3.7.1

Nature & Preparation of Amines

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Nature of Amines

Amines are organic compounds that contain nitrogen. They can be thought of as alkylated forms of ammonia (e.g. NRH2). You can have both aliphatic and aromatic amines.

Aliphatic amines

Aliphatic amines

  • Aliphatic amines are amines containing aliphatic -R groups, such as alkyl chains.
  • The alkyl chain may be as short as methyl, or much longer.
Aromatic amines

Aromatic amines

  • Aromatic amines share the same general formula as aliphatic amines.
  • But aromatic amines must have an aromatic -R group.
Amides

Amides

  • Amides are different to amines but we must also be able to identify them - they crop up throughout this course.
  • An amide contains a -RCONH2 group, as shown above.

Classification of Amines

Amines, both aliphatic and aromatic, can be classified into primary, secondary and tertiary amines.

Primary amines

Primary amines

  • Primary amines contain ONE -R group and TWO -H groups.
    • NRH2.
Secondary amines

Secondary amines

  • Secondary amines contain TWO -R groups and ONE -H group.
    • NR2H.
Tertiary amines

Tertiary amines

  • Tertiary amines contain THREE -R groups and NO -H groups.
    • NR3.
Ammonium ions

Ammonium ions

  • Under certain conditions, there is a possibility of a fourth group being added through a dative covalent bond.
    • This is possible because of the lone pair on the nitrogen.
    • An example is methylamine, N(CH3)H2. in acid; N(CH3)H3+
  • These molecules are called ammonium ions and are often found as ammonium salts - as the ion is much more stable in this form (e.g. (CH3)H3N+Cl−).

Preparation of Amines

We will consider ways to prepare aliphatic and aromatic amines.

Halogenoalkane and ammonia

Halogenoalkane and ammonia

  • We can produce amines by heating halogenoalkanes with excess ammonia.
  • Above shows the mechanism of how this happens.
  • The overall reaction is:
    • NH3 + CH3Cl → CH3NH2 + HCl
Diagram
Halogenoalkane and ammonia

Halogenoalkane and ammonia

  • There is one issue with this method.
  • The primary amine produced is also nucleophilic because it too has a lone pair of electrons and can react with the halogenoalkane itself to produce a secondary amine.
    • This process can happen again to produce a tertiary amine and a quaternary ammonium ion - as shown above.
Diagram
Reducing a nitrile

Reducing a nitrile

  • You can form an amine by the reduction of a nitrile in two ways.
  • First method:
    • LiAlH4.
    • Dilute acid.
  • In the equation above the [H] term represents the reducing agent which is LiAlH4!
Reducing a nitrile

Reducing a nitrile

  • The previous method is good but LiAlH4 is expensive.
  • Instead, the second method is catalytic hydrogenation.
  • You need:
    • Hydrogen gas.
    • Metal catalyst e.g. platinum or nickel.
    • High temperature and pressure.
Preparing aromatic amines

Preparing aromatic amines

  • These are produced by reducing nitrobenzene, a two step process.
  • First step:
    • Tin.
    • Conc. HCl.
    • Under reflux.
  • This forms an ionic salt. To obtain the amine we carry out the second step:
    • Add NaOH, a base.
Jump to other topics
1

Physical Chemistry

1.1

Atoms, Molecules & Stoichiometry

1.1.1Relative Masses1.1.2The Mole1.1.3Mass Spectrometry1.1.4Empirical & Molecular Formulae1.1.5Balanced Equations1.1.6Molar Volume1.1.7End of Topic Test - Amount of Substance
1.2

Atomic Structure

1.2.1Fundamental Particles1.2.2Isotopes & Mass Number1.2.3Electron Shells, Sub-Shells & Orbitals1.2.4Electron Configuration1.2.5Ionisation Energy1.2.6Factors Affecting Ionisation Energies1.2.7Trends of Ionisation1.2.8Specific Impacts on Ionisation Energies1.2.9Electron Affinity1.2.10End of Topic Test - Atomic Structure1.2.11A-A* (AO2/3) - Atomic Structure
1.3

Chemical Bonding

1.3.1Ionic Bonding1.3.2Covalent & Dative Bonding1.3.3Shapes of Molecules1.3.4Intermolecular Forces1.3.5Intermolecular Forces 21.3.6Electronegativity1.3.7Bond Length, Bond Energy, & Bond Polarity1.3.8Metallic Bonding1.3.9Physical Properties1.3.10End of Topic Test - Bonding1.3.11A-A* (AO2/3) - Bonding
1.4

States of Matter

1.4.1Simple Covalent Molecules1.4.2The Ideal Gas Equation1.4.3States of Matter1.4.4Particle Diagrams1.4.5The Liquid State1.4.6Giant Ionic Lattices1.4.7Giant Metallic Lattices1.4.8Giant Covalent Structures1.4.9Graphene & Fullerene1.4.10Recycling
1.5

Chemical Energetics

1.5.1Calorimetry1.5.2Bond Enthalpies1.5.3Enthalpy Changes1.5.4Hess' Law1.5.5Born-Haber Cycles1.5.6Born-Haber Cycle Calculations1.5.7Entropy1.5.8Free Energy1.5.9End of Topic Test - Energetics
1.6

Electrochemistry

1.6.1Electrochemical Cells1.6.2Electrochemical Series1.6.3Commercial Application1.6.4Nernst Equation1.6.5Redox
1.7

Equilibria

1.7.1Dynamic Equilibrium & Le Chatelier1.7.2Kc1.7.3Kp1.7.4pH1.7.5The Ionic Product of Water1.7.6Weak Acids & Bases1.7.7Introduction to Solubility Equilibria1.7.8Solubility Equilibria Calculations1.7.9Free Energy of Dissolution1.7.10pH and Solubility1.7.11Common-Ion Effect1.7.12End of Topic Test - Kp & Electrochemistry1.7.13A-A* (AO2/3) - Electrochemical Cells
1.8

