Alcohols Phenols And Ethers

i. Ethyl Alcohol to Ethyl Acetate:

CH₃CH₂OH + CH₃COOH ⟶_{H2SO4, heat} CH₃COOCH₂CH₃ + H₂O

Explanation: Ethyl alcohol reacts with acetic acid in the presence of concentrated sulphuric acid and heat to form ethyl acetate (an ester) and water. This reaction is known as **esterification**.

ii. Phenol to Benzene:

C₆H₅OH ⟶_{Zn dust, heat} C₆H₆ + ZnO

Explanation: When phenol is heated with zinc dust, it undergoes reduction. The –OH group is removed as ZnO and the product formed is **benzene**.

iii. Diethyl Ether to Ethyl Chloride:

(C₂H₅)₂O + 2HCl ⟶_{ZnCl2, heat} 2C₂H₅Cl + H₂O

Explanation: Diethyl ether reacts with concentrated hydrochloric acid in the presence of anhydrous zinc chloride upon heating to form **ethyl chloride** and water. This is an example of **cleavage of ether** by halogen acids.

Topic: Alcohols, Phenols, and Ethers — Conversion Reactions

Answer: In the Dow process, phenol is prepared by heating chlorobenzene with aqueous sodium hydroxide at high temperature and pressure.

Explanation:

The reaction involves nucleophilic substitution of the –Cl group by –OH group.

Reaction:

Thus, phenol is obtained after acidification of sodium phenoxide.

Answer:

Phenol reacts readily with bromine water to form 2,4,6-tribromophenol, which is a white precipitate.

Explanation:

Reaction:

The white precipitate formed is 2,4,6-tribromophenol.

Reason: The –OH group activates the benzene ring towards electrophilic substitution, especially at the ortho and para positions, making bromination easy even in mild conditions.

Give reason: Group 16 elements have lower ionisation enthalpy compared to Group 15 elements.

Answer:

Group 16 elements have lower ionisation enthalpy than Group 15 elements because of extra electron–electron repulsion due to paired electrons in the p-orbitals.

Explanation:

Group 15 elements have half-filled p-orbitals (more stable configuration), whereas in Group 16 elements, one of the p-orbitals contains a pair of electrons.

This extra electron–electron repulsion in Group 16 elements reduces the energy required to remove an electron, thereby lowering ionisation enthalpy.

Write two uses of dioxygen.

Answer:

(i) Dioxygen is used in oxy-acetylene flames for welding and cutting metals.
(ii) It is essential for respiration and combustion processes.

Explanation:

- Oxygen supports combustion and is vital for life processes. - It is also used in industries for the manufacture of steel, nitric acid, and as an oxidizing agent in various chemical reactions.