Question 81 markMCQSection A

$At low temperature, phenol reacts with dil. HNO₃ to yield$

Q: At low temperature, phenol reacts with dil. HNO₃ to yield

**Correct option: (D) ortho- and para-nitrophenol** Phenol with **dilute HNO₃ at low temperature (~298 K)** undergoes electrophilic substitution to give a **mixture of o-nitrophenol and p-nitrophenol**. - The –OH group is a strong **activating, o/p-directing** group. - Dilute acid + low temperature = mild condition → only mono-nitration, at both o and p positions.

Alcohols, Phenols and Ethers

Nitration of phenol

Options

(A)

2, 4, 6-Trinitrophenol

(B)

o-Nitrophenol only

(C)

p-Nitrophenol only

(D)

ortho-and para-nitrophenol

Official answer

Correct option: (D) ortho- and para-nitrophenol Phenol with dilute HNO₃ at low temperature (~298 K) undergoes electrophilic substitution to give a mixture of o-nitrophenol and p-nitrophenol . The -OH group is a strong activating, o/p-directing group. Dilute acid + low temperature = mild condition \to only mono-nitration, at both o and p positions.

phenol nitration

dilute nitric acid

o-nitrophenol

p-nitrophenol

ortho para directing

electrophilic substitution

activating group

steam distillation

Marking scheme

1. $1 mark: correct option (D) ortho- and para-nitrophenol.$
2. $No partial credit; 'o only' or 'p only' or trinitrophenol are incorrect.$

Hint

$Dilute acid + low temperature = mild mono-nitration; -OH is ortho/para directing, so both isomers form.$

Quick oral answer

$Because the hydroxyl group activates the ring and directs ortho/para, dilute nitric acid at low temperature gives a mixture of ortho- and para-nitrophenol, later separated by steam distillation.$

Common mistakes

1. $Choosing picric acid (2,4,6-trinitrophenol) — that needs concentrated HNO₃, not dilute.$
2. $Assuming only one isomer forms; -OH directs to both ortho and para.$
3. $Forgetting that the o- and p-nitrophenols are later separated by steam distillation.$

Analysis and explanation

Concept The -OH group donates electron density into the ring (+R effect), making phenol far more reactive than benzene and directing incoming electrophiles to the ortho and para positions. Reaction (mild condition) With dilute HNO₃ at low temperature the nitronium ion supply is limited, so substitution stops at the mono-nitro stage, producing both o- and p-nitrophenol. Separation point (favourite in exams) The two products are separated by steam distillation : o-nitrophenol is steam-volatile (intramolecular H-bonding, chelation) while p-nitrophenol is not (intermolecular H-bonding). Why the distractors are wrong (A) 2,4,6-Trinitrophenol (picric acid) forms only with concentrated HNO₃ (with H₂SO₄), a much harsher condition. (B) & (C) 'only' one isomer is wrong — both o and p form simultaneously.

Interesting facts

$o-Nitrophenol boils lower than p-nitrophenol because it forms an intramolecular hydrogen bond (chelation), making it steam-volatile.$

$Picric acid (2,4,6-trinitrophenol) from concentrated nitration was once used both as a yellow dye and as a military explosive.$

Question details

Q8 of 37 questions

Board: CBSE
Class: Class 12
Subject: Chemistry
Year: 2026
Section: Section A
Marks: 1
Type: MCQ
Chapter: Alcohols, Phenols and Ethers
Topic: $Nitration of phenol$
Bloom's level: remember
Syllabus topic: $Unit: Alcohols, Phenols and Ethers — Chemical Reactions of Phenols: Electrophilic Aromatic Substitution (Nitration)$
Author: CBSE
Reviewed by: Padhantu Academic Team

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Frequently asked questions

$How are o-nitrophenol and p-nitrophenol separated?$

$By steam distillation. o-Nitrophenol has intramolecular hydrogen bonding (chelation), so it is volatile in steam and distils over; p-nitrophenol has intermolecular hydrogen bonding, is less volatile, and remains behind.$

$What forms if concentrated HNO₃ is used instead?$

$Concentrated HNO₃ (usually with H₂SO₄) causes complete nitration to give 2,4,6-trinitrophenol, known as picric acid.$