Study Notes On Crossed Aldol Condensation (Chemical Science) - Download PDF!

By Renuka Miglani|Updated : April 25th, 2022

Are you an Aspirant of CSIR-NET and looking for some short and reliable notes for Chemical Sciences to strong your base for preparations? We have got you covered!

Candidates preparing for their CSIR NET exam can really make their preparation journey easier with the help of some reliable study notes that cover the topics in the most simple way. We at BYJU'S Exam Prep have come up with the idea of providing short notes on Crossed Aldol Condensation, which comes under the Organic Chemistry section of the Chemical Science syllabus. 

The short notes on Crossed Aldol Condensation are developed by our experienced subject-matter experts to provide you with the most standard and authentic set of study materials to be focused upon. The students need the best resources for their preparation to clear the CSIR NET examination, Here are the most reliable study notes to make the topics easier for you and also help you to save your time for the preparations for the upcoming CSIR-NET 2022 exam.

Study Notes On Crossed Aldol Condensation

An aldol reaction occurring between two different carbonyl compounds is known as Crossed Aldol. It is also known as ‘Mixed Aldol Reaction’. Here, both carbonyl compounds so involved must have an α-hydrogen each. It is a kind of condensation reaction in which up to four different products are formed.

This reaction occurs in Protic solvent, such as water or alcohol.

Note: This reaction can be carried out in the following combinations to yield four products-

(i). Between two different aldehydes

(ii). Between two different ketones

(iii). Between an aldehyde and a ketone.

Here, both reactants should have an α hydrogen.

Example- Ethanal and propanal react to give four products.


Note: Mixed aldol reaction occurs due to two factors-

1. Aldehydes are more reactive acceptor Electrophiles than ketones and formaldehyde is more reactive than other aldehydes, i.e., reactivity order is as follows-

Formaldehyde > aldehydes > ketones.


2. All aldehydes which do not possess hydrogen can only act as acceptors and therefore the number of products so formed decreases. Whereas mixed aldols both having hydrogen gives complex mixture of products thus it is not preferred until one reactant has no -hydrogen.

In such case, number of products can be calculated using this formula- 



It is a useful synthetic reaction only if one of the aldehydes does not contain α-hydrogen atoms, such as- formaldehyde, benzaldehyde etc. 

(i) With formaldehyde


(ii) With benzaldehyde. It is known as the Claisen Schmidt reaction.

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