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JEE Main Previous Year Papers Questions With Solutions Chemistry Haloalkanes and Haloarenes

JEE Main Previous Year Papers Questions With Solutions Chemistry Haloalkanes and Haloarenes

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Ans.(2) The reaction is nucleophilic sustitution reaction.
2.On mixing a certain alkane with chlorine and irradiating it with ultraviolet light, it forms only one monochloroalkane. This alkane could  be  (2003)
1) pentane                    2) isopentane
3) neopentane             4) propane

Ans.
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Ans.(1) Rate of reaction will be fastest when Z is Cl because it is a weakest base.
4.The compound  formed on heating chlorobenzene with chloral in the presence concentrated sulphuric   acid  is    (2004)
1) gammexene              2)  hexachloroethane
3) Freon                        4) DDT

Ans.(4) Dicholodiphenyl trichloroethene.
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Ans.(4) Due to steric hindrance.
6.Reaction of one molecule of HBr with one molecule of 1,3-butadiene at 40°C gives predominantly         (2005)
1)3-bromobutene under kinetically controlled conditions
2)l-bromo-2-butene under thermodymically controlled conditions
3)3-bromobutene under thermodynamically controlled conditions
4)l-bromo-2-butene under kinetically controlled conditions

Ans.(2)CH3 – CH = CH2
7. Alkyl halides react with dialkyl copper reagents to give          (2005)
1)alkenes
2)alkyl copper halides
3)alkanes
4)alkenyl halides

Ans.(3)R2CuLi + R’X—>R-R +R-Cu + LiX
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Ans.CH30 is more reactive and PhO- is least reactive.
9.Reaction of trans-2-phenyl-l bromo cyclopentane on reaction with alcoholic KOH produces.     (2006)
1)4-phenylcyclopentene
2)2-phenylcyclopentene
3)1-phenylcyclopentene
4)3-phenylcyclopentene

Ans.(4) Nucleophilic substitution of Cl by CN.
10. The structure of the major product formed in the following reaction is   (2006)
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Ans.(4) According to E2 elimination mechanism.
11.Which of the following is the correct order of decreasing SN2 reactivity ?  (2007)
1)RCH2x > R3CX > R2CHX
2)RCH2X>R2CHX>R3CX
3)R3CX >R2CHX > RCH2X
4)R2CHX>R3CX>RCH2X

Ans.(2)More is the steric hindrance at the carbon bearing the halogen, lesser is the SN2 reactivity.
12.The organic chloro compound, which shows complete stereochemical inversion during a Sn2 reaction, is    (2008)
1)(C2H5)2CHCl            2) (CH3)3CCl
3) (CH3)2CHCl             4) CH3Cl

Ans.(4) For Sn2 reaction, the C atom is least hindered towards the attack of nucleophile in the case of CH3Cl.
13.Consider the following bromides :
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Ans.(1) SN1 proceeds via carbocation intermediate, the most stable one forming the product faster. Hence reactivity order for A, B, C depends on stability of carbocation created
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14.Phenol is heated with a solution of mixture of KBr and KBr03. The major product obtained in the reaction is  (2011)
1)4-Bromophenol
2)2, 4, 6-Tribromophenol
3)2-Bromophenol
4)3-Bromophenol

Ans.
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15.Which branched chain isomer of the hydrocarbon with molecular mas 72u gives only one isomer of mono substituted alkyl halide ?  (2012)
1) Tertiarybutylchloride
2) Neopentane
3) Isohexane
4) Neohexane

Ans.(2) Neopentane, (CH3)4C, on monochlorination gives only one isomer.
16.In Sn2 reactions, the correct order of reactivity for the following compounds :
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Ans.(3) Order of required reactivity :
CH3C1 > CH3CH2C1 > (CH3)2CHC1 > (CH3)3CC1
17.The synthesis of alkyl fluorides is best accom­plished by (2015)
1)Free radical fluorination
2)Sandmeyer’s reaction
3)Finkelstein reaction
4)Swarts reaction

Ans.(4) R -X + AgF —> R – F + AgX.

Courtesy : CBSE