Hydrocarbons - JEE Main Previous Year Questions with Solutions
This Hydrocarbons chapter summary covers key JEE Main reactions and concepts including ozonolysis, hydroboration-oxidation, alkyne reductions, polymerization, bromination, Markovnikov/anti-Markovnikov additions, and important previous-year questions with solutions.
eSaral › JEE › JEE Main ›Hydrocarbons
🚀 Checkout eSaral Courses
JEE Main Previous Year Papers Questions of Chemistry With Solutions are available at eSaral. Simulator Previous Years AIEEE/JEE Mains Questions
[AIEEE-2010] 
[AIEEE-2012] 
[AIEEE-2012] 
(1) $\mathrm{H}_{2} /$ lindlar Cat. (2) Cat. Hydrogenatio 
(4) LiNH $_{3}$ [Jee-Main offline 2014] 
on mercuration- demercuration produces the major product :- 
[Jee-Main offline 2014] 
Rearrangement of carbocation formed is not possible due to formatiion of cyclic non-classical carbocation. 
relectivity ratio for bromination is $1^{\circ}: 2^{\circ}: 3^{\circ}: 1: 82: 1600$ Hence $3^{\circ}$ product will be major product. 
[Jee-Main offline 2015] 
Birch reduction is anti addition. So trans alkene will be produced. Frequently Asked Questions
Find answers to common questions.
How many questions from Hydrocarbons appear in JEE Main each year?
JEE Main typically includes 1–2 questions from Hydrocarbons per session (4–8 marks per year across sessions). Based on NTA's released papers from 2010 to 2024, ozonolysis and alkene addition reactions are the most frequently tested sub-topics. Expect at least one question on reaction mechanism or product identification.
Is the Hydrocarbons chapter important for JEE Main 2025 and 2026?
Yes. Hydrocarbons appears in the JEE Main Chemistry syllabus under Organic Chemistry – Part 1 (Class 11 topic) and has been tested without interruption since AIEEE 2010. The NTA has not removed it from the official syllabus. Prioritise ozonolysis, Markovnikov rule, and alkyne reduction reactions.
What is the difference between Lindlar's catalyst and Na/liq. NH₃ in alkyne reductions?
Lindlar's catalyst (Pd/CaCO₃ with quinoline) gives cis (Z)-alkene through syn addition of H₂. Na/liquid NH₃ (Birch reduction) gives trans (E)-alkene through anti addition via radical anion intermediates. JEE Main has asked this distinction directly at least three times between 2012 and 2018.
Why do HCl and HI not show the peroxide effect with alkenes?
HCl and HI do not give anti-Markovnikov addition with peroxides because one step in their radical chain mechanism is endothermic — making the overall chain non-propagating. Only HBr has all radical chain steps exothermic, enabling anti-Markovnikov (peroxide) addition. This was directly tested in JEE Main 2014.
How do I identify an unknown alkene from its ozonolysis products in JEE Main?
Replace each C=O group in the ozonolysis products with a C= carbon, then join those two carbons with a double bond. If one product is formaldehyde (HCHO), the original compound had a terminal =CH₂ (vinyl group). If both products are identical aldehydes or ketones, the alkene was symmetrical. This reverse-engineering approach solves most JEE ozonolysis problems in under a minute.