3.9.4

IR Spectroscopy

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Infrared Spectroscopy

Infrared (IR) spectroscopy is used to identify certain bonds within a compound. This means it's pretty useful in distinguishing between different functional groups.

Bonds and infrared

Bonds and infrared

Infrared radiation is absorbed by any polar bond. Non-polar bonds do not absorb radiation.
Polar bonds only absorb radiation of specific frequencies.
The absorbed infrared radiation makes the bonds vibrate.
The frequency absorbed is specific to each bond.
Different bonds in different places can have different frequencies.
- E.g. An alcohol OH is different to a carboxylic acid OH.

Common frequencies

Common frequencies

The frequency is normally reported as a wavenumber.
- A wavenumber is $\frac{1}{\lambda}$ , where λ is the wavelength.
The image above shows the common frequencies of several different bonds. You don’t need to learn them, as they’ll be supplied in an exam.

IR spectrum

IR spectrum

Above is a graph showing the IR spectrum of ethanoic acid.

Interpreting spectra

Interpreting spectra

The section from 1,500 to 500 cm^-1 is called the fingerprint region. This is usually full of small peaks and is specific to any molecule.
There are large databases of fingerprint regions and you can search for a match to identify your compound.
If you don’t have access to a database, most helpful bonds are outside of this region.
- E.g. The previous slide showed ethanoic acid, which has a peak at 3,000, because of a carboxylic acid OH, and one at 1,720, because of a CO double bond.

1

Physical Chemistry

1.1

Atoms, Molecules & Stoichiometry

1.1.1Relative Masses 1.1.2The Mole 1.1.3Mass Spectrometry 1.1.4Empirical & Molecular Formulae 1.1.5Balanced Equations 1.1.6Molar Volume 1.1.7End of Topic Test - Amount of Substance

1.2

Atomic Structure

1.2.1Fundamental Particles 1.2.2Isotopes & Mass Number 1.2.3Electron Shells, Sub-Shells & Orbitals 1.2.4Electron Configuration 1.2.5Ionisation Energy 1.2.6Factors Affecting Ionisation Energies 1.2.7Trends of Ionisation 1.2.8Specific Impacts on Ionisation Energies 1.2.9Electron Affinity 1.2.10End of Topic Test - Atomic Structure 1.2.11A-A* (AO2/3) - Atomic Structure

1.3

Chemical Bonding

1.3.1Ionic Bonding 1.3.2Covalent & Dative Bonding 1.3.3Shapes of Molecules 1.3.4Intermolecular Forces 1.3.5Intermolecular Forces 2 1.3.6Electronegativity 1.3.7Bond Length, Bond Energy, & Bond Polarity 1.3.8Metallic Bonding 1.3.9Physical Properties 1.3.10End of Topic Test - Bonding 1.3.11A-A* (AO2/3) - Bonding

1.4

States of Matter

1.4.1Simple Covalent Molecules 1.4.2The Ideal Gas Equation 1.4.3States of Matter 1.4.4Particle Diagrams 1.4.5The Liquid State 1.4.6Giant Ionic Lattices 1.4.7Giant Metallic Lattices 1.4.8Giant Covalent Structures 1.4.9Graphene & Fullerene 1.4.10Recycling

1.5

Chemical Energetics

1.5.1Calorimetry 1.5.2Bond Enthalpies 1.5.3Enthalpy Changes 1.5.4Hess' Law 1.5.5Born-Haber Cycles 1.5.6Born-Haber Cycle Calculations 1.5.7Entropy 1.5.8Free Energy 1.5.9End of Topic Test - Energetics

1.6

Electrochemistry

1.6.1Electrochemical Cells 1.6.2Electrochemical Series 1.6.3Commercial Application 1.6.4Nernst Equation 1.6.5Redox

1.7

Equilibria

1.7.1Dynamic Equilibrium & Le Chatelier 1.7.2Kc 1.7.3Kp 1.7.4pH 1.7.5The Ionic Product of Water 1.7.6Weak Acids & Bases 1.7.7Introduction to Solubility Equilibria 1.7.8Solubility Equilibria Calculations 1.7.9Free Energy of Dissolution 1.7.10pH and Solubility 1.7.11Common-Ion Effect 1.7.12End of Topic Test - Kp & Electrochemistry 1.7.13A-A* (AO2/3) - Electrochemical Cells

