Chemistry — Organic Chemistry for the JEE Main Exam

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.

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.