Eduqas A-Level Chemistry A410QS
Formulae and Equations
Basic Ideas About Atoms
Chemical Calculations
Bonding
Solid Structures
The Periodic Table
Simple Equilibria and Acid-Base Reactions
Thermochemistry
Rates of Reaction
The Wider Impact of Chemistry
Organic Compounds
Hydrocarbons
Halogenoalkanes
Alcohols and Carboxylic Acids
Instrumental Analysis
Redox and Standard Electrode Potential
Redox Reactions
Chemistry of the P-Block
Chemistry of the D-Block Transition Metals
Chemical Kinetics
Enthalpy Changes for Solids and Solutions
Entropy and Feasibility of Reactions
Equilibrium Constants
Acid-Base Equilibria
Stereoisomerism
Aromaticity
Alcohols and Phenols
Aldehydes and Ketones
Carboxylic Acids and Their Derivatives
Amines
Amino Acids, Peptides and Proteins
Organic Synthesis and Analysis
Specified Practical Work
Practical Skills and Techniques
Mathematical Skills in Chemistry
Alcohols and Phenols
Reactions of phenol and the iron(III) chloride test
- 3 things to know
- Component 2
Overview
Recall questions on the reaction of phenol with bromine water and with ethanoyl chloride, the observations and the equations, why phenol brominates so much more readily than benzene, the iron(III) chloride test and its result, and how phenol is distinguished from an alcohol.
What you need to know
Answer each one before you reveal it.
State what is seen when bromine water is added to an aqueous solution of phenol at room temperature.
Explain why phenol brominates readily in water when benzene needs a halogen carrier to brominate at all.
Questions from this subtopic
Each one with the model answer underneath.
- 1
State what is seen when bromine water is added to an aqueous solution of phenol at room temperature.
Model answer
The orange colour disappears immediately and a white precipitate forms, accompanied by a sharp antiseptic smell.
- 2
Name the precipitate formed when phenol reacts with bromine water and give the equation.
Model answer
It is 2,4,6-tribromophenol, formed by C₆H₅OH + 3Br₂ → C₆H₂Br₃OH + 3HBr.
- 3
Explain why phenol brominates readily in water when benzene needs a halogen carrier to brominate at all.
Model answer
A lone pair on the oxygen atom is partly delocalised into the ring, which raises the electron density there so that the ring itself can polarise a bromine molecule and generate the electrophile unaided.
- 4
At which positions on the ring does bromine substitute in phenol?
Model answer
At positions 2, 4 and 6, that is the two carbons either side of the hydroxyl group and the one directly opposite it.
- 5
Name the type of reaction that takes place when phenol reacts with bromine water.
Model answer
It is an electrophilic substitution, with three hydrogen atoms of the ring replaced in turn.
- 6
Both phenol and an alkene decolourise bromine water. How can the two be told apart in the test tube?
Model answer
Phenol also throws down a white precipitate, whereas the alkene gives a soluble colourless product and leaves the mixture clear.
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