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Organic Chemistry – Some Basic Principles and Techniques cheat sheet
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Class 11 · Chapter 8Organic Chemistry: Some Basic Principles and Techniques
Electron effects: Inductive, Resonance, Hyperconjugation — I R H.
1. IUPAC Naming
- Find the longest chain with the principal functional group.
- Number to give the functional group the lowest locant.
- Prefix (substituents, alphabetical) + root + suffix.
| Group | Suffix |
|---|---|
| –COOH | -oic acid |
| –CHO | -al |
| C=O (ketone) | -one |
| –OH | -ol |
| –NH₂ | -amine |
2. Isomerism
- Structural: chain, position, functional group, metamerism.
- Stereo: geometrical (cis/trans), optical (chiral carbon).
3. Electronic Effects
| Effect | What happens | Example |
|---|---|---|
| Inductive (−I / +I) | σ-bond polarisation, fades with distance | −I: –NO₂, –Cl; +I: alkyl |
| Resonance (±R) | π-electron delocalisation | +R: –OH, –NH₂; −R: –NO₂, –CHO |
| Hyperconjugation | σ(C–H) and π/p overlap | stabilises carbocations, alkenes |
| Electromeric | temporary, in presence of reagent | addition to C=C |
Carbocation stability: 3° > 2° > 1° > methyl. Carbanion: the reverse.
4. Reagents
- Electrophiles: electron-seeking (H⁺, NO₂⁺, BF₃).
- Nucleophiles: electron-rich (OH⁻, CN⁻, NH₃).
- Homolytic fission → free radicals; heterolytic → ions.
5. Purification & Analysis
- Crystallisation, sublimation, distillation (simple, fractional, steam, reduced pressure), chromatography.
- Lassaigne's test: N (Prussian blue), S (violet with nitroprusside), halogens (AgX).
- Estimation: Dumas & Kjeldahl (N), Carius (halogens, S).
6. Key Points
- R_f = distance by substance / distance by solvent.
- Kjeldahl not for nitro, azo or ring N.
- Free radicals stability: 3° > 2° > 1°.
- Resonance structures differ only in electron positions.
Remember: IUPAC steps | I, R, hyperconjugation | purification & Lassaigne
Organic Chemistry – Some Basic Principles and Techniques: questions and notes
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