Apply phenol chemistry to naphthol
Transfer phenol's acid-base and directing principles to a phenolic group on a fused aromatic ring while checking available positions.
A Level; Cambridge International Chemistry 9701, 2028–2030 syllabus, Topic 32. Distinguish phenol (–OH directly on an aromatic ring) from an alcohol (–OH on an aliphatic carbon). Use the specified reagents, temperatures and products; phenol reactions are limited to those listed in the syllabus. Written practice is self-checked
Before you begin
- Recognise alcohols and phenols, aromatic substitution, acids and bases, and diazonium ions from the preceding organic topics.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What makes the –OH in naphthol phenolic?
What you will learn
- Recognise a phenolic –OH in another aromatic structure
- Apply acid-base and electrophilic-substitution behavior qualitatively
- Use the supplied structure to identify available directed positions
Identify phenolic connectivity in naphthol
Naphthol contains an –OH group attached directly to an aromatic carbon in a fused-ring system. That makes the hydroxy group phenolic rather than an aliphatic alcohol group.
Apply the chemistry of phenol to another phenolic compound: the O–H can show weak acidity, and oxygen lone-pair donation can influence electrophilic substitution. The exact ring positions depend on the naphthol isomer and on which positions are already occupied.
Transfer the rule, then inspect the structure
Start by locating the carbon bonded to –OH. Use the supplied ring numbering to identify the available ortho/para-like positions around the phenolic ring; do not blindly copy a benzene position number onto a fused system.
The syllabus asks you to apply phenol knowledge to compounds such as naphthol. It does not require memorising a universal list of naphthol products; use the structure and conditions in the question.
Pause and explain
When applying phenol's directing effect to a fused aromatic ring, what must you inspect?
Worked example
How should you approach a question about brominating a supplied naphthol structure?
Show the worked solution
- Identify the phenolic –OH attached directly to an aromatic carbon.
- Apply the principle that –OH activates and directs electrophilic substitution.
- Use the supplied fused-ring numbering to choose available positions.
Answer Apply phenol's activating/directing effect, then use the given naphthol structure to identify available positions; do not assume benzene numbering transfers unchanged.
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Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
A supplied fused-ring compound has –OH directly attached to an aromatic carbon. Classify the group and state one relevant phenol principle.
Give me a hint
Check the O–H attachment and apply a syllabus behavior.
Compare my reasoning
- The hydroxy group is ring-bound.
- It is phenolic.
- Phenolic –OH can donate electron density and direct electrophilic substitution.
It is a phenolic –OH; its lone pair can activate the aromatic system and influence substitution positions.
Look for these in your work
- Connectivity checked
- Phenol class named
- Relevant principle applied
Why is the exact product position for naphthol not safely determined from a benzene diagram alone?
Give me a hint
Account for the fused ring and existing substituents.
Compare my reasoning
- Naphthol has a fused aromatic framework.
- Its numbering differs from a single benzene ring.
- The supplied structure shows available positions and any competing substituents.
A fused ring has its own numbering and occupied sites, so use the supplied structure to map phenolic directing positions rather than copying benzene locants blindly.
Look for these in your work
- Fused structure recognised
- Numbering issue stated
- Evidence source identified
A question supplies a naphthol isomer and asks for a likely electrophilic substitution site. Give a safe method without memorising an unsupported product.
Give me a hint
Apply the director to the actual numbered structure.
Compare my reasoning
- Locate the ring carbon bonded to –OH.
- Mark nearby available positions influenced by oxygen donation.
- Consider other substituents and choose among unoccupied sites using the supplied conditions.
Use the given numbering, identify positions influenced by phenolic –OH, remove occupied positions and account for other directors; infer the product from the provided structure and conditions.
Look for these in your work
- Reference carbon identified
- Available sites considered
- Other effects incorporated
Common mistakes
- Calling a ring-bound –OH an alcohol
- Copying benzene numbering directly onto a fused ring
- Naming a specific naphthol product without reading the supplied structure
- Ignoring positions already occupied by other groups
What can you explain now?
What makes the –OH in naphthol phenolic?
Compare with the explanation
It is attached directly to an aromatic carbon
Direct ring attachment defines a phenolic group.
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Make it stick
What can be transferred from phenol to naphthol, and what must be re-read from the supplied structure?
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.