CCEA A-Level Chemistry 1110
Formulae, Equations and Amounts of Substance
Atomic Structure
Bonding
Intermolecular Forces and Structure
Shapes of Molecules and Ions
Redox
The Halogens
Acid-Base Titrations
Qualitative Tests
Formulae and Amounts of a Substance
Nomenclature and Isomerism in Organic Chemistry
Alkanes
Alkenes
Halogenoalkanes
Alcohols
Infrared Spectroscopy
Energetics
Kinetics
Equilibrium
Group II Elements and Their Compounds
Lattice Enthalpy, Entropy and Free Energy
Rates of Reaction
Equilibrium and Acid-Base Equilibria
Isomerism
Aldehydes and Ketones
Carboxylic Acids
Derivatives of Carboxylic Acids
Aromatic Chemistry
Spectroscopy and Chromatography
Volumetric Analysis
Transition Metals
Electrode Potentials
Amines
Amides and Polymers
Amino Acids and Proteins
Amines
Diazonium salts and coupling
- 3 things to know
- Unit A2 2
Overview
Coupling reaction, formed when benzenediazonium chloride couples with phenol and formed when benzenediazonium chloride couples with phenylamine.
What you need to know
Answer each one before you reveal it.
Why must the temperature be kept below about 10 °C when benzenediazonium chloride is made?
Why is the nitrous acid generated in the reaction mixture rather than added?
Questions from this subtopic
Each one with the model answer underneath.
- 1
How is benzenediazonium chloride formed?
Model answer
Phenylamine is treated with nitrous acid, made in situ from sodium nitrite and hydrochloric acid, below about 10 °C.
- 2
Why must the temperature be kept below about 10 °C?
Model answer
The diazonium salt decomposes above that temperature, giving phenol and nitrogen gas.
- 3
Why is the nitrous acid generated in the reaction mixture rather than added?
Model answer
Nitrous acid is unstable and cannot be stored, so it is made as it is needed from sodium nitrite and the acid present.
- 4
Write the formula of the benzenediazonium ion.
Model answer
C₆H₅N₂⁺.
- 5
What is a coupling reaction?
Model answer
The reaction of a diazonium ion with an activated aromatic compound to form an azo compound joined by a −N=N− group.
- 6
What is formed when benzenediazonium chloride couples with phenol?
Model answer
An orange or yellow azo dye, formed under alkaline conditions.
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