CBSE Class 12 Chemistry 2023 Outside Delhi Set 1 Solved Paper

SECTION - D

The following questions are case based questions. Read the passage carefully and answer the questions that follow:

Question : 31

Total: 35

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 presence of dry HCl.
(b) Why carboxylic acid is a stronger acid than phenol?
(c) (i) Arrange the following compounds in increasing order of their reactivity towards CH3MgBr:
CH3CHO,(CH3)3C−

∥

−CH3, CH3−

∥

−CH3
(ii) Write a chemical test to distinguish between propanal and propanone.
OR
(c) Write the main product in the following:

Solution: 👈: Video Solution

(a) It yield alkoxyalcohol intermediate, known as hemiacetals which further reacts to give gemdialkoxy compound known as acetal.
(b) Due to the resonance in carboxylic acids, the negative atom (oxygen atom), whereas, in alcohol or phenols, the negative charge is on the less electronegative atom.
(c) (i) (CH3)3C−

∥

−CH3< CH3−

∥

−CH3<CH3CHO
(ii) We can use iodoform test to distinguish between propanol and propanone as aldehyde group shows this test where as ketones does not.
OR

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