Chemistry Class 12 NCERT Solutions: Chapter 11 Alcohols Phenols and Ethers Part 3

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Q: 3. (i) Draw the structures of all isomeric alcohols of molecular formula and give their IUPAC names.

(ii) Classify the isomers of alcohols in question (i) as primary, secondary and tertiary alcohols.

Answer:

(i) The structures of all isomeric alcohols of molecular formula, are shown below:

(A)

(B)

(C)

3-Methylbutan-1-ol(1°)

(D)

(E)

Pentan-2-ol(2°)

(F)

3-Methybutan-2-ol (2°)

(G)

(H)

2-Methylbutan-2-ol (3°)

(ii) Primary alcohol: Pentan-1-ol; 2-Methylbutan-1-ol;

3-Methylbutan-1-ol; 2, 2−Dimethylpropan-1-ol

Secondary alcohol: Pentan-2-ol; 3-Methylbutan-2-ol;

Pentan-3-ol

Tertiary alcohol: 2-methylbutan-2-ol

Q: 4. Explain why propanol has higher boiling point than that of the hydrocarbon, butane?

Answer

Propanol undergoes intermolecular H-bonding because of the presence of group On the other hand, butane does not

Q 4 1 The Presence of -OH group the other Hand, Butane does not

Q 4 1 the Presence of -OH Group the Other Hand, Butane Does Not

Q 4 1 The Presence of -OH group the other Hand, Butane does not

Therefore, extra energy is required to break hydrogen bonds. For this reason, propanol has a higher boiling point than hydrocarbon butane.

Q: 5. Alcohols are comparatively more soluble in water than hydrocarbons of comparable molecular masses. Explain this fact.

Answer:

Alcohols form with water due to the presence of group. However, hydrocarbons cannot form with water.

Q 5 1 Hydrocarbons cannot form H-bonds with Water

Q 5 1 Hydrocarbons Cannot Form H-Bonds With Water

Q 5 1 Hydrocarbons cannot form H-bonds with Water

As a result, alcohols are comparatively more soluble in water than hydrocarbons of comparable molecular masses.