Chemistry Class 12 NCERT Solutions: Chapter 11 Alcohols Phenols and Ethers Part 4 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Q: 6. What is meant by hydroboration-oxidation reaction? Illustrate it with an example.

Answer:

The addition of borane followed by oxidation is known as the hydroboration-oxidation reaction. For example, propan-1-ol is produced by the hydroboration-oxidation reaction of propene. In this reaction, propene reacts with diborane to form trialkyl borane as an addition product. This addition product is oxidized to alcohol by hydrogen peroxide in the presence of aqueous sodium hydroxide.

Q_6_The Presence of Aqueous Sodium Hydroxide

Q: 7. Give the structures and IUPAC names of monohydric phenols of molecular formula .

Answer:

Q_7_1_The Structure and IUPAC Names of Monohydric Phenols of …

Q: 8. While separating a mixture of ortho and para nitrophenols by steam distillation, name the isomer which will be steam volatile. Give reason.

Answer:

Intramolecular H-bonding is present in o-nitrophenol. In p-nitrophenol, the molecules are strongly associated due to the presence of intermolecular bonding. Hence, o-nitrophenol is steam volatile.

Q_8_O-Nitrophenol is Steam Volatile

Q: 9. Give the equations of reactions for the preparation of phenol from cumene.

Answer:

To prepare phenol, cumene is first oxidized in the presence of air of cumene hydro peroxide.

Q_9_1_The Presence of Air of Cumene Hydro Peroxide

Then, cumene hydroxide is treated with dilute acid to prepare phenol and acetone as by products.

Q_9_2_Cumene Hydroxide is Treated with Dilute Acid to Prepar …

Q: 10. Write chemical reaction for the preparation of phenol from chlorobenzene.

Answer:

Chlorobenzene is fused with (at and atm pressure) to produce sodium phenoxide, which gives phenol on acidification.

Q_10_Chlorobenzene is Fused with NaOH to Produce Sodium Phen …

Q: 11. Write the mechanism of hydration of ethene to yield ethanol.

Answer:

The mechanism of hydration of ethene to form ethanol involves three steps.

Step 1:-

Protonation of ethene to form carbocation by electrophilic attack of

Q_11_1_Protonation of Ethene to Form Carbocation by Electrop …

Step 2:

Nucleophilic attack of water on carbocation:

Q_11_2_Nucleophilic Attack of Water on Carbocation

Step 3:

Deprotonation to form ethanol:

Q_11_3_Deprotonation to Form Ethanol

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