Questions
4 questions per paper
Difficulty
Medium
Importance
Core — never skip
Overview
Organic Chemistry Basic Principles serves as the foundation for the entire carbon-based chemistry curriculum, introducing the rules of molecular structure and reactivity. Mastering IUPAC nomenclature and electronic effects is essential as they dictate the behavior of complex reaction mechanisms in advanced chapters.
IUPAC Nomenclature
IUPAC nomenclature provides a systematic method for naming organic compounds, ensuring a universal language for chemical structures. Exam questions often test your ability to identify the longest carbon chain, prioritize functional groups, and assign the correct locants.
- Priority order: Acid > Ester > Amide > Nitrile > Aldehyde > Ketone > Alcohol > Amine
- Numbering must give substituents the lowest possible locant set
- Alphabetical order is strictly followed for naming substituents
- Suffixes define the principal functional group
- Cyclic structures use the prefix 'cyclo-'
Isomerism
Isomerism covers compounds with the same molecular formula but different arrangements of atoms. A solid grasp of structural and stereoisomerism is crucial for predicting product behavior in later reactions.
- Structural: Chain, Position, Functional, Metamerism, Tautomerism
- Stereoisomerism: Geometrical (cis/trans/E-Z) and Optical (d/l/R/S)
- Tautomerism requires alpha-hydrogen availability
- Enantiomers are non-superimposable mirror images
- Diastereomers are non-mirror image stereoisomers
Electronic Effects
Electronic effects, including Inductive, Mesomeric, and Hyperconjugation, explain the stability of intermediates like carbocations and carbanions. These are the mechanical 'engine' behind organic transformations and acidity/basicity comparisons.
- Inductive Effect (I): Distance-dependent, permanent polarity through sigma bonds
- Resonance/Mesomeric Effect (M): Delocalization of pi electrons
- Hyperconjugation: Sigma-bond delocalization into p-orbitals (No-bond resonance)
- Stability: Tertiary > Secondary > Primary for carbocations
- Acidity increases with electron-withdrawing groups (-I/-M)
Formula Sheet
Degrees of Unsaturation (DU) = C + 1 - (H+X-N)/2
R/S Priority: Cahn-Ingold-Prelog (CIP) Rules
Exam Tip
Always identify the principal functional group first, as all numbering and naming depend entirely on that singular choice.
Common Mistakes
- Miscalculating the principal functional group, leading to incorrect parent chain selection.
- Ignoring the distance-dependent nature of the Inductive effect in stability problems.
- Forgetting to check for alpha-hydrogens when assessing hyperconjugation or tautomerism.
More Revision Notes
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