Partition Coefficient

1.8.1Kpc
1.9

Reaction Kinetics

1.9.1Collision Theory1.9.2Orders, Rate Constants & Equations1.9.3Rate Graphs1.9.4Rate Determining Step1.9.5Maxwell-Boltzmann Distribution1.9.6Catalysts1.9.7Homogeneous Catalysts1.9.8Heterogeneous Catalysts1.9.9End of Topic Test - Kinetics1.9.10End of Topic Test - Rate Equations1.9.11A-A* (AO2/3) - Rate Equations
2

Inorganic Chemistry

2.1

The Periodic Table

2.1.1The Periodic Table2.1.2Trends in the Periodic Table2.1.3End of Topic Test - Periodicity & Trends2.1.4Ceramics2.1.5Period 3 Elements & Oxides2.1.6Period 3 Oxides2.1.7End of Topic Test - Period 3
2.2

Group 2

2.2.1Group 2 Chemistry
2.3

Group 17

2.3.1Introduction to Halogens2.3.2Reactions of Halogens2.3.3Chlorine & Chlorate(I)2.3.4End of Topic Test - Group 172.3.5A-A* (AO2/3) - Periodicity, Group 2 & 17
2.4

Transition Metals

2.4.1General Properties2.4.2Titrations2.4.3Shapes of Complex Ions2.4.4Variable Oxidation States2.4.5Ligands2.4.6Colours of Ions2.4.7Stereoisomerism of Complex Ions2.4.8Cisplatin2.4.9Ligand Substitutions & Kstab2.4.10End of Topic Test - Transition Metals2.4.11A-A* (AO2/3) - Transition Metals
2.5

Nitrogen & Sulfur

2.5.1Nitrogen & Ammonia2.5.2Formulated vs Manure Fertilisers2.5.3Nitrogen Containing Fertilisers2.5.4Fertilizers & Eutrophication2.5.5Common Atmospheric Pollutants & Their Properties2.5.6Catalytic Converters2.5.7Atmospheric Oxides
3

Organic Chemistry & Analysis

3.1

Introduction to Organic Chemistry

3.1.1Naming Conventions3.1.2Mechanism3.1.3Isomerism3.1.4End of Topic Test - Introduction to Organic Chem
3.2

Hydrocarbons

3.2.1Fractional Distillation3.2.2Cracking3.2.3Combustion3.2.4Chlorination3.2.5End of Topic Test - Alkanes3.2.6Introduction to Alkenes3.2.7Reactions of Alkenes3.2.8Polymerisation Reactions3.2.9End of Topic Test - Alkenes3.2.10Arenes3.2.11Evidence for Structure of Arenes3.2.12Reactions of Benzene3.2.13End of Topic Test -Arenes
3.3

Halogen Derivatives

3.3.1Properties of Haloalkanes3.3.2Substitution Reactions of Haloalkanes3.3.3Environmental Impacts of Haloalkanes3.3.4End of Topic Test - Halogenoalkanes
3.4

Hydroxy Compounds

3.4.1Types of Alcohol3.4.2Oxidation 13.4.3Oxidation 23.4.4Elimination3.4.5Acids & Esters3.4.6Acyl Chlorides & Acylation3.4.7Phenols & Their Reactions3.4.8End of Topic Test - Alcohols
3.5

Carbonyl Compounds

3.5.1Carbonyls3.5.2Hydrogen Bonding & Carbonyls3.5.3Aldehydes & Ketones3.5.4Tri-Iodomethane Reaction3.5.5End of Topic Test -Carbonyls
3.6

Carboxylic Acids & Derivatives

3.6.1Properties of Carboxylic Acids3.6.2Esters3.6.3Acyl Chlorides3.6.4End of Topic Test - Carboxylic Acids
3.7

Nitrogen Compounds

3.7.1Nature & Preparation of Amines3.7.2Basicity & Nucleophilicity3.7.3Amides3.7.4Reactions of Amino Acids3.7.5Amino Acids
3.8

Polymerisation

3.8.1Properties of Addition Polymers3.8.2Condensation Polymerisation3.8.3Effects of Side-Chains on Polymers3.8.4Hydrolysis of Ester & Amide Groups3.8.5Proteins3.8.6DNA3.8.7Adhesive & Conducting Polymers3.8.8End of Topic Test - Amines & Proteins
3.9

Analytical Techniques

3.9.1Chromatography3.9.2High-Performance Liquid Chromatography3.9.3Gas Chromatography3.9.4IR Spectroscopy3.9.5Uses of IR Spectroscopy3.9.6Mass Spectrometry3.9.7Mass Spectrometry Analysis3.9.8Nuclear Magnetic Resonance3.9.9Carbon-13 NMR3.9.10Proton NMR I3.9.11Proton NMR II3.9.12End of Topic Test - Analytical Techniques3.9.13A-A* (AO2/3) - Analytical Techniques
3.10

Organic Synthesis

3.10.1Chirality & Drug Synthesis3.10.2Organic Synthesis3.10.3Examples of Synthetic Routes3.10.4End of Topic Test - Organic Synthesis

Practice questions on Nature & Preparation of Amines

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  1. 1
    Two type of amine:Fill in the list
  2. 2
    How many bonds does the nitrogen in amine molecules have?Multiple choice
  3. 3
    What does the functional group of amides contain that makes them very different to amines?Multiple choice
  4. 4
    Examples of amines:Fill in the list
  5. 5
    Any tertiary amine contains no -H groups. True or false?Flashcard
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End of Topic Test - Carboxylic Acids

Basicity & Nucleophilicity