1.8

Partition Coefficient

1.9

Reaction Kinetics

1.9.1Collision Theory 1.9.2Orders, Rate Constants & Equations 1.9.3Rate Graphs 1.9.4Rate Determining Step 1.9.5Maxwell-Boltzmann Distribution 1.9.6Catalysts 1.9.7Homogeneous Catalysts 1.9.8Heterogeneous Catalysts 1.9.9End of Topic Test - Kinetics 1.9.10End of Topic Test - Rate Equations 1.9.11A-A* (AO2/3) - Rate Equations

2

Inorganic Chemistry

2.1

The Periodic Table

2.1.1The Periodic Table 2.1.2Trends in the Periodic Table 2.1.3End of Topic Test - Periodicity & Trends 2.1.4Ceramics 2.1.5Period 3 Elements & Oxides 2.1.6Period 3 Oxides 2.1.7End of Topic Test - Period 3

2.2

Group 2

2.2.1Group 2 Chemistry

2.3

Group 17

2.3.1Introduction to Halogens 2.3.2Reactions of Halogens 2.3.3Chlorine & Chlorate(I)2.3.4End of Topic Test - Group 17 2.3.5A-A* (AO2/3) - Periodicity, Group 2 & 17

2.4

Transition Metals

2.4.1General Properties 2.4.2Titrations 2.4.3Shapes of Complex Ions 2.4.4Variable Oxidation States 2.4.5Ligands 2.4.6Colours of Ions 2.4.7Stereoisomerism of Complex Ions 2.4.8Cisplatin 2.4.9Ligand Substitutions & Kstab 2.4.10End of Topic Test - Transition Metals 2.4.11A-A* (AO2/3) - Transition Metals

2.5

Nitrogen & Sulfur

2.5.1Nitrogen & Ammonia 2.5.2Formulated vs Manure Fertilisers 2.5.3Nitrogen Containing Fertilisers 2.5.4Fertilizers & Eutrophication 2.5.5Common Atmospheric Pollutants & Their Properties 2.5.6Catalytic Converters 2.5.7Atmospheric Oxides

3

Organic Chemistry & Analysis

3.1

Introduction to Organic Chemistry

3.1.1Naming Conventions 3.1.2Mechanism 3.1.3Isomerism 3.1.4End of Topic Test - Introduction to Organic Chem

3.2

Hydrocarbons

3.2.1Fractional Distillation 3.2.2Cracking 3.2.3Combustion 3.2.4Chlorination 3.2.5End of Topic Test - Alkanes 3.2.6Introduction to Alkenes 3.2.7Reactions of Alkenes 3.2.8Polymerisation Reactions 3.2.9End of Topic Test - Alkenes 3.2.10Arenes 3.2.11Evidence for Structure of Arenes 3.2.12Reactions of Benzene 3.2.13End of Topic Test -Arenes

3.3

Halogen Derivatives

3.3.1Properties of Haloalkanes 3.3.2Substitution Reactions of Haloalkanes 3.3.3Environmental Impacts of Haloalkanes 3.3.4End of Topic Test - Halogenoalkanes

3.4

Hydroxy Compounds

3.4.1Types of Alcohol 3.4.2Oxidation 1 3.4.3Oxidation 2 3.4.4Elimination 3.4.5Acids & Esters 3.4.6Acyl Chlorides & Acylation 3.4.7Phenols & Their Reactions 3.4.8End of Topic Test - Alcohols

3.5

Carbonyl Compounds

3.5.1Carbonyls 3.5.2Hydrogen Bonding & Carbonyls 3.5.3Aldehydes & Ketones 3.5.4Tri-Iodomethane Reaction 3.5.5End of Topic Test -Carbonyls

3.6

Carboxylic Acids & Derivatives

3.6.1Properties of Carboxylic Acids 3.6.2Esters 3.6.3Acyl Chlorides 3.6.4End of Topic Test - Carboxylic Acids

3.7

Nitrogen Compounds

3.7.1Nature & Preparation of Amines 3.7.2Basicity & Nucleophilicity 3.7.3Amides 3.7.4Reactions of Amino Acids 3.7.5Amino Acids

3.8

Polymerisation

3.8.1Properties of Addition Polymers 3.8.2Condensation Polymerisation 3.8.3Effects of Side-Chains on Polymers 3.8.4Hydrolysis of Ester & Amide Groups 3.8.5Proteins 3.8.6DNA 3.8.7Adhesive & Conducting Polymers 3.8.8End of Topic Test - Amines & Proteins

