Skip to content
Worked Examples · Example 7.5

Q.Write the structures of the major products expected from the following reactions:

(a) Mononitration of 3-methylphenol
(b) Dinitration of 3-methylphenol
(c) Mononitration of phenyl methanoate.
CBSENCERTSubjective· 3mImportance★★★★★
4% · 5/135 Questions
🔒 Locked · start free trial →

You're viewing a preview — the full solution, concept, methods & PYQ mapping are locked.

Start your 14-day free trial to unlock the full solution →

In electrophilic aromatic substitution, the directing effects of substituents determine the position of attack. For 3-methylphenol, both -OH and -CH3 are activating and o/p-directing, and they reinforce each other at C-4 and C-6; nitration occurs at both reinforced positions (C-4 and C-6), giving the 4-nitro and 2-nitro products. A second nitro group then goes meta to the first -NO2 (which is now the dominant deactivator) and ortho/para to -OH, landing at C-6. For phenyl methanoate, the -OCHO group is a weaker, ester-type o/p-director, and nitration occurs mainly para to it.

Let's number the ring for 3-methylphenol with -OH at C-1 and -CH3 at C-3 throughout.

(a) Mononitration of 3-methylphenol

-OH (C-1) directs to its ortho/para positions: C-2, C-4, C-6. -CH3 (C-3) directs to its ortho/para positions: C-2, C-4, C-6 as well -- the same three positions, so the two groups reinforce rather than compete.

  • C-2 sits between -OH and -CH3 (ortho to both) and is too sterically crowded to be the major site.
  • C-4 is para to -OH and ortho to -CH3 -- reinforced, and -OH is the stronger activator, so this position benefits most from the dominant group's own para preference.
  • C-6 is ortho to -OH and para to -CH3 -- also reinforced.

Both reinforced positions are attacked: mononitration gives 4-nitro-3-methylphenol (attack at C-4) together with 5-methyl-2-nitrophenol (attack at C-6). Only C-2, sandwiched between the two groups, is ruled out sterically.

Watch out

A common mistake is to report only the para product. Both C-4 and C-6 are reinforced by the two directors, and the expected answer includes both mononitration products; only C-2 (between the two groups) is excluded, on steric grounds.

(b) Dinitration of 3-methylphenol

After the first nitro group is installed at C-4, the ring carries -OH (C-1, strong activator), -CH3 (C-3, weak activator) and -NO2 (C-4, strong deactivator). The new -NO2 group now dominates the directing pattern: it sends the second electrophile to its own meta positions, which are C-2 and C-6.

Of these two positions, C-6 is ortho to -OH and para to -CH3 (both still activating there), while C-2 is ortho to both -OH and -CH3 and is sterically crowded (flanked on both sides). C-6 is the less hindered, doubly-activated site, so the second nitro group goes there. The major product is 4,6-dinitro-3-methylphenol.

Tip

In dinitration, the first nitro group deactivates the ring and becomes the dominant meta-director for the second attack; -OH and -CH3 still narrow the choice between the two remaining meta positions by their own steric and electronic preferences.

(c) Mononitration of phenyl methanoate (phenyl formate) …

Unlock everything free for 14 days

  • Full step-by-step solutions
  • Concept-first explanations
  • Methods, shortcuts & mistakes
  • PYQ mapping + timed mock tests

Full access for 14 days. No credit card required.