Isomerism

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Structural Isomerism

Structural isomers are molecules which have the same molecular formula but a different arrangement of atoms in space.

Chain isomers

Chain isomers are molecules that have the same molecular formula but one is linear and one is branched. For example:
- Butane is a linear molecule with the molecular formula C₄H₁₀.
- Methylpropane is a branched molecule with the molecular formula C₄H₁₀.

Position isomers

Position isomers are molecules that have the same molecular formula but have their functional group in different places. For example:
- Butan-1-ol has a hydroxyl group attached to carbon-1.
- Butan-2-ol has a hydroxyl group attached to carbon-2.

Functional group isomers

Functional group isomers are isomers that have had their structures changed so that they have different functional groups. For example:
- Propanoic acid.
- Methyl ethanoate.

Stereoisomerism

Stereoisomers are molecules that have the same molecular formula, same functional groups and same functional group positions but different arrangements of atoms in space.

Alkene stereoisomerism

Stereoisomerism can be seen in alkenes.
It is possible in alkenes because of the presence of double bonds:
- Unlike single bonds, double bonds are rigid and you cannot rotate around them.
- So alkenes can display stereoisomerism at the double bond.

An example

The simplest way to understand what this means is with an example.
- Above are the two different alkenes, (E)-but-2-ene and (Z)-but-2-ene.
  - The molecules are the same in every way, except for the atoms' position in space.

What do E and Z mean?

E and Z come from the German words 'entgegen' and 'zusammen' for 'opposite' and 'together'.
- An E-alkene has the larger groups on opposite sides.
- A Z-alkene has the larger groups on the same side.
A good way to remember this is that Z alkenes have large groups on the 'zame zide'.

Cahn-Ingold Prelog Rules

The Cahn-Ingold Prelog rules help us assign E/Z isomerism to more complicated molecules.

The Cahn-Ingold Prelog rules

They help to distinguish between E and Z isomers for more complicated cases.
The rules work by numbering the four directly connecting atoms in order of their atomic mass number. From this, we give them a 'priority'.
- The highest atomic number gets priority 1.
- The second highest atomic number gets priority 2, and so on.

E vs Z

E:
- Priority 1 and 2 are on different sides of the double bond.
  - I.e. The two atoms with the highest atomic mass number are on different sides.
Z:
- Priority 1 and 2 are on the same side of the double bond.
  - I.e. The two atoms with the highest atomic mass number are on the same side.

An example: E

The shown but-2-ene is an E geometry because the two methyl groups are on opposite sides of the double bond.

An example: Z

The shown but-2-ene is a Z geometry because the two methyl groups are on the same side of the double bond.

1Physical Chemistry

1.1Atoms, 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

1.2Atomic 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

1.3Chemical 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

1.4States 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

1.5Chemical 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

1.6Electrochemistry

1.6.1Electrochemical Cells

1.6.2Electrochemical Series

1.6.3Commercial Application

1.6.4Nernst Equation

1.6.5Redox

1.7Equilibria

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

1.8Partition Coefficient

1.8.1Kpc

1.9Reaction 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

2Inorganic Chemistry

2.1The 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

2.2Group 2

2.2.1Group 2 Chemistry

2.3Group 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

2.4Transition 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

2.5Nitrogen & 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

3Organic Chemistry & Analysis

3.1Introduction to Organic Chemistry

3.1.1Naming Conventions

3.1.2Mechanism

3.1.3Isomerism

3.1.4End of Topic Test - Introduction to Organic Chem

3.2Hydrocarbons

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

3.3Halogen 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

3.4Hydroxy 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

3.5Carbonyl 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

3.6Carboxylic Acids & Derivatives

3.6.1Properties of Carboxylic Acids

3.6.2Esters

3.6.3Acyl Chlorides

3.6.4End of Topic Test - Carboxylic Acids

3.7Nitrogen Compounds

3.7.1Nature & Preparation of Amines

3.7.2Basicity & Nucleophilicity

3.7.3Amides

3.7.4Reactions of Amino Acids

3.7.5Amino Acids

3.8Polymerisation

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

3.9Analytical 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

3.10Organic Synthesis

3.10.1Chirality & Drug Synthesis

3.10.2Organic Synthesis

3.10.3Examples of Synthetic Routes

3.10.4End of Topic Test - Organic Synthesis

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