3.9

Analytical Techniques

3.9.1Chromatography 3.9.2High-Performance Liquid Chromatography 3.9.3Gas Chromatography 3.9.4IR Spectroscopy 3.9.5Uses of IR Spectroscopy 3.9.6Mass Spectrometry 3.9.7Mass Spectrometry Analysis 3.9.8Nuclear Magnetic Resonance 3.9.9Carbon-13 NMR 3.9.10Proton NMR I 3.9.11Proton NMR II 3.9.12End of Topic Test - Analytical Techniques 3.9.13A-A* (AO2/3) - Analytical Techniques

3.10

Organic Synthesis

3.10.1Chirality & Drug Synthesis 3.10.2Organic Synthesis 3.10.3Examples of Synthetic Routes 3.10.4End of Topic Test - Organic Synthesis

Jump to other topics

1

Physical Chemistry

1.1

Atoms, Molecules & Stoichiometry

1.1.1Relative Masses 1.1.2The Mole 1.1.3Mass Spectrometry 1.1.4Empirical & Molecular Formulae 1.1.5Balanced Equations 1.1.6Molar Volume 1.1.7End of Topic Test - Amount of Substance

1.2

Atomic Structure

1.2.1Fundamental Particles 1.2.2Isotopes & Mass Number 1.2.3Electron Shells, Sub-Shells & Orbitals 1.2.4Electron Configuration 1.2.5Ionisation Energy 1.2.6Factors Affecting Ionisation Energies 1.2.7Trends of Ionisation 1.2.8Specific Impacts on Ionisation Energies 1.2.9Electron Affinity 1.2.10End of Topic Test - Atomic Structure 1.2.11A-A* (AO2/3) - Atomic Structure

1.3

Chemical Bonding

1.3.1Ionic Bonding 1.3.2Covalent & Dative Bonding 1.3.3Shapes of Molecules 1.3.4Intermolecular Forces 1.3.5Intermolecular Forces 2 1.3.6Electronegativity 1.3.7Bond Length, Bond Energy, & Bond Polarity 1.3.8Metallic Bonding 1.3.9Physical Properties 1.3.10End of Topic Test - Bonding 1.3.11A-A* (AO2/3) - Bonding

1.4

States of Matter

1.4.1Simple Covalent Molecules 1.4.2The Ideal Gas Equation 1.4.3States of Matter 1.4.4Particle Diagrams 1.4.5The Liquid State 1.4.6Giant Ionic Lattices 1.4.7Giant Metallic Lattices 1.4.8Giant Covalent Structures 1.4.9Graphene & Fullerene 1.4.10Recycling

1.5

Chemical Energetics

1.5.1Calorimetry 1.5.2Bond Enthalpies 1.5.3Enthalpy Changes 1.5.4Hess' Law 1.5.5Born-Haber Cycles 1.5.6Born-Haber Cycle Calculations 1.5.7Entropy 1.5.8Free Energy 1.5.9End of Topic Test - Energetics

1.6

Electrochemistry

1.6.1Electrochemical Cells 1.6.2Electrochemical Series 1.6.3Commercial Application 1.6.4Nernst Equation 1.6.5Redox

1.7

Equilibria

1.7.1Dynamic Equilibrium & Le Chatelier 1.7.2Kc 1.7.3Kp 1.7.4pH 1.7.5The Ionic Product of Water 1.7.6Weak Acids & Bases 1.7.7Introduction to Solubility Equilibria 1.7.8Solubility Equilibria Calculations 1.7.9Free Energy of Dissolution 1.7.10pH and Solubility 1.7.11Common-Ion Effect 1.7.12End of Topic Test - Kp & Electrochemistry 1.7.13A-A* (AO2/3) - Electrochemical Cells

1.8

Partition Coefficient

1.9

Reaction Kinetics

1.9.1Collision Theory 1.9.2Orders, Rate Constants & Equations 1.9.3Rate Graphs 1.9.4Rate Determining Step 1.9.5Maxwell-Boltzmann Distribution 1.9.6Catalysts 1.9.7Homogeneous Catalysts 1.9.8Heterogeneous Catalysts 1.9.9End of Topic Test - Kinetics 1.9.10End of Topic Test - Rate Equations 1.9.11A-A* (AO2/3) - Rate Equations

2

Inorganic Chemistry

2.1

The Periodic Table

2.1.1The Periodic Table 2.1.2Trends in the Periodic Table 2.1.3End of Topic Test - Periodicity & Trends 2.1.4Ceramics 2.1.5Period 3 Elements & Oxides 2.1.6Period 3 Oxides 2.1.7End of Topic Test - Period 3

2.2

Group 2

2.2.1Group 2 Chemistry

2.3

Group 17

2.3.1Introduction to Halogens 2.3.2Reactions of Halogens 2.3.3Chlorine & Chlorate(I)2.3.4End of Topic Test - Group 17 2.3.5A-A* (AO2/3) - Periodicity, Group 2 & 17

