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Condensation Reaction:Types of Condensation Reactions, Practice problems and Frequently asked questions(FAQs)

Condensation Reaction:Types of Condensation Reactions, Practice problems and Frequently asked questions(FAQs)

Condensation is a phenomenon that we encounter on a daily basis.

On a hot day with high temperatures, you will notice that the mirror has fogged up after taking a hot water shower.

There are little beads of water on the mirror when you touch it.

How did this fog form? Where did these water beads come from?

This phenomenon is known as condensation.

It is the process of converting water vapour in the air into liquid water. Water vapour is the gaseous form of water that is present in the air.

Condensation is vital to the survival of life on Earth. When water molecules are heated, they begin to attract one another. They start to move rapidly and lose mass, causing them to rise. When a gas cools, the water molecules attract one another and fall as rain. Rain is the world's primary source of freshwater. Condensation is also beneficial in agriculture. When condensed water falls to the earth as precipitation, it makes water available to plants and animals. The process of condensation is crucial to human life. If condensation did not occur, water vapor would remain gaseous, and gaseous water would be incapable of supporting human life.

Table of content:

  • Condensation reactions
  • Types of condensation reactions
  • Practice problems
  • Frequently asked questions(FAQs)

Condensation reactions:

In organic chemistry, a condensation reaction is a specific type of chemical reaction in which two molecules combine to form one molecule, typically with the loss of a minor molecule like water. If water is lost during the reaction, it is also referred to as a dehydration synthesis. Other substances can also be lost, including ammonia, ethanol, acetic acid, and hydrogen sulfide.

Amino acids are biological compounds that have an amine functional group on one end of the molecule and a carboxylic acid functional group on the other. Two amino acids can combine in a condensation reaction, and a covalent bond is formed between the amine nitrogen of the first amino acid and the carboxyl carbon of the second amino acid. This produces a water molecule, which is eliminated during the condensation process.

Types of condensation reactions:

1. Aldol condensation:

In the presence of a diluted base, aldol condensation takes place in -hydrogen-containing aldehydes and ketones, resulting in the formation of -hydroxy aldehydes or -hydroxy ketones, which are known as aldols. When aldol is subjected to condensation (or elimination) in the presence of heat, this reaction is most frequently referred to as aldol condensation.When a condensation reaction occurs between two different carbonylcompounds, it is calledcross-aldol condensation. A noteworthy feature of the Aldol reaction is that the carbon-carbon bond formation takes place between the alpha-carbon atom of one aldehyde and the carbonyl group of the other. This is because the generation of the enolate of one carbonyl can involve the proton abstraction from the alpha-carbon atom of the other carbonyl.

The process of aldol condensation involves a nucleophilic attack of enolate on a carbonyl to produce a β-hydroxy ketone or β-hydroxy aldehyde. The catalyzation of the aldol condensation reaction can be carried out with the help of an acidic or basic solution in the presence of heat.

Bases such as hydroxide ions and alkoxide ions are used for the partial conversion of an aldehyde to its enolate anion.

The enolate undergoes a nucleophilic addition to the carbonyl group. This is achieved in a solution that contains both an aldehyde and its enolate. Aldol condensation is prominent in those aldehydes that have an α-hydrogen along with a dilute base to give β-hydroxy aldehydes, also called aldols. When the above reaction takes place between two different carbonyl compounds, it is referred to as the Crossed Aldol Condensation Reaction. When both the aldehydes possess α-hydrogens, then they can both form carbanions (enolate) and that can also act as acceptors of enolates. Thus, the reaction results in a mixture of four products that have a minute synthetic value. In case any of the aldehydes does not have α-hydrogen, then it can only act as an acceptor of Carbanion. Thus, only two products will be formed on the completion of the reaction. Also, the condensation of the initial products takes place rapidly and thus leads to the formation of -unsaturated ketone or aldehyde.

Mechanism of Aldol condensation:

STEP 1: Aldehyde is subjected to deprotonation done by the hydroxide ion that functions as a base and thus abstracts the alpha-hydrogen which results in the formation of the enolate/carbanion.


STEP 2: Enolate ion/carbanion attaches itself to the aldehyde at the site of the electrophilic carbonyl carbon, and results in the formation of an alkoxide intermediate.