Chemistry Class 12 NCERT Solutions: Chapter 12 Aldehydes Ketones and Carboxylic Acids Part 16 (For CBSE, ICSE, IAS, NET, NRA 2023)

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Q: 3. Arrange the following compounds in increasing order of their boiling points.

Answer:

The molecular masses of the given compounds are in the range . undergoes extensive intermolecular H-bonding, resulting in the association of molecules. Therefore, it has the highest boiling point. is more polar than and so has stronger intermolecular dipole − dipole attraction than has only weak van der Waals force. Thus, the arrangement of the given compounds in the increasing order of their boiling points is given by:

Q: 4. Arrange the following compounds in increasing order of their reactivity in nucleophilic addition reactions.

(i) Ethanal, Propanal, Propanone, Butanone.

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

Hint:- Consider steric effect and electronic effect

Answer:

(i)

The Alkyl Group Increases in the Order

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

Ethanal < Propanal < Propanone < Butanone

The electron density at the carbonyl carbon increases with the increase in the + I effect.

As a result, the chances of attack by a nucleophile decrease. Hence, the increasing order

of the reactivities of the given carbonyl compounds in nucleophilic addition reactions is:

Butanone < Propanone < Propanal < Ethanal

(ii)

The Increasing Order of the Reactivities

The + I effect is more in ketone than in aldehyde. Hence, acetophenone is the least reactive in nucleophilic addition reactions. Among aldehydes, the + I effect is the highest in p-tolualdehyde because of the presence of the electron-donating group and the lowest in p-nitrobenzaldehyde because of the presence of the electron-withdrawing group. Hence, the increasing order of the reactivities of the given compounds is: Acetophenone < p-tolualdehyde < Benzaldehyde < p-Nitrobenzaldehyde

Q: 5. Predict the products of the following reactions:

(i)

Predict the Products

(ii)

Predict the Products

(iii)

(iv)

Predict the Products

Answer:

(i)

Predict the Products

(ii)

Predict the Products

(iii)

Predict the Products

(iv)

Predict the Products