Organic chemistry holds a high weight according to JEE chemistry syllabus. The questions asked from organic chemistry are generally mechanism based where the final product of a reaction has to be determined. Kolbe’s reaction is one of the important reactions for JEE chemistry. Some frequently asked questions in Kolbe’s reaction that may help you in JEE preparation are as follows:
Question 1: What is Kolbe’s reaction?
When phenol is treated with sodium hydroxide, phenoxide ion is generated. The phenoxide ion generated is more reactive than phenol towards electrophilic aromatic substitution reaction. Hence it undergoes electrophilic substitution reaction with carbon dioxide which is a weak electrophile. Ortho-hydroxybenzoic acid (salicylic acid) is formed as the major product. This reaction is popularly known as Kolbe’s reaction. It is named after the scientist Hermann Kolbe.
Question 2: Explain the mechanism of Kolbe’s reaction.
Answer: Kolbe’s reaction is a carboxylation chemical reaction. This reaction is preceded by allowing sodium phenoxide to absorb carbon dioxide and then heating this product at a temperature of 125°C under the pressure of several atmospheres of carbon dioxide. The unstable intermediate formed undergoes a proton shift which leads to the formation of sodium salicylate. The subsequent acidification of the mixture produces salicylic acid.
The reaction of salicylic acid with acetic anhydride yields the most commonly used painkiller – aspirin.
Question 3: Which reference books can be followed to prepare for Kolbe’s reaction?
For studying Kolbe’s reaction one can follow NCERT chemistry textbook part-2 for class 12th. The chapter named ‘Alcohols, Phenols and Ethers’ in this book contains the details in a very precise way. A thorough reading of this chapter will help in understanding the reaction. Apart from NCERT one can use reference books such as ‘Organic Chemistry’ written by Solomons & Fryhle to study more about this reaction and it’s mechanism. For more details on JEE or this topic install Byju’s the learning app.