CLASS XII CHEMISTRY (HALOALKANES AND HALOARENES)

Which of the following undergoes nucleophilic substitution exclusively by SN1 mechanism?

• Ethyl chloride

• Isopropyl chloride

• Choro benzene

• Benzyl chloride

Toluene reacts with a halogen in the presence of iron (III) chloride giving ortho and para halo compounds. The reaction is

• Electrophilic elimination reaction

• Electrophilic substitution reaction

• Free radical addition reaction

• Nucleophilic substitution reaction

Haloalkane is a polar molecule that undergoes nucleophilic substitution through S_N1 and S_N2. Arrange the following haloalkanes in order of increasing rate of unimolecular nucleophilic substitution reaction:

I. 2-chloro-2-methylpropane

II. 2-chlorobutane

III. 1-chlorobutane

• I< II < III

• I< III < II

• III< I < II

• III< II < I

Which is the correct increasing order of boiling points of the following compounds? 1-Iodobutane, 1-Bromobutane, 1-Chlorobutane, Butane

• Butane < 1-Chlorobutane < 1-Bromobutane < 1-Iodobutane

• 1-Iodobutane < 1-Bromobutane < 1-Chlorobutane < Butane

• Butane < 1-Iodobutane < 1-Bromobutane < 1-Chlorobutane

• Butane < 1-Chlorobutane < 1-Iodobutane < 1-Bromobutane

In SN¹ the order of reactivity of halide is:

• 3⁰ > 2⁰ > 1⁰ > methyl

• Methyl > 1⁰>2⁰ > 3⁰

• 3⁰ > 2⁰ > methyl > 1⁰

• 2⁰ > 1⁰ > methyl > 3⁰

Assertion: Electron withdrawing groups in aryl halides increases the reactivity towards nucleophilic substitution.

Reason: 2, 4-Dinitrochlorobenzene is more reactive than chlorobenzene.

• Both assertion and reason are true and the reason is the correct explanation of the assertion.

• Both assertion and reason are true but reason is not the correct explanation of the assertion

• Assertion is true but reason is false

• Assertion is false but reason is true.

Complete the following reaction
R-OH + PCl5  $\rightarrow$  RCl + X + HCl
X is

• PCl3

• PCl5

• POCl3

• POBr3

. Which is the correct increasing order of boiling points of the following compounds?

• Bromobenzene < 1-Bromobutane < 1-Bromopropane < 1-Bromoethane

• Bromobenzene < 1-Bromoethane < 1-Bromopropane < 1-Bromobutane

• 1-Bromopropane < 1-Bromobutane < 1-Bromoethane < Bromobenzene

• 1-Bromoethane < 1-Bromopropane < 1-Bromobutane < Bromobenzene

Which of the following is a chiral molecule?

• CH₂BrI

• CH₃CBr₂Cl

• (CH₃)₂CHCl

• CH₃CHBrCH₂CH₃

In a SN1 reaction on chiral centres, there is

• 100% retention

• 100% inversion

• Racemization

• None