Chemistry — Organic Chemistry for the JEE Main Exam — Chinese candidates

Common failure modes

These are the patterns that cause most candidates to lose marks on this topic. Recognising them in advance is half the work.

• !Confusing Markovnikov vs anti-Markovnikov addition — especially forgetting peroxide effect for HBr
• !Misidentifying whether a substrate undergoes SN1 or SN2 based on steric hindrance and solvent
• !Forgetting to account for stereochemistry in product prediction (racemic mixture from SN1 vs inversion from SN2)
• !Treating aldol condensation and Claisen condensation interchangeably
• !Skipping Tollens' and Fehling's test distinctions — aldehyde vs ketone is a classic JEE trap

Study tips

• 1Master the mechanism flowchart for nucleophilic substitution: 1° → SN2; 3° → SN1; 2° → solvent-dependent. Apply before attempting any substitution problem.
• 2Make a named-reaction reference list: Aldol, Cannizzaro, Reimer-Tiemann, Friedel-Crafts, Diels-Alder, Hoffmann rearrangement, Wolff-Kishner. JEE tests at least three per paper.
• 3Practice retrosynthesis for 4–5 step conversions — JEE Advanced routinely asks for multi-step synthesis.
• 4For biomolecules, memorise the structures of glucose (open-chain and Haworth projection), amino-acid classification, and nucleotide components.
• 5Drill carbonyl chemistry: nucleophilic addition mechanism, distinction between aldehyde/ketone reactivity, and oxidation-reduction reactions.
• 6中国考生备考 JEE Main 时，建议优先攻克英语听力与写作两个最易失分的板块 — 每日固定时段做真题模拟。

Sample JEE Main Chemistry — Organic Chemistry questions

These sample items mirror the format and difficulty of real JEE Main questions. Practice with thousands more on the free Koydo question bank.

1. 1

   The reaction of 2-methylpropene (isobutylene) with HBr in the absence of peroxides gives:

   • A1-bromo-2-methylpropane
   • B2-bromo-2-methylpropaneCorrect
   • C2-bromo-1-methylpropane
   • D1-bromo-1-methylpropane
   Why this answer?

   Illustrative JEE-style: In the absence of peroxides, HBr adds according to Markovnikov's rule. The proton adds to the less-substituted carbon (=CH₂) forming a tertiary carbocation at C2, which then reacts with Br⁻ to give 2-bromo-2-methylpropane.

2. 2

   Which reagent is used to distinguish between an aldehyde and a ketone?

   • ALucas reagent
   • BTollens' reagent
   • CFehling solution alone
   • DBoth Tollens' reagent and Fehling solutionCorrect
   Why this answer?

   Illustrative JEE-style: Both Tollens' reagent (silver mirror test) and Fehling's solution give a positive test for aldehydes but not for most ketones (except α-hydroxy ketones). Either can distinguish, so both are correct answers.

3. 3

   Friedel-Crafts acylation of benzene requires:

   • AAn acid chloride and AlCl₃Correct
   • BAn acyl chloride and NaOH
   • CA ketone and H₂SO₄
   • DAn alkyl halide and FeBr₃
   Why this answer?

   Illustrative JEE-style: Friedel-Crafts acylation uses an acyl (acid) chloride and a Lewis acid catalyst (AlCl₃) to introduce an acyl group onto the aromatic ring via electrophilic aromatic substitution.

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