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Chapter 12- Aldehydes, Ketones, and Carboxylic Acids 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





Question 2 :

Write the structures of products of the followingreactions;

Answer 2 :





Question 3 :

Arrange the following compounds in increasing order oftheir boiling points.


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:


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.



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



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 :