Question

Br\(_2\)/CS\(_2\)

Answer 1

When phenol reacts with bromine in carbon disulfide (CS\(_2\)), an electrophilic substitution reaction occurs, where the hydroxyl group (OH) activates the ring towards substitution at the ortho and para positions. The major product is 2,4,6-Tribromophenol, as bromine atoms are added at the ortho and para positions relative to the hydroxyl group. \[ \text{C}_6\text{H}_5\text{OH} + 3\text{Br}_2 \xrightarrow{\text{CS}_2} \text{C}_6\text{H}_2\text{Br}_3\text{OH} \]

Answer 2

When phenol reacts with concentrated nitric acid (HNO\(_3\)), it undergoes nitration at the ortho and para positions relative to the hydroxyl group. The major product is 2,4,6-Trinitrophenol (picric acid), which is highly reactive due to the electron-donating effect of the hydroxyl group, activating the ring for nitration. \[ \text{C}_6\text{H}_5\text{OH} + 3\text{HNO}_3 \rightarrow \text{C}_6\text{H}_2\text{NO}_3\text{OH} \]

Answer 3

Phenol does not undergo protonation readily because the lone pair of electrons on the oxygen of the hydroxyl group is delocalized into the benzene ring through resonance. This reduces the electron density on the oxygen atom, making it less available to accept a proton. As a result, phenol is less basic than alcohols and does not readily undergo protonation.

Answer 4

Phenol is a stronger acid than cresol because cresol has a methyl group (\(-CH_3\)) attached to the aromatic ring. The methyl group is an electron-donating group, which increases the electron density on the ring and on the oxygen atom of the hydroxyl group. This reduces the ability of the oxygen atom to lose a proton, making cresol less acidic than phenol. In contrast, phenol’s hydroxyl group is less stabilized and more likely to lose a proton, making it more acidic.

Answer 5

The Reimer-Tiemann reaction involves the formylation of phenol, where the hydroxyl group is activated to form an ortho-formylated product. In the presence of chloroform (CHCl\(_3\)) and a base like NaOH, the major product is 2-formylphenol (also known as ortho-hydroxybenzaldehyde).
The IUPAC name of the product is 2-formylphenol.