How does phenol differ from an aliphatic alcohol, and why is it more acidic and more reactive in the ring?
The properties and reactions of phenol, its weak acidity compared with alcohols, the activation of the aromatic ring towards electrophilic substitution, and tests to distinguish phenol from an alcohol.
An Eduqas A-Level Chemistry OA2.1 answer on the reactions of phenol, its acidity compared with alcohols, the activation of the aromatic ring to electrophilic substitution, and distinguishing tests.
Reviewed by: AI editorial process; not yet individually human-reviewed
Have a quick question? Jump to the Q&A page
Jump to a section
What this topic is asking
Eduqas topic OA2.1 contrasts phenol (an aromatic alcohol, with -OH bonded directly to a benzene ring) with the aliphatic alcohols met at AS. It covers phenol's weak acidity and the reason for it, the activation of the ring toward electrophilic substitution, the reactions of phenol, and tests that distinguish a phenol from an alcohol. The interplay between the -OH group and the ring is the key idea.
Phenol as a weak acid
Activation of the ring
A lone pair on the oxygen of the -OH group is partially delocalised into the aromatic ring, raising the ring's electron density. This activates the ring toward electrophiles, so phenol reacts much more readily than benzene.
Reactions of phenol
Phenol reacts with sodium metal (releasing hydrogen, like an alcohol) and with sodium hydroxide (forming sodium phenoxide and water, showing its acidity). In the ring it undergoes electrophilic substitution more readily than benzene, including bromination (as above) and nitration with dilute nitric acid.
Distinguishing phenol from an alcohol
Examples in context
Example 1. Antiseptics. Phenol (carbolic acid) was the first surgical antiseptic; modern relatives such as TCP and Dettol exploit the reactivity of substituted phenols, which trace back to the activating effect of the -OH group.
Example 2. Phenolic resins. Phenol reacts readily at the activated ring positions with methanal to form cross-linked phenol-formaldehyde resins (Bakelite), an early plastic whose formation depends on the ring's enhanced reactivity.
Try this
Q1. State the observation when neutral iron(III) chloride solution is added to phenol. [1 mark]
- Cue. A violet (purple) colour forms (an alcohol gives no colour change).
Q2. Explain why phenol reacts with sodium hydroxide but ethanol does not. [2 marks]
- Cue. Phenol is a weak acid (its phenoxide ion is stabilised by delocalisation), so it is acidic enough to react with the alkali to form a salt; ethanol is neutral and does not react.
Exam-style practice questions
Practice questions written in the style of WJEC Eduqas exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Eduqas 20194 marksPhenol is a weak acid. (a) Write an equation for the reaction of phenol with sodium hydroxide. (b) Explain why phenol is more acidic than ethanol.Show worked answer →
(a) (1).
(b) When phenol loses its , the negative charge on the phenoxide ion is delocalised into the aromatic ring (1), which stabilises the ion (1). Ethanol's alkoxide ion has no such delocalisation, so phenol releases its proton more readily and is the stronger acid (1).
Eduqas 20214 marks(a) Describe what is observed when bromine water is added to phenol, and write the equation. (b) Explain why phenol reacts with bromine water at room temperature whereas benzene does not.Show worked answer →
(a) The bromine water is decolourised and a white precipitate (2,4,6-tribromophenol) forms: (2).
(b) A lone pair on the oxygen of the -OH group is delocalised into the ring, increasing its electron density (1), so the ring is activated and reacts with bromine at room temperature without a catalyst, unlike benzene (1).
Related dot points
- The structure and bonding of benzene, evidence for the delocalised model, the stability of the aromatic ring, and electrophilic substitution reactions such as nitration and halogenation.
An Eduqas A-Level Chemistry OA1.2 answer on the structure and bonding of benzene, the delocalised model and its evidence, the stability of the aromatic ring, and electrophilic substitution reactions.
- Classification of alcohols, oxidation of primary and secondary alcohols, dehydration and esterification, the acidity and reactions of carboxylic acids, and ester formation and hydrolysis.
An Eduqas A-Level Chemistry C3.4 answer on classifying and oxidising alcohols, dehydration, the acidity and reactions of carboxylic acids, and the formation and hydrolysis of esters.
- The carbonyl group, nucleophilic addition reactions (with HCN and with reducing agents), oxidation of aldehydes, and the tests that distinguish aldehydes from ketones.
An Eduqas A-Level Chemistry OA2.2 answer on the carbonyl group, nucleophilic addition with HCN and reducing agents, oxidation of aldehydes, and the tests distinguishing aldehydes from ketones.
- The acidity and reactions of carboxylic acids, the derivatives (esters, acyl chlorides, acid anhydrides and amides), their interconversion, esterification and hydrolysis, and the reactivity of acyl chlorides.
An Eduqas A-Level Chemistry OA2.3 answer on the acidity and reactions of carboxylic acids, the derivatives (esters, acyl chlorides, anhydrides, amides), their interconversion, and the reactivity of acyl chlorides.
Sources & how we know this
- WJEC Eduqas GCE A Level Chemistry specification (from 2015) — WJEC Eduqas (2015)