Organic Chemistry Questions and Answers for Aptitude test on “Claisen and Cross Claisen Condensation”.
1. Which of the following reaction shows Claisen condensation?
a) 
b) 
c) 
d) 
Answer: c
Clarification: The Claisen condensation is a carbon–carbon bond forming reaction that occurs between two esters or one ester and another carbonyl compound in the presence of a strong base, resulting in a β-keto ester or a β-diketone.
2. Which ester will not give a good yield of the Claisen condensation product with NaOEt in EtOH?
a) 
b)
c) 
d) 
Answer: c
Clarification: The Claisen condensation is reversible and it is formation of a stabilized enolate of the product which leads to a high yield at equilibrium. When the product cannot give a stabilized enolate, the yield will be poor.
3. Which of the following is a product formed in Claisen condensation?
a) β- ester
b) β-ketone
c) β-keto ester
d) Y-diketone
Answer: c
Clarification: The Claisen condensation is a carbon–carbon bond forming reaction that occurs between two esters or one ester and another carbonyl compound in the presence of a strong base, resulting in a β-keto ester or a β-diketone.
4. Which of the following stamen is incorrect about Claisen condensation?
a) The product is a β-keto ester which resists deprotonation by the strong base in the reaction mixture
b) The reaction involves the condensation of two esters in the presence of strong base
c) A strong base is required to remove H+ from an α-H position in one of the starting esters
d) A strong base is required to remove H+ from an α-H position in one of the starting esters
Answer: a
Clarification: The product is a β-keto ester which gets deprotonated by the strong base in the reaction mixture and get converted into simple keto group.
5. What will be the product of the following reaction?
a) Ethyl acetoacetate
b) Methyl acetoacetate
c) Propyl acetoacetate
d) Butyl acetoacetate
Answer: a
Clarification: The Claisen Condensation between esters containing α-hydrogens, promoted by a base such as sodium ethoxide, affords β-keto esters.
6. What will be the product of the following reaction?
a)
b) 
c) 
d) 
Answer: d
Clarification: The Claisen Condensation between esters containing α-hydrogens, promoted by a base such as sodium ethoxide, affords β-keto esters.
