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Last updated date: 30th Nov 2023
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MVSAT Dec 2023

What happens when a ketone is mixed with $ NaOH $ ?

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Hint :We know that the Ethanal reacts with sodium hydroxide to form beta-hydroxy butyraldehyde. The product is known as aldol and this is the example of the aldol condensation reaction. It is given by ketones or aldehydes having an alpha hydrogen atom. Aldehyde and alcohol are represented by “Aldol”.

Complete Step By Step Answer:
When an aldehyde reacts with carbon at the (alpha) site to the carbonyl of another molecule under basic or acidic conditions to obtain beta-hydroxy aldehyde. The molecular formula of ethanal. Aldol condensation is an organic reaction in which enolate ion reacts with a carbonyl compound to form hydroxy aldehyde. It is followed by dehydration to give a conjugated enone and it plays a vital role in organic synthesis. It is creating a path to form carbon-carbon bonds.
The Aldol reaction is an important organic reaction of ketones and aldehydes and is shown by these compounds because they contain alpha – hydrogen atoms. They will undergo self-condensation in the presence of dilute alkalis like dilute sodium hydroxide. In the reaction, the aldol or ketol are formed by eliminating the water molecule or they undergo dehydration.
Let's use acetone as an example. The reaction involves several steps.
Step 1. Proton abstraction to form a resonance-stabilized enolate ion.
 $ H{{O}^{-}}+C{{H}_{3}}COCC{{H}_{3}}\rightleftharpoons \left[ C{{H}_{2}}COC{{H}_{3}}\leftrightarrow C{{H}_{2}}=C\left( C{{H}_{3}} \right)-O \right]+{{H}_{2}}O. $
Step2. The enolate anion attacks the carbonyl carbon in another acetone molecule.
 $ C{{H}_{3}}COC{{H}_{2}}+C{{H}_{3}}COC{{H}_{3}}\to C{{H}_{3}}COC{{H}_{2}}C{{\left( C{{H}_{3}} \right)}_{2}}-O $
Step 3. Protonation of the enolate ion to form an $ \alpha - $ hydroxy ketone.
 $ C{{H}_{3}}COC{{H}_{2}}C{{\left( C{{H}_{3}} \right)}_{2}}-O+{{H}_{2}}O\to C{{H}_{3}}COC{{H}_{2}}-C{{\left( C{{H}_{3}} \right)}_{2}}-OH+O{{H}^{-}} $
Step 4. Dehydration to form an $ \alpha ,\beta - $ unsaturated ketone.
 $ C{{H}_{3}}COC{{H}_{2}}-C{{\left( C{{H}_{3}} \right)}_{2}}-OH\to C{{H}_{3}}COCH=C{{\left( C{{H}_{3}} \right)}_{2}}+{{H}_{2}}O $

Note :
Remember that aldol condensation reaction is also given by ketone compounds. Ketone compounds undergo self- condensation to form (beta) - hydroxyketone (ketol) in the presence of dilute $ Ba{{\left( OH \right)}_{2}}. $ When two compounds exchange parts to form two different compounds, the reaction is known as a double displacement reaction. Thus, the reaction of sodium hydroxide with zinc sulphate is a double displacement reaction.