Q: Which of the following gives positive iodoform test?

The correct option is Ethanol. Ethanol contains the $\text{CH}3\text{-CH(OH)-}$ group, which upon oxidation with iodine and sodium hydroxide yields a yellow precipitate of iodoform ($\text{CHI}3$).

Question 1

Which of the following compounds has the highest boiling point?

Accepted Answer

The correct option is Butan-1-ol. Alcohols have higher boiling points than hydrocarbons, ethers, and haloalkanes of comparable molecular masses due to the presence of intermolecular hydrogen bonding, which is quite strong in primary alcohols.

Question 2

The reaction of sodium ethoxide with chloroethane to form diethyl ether is known as:

Accepted Answer

The correct option is Williamson synthesis. Williamson synthesis is an important laboratory method for the preparation of symmetrical and unsymmetrical ethers by the reaction of an alkyl halide with a sodium alkoxide.

Question 3

Phenol reacts with concentrated nitric acid to give:

Accepted Answer

The correct option is Picric acid. When phenol is treated with concentrated nitric acid in the presence of concentrated sulfuric acid, it undergoes nitration at all three ortho and para positions, yielding 2,4,6-trinitrophenol, commonly known as picric acid.

Question 4

Which of the following gives positive iodoform test?

Accepted Answer

The correct option is Ethanol. Ethanol contains the $	ext{CH}3	ext{-CH(OH)-}$ group, which upon oxidation with iodine and sodium hydroxide yields a yellow precipitate of iodoform ($	ext{CHI}3$).

Question 5

When phenol is distilled with zinc dust, it gives:

Accepted Answer

The correct option is Benzene. Zinc dust reduces the phenolic group to a hydrogen atom, effectively removing the oxygen atom from the phenol ring and converting it into benzene.

Alcohols, Phenols and Ethers — CBSE Class 12 Chemistry Important Questions & Revision Notes