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प्रश्न
What is meant by the following term? Give an example of the reaction in the following case.
Acetal
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उत्तर
Gem-dialkoxy compounds in which two alkoxy groups are present on the terminal carbon atom are called acetals. These are formed when the aldehyde reacts with two equivalents of monohydric alcohol in the presence of dry hydrogen chloride.
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संबंधित प्रश्न
Write balanced chemical equations for action of ammonia on - formaldehyde
Arrange the following in the increasing order of their reactivity towards nucleophilic addition reaction:
C6H5COCH3, CH3-CHO, CH3COCH3
Draw the structure of the semicarbazone of ethanal.
Arrange the following compound in increasing order of its reactivity in nucleophilic addition reactions.
Benzaldehyde, p-Tolualdehyde, p-Nitrobenzaldehyde, Acetophenone.
Hint: Consider steric effect and electronic effect.
Give plausible explanation for the following:
Cyclohexanone forms cyanohydrin in good yield but 2, 2, 6 trimethylcyclohexanone does not.
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benzaldehyde from benzoyl chloride
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H2N- NH2 followed by heating with KOH in ethylene glycol.
How will you convert benzoic acid to m-bromobenzoic acid?
Benzaldehyde can be obtained from benzal chloride. Write reactions for obtaining benzalchloride and then benzaldehyde from it.
Which among the following is most reactive to give nucleophilic addition?
Arrange the following in the increasing order of their property indicated:
Ethanal, Propanone, Propanal, Butanone (reactivity towards nucleophilic addition)
What happens when propanone is treated with CH3MgBr and then hydrolysed?
What happens when ethanal is treated with excess ethanol and acid?
Which of the following is most reactive in nucleophilic addition reactions?
The following questions are case-based questions. Read the passage carefully and answer the questions that follow:
| The carbon-oxygen double bond is polarised in aldehydes and ketones due to higher electronegativity of oxygen relative to carbon. Therefore, they undergo nucleophilic addition reactions with a number of nucleophiles such as HCN, NaHSO3, alcohols, ammonia derivatives and Grignard reagents. Aldehydes are easily oxidised by mild oxidising agents as compared to ketones. The carbonyl group of carboxylic acid does not give reactions of aldehydes and ketones. Carboxylic acids are considerably more acidic than alcohols and most of simple phenols. |
Answer the following:
(a) Write the name of the product when an aldehyde reacts with excess alcohol in the presence of dry HCl. (1)
(b) Why carboxylic acid is a stronger acid than phenol? (1)
(c) (i) Arrange the following compounds in increasing order of their reactivity towards CH3MgBr: (1)
CH3CHO, \[\begin{array}{cc}
\ce{(CH3)3C-C-CH3}\\
\phantom{....}||\\
\phantom{....}\ce{O}
\end{array}\], \[\begin{array}{cc}
\ce{CH3-C-CH3}\\
||\\
\ce{O}
\end{array}\]
(ii) Write a chemical test to distinguish between propanal and propanone. (1)
OR
(c) Write the main product in the following: (2)
| (i) |  |
| (ii) |  |
Why dissociation of HCN is suppressed by the addition of HCL?
Draw structure of the following derivative.
The ethylene ketal of hexan-3-one
Draw the structure of the following derivative.
Acetaldehydedimethylacetal
Give an example of the reaction in the following case.
Imine
