JEE Main Previous Year Papers Questions With Solutions Chemistry Alkanes ,Alkenes ,Alkynes and Arenes

JEE Main Previous Year Papers Questions With Solutions Chemistry Alkanes ,Alkenes ,Alkynes and Arenes

1.Which of these will not react with acetylene ?(2002)
1) NaOH                                 2)  Ammonical  AgB0₃
3) Na                                        4) HCl
Ans.

2.What is the product when acetylene reacts with hypochlorous acid ?    (2002)
1) CH3COCI                         2)   C1CH₂CH0
3) Cl₂CHCHO                        4)  C1CHCOOH
Ans.

3.Bottles containing C₆H₅I and C₆H_SCH₂I lost their original tables. They were labelled A and B for testing. A and B were separately taken in test tubes and boiled with NaOH solution. The end solution in each tube was made acidic with dilute HNO_a and then some AgN0₃ solution was added. Substance B gave a yellow’ precipitate. Which one of the following statements is true for this experiment? (2003)
1)AandC₆H₅CH₂I
2)B and C₆H₅I
3)Addition of HN0₃ was unnecessary
4) A was C₆H₅I
Ans.(4) C₆H₅I will not respond to silver nitrate test because C-I bond has a partial double bond character.

4. Butene-1 may be converted to butane by reaction with (2003)
1) Sn-HCl                  2) Zn-Hg
3) Pd /H₂                     4) Zn- HCl
Ans.(3) Hydrogenation.

5.Which one of the following has the minimum boiling point ?   (2004)
1) n-butane                                                2)  isobutane
3) 1-butene                                               4) 1-butyne
Ans.(2) Lower van der Waals forces.

6.Which one of the following reduced with zinc and hydrochloric acid to give the  corresponding hydrocarbon  ?   (2004)
1) Ethyl acetate                     2) Butan-2-one
3) Acetamide                         4) Acetic acid
Ans.(2) Total reduction of carbonyl.

7.2 methylbutane on reacting with bromine in the presence of sunlight gives mainly (2005)
1)1- bromo -2 – methylbutane
2)2 – bromo -2 – methylbutane
3)2- bromo -3 – methylbutane
4)1 – bromo -3 – methylbutane
Ans.

8.Acid catalyzed hydration of alkenes except ethene leads to the formation of (2005)
1)Primary alcohol
2)Secondary or tertiary alcohol
3)Mixture of primary and secondary alcohols
4)Mixture of secondary and tertiary alcohols
Ans.(4) concept of hydration.

Ans.(1) Conjugated acid of Cl^– is a stronger acid. The acid is HCl.

10.Elimination of bromine from 2-bromobutane results in the formation of-       (2005)
1)Equimolar mixture of 1 and 2-butene
2)Predominantly 2-butene
3)Predominantly 1-butene
4)Predominantly 2-butyne
Ans.(2) Saytzeff’s product.

11.HBr reacts with CH₂ = CH – OCH₃ under anhydrous conditions at room temperature to give
1)CH₃CHO and CH₃Br
2)BrCH₂CHO and CH₃OH
3)BrCH₂ – CH₂ – OCH₃
4)H₃C – CHBr – OCH₃
Ans.(4) Electrophilic addition reaction is more favourable.

Ans.(2) Ethylene

13.Which of the following reactions will yield 2, 2-dibromopropane ?    (2007)
1)CH₃ – C = CH + 2HBr —>
2)CH₃CH = CHBr + HBr ->
3)CH = CH + 2HBr —>
4)CH₃ – CH = CH₂ + HBr ->
Ans.

14.The reaction of toluene with Cl₂ in presence of FeCl₃ gives predominantly       (2007)
1)benzoyl chloride
2)benzyl chloride
3)o-and p-chlorotoluene
4)m-chlorotoluene
Ans.

15.Presence of a nitro group in a benzene ring (2007)
1)activates the ring towards electrophilic substitution
2)renders the ring basic .
3)deactivates the ring towards nucleophilic substitution
4)deactivates the ring towards electrophilic substitution
Ans.(4) -N0₂ group shows -M effect. It withdraws the electron density from the ring and hence deactivate the ring towards electrophilic aro­matic substitution.

16.In the following sequence of reactions, the alkene affords the compound ‘B’

Ans.

Ans.(2) – N0₂ is electron withdrawing which will destabilize a-complex.

18.The hydrocarbon which can react with sodium in liquid ammonia is (2008)
1)CH₃CH₂CH₂C=CCH₂CH₂CH₃
2)CH₃CH₂C =CH .
3)CH₃CH = CHCH₃
4)CH₃CH₂C =CCH₂CH₃
Ans.

19.The treatment of CH₃MgX with CH₃OC-H produces (2008)

Ans.

20.One mole of a symmetrical alkene on ozonolysis gives two moles of an aldehyde having a molecular mass of 44u. The alkene is               (2010)
1)propene   2) 1-butene   3) 2-butene  4) ethene
Ans.

21.Ozonolysis of an organic compound gives formaldehyde as one of the products. This confirms the presence  of :          (2011)
1)an isopropyl group
2)an acetylenic triple bond
3)two ethylenic double bonds
4)a vinyl group
Ans.(4) Ozonolysis of an organic compound give formaldehyde when it containing atleast one vinylic double bond. HjC = CH – R.

22.2-Hexyne gives trans-2-hexene on treatment with  (2012)
1) Pt/H₂                                    2)    Li / NH₃
3) Pd / BaS0₄                          4)      LiAlH₄
Ans.

23.The major organic compound formed by the reaction of 1,1,1 – trichloroethane with silver powder is              (2014)
1) 2-Butene                             2) Acetylene
3) Ethene                                 4)   2-Butyne
Ans.

24.Which compound would give 5-keto-2-methyl hexanal upon ozonlysis ?

Ans.