practise This Question

Which of the following statement is correct