Chemistry Class 12 NCERT Solutions: Chapter 11 Alcohols Phenols and Ethers Part 6

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Q: 17. Give equations of the following reactions:

(i) Oxidation of propan-1-ol with alkaline solution

(ii) Bromine in with phenol

(iii) Dilute with phenol

(iv) Treating phenol with chloroform in presence of aqueous

Answer:

(ii)

Q 17 ii Bromine in CS 2 with Phenol

Q 17 II Bromine in CS 2 with Phenol

(iii)

Q 17 iii Dilute HNO3 with phenol

Q 17 III Dilute HNO3 with Phenol

(iv)

Q 17 iv Treating phenol with chloroform in presence of aqueo …

Q 17 IV Treating Phenol with Chloroform

Q: 18. Explain the following with an example

(i) Kolbe’s reaction

(ii) Reimer-Tiemann reaction

(iii) Williamson ether synthesis

(iv) Unsymmetrical ether

Answer:

(i) Kolbe’s reaction

When phenol is treated with sodium hydroxide, sodium phenoxide is produced. This sodium phenoxide when treated with carbon dioxide, followed by acidification, undergoes electrophilic substitution to give ortho-hydroxybenzoic acid as the main product. This reaction is known as Kolbe’s reaction.

Q 18 Kolbe’s reaction

Q 18 Kolbe’S Reaction

(ii) Reimer-Tiemann reaction

When phenol is treated with chloroform in the presence of sodium hydroxide, a - group is introduced at the ortho position of the benzene ring

Q 18 ii Reimer-Tiemann Reaction

Q 18 II Reimer-Tiemann Reaction

This reaction is known as the Reimer-Tiemann reaction.

The intermediate is hydrolyzed in the presence of alkalis to produce salicylaldehyde

Q 18 ii 1 Reimer-Tiemann Reaction

Q 18 II 1 Reimer-Tiemann Reaction

(iii) Williamson ether synthesis:

Williamson ether synthesis is a laboratory method to prepare symmetrical and unsymmetrical ethers by allowing alkyl halides to react with sodium alkoxides.

Q 18 iii 1 Williamson ether synthesis

Q 18 III 1 Williamson Ether Synthesis

This reaction involves attack of the alkoxide ion on the alkyl halide. Better results are obtained in case of primary alkyl halides.

Q 18 iii 2 Williamson ether synthesis

Q 18 III 2 Williamson Ether Synthesis

If the alkyl halide is secondary or tertiary, then elimination competes over substitution

(iv) Unsymmetrical ether:

An unsymmetrical ether is an ether where two groups on the two sides of an oxygen atom differ (i.e., have an unequal number of carbon atoms). For example: ethyl methyl ether

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