Chugaev reaction mechanism: Useful application

Table of Contents

Chugaev reaction mechanism is a concerted process, which has been discussed below along with its application and limitation. Chugaev reaction was first of all reported by Chugaev in 1899. It is a type of elimination reaction, also known as pyrolytic elimination.

Chugaev reaction

Alcohol reacts with carbon disulfide in presence of sodium hydroxide to give sodium xanthate, which on further alkylation with methyl iodide (generally) gives xanthate ester. This xanthate upon pyrolysis produces olefin or alkene. Thus, the conversion of alcohol into olefin by the corresponding xanthate esters is called Chugaev reaction. This reaction is also known as Chugaev elimination or Chugaev xanthate reaction.

chugaev reaction mechanism

This reaction is very useful for the conversion of secondary and tertiary alcohol into an alkene. You may have questions on your head, why primary alcohol is not suitable for this purpose? right. Its because the xanthate ester of primary alcohol generally has high thermal stability therefore, it is difficult to decompose by heating.

  • This pyrolysis takes place via an intramolecular cis-elimination without the rearrangement of carbon framework.

Chugaev reaction mechanism

The mechanism of Chugaev reaction is discussed below.

Step 1: Formation of xanthate ester

In this process, alcohol reacts with CS2 in presence of NaOH, followed by alkylation produces xanthate ester.

chugaev reaction mechanism

Step 2: Pyrolysis of xanthate ester.

This step is a concerted process, which takes place in presence of heat. Actually, this step is the Chagaev reaction in which the pyrolysis of xanthate ester takes place.

chugaev reaction mechanism

Some examples of Chugaev Reaction

Let’s see examples of this reaction.

chugaev reaction mechanism

Application of Chugaev reaction

This reaction can be used for the preparation of different types of olefins including bornylene, menthene, etc.

Limitation

If the Beta-carbon contains more than one hydrogen or if the elimination is possible in more than one position, a mixture of isomeric olefins is produced. For example,

chugaev reaction mechanism

References

  • Wang, Z., Comprehensive Organic Name Reactions and Reagents, John Wiley & Sons, Inc.,2010
  • Laue T.,Plagens A.,Named Organic Reactions, Second edition, John Wiley & Sons, Ltd, 2005

chugaev reaction mechanism

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