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Chapter 12- Aldehydes-Ketones and Carboxylic Acids Interview Questions Answers

Question 1 :

Write the structures of the following compounds.

Answer 1 :

(i) α-Methoxypropionaldehyde

(ii) 3-Hydroxybutanal

(iii) 2-Hydroxycyclopentane carbaldehyde

(iv) 4-Oxopentanal

(v) Di-sec-butyl ketone

(vi) 4-Fluoroacetophenone

Answer

(iv)

(v)

(vi)

Question 2 :

Write the structures of products of the followingreactions;

Answer 2 :

(i)


Answer

3

4


Question 3 :

Arrange the following compounds in increasing order oftheir boiling points.

CH3CHO,CH3CH2OH,CH3OCH3,CH3CH2CH3

Answer 3 :

The molecular masses of the given compoundsare in the range 44 to 46. CH3CH2OHundergoes extensive intermolecular H-bonding, resulting in the association ofmolecules. Therefore, it has the highest boiling point. CH3CHOis more polar than CH3OCH3 and so CH3CHO has strongerintermolecular dipole − dipole attraction than CH3OCH3 CH3CH2CH3 hasonly weak van der Waals force. Thus, the arrangement of the given compounds inthe increasing order of their boiling points is given by:

CH3CH2CH3 3OCH3 3CHO< CH3CH2OH

Question 4 :

Arrange the following compounds in increasing order oftheir reactivity in nucleophilic addition reactions.


Answer 4 :

(i)Ethanal, Propanal, Propanone, Butanone.

(ii)Benzaldehyde, p-Tolualdehyde, p-Nitrobenzaldehyde, Acetophenone.

Hint:Consider steric effect and electronic effect.


Answer

(i)

The +I effect of the alkyl group increases in the order:

Ethanal < Propanal < Propanone < Butanone

The electron density at the carbonyl carbon increases withthe increase in the +I effect. As a result, the chances of attack by anucleophile decrease. Hence, the increasing order of the reactivities of thegiven carbonyl compounds in nucleophilic addition reactions is:

Butanone < Propanone < Propanal < Ethanal

(ii)

 

The +I effect is more in ketone than inaldehyde. Hence, acetophenone is the least reactive in nucleophilic addition reactions.Among aldehydes, the +I effect is the highest in p-tolualdehydebecause of the presence of the electron-donating −CH3 groupand the lowest in p-nitrobezaldehyde because of the presence of theelectron-withdrawing −NO2 group. Hence, the increasing order of thereactivities of the given compounds is:

Acetophenone < p-tolualdehyde< Benzaldehyde < p-Nitrobenzaldehyde

Question 5 :

Predict the products of the followingreactions:

Answer 5 :

(i)

(iv)


Answer

(i)

(iv)

Question 6 : Show how each of the following compounds can be converted to benzoic acid.

Answer 6 :

(i) Ethylbenzene           (ii) Acetophenone

(iii) Bromobenzene      (iv) Phenylethene(Styrene)


Answer

(i)

(ii)

(iii)

(iv)

Question 7 :

Which acid of each pair shown here would you expect to bestronger?

Answer 7 :

(i) CH3CO2H orCH2FCO2H

(ii)CH2FCO2H orCH2ClCO2H

(iii) CH2FCH2CH2CO2H or CH3CHFCH2CO2H

(iv)


Answer

(i)

The +I effect of −CH3 groupincreases the electron density on the O−H bond. Therefore, release of protonbecomes difficult. On the other hand, the −I effect of F decreases the electrondensity on the O−H bond. Therefore, proton can be released easily. Hence, CH2FCO2H isa stronger acid than CH3CO2H.

(ii)