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
Amines
Amines from halogenoalkanes and ammonia
- 3 things to know
- Component 2
Overview
Why a large excess of ammonia is used, mechanism by which ammonia converts a halogenoalkane into an amine and why the reaction is carried out in a sealed tube.
What you need to know
Answer each one before you reveal it.
Write the equation for the reaction of bromoethane with excess ammonia.
Explain why a large excess of ammonia is used when an amine is made from a halogenoalkane
Questions from this subtopic
Each one with the model answer underneath.
- 1
State the reagent and conditions used to make a primary aliphatic amine from a halogenoalkane.
Model answer
The halogenoalkane is heated with a large excess of ammonia dissolved in ethanol, in a sealed tube.
- 2
Write the equation for the reaction of bromoethane with excess ammonia.
Model answer
CH₃CH₂Br + 2NH₃ → CH₃CH₂NH₂ + NH₄Br.
- 3
Explain why a large excess of ammonia is used.
Model answer
The amine produced is itself a nucleophile and attacks more halogenoalkane, so a large excess of ammonia makes it far more likely that a halogenoalkane molecule meets ammonia rather than the amine.
- 4
Name the mechanism by which ammonia converts a halogenoalkane into an amine, and identify the nucleophile.
Model answer
It is nucleophilic substitution, and the ammonia molecule is the nucleophile through the lone pair on its nitrogen.
- 5
Describe the part played by the second ammonia molecule when a halogenoalkane is converted into a primary amine.
Model answer
The first ammonia molecule bonds to the carbon to give an alkylammonium ion, and a second ammonia molecule then removes a proton from the nitrogen to release the free amine.
- 6
Explain why the reaction is carried out in a sealed tube.
Model answer
Ammonia is a gas at room temperature and the mixture must be heated, so a sealed vessel is needed to keep the ammonia in contact with the halogenoalkane under pressure.
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