Organic Chemistry: Basic Principles and Techniques for NEET UG
General organic chemistry is the grammar of organic reactions. Naming, isomerism and electron effects (inductive, resonance, hyperconjugation) let you predict how any organic molecule will behave.
ChemistryClass 1169 MCQs3 lessons13 flashcards4 memory tricks
Practise Organic Chemistry: Basic Principles and Techniques free
What you'll learn
- IUPAC naming and isomerism
Name simple organic compounds and identify types of isomerism. - Electronic effects
Use inductive, resonance and hyperconjugation effects to compare acid strength and stability of intermediates. - Reaction intermediates, reagents and purification
Classify reagents as electrophiles or nucleophiles and choose a purification method.
Key formulas
| Carbocation stability | 3° > 2° > 1° > methyl |
|---|---|
| Carbanion stability | methyl > 1° > 2° > 3° |
| Free radical stability | 3° > 2° > 1° > methyl |
Memory tricks
3° > 2° > 1° > CH₃⁺, because alkyl groups donate electrons by +I and hyperconjugation. Benzyl and allyl cations are extra stable by resonance.
Nucleophiles: OH⁻, CN⁻, NH₃, H₂O. Electrophiles: H⁺, NO₂⁺, carbocations, BF₃.
Sublimation: camphor, naphthalene, iodine. Steam distillation: steam-volatile, water-immiscible liquids like aniline. Fractional distillation: liquids with close boiling points.
Cl₃C–COOH > Cl₂CH–COOH > ClCH₂–COOH > CH₃COOH. The −I effect stabilises the carboxylate ion, and it fades with distance.
Try 3 NEET-style questions
Q1. On complete combustion, 0.2 g of an organic compound gives 0.44 g of CO₂. The percentage of carbon in the compound is
- 44%
- 12%
- 60%
- 30%
Show answer
Answer: (3) 60%
Mass of C = 0.44 × 12/44 = 0.12 g. % C = 0.12/0.2 × 100 = 60%.
Q2. A carbocation has
- an sp³ hybridised carbon with a lone pair
- an unpaired electron on carbon
- an sp² hybridised positive carbon with trigonal planar geometry and a vacant p orbital
- a linear sp carbon
Show answer
Answer: (3) an sp² hybridised positive carbon with trigonal planar geometry and a vacant p orbital
The positively charged carbon in a carbocation is sp² hybridised, trigonal planar, with an empty unhybridised p orbital perpendicular to the plane.
Q3. In Lassaigne's test, the sodium fusion extract gives a blood-red colour with FeCl₃ when the compound contains
- only nitrogen
- only sulphur
- halogens
- both nitrogen and sulphur
Show answer
Answer: (4) both nitrogen and sulphur
N and S together form NaSCN, which gives blood-red Fe(SCN)²⁺ with Fe³⁺.
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