Phenols

Phenol activates the aromatic ring and reacts readily with bromine water without a halogen carrier.

Functional group
Ar-OH

Overview

Aromatic compounds with hydroxyl groups bonded directly to the ring.

Phenol activates the aromatic ring and reacts readily with bromine water without a halogen carrier.

In a phenol the hydroxyl group is attached directly to an aromatic ring. Phenol is more acidic than an ordinary alcohol because its conjugate base is resonance-stabilised. Benzyl alcohol has a -CH2- spacer and must be treated as an alcohol, not as a phenol.

Identifiers

Functional group
Ar-OH
Chemical identifiers
SMILES
Oc1ccccc1

Properties

Acid-base behaviour
Aqueous hydroxide can convert phenol into phenoxide; acidification recovers the neutral phenol.
Ring reactivity
The OH substituent activates the ring toward electrophilic substitution; available positions control products.

Diagnostic tests

bromine-water phenol test

Reagent
bromine water
Conditions
Add bromine water to an aqueous sample at room temperature and shake.
Positive observation
the bromine colour disappears and a white precipitate of 2,4,6-tribromophenol forms
Negative observation
no white precipitate forms
Interpretation
Decolourisation together with the white precipitate supports the presence of phenol or a similarly activated phenolic ring.
Scope
Phenol reacts readily with bromine water without a halogen carrier.
Limitations
Decolourisation alone is not diagnostic because alkenes also discharge bromine water; the precipitate is the more useful distinguishing observation.
Evidence
textbook core

Related compounds

  • Bisphenol A

    The two-ended phenolic building block in the selected PC route.

  • Phenol

    An aromatic hydroxyl compound whose acidity differs from that of an alcohol.

  • 2-Methylphenol

    2-Methylphenol is an organic compound with the molecular formula C7H8O.

  • 3-Methylphenol

    3-Methylphenol is an organic compound with the molecular formula C7H8O.

  • 4-Methylphenol

    4-Methylphenol is an organic compound with the molecular formula C7H8O.

  • Catechol

    Catechol is an organic compound with the molecular formula C6H6O2.

  • Resorcinol

    Resorcinol is an organic compound with the molecular formula C6H6O2.

  • Hydroquinone

    Hydroquinone is an organic compound with the molecular formula C6H6O2.

  • Paracetamol

    Paracetamol is an organic compound with the molecular formula C8H9NO2.

  • Salicylic acid

    A molecule with adjacent phenol and carboxylic-acid groups, central to aspirin chemistry.

  • Methyl salicylate

    An aromatic ester that retains a separate phenolic hydroxyl group.

  • Vanillin

    Vanillin is an organic compound with the molecular formula C8H8O3.

  • Eugenol

    Eugenol is an organic compound with the molecular formula C10H12O2.

  • 2,4,6-Tribromophenol

    A phenol with bromine at both ortho positions and the para position.

  • 2-Nitrophenol

    A phenol with a nitro group adjacent to the hydroxyl-bearing carbon.

  • 4-Nitrophenol

    A phenol with hydroxyl and nitro groups opposite one another on the ring.

Connected reactions

References

  1. Organic Chemistry: Properties of Alcohols and PhenolsJohn McMurry · OpenStax Organic Chemistry · 2023

    Supports functional-group chemistry used to curate the linked examples. Checked 2026-09-16; named examples are applications of textbook scope, without claimed experimental yields.

  2. Organic Chemistry: Reactions of PhenolsJohn McMurry · OpenStax Organic Chemistry · 2023

    Supports the hydroxyl group as a strongly activating, ortho- and para-directing substituent in electrophilic aromatic halogenation of phenols.

  3. Pearson Edexcel International Advanced Level Chemistry Practical GuidePearson Education Limited · Pearson qualifications · 2018

    Official Pearson practical guidance for organic qualitative tests, including bromine water, acidified dichromate, silver nitrate, carbonyl reagents and the iodoform reaction.

  4. Polycarbonate melt polymerisation from bisphenol A and diphenyl carbonateAsahi Kasei
  5. PubChem Compound Summary: Phenol (CID 996)National Center for Biotechnology Information · PubChem

    Identity, molecular formula, molecular weight and aliases retrieved via PUG REST on 2026-09-08.

  6. PubChem Compound Summary: 2-Methylphenol (CID 335)National Center for Biotechnology Information · PubChem

    Identity, molecular formula, molecular weight and aliases retrieved via PUG REST on 2026-09-08.

  7. PubChem Compound Summary: 3-Methylphenol (CID 342)National Center for Biotechnology Information · PubChem

    Identity, molecular formula, molecular weight and aliases retrieved via PUG REST on 2026-09-08.

  8. PubChem Compound Summary: 4-Methylphenol (CID 2879)National Center for Biotechnology Information · PubChem

    Identity, molecular formula, molecular weight and aliases retrieved via PUG REST on 2026-09-08.

  9. PubChem Compound Summary: Catechol (CID 289)National Center for Biotechnology Information · PubChem

    Identity, molecular formula, molecular weight and aliases retrieved via PUG REST on 2026-09-08.

  10. PubChem Compound Summary: Resorcinol (CID 5054)National Center for Biotechnology Information · PubChem

    Identity, molecular formula, molecular weight and aliases retrieved via PUG REST on 2026-09-08.

  11. PubChem Compound Summary: Hydroquinone (CID 785)National Center for Biotechnology Information · PubChem

    Identity, molecular formula, molecular weight and aliases retrieved via PUG REST on 2026-09-08.

  12. PubChem Compound Summary: Paracetamol (CID 1983)National Center for Biotechnology Information · PubChem

    Identity, molecular formula, molecular weight and aliases retrieved via PUG REST on 2026-09-08.

  13. PubChem Compound Summary: Salicylic acid (CID 338)National Center for Biotechnology Information · PubChem

    Identity, molecular formula, molecular weight and aliases retrieved via PUG REST on 2026-09-08.

  14. PubChem Compound Summary: Methyl salicylate (CID 4133)National Center for Biotechnology Information · PubChem

    Identity, molecular formula, molecular weight and aliases retrieved via PUG REST on 2026-09-08.

  15. PubChem Compound Summary: Vanillin (CID 1183)National Center for Biotechnology Information · PubChem

    Identity, molecular formula, molecular weight and aliases retrieved via PUG REST on 2026-09-08.

  16. PubChem Compound Summary: Eugenol (CID 3314)National Center for Biotechnology Information · PubChem

    Identity, molecular formula, molecular weight and aliases retrieved via PUG REST on 2026-09-08.

  17. PubChem Compound Summary: 2,4,6-Tribromophenol (CID 1483)National Center for Biotechnology Information · PubChem

    Identity, molecular formula, molecular weight and selected English aliases retrieved via PUG REST on 2026-09-16. Chinese search names are curated nomenclature translations. Unspecified stereochemistry remains unspecified.

  18. PubChem Compound Summary: 2-Nitrophenol (CID 6947)National Center for Biotechnology Information · PubChem

    Identity, molecular formula, molecular weight and selected English aliases retrieved via PUG REST on 2026-09-16. Chinese search names are curated nomenclature translations. Unspecified stereochemistry remains unspecified.

  19. PubChem Compound Summary: 4-Nitrophenol (CID 980)National Center for Biotechnology Information · PubChem

    Identity, molecular formula, molecular weight and selected English aliases retrieved via PUG REST on 2026-09-16. Chinese search names are curated nomenclature translations. Unspecified stereochemistry remains unspecified.