JEE Main Previous Year Papers Questions With Solutions Chemistry Haloalkenes and Haloarenes
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.(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.
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)
2)alkyl copper halides
Ans.(3)R2CuLi + R’X—>R-R +R-Cu + LiX
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)
Ans.(4) Nucleophilic substitution of Cl– by CN–.
10. The structure of the major product formed in the following reaction is (2006)
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
3)R3CX >R2CHX > 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 :
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
14.Phenol is heated with a solution of mixture of KBr and KBr03. The major product obtained in the reaction is (2011)
2)2, 4, 6-Tribromophenol
15.Which branched chain isomer of the hydrocarbon with molecular mas 72u gives only one isomer of mono substituted alkyl halide ? (2012)
Ans.(2) Neopentane, (CH3)4C, on monochlorination gives only one isomer.
16.In Sn2 reactions, the correct order of reactivity for the following compounds :
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
Ans.(4) R -X + AgF —> R – F + AgX.