Question

Alcohols and Phenols are acidic in nature. Electron withdrawing groups in phenol increase its acidic strength and electron releasing groups decrease it. Alcohols undergo nucleophilic substitution with hydrogen halides to yield alkyl halides. Dehydration of alcohols gives alkenes. On oxidation, primary alcohols yield aldehydes with mild oxidising agents and carboxylic acids with strong oxidising agents, while secondary alcohols yield ketones. Tertiary alcohols are resistant to oxidation. The presence of - OH group in phenols activates the aromatic ring towards electrophilic substitution and directs the incoming group to ortho and para positions due to resonance effect.

Answer the following questions :

(ii) Write the structure of the major product expected from the dinitration of 3-methylphenol.

Hint:

Both OH and CH3 direct to positions 2, 4 and 6, but position 2 is crowded, so the nitro groups go to 4 and 6.

Answer 1

Step 1: Understanding the Concept:
In 3-methylphenol the -OH group is on C-1 and the \(\mathrm{-CH_3}\) group is on C-3.
Both groups activate the ring and both direct the new group to ortho and para positions.

Step 2: Find the activated positions:
The -OH group (strong activator) directs to C-2, C-4 and C-6.
The methyl group directs to C-2 and C-4 (ortho to it) and to C-6 (para to it).
So both groups point to the same three positions: C-2, C-4 and C-6.

Step 3: Choose the two positions for the nitro groups:
C-2 lies between the -OH and the \(\mathrm{-CH_3}\) groups. It is crowded, so the attack there is hindered.
The less hindered positions C-4 and C-6 take the two \(\mathrm{-NO_2}\) groups.
\[ \mathrm{3\text{-}CH_3C_6H_4OH + 2\,HNO_3 \rightarrow 3\text{-}CH_3\text{-}4,6\text{-}(NO_2)_2C_6H_2OH + 2\,H_2O} \]

Step 4: Describe the structure:
It is a benzene ring with an -OH on C-1, \(\mathrm{-NO_2}\) groups at C-4 and C-6 and a \(\mathrm{-CH_3}\) group at C-3.
Renumbered to give the lowest locants, the IUPAC name is 5-methyl-2,4-dinitrophenol.

Final Answer:
The major product is 3-methyl-4,6-dinitrophenol (named 5-methyl-2,4-dinitrophenol): a phenol with two nitro groups ortho and para to -OH and the methyl group meta to -OH. \[ \boxed{\text{3-methyl-4,6-dinitrophenol}} \]