2.4

Transition Metals

2.4.1General Properties 2.4.2Titrations 2.4.3Shapes of Complex Ions 2.4.4Variable Oxidation States 2.4.5Ligands 2.4.6Colours of Ions 2.4.7Stereoisomerism of Complex Ions 2.4.8Cisplatin 2.4.9Ligand Substitutions & Kstab 2.4.10End of Topic Test - Transition Metals 2.4.11A-A* (AO2/3) - Transition Metals

2.5

Nitrogen & Sulfur

2.5.1Nitrogen & Ammonia 2.5.2Formulated vs Manure Fertilisers 2.5.3Nitrogen Containing Fertilisers 2.5.4Fertilizers & Eutrophication 2.5.5Common Atmospheric Pollutants & Their Properties 2.5.6Catalytic Converters 2.5.7Atmospheric Oxides

3

Organic Chemistry & Analysis

3.1

Introduction to Organic Chemistry

3.1.1Naming Conventions 3.1.2Mechanism 3.1.3Isomerism 3.1.4End of Topic Test - Introduction to Organic Chem

3.2

Hydrocarbons

3.2.1Fractional Distillation 3.2.2Cracking 3.2.3Combustion 3.2.4Chlorination 3.2.5End of Topic Test - Alkanes 3.2.6Introduction to Alkenes 3.2.7Reactions of Alkenes 3.2.8Polymerisation Reactions 3.2.9End of Topic Test - Alkenes 3.2.10Arenes 3.2.11Evidence for Structure of Arenes 3.2.12Reactions of Benzene 3.2.13End of Topic Test -Arenes

3.3

Halogen Derivatives

3.3.1Properties of Haloalkanes 3.3.2Substitution Reactions of Haloalkanes 3.3.3Environmental Impacts of Haloalkanes 3.3.4End of Topic Test - Halogenoalkanes

3.4

Hydroxy Compounds

3.4.1Types of Alcohol 3.4.2Oxidation 1 3.4.3Oxidation 2 3.4.4Elimination 3.4.5Acids & Esters 3.4.6Acyl Chlorides & Acylation 3.4.7Phenols & Their Reactions 3.4.8End of Topic Test - Alcohols

3.5

Carbonyl Compounds

3.5.1Carbonyls 3.5.2Hydrogen Bonding & Carbonyls 3.5.3Aldehydes & Ketones 3.5.4Tri-Iodomethane Reaction 3.5.5End of Topic Test -Carbonyls

3.6

Carboxylic Acids & Derivatives

3.6.1Properties of Carboxylic Acids 3.6.2Esters 3.6.3Acyl Chlorides 3.6.4End of Topic Test - Carboxylic Acids

3.7

Nitrogen Compounds

3.7.1Nature & Preparation of Amines 3.7.2Basicity & Nucleophilicity 3.7.3Amides 3.7.4Reactions of Amino Acids 3.7.5Amino Acids

3.8

Polymerisation

3.8.1Properties of Addition Polymers 3.8.2Condensation Polymerisation 3.8.3Effects of Side-Chains on Polymers 3.8.4Hydrolysis of Ester & Amide Groups 3.8.5Proteins 3.8.6DNA 3.8.7Adhesive & Conducting Polymers 3.8.8End of Topic Test - Amines & Proteins

3.9

Analytical Techniques

3.9.1Chromatography 3.9.2High-Performance Liquid Chromatography 3.9.3Gas Chromatography 3.9.4IR Spectroscopy 3.9.5Uses of IR Spectroscopy 3.9.6Mass Spectrometry 3.9.7Mass Spectrometry Analysis 3.9.8Nuclear Magnetic Resonance 3.9.9Carbon-13 NMR 3.9.10Proton NMR I 3.9.11Proton NMR II 3.9.12End of Topic Test - Analytical Techniques 3.9.13A-A* (AO2/3) - Analytical Techniques

3.10

Organic Synthesis

3.10.1Chirality & Drug Synthesis 3.10.2Organic Synthesis 3.10.3Examples of Synthetic Routes 3.10.4End of Topic Test - Organic Synthesis

Practice questions on IR Spectroscopy

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1
What happens when bonds absorb infrared radiation?Multiple choice
2
Amines and amides both contain a C-N bond. Do they absorb the same frequency of infrared radiation?Flashcard
3
On a spectrum, what's the absorbed frequency actually reported as?Multiple choice

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Gas Chromatography

Uses of IR Spectroscopy