The key difference between Claisen and Dieckmann condensation is that Claisen condensation reaction is a type of coupling reaction whereas Dieckmann condensation reaction is a type of ring formation reaction.
A condensation reaction in chemistry is a chemical reaction in which a water molecule(s) or an alcohol is formed as a byproduct of the reaction. This water/alcohol molecule is formed by the combination of a hydrogen atom and a –OH group, which come from two different molecules that react with each other.
CONTENTS
1. Overview and Key Difference
2. What Claisen Condensation
3. What is Dieckmann Condensation
4. Side by Side Comparison – Claisen vs Dieckmann Condensation in Tabular Form
5. Summary
What is Claisen Condensation?
Claisen condensation is a type of coupling reaction in which a carbon-carbon bond forms between two esters or an ester and a carbonyl compound. This reaction occurs in the presence of a strong base which results in a beta-keto ester or a beta-diketone. The reaction was named after the scientist Rainer Ludwig Claisen. The general reaction formula is as follows:
Figure 01: Chemical Equation for Claisen Condensation
There are a few requirements for this reaction to occur. One requirement is that there should be at least one reagent which is enolizable. In other words, at least one reactant must have an alpha proton and this proton should be able to undergo deprotonation, forming the enolate anion. There are some combinations of enolizable and nonenolizable carbonyl compounds that can undergo Claisen condensation reaction. Another factor in addition to this requirement is that the strong base must not interfere with the Claisen reaction through nucleophilic substitution or addition with carbonyl carbon atoms. Another requirement is the alkoxy proton of ester, which must be a relatively good leaving group.
What is Dieckmann Condensation?
Dieckmann condensation is a type of ring-forming reaction in which diesters react to give beta-keto esters. It is, therefore, an intramolecular chemical reaction and it was named after the German scientist Walter Dieckmann. This is the intramolecular reaction that is equivalent to the Claisen condensation, which is an intermolecular reaction. The general reaction formula for this reaction is as follows:
Figure 02: Dieckmann Condensation Reaction
When considering the reaction mechanism of Dieckmann condensation reaction, it involves the deprotonation of an ester at the alpha position which generates an enolate ion that can undergo a 5-exo-trig nucleophilic attack, giving a cyclic enol. However, protonation of this product with a Bronsted-Lowry acid re-generates a beta-keto ester. In this reaction, five and six-membered rings form due to the steric stability. For example, 1,6-diesters can form five-membered beta-keto ester rings while 1,7-diesters form six-membered beta-keto ester rings.
What is the Difference Between Claisen and Dieckmann Condensation?
Claisen condensation is a type of coupling reaction in which a carbon-carbon bond forms between two esters or an ester and a carbonyl compound. Dieckmann condensation is a type of ring-forming reaction in which diesters react to give beta-keto esters. Therefore, the key difference between Claisen and Dieckmann condensation is that Claisen condensation reaction is a type of coupling reaction, whereas Dieckmann condensation reaction is a type of ring formation reaction.
Below infographic lists more details of the difference between Claisen and Dieckmann condensation.
Summary – Claisen vs Dieckmann Condensation
Claisen condensation and Dieckmann condensation are types of condensation reactions where water/alcohol is formed as a byproduct of the reaction. The key difference between Claisen and Dieckmann condensation is that Claisen condensation reaction is a type of coupling reaction whereas Dieckmann condensation reaction is a type of ring formation reaction.
Reference:
1. “23.8: The Claisen Condensation Reaction.” Libretext. Available here.
Image Courtesy:
1. “Claisen condensation overall” By Jesse – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Dieckmann Condensation” By Choij – Own work (Public Domain) via Commons Wikimedia
Leave a Reply