Aldehydes, Ketones and Carboxylic Acids · Chemistry · Class 12

Give the structure of the major product expected from the following reactions:

(a) Reaction of ethanal with methyl-magnesium bromide followed by hydrolysis.

(b) Hydration of But-1-ene in the presence of dilute sulphuric acid.

(c) Reaction of phenol with bromine water.

Draw the structures of major product(s) in each of the following reactions:

(a) An organic compound (A) with the molecular formula $\mathrm{C}_9 \mathrm{H}_{10} \mathrm{O}$ forms 2, 4-DNP derivative, reduces Fehling solution and undergoes Cannizzaro reaction. On vigorous oxidation, it gives 1, 2-benzene dicarboxylic acid.

(i) Identify the compound (A) and write its IUPAC name.

(ii) Write the reaction of compound (A) with

(1) 2,4-Dinitrophenyl hydrazine and

(2) Fehling solution

(iii) Write the equation of compound (A) when it undergoes Cannizzaro reaction.

OR

(b) (i) Account for the following:

(1) The alpha ( $\alpha$ )-hydrogens of aldehydes and ketones are acidic in nature.

(2) Oxidation of aldehydes is easier than ketones.

(ii) Arrange the following in :

(1) Decreasing reactivity towards nucleophilic addition reaction propanal, acetone, benzaldehyde.

(2) Increasing order of boiling point: Propane, Ethanol, Dimethylether, Propanal

(iii) Give simple chemical test to distinguish between Benzoic acid and Benzaldehyde.

(a) (i) Write the reaction involved in Cannizaro's reaction.

(ii) Why are the boiling point of aldehydes and ketones lower than that of corresponding carboxylic acids?

(iii) An organic compound '$$\mathrm{A}$$' with molecular formula $$\mathrm{C}_5 \mathrm{H}_8 \mathrm{O}_2$$ is reduced to $$\mathrm{n}$$-pentane with hydrazone followed by heating with $$\mathrm{NaOH}$$ and Glycol. 'A' forms a dioxime with hydroxylamine and gives a positive Iodoform and Tollen's test. Identify '$$A$$' and give its reaction for Iodoform and Tollen's test.

OR

(b) (i) Give a chemical test to distinguish between ethanol acid and ethanoic acid.

(ii) Why is the $$\alpha$$-hydrogens of aldehydes and ketones are acidic in nature?

(iii) An organic compound '$$\mathrm{A}$$' with molecular formula $$\mathrm{C}_4 \mathrm{H}_8 \mathrm{O}_2$$ undergoes acid hydrolysis to form two compounds '$$\mathrm{B}$$' and '$$\mathrm{C}$$'. Oxidation of '$$C$$' with acidified potassium permanganate also produces 'B'. Sodium salt of 'B' on heating with soda lime gives methane.

(1) Identify 'A', 'B' and 'C'.

(2) Out of 'B' and 'C', which will have higher boiling point? Give reason.

Which one of the following has lowest $$\mathrm{pK}_{\mathrm{a}}$$ value?

Assertion (A): Acetic acid but not formic acid can be halogenated in presence of red $$\mathrm{P}$$ and $$\mathrm{Cl}_2$$.

Reason (R): Acetic acid is a weaker acid than formic acid.