Hydrocarbons are a fundamental topic in Organic Chemistry for JEE Main, and understanding them is crucial for performing well in the exam. This section includes Previous Year Questions (PYQs) related to hydrocarbons, along with detailed solutions to help you grasp the key concepts and improve your exam preparation.
Hydrocarbons are organic compounds made up of hydrogen and carbon atoms. In JEE Main, this topic typically covers:
The questions on hydrocarbons in JEE Main often test students on various properties, reactions, and mechanisms related to these compounds.
Hydrocarbons are a fundamental topic in Organic Chemistry for JEE Main, and understanding them is crucial for performing well in the exam. This section includes Previous Year Questions (PYQs) related to hydrocarbons, along with detailed solutions to help you grasp the key concepts and improve your exam preparation.
Here are some of the important JEE Main questions from previous years on Hydrocarbons:
1. The gas liberated by the electrolysis of Dipotassium succinate solution is :
(1) Ethyne
(2) Ethene
(3) Propene
(4) Ethane
Solution:
The correct option for the given question is (2).
2. Which one of the following classes of compounds is obtained by polymerization of acetylene?
(1) Poly-ene
(2) Poly-yne
(3) Poly-amide
(4) Poly-ester
Solution:
The correct option for the given question is (2).
3. One mole of a symmetrical alkene on ozonolysis gives two moles of an aldehyde having a molecular mass of 44 u. The alkene is:-
(1) Ethene
(2) Propene
(3) 1-Butene
(4) 2-Butene
Solution:
The correct option for the given question is (4).
4. Which branched chain isomer of the hydrocarbon with molecular mass 72 u gives only one isomer of mono substituted alkyl halide?
(1) Neopentane
(2) Isohexane
(3) Neohexane
(4) Tertiary butyl chloride
Solution:
The correct option for the given question is (1).
5. Ozonolysis of an organic compound gives formaldehyde as one of the products. This confirms the presence of:-
(1) an isopropyl group
(2) an acetylenic triple bond
(3) two ethylenic double bonds
(4) a vinyl group
Solution:
The correct option for the given question is (3).
6. In the given transformation, which of the following is the most appropriate reagent?
(1) NaBH4
(2) NH2-NH2, OH
(3) Zn – Hg / HCl
(4) Na, Liq.NH3
Solution:
The correct option for the given question is (2).
7. The number and type of bonds in C22- ion in CaC2 are:
(1) Two σ bonds and one π – bond
(2) Two σ bonds and two π – bonds
(3) One σ bond and two π – bonds
(4) One σ bond and one π bond
Solution:
The correct option for the given question is (3).
8. In the hydroboration – oxidation reaction of propene with diborane, H2O2 and NaOH, the organic compound formed is :
(1) CH3CH2CH2OH
( 2) (CH3)3COH
(3) CH3CHOHCH3
(4) CH3CH2OH
Solution:
The correct option for the given question is (1).
9. Which one of the following has the minimum boiling point?
(1) n-Butane
(2) 1-Butyne
(3) 1-Butene
(4) Isobutene
Solution:
The correct option for the given question is (4).
10. The gas evolved on heating CH3MgBr in methanol is
(1) methane
(2) ethane
(3) propane
(4) HBr
Solution:
The correct option for the given question is (1).
11. The reagent needed for converting
is
(1) H2 / lindlar Cat.
(2) Catalytic Hydrogenation
(3) LiAlH4
(4) Li/ NH3
Solution:
The correct option for the given question is (4).
12. In the presence of peroxide, HCl and HI do not give anti-Markovnikov’s addition to alkenes because
(1) All the steps are exothermic in HCl and HI
(2) One of the steps is endothermic in HCl and HI
(3) HCl is oxidizing and the HI is reducing
(4) Both HCl and HI are strong acids
Solution:
The correct option for the given question is (2).
13. Polysubstitution is a major drawback in
(a) Reimer-Tiemann reaction
(b) Friedel-Crafts acylation
(c) Friedel-Crafts alkylation
(d) Acetylation of aniline.
Solution:
The correct option for the given question is (3).
14. Which one of the following is reduced with zinc and hydrochloric acid to give the corresponding hydrocarbon?
(1) Ethyl acetate
(2) Acetic acid
(3) Acetamide
(4) Butan-2-one
Solution:
The correct option for the given question is (4).
15. The hydrocarbon which can react with sodium in liquid ammonia is
(1) CH3CH2C ≡ CCH2CH3
(2) CH3CH2CH2C ≡ CCH2CH2CH3
(3) CH3CH2C ≡ CH
(4) CH3CH ≡ CHCH3
Solution:
The correct option for the given question is (3).
Hydrocarbons are organic compounds made entirely of carbon and hydrogen atoms. They are crucial for JEE Main as they form a significant portion of Organic Chemistry. Hydrocarbons include alkanes (saturated hydrocarbons), alkenes (unsaturated hydrocarbons with double bonds), alkynes (unsaturated hydrocarbons with triple bonds), and aromatic hydrocarbons (such as benzene). Understanding their reactions, properties, and mechanisms is essential for answering related questions in the exam.
Electrophilic substitution reactions are vital for understanding the reactivity of aromatic hydrocarbons, like benzene. In JEE Main, questions often test the ability to identify and predict products from electrophilic substitution reactions. For instance, the methyl group in toluene increases its reactivity towards electrophilic substitution, whereas groups like nitro (-NO2) deactivate the ring. This knowledge is crucial for solving questions related to aromatic chemistry.
To strengthen your understanding of hydrocarbons for JEE Main, focus on mastering key concepts such as:
Types of hydrocarbons (alkanes, alkenes, alkynes, and aromatic hydrocarbons).
Common reactions like substitution, addition, and oxidation.
Practice with previous year questions to familiarize yourself with the exam pattern.
Pay attention to mechanisms like electrophilic substitution and free radical substitution. Regular practice and understanding the underlying concepts will help you perform well in JEE Main Organic Chemistry questions related to hydrocarbons.