Aldehyde,ketones and carboxylic acid Most Important NCERT QnA

Q1. Write the iupac name of the following ketones and aldehyde:

(i)

Ans. Heptan-2-al

(ii)

Ans. 4-Bromo-2-methylhexanal

(iii)

Ans. 3-phenylprop-2-enal

(iv)

Ans. Cyclopentane-1-carbaldehyde

(v)

Ans. Pent-2-enal

(vi)

Ans. Benzophenone

Q2. Draw the structures of the following:

(i) 4-methlypent-3-en-2-one

Ans.

(ii) p-methylbenzaldehyde

Ans.

Q3. Arrange the following compound in the increasing order of boiling point

CH3CHO,CH3CH2OH,CH3OCH3,CH3CH2CH3.

Ans. CH3CH2CH3<CH3OCH3<CH3CHO<CH3CH2OH

Q4. Arrange the following compound in the increasing order of their reactivity nucleophilic addition reaction .

(i) ethanol,propanol,propanone,butanone

Ans. Butanone<propanone<propanal<ethanal

(ii) Benzaldehyde,p-tolualdehyde,p-nitrobenzaldehyde,acetophenone

Ans. Acetophenone<p-tolualdehyde<Benzaldehyde<p-nitrobenzaldehyde

Q5. Complete the following reactions:

(i)

Ans.

(ii)
Ans.

(iii)
Ans.

(iv)
Ans.

Q6. Arrange the following in the increasing order of acidic strength :

(i) ClCH2COOH,FCH2COOH,CH3COOH

Ans. CH3COOH<ClCH2COOH<FCH2COOH

(ii) CH3CH2CH(Br)COOH,CH3CH(Br)CH2COOH,(CH3)2CHCOOH,CH3CH2CH2COOH

Ans.

(iii)Benzoic acid, 4-nitrobenzoic acid, 3,4-dinitrobenzoic acid, 4-methoxy benzoic acid

Ans.

Q7. Although phenoxide ion has more number of resonating structure than carboxylate ion. Carboxylic acid is a strong acid than pheno,Give reason.

Ans.

Phenoxide ion has more number of

resonating structure than carboxylate ion but carboxylic acid is more acidic than phenol it is because in the resonating structure of phenoxide ion carbon atom has negative charge which is highly unstable while in the resonating structure of carboxylate ion there is negative charge on oxygen atom which is highly stable as compared to carbon so that is why carboxylic acid is more stable than phenol.

Q8. Give simple chemical test to distinguish:

(i) Acetophenone and benzophenone

Ans. When we react acetophenone with sodium hypoiodite it gives a yellow precipitate where as benzophenone do not.

(ii) Phenol and benzoic acid

Ans. When we react sodium bicarbonate with benzoic acid it will give a brisk effervescence while in phenol no reaction occur .

Alternate method

(iii) benzoic acid and ethly benzoate

Ans. When we react sodium bicarbonate with benzoic acid it will give a brisk effervescence while in ethyl benzoate no reaction occur .

(iv) Pentan-2-one and Pentan-3-one

Ans. When we react pentan-2-one with sodium hypoiodite it gives a yellow precipitate where as Pentan-3-one do not.

(v) ethanal and propanal

Ans. When we react ethanal with sodium hypoiodite it gives a yellow precipitate where as propanal do not.

Q9. Describe the following:

(i) Acetylation:-

Ans. Acetylation is the process of introducing an RCO-- group in compound that contain a replaceable hydrogen atom.

(ii) Cannizaro reaction:-

Aldehyde ketone which doesn't have an alpha hydrogen . Such carbonyl compounds in the presence of conc. NaOH and heat undergo disproportionation reaction to produce corresponding carboxylate ion and alcohol.