Page No. 195

7.1. Classify the following as primary, secondary and tertiary alcohols:

Solution

Primary alcohol → (i), (ii), (iii)

Secondary alcohol → (iv), (v)

Tertiary alcohol → (vi)

7.2. Identify allylic alcohols in the above examples.

Solution

The alcohols given in (ii) and (vi) are allylic alcohols.

Page No. 198

7.3. Name the following compound according to IUPAC system.

Solution

(i) 3-Chloromethyl-2-isopropylpentan-1-ol

(ii) 2, 5-Dimethylhexane-1, 3-diol

(iii) 3-Bromocyclohexanol

(iv) Hex-1-en-3-ol

(v) 2-Bromo-3-methylbut-2-en-1-ol

Page No. 203

7.4. Show how are the following alcohols prepared by the reaction of a suitable Grignard reagent on methanal?

Solution

(i)

(ii)

7.5. Write structures of the products of the following reaction:

Solution

(i) Propene to Propene-2-ol

(ii) Methyl (2-oxocyclohexyl) ethanoate to Methyl (2-hydroxycyclohexyl) ethanoate

(iii) 2-Methylbutanal to 2-Methylbutan-1-ol

Page No. 213

7.6. Give structures of the products you would expect when each of the following alcohol reacts with (a) HCl-ZnCl₂ (b) HBr and (c) SOCl₂

(i) Butan-1-ol

(ii) 2-Methylbutan-2-ol

Solution

(a) Reaction with HCl-ZnCl₂:

(i) Primary alcohols do not react appreciably with Lucas’ reagent (HCl-ZnCl₂) at room temperature.

(ii) Tertiary alcohols react immediately with Lucas’ reagent.

(b) Reaction with HBr :

(i)

(ii)

(c) Reaction with SOCl₂:

(i)

(ii)

7.7. Predict the major product of acid catalysed dehydration of:

(i) 1-Methylcyclohexanol

(ii) Butan-1-ol

Solution

(i) 1-Methylcyclohexanol

(ii) Butan-1-ol

Solution

Resonance structure of the phenoxide ion

Resonance structures of p-nitrophenoxide ion

Resonance structures of o-nitrophenoxide ion

It can be observed that the presence of nitro groups increases the stability of phenoxide ion.