Unit Overview
R3: What are the mechanisms of chemical change?
IB Chemistry HLΒ· 5 min read π n/a
1. Unit at a Glance
This unit builds sequentially from foundational skills to advanced content, starting with core organic chemistry basics, then moving into reaction classification, mechanism fundamentals, and core electrochemistry. After mastering core topics, you will progress to higher level (AHL) extensions including stereoisomerism, advanced mechanisms, electrolytic cells, catalysis, and spectroscopic identification of organic compounds.
This unit includes the following sub-topics, ordered from core to AHL content:
Introduction to organic chemistry: functional groups
Classify organic compounds by their functional groups and recognize key structural features.
β β± 7 min
Nomenclature of organic compounds
Apply IUPAC rules to name and draw straight-chain and branched organic compounds.
β β β± 8 min
Types of organic reactions
Classify common reaction types including substitution, addition, elimination, and condensation.
β β β± 6 min
Redox reactions and electrochemistry basics
Introduce core oxidation and reduction concepts and their role in electrochemical processes.
β β β± 7 min
Oxidation numbers and voltaic cells
Calculate oxidation numbers and explain the structure and operation of simple voltaic cells.
β β β β± 8 min
Reaction mechanism basics
Learn how mechanisms describe stepwise bond breaking and forming during chemical change.
β β β β± 7 min
AHL: Stereoisomerism
Explore stereoisomerism including enantiomers and apply Cahn-Ingold-Prelog naming rules.
β β β β β± 9 min
AHL: Advanced organic reaction mechanisms
Study detailed mechanisms for common organic reactions including SN1, SN2, and electrophilic addition.
β β β β β± 10 min
AHL: Electrolytic cells and standard electrode potentials
Calculate standard cell potentials and explain the operation of electrolytic cells and electrolysis.
β β β β β± 9 min
AHL: Catalysis and reaction mechanisms
Explain how homogeneous and heterogeneous catalysts alter reaction mechanisms to speed up reactions.
β β β β± 8 min
AHL: Spectroscopic identification of organic compounds
Use IR, mass spectrometry, and NMR data to determine the structure of unknown organic compounds.
β β β β β± 10 min
2. Common Pitfalls
Wrong move:
Confusing anode/cathode charge and redox roles in voltaic vs electrolytic cells
Why:
The charge of electrodes swaps between cell types, leading to confusion about where oxidation/reduction occurs
Correct move:
Remember 'AN OX RED CAT' applies to all cells: oxidation at anode, reduction at cathode, regardless of charge
Wrong move:
Numbering parent chains or naming organic compounds without checking functional group priority
Why:
Many students number chains or assign names based on the first substituent they see instead of the highest priority group
Correct move:
Always identify the highest priority functional group first to set parent chain numbering
Wrong move:
Drawing curly arrows in mechanisms starting from the electrophile
Why:
Curly arrows represent electron movement, not atom movement
Correct move:
Always start curly arrows at a lone pair or bonding electron pair, moving to the electron-deficient site
3. Quick Reference Cheatsheet
Concept / Key Formula | Description |
|---|---|
Organic oxidation | Loss of H / gain of O / loss of electrons |
Organic reduction | Gain of H / loss of O / gain of electrons |
AN OX RED CAT | Oxidation at anode, reduction at cathode (all electrochemical cell types) |
Calculates standard cell potential; positive = spontaneous reaction | |
Curly arrow notation | Represents movement of a pair of electrons from electron-rich to electron-poor site |
Common functional group priority | Carboxylic acids > esters > aldehydes > ketones > alcohols > alkenes > alkanes |
Catalysis definition | Catalysts lower activation energy by providing an alternate reaction mechanism, and are not consumed |
What's Next
Begin your study of this unit with the first sub-topic on organic functional groups, then progress through the sub-topics in the order listed to build core knowledge before moving to advanced AHL content. Core concepts build sequentially, so working in order will help you master reaction mechanism logic. After completing all topics in this unit, you will move on to the next unit covering chemical kinetics.