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प्रश्न
What is meant by the following term? Give an example of the reaction in the following case.
Aldol
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उत्तर
Aldehydes and ketones having at least one α-hydrogen undergo a reaction in the presence of dilute alkali as catalyst to form β-hydroxy aldehydes (aldol) or β-hydroxy ketones (ketol), respectively. This is known as the aldol reaction.
\[\begin{array}{cc}
\ce{\underset{Ethanal}{2CH3-CHO}<=>[dil.NaOH] CH3 - CH - CH2 - CHO ->[\Delta][-H2O]\underset{But-2-enal}{CH3 - CH = CH - CHO}}\\
|\phantom{.....................}\\
\ce{\underset{(Aldol)}{\underset{3-Hydroxybutanal}{OH}}}\phantom{...................}\
\end{array}\]
\[\begin{array}{cc}
\phantom{..................}\ce{CH3}\phantom{.............................}\ce{CH3}\\
\phantom{..............}|\phantom{.................................}|\\
\ce{\underset{Propanone}{2CH3 - CO - CH3} <=>[Ba(OH)2] CH3 - C - CH2CO - CH3->[\Delta][-H2O]\underset{(Aldol condensation product)}{\underset{4-Methylpent-3-en-2-one}{CH3 - C = CH - CO - CH3}}}\\
|\phantom{...................}\\
\ce{\underset{4-Hydroxy-4-methylpentan-2-one}{\underset{(Ketol)}{OH}}}\phantom{................}\
\end{array}\]
APPEARS IN
संबंधित प्रश्न
How will you convert ethanal into the following compound?
But-2-enal
Write chemical equations of the following reaction :
Propanone is treated with dilute Ba (OH)2-.
Write a chemical equation for the following reaction:
Propanone is treated with dilute Ba( OH)2.
What is substituted imine called?
Compounds A and C in the following reaction are:
\[\ce{CH3CHO ->[(i) CH3MgBr][(ii) H2O] (A) ->[H2SO4, Δ] (B) ->[Hydroboration oxidation] (C)}\]
Which of the following compounds do not undergo aldol condensation?
(i) \[\ce{CH3 - CHO}\]
(ii) 
(iii) \[\begin{array}{cc}
\phantom{}\ce{O}\\
\phantom{}||\\
\ce{CH3 - C - CH3}
\end{array}\]
(iv) \[\begin{array}{cc}
\phantom{}\ce{CH3}\\
|\phantom{...}\\
\ce{CH3 - C - CHO}\phantom{..}\\
|\phantom{...}\\
\phantom{}\ce{CH3}\\
\end{array}\]
Which of the following conversions can be carried out by Clemmensen Reduction?
(i) Benzaldehyde into benzyl alcohol
(ii) Cyclohexanone into cyclohexane
(iii) Benzoyl chloride into benzaldehyde
(iv) Benzophenone into diphenyl methane
Why is there a large difference in the boiling points of butanal and butan-1-ol?
What product will be formed on reaction of propanal with 2-methylpropanal in the presence of \[\ce{NaOH}\]? What products will be formed? Write the name of the reaction also.
Why are carboxylic acids more acidic than alcohols or phenols although all of them have hydrogen atom attached to a oxygen atom \[\ce{(-O-H)}\]?
Which of the following gives aldol con~ensation reaction?
Predict the reagent for carrying out the following transformations:
Ethanal to 3-hydroxy butanal
Why is the α-hydrogens of aldehydes and ketones are acidic in nature?
Assertion (A): The final product in Aldol condensation is always α, β-unsaturated carbonyl compound.
Reason (R): α, β-unsaturated carbonyl compounds are stabilised due to conjugation.
Identify A and B:
When acetaldehyde is treated with dilute NaOH, the following reaction is observed.
\[\begin{array}{cc}
\ce{2CH3 - CHO ->[dil.NaOH] CH3 - CH - CH2 - CHO}\\
\phantom{...............}|\\
\phantom{.................}\ce{OH}
\end{array}\]
- What are the functional groups in the product?
- Can another product be formed during the same reaction? (Deduce the answer by doing atomic audit of reactant and product).
- Is this an addition reaction or condensation reaction?
