Question

Chemical properties of haloalkanes n haloarenes

Answer 1

Haloakanes are high reactively and undergoes a number of reaction

Answer 2

Chemical Properties

of Haloalkanes and Haloarenes

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1) Nucleophilic Substitution Reaction:

a) SN¹ Mechanism (Unimolecular Nucleophilc Substitution)

RDS = Rate Determining Step

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• Reactivity Order :-

3° > 2° > 1° Haloalkane

Due to +I effect and stability of 3° carbocation.

b) SN² Mechanism (Bimolecular Nucleophilc Substitution)

• Stability Order :-

1° > 2° > 3° Haloalkane

Due to less steric hindrance.

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$\sf{\green{Ques:}}$ What do you mean by Ambident Nucleophile?

$\sf{\green{Ans:}}$ Nucleophile which can attack from both sides.

Example :

• -CN = Nitro
• -NC = Isocyanide
• -ONO = Nitrite
• $\sf{-NO_2}$ = Nitro

$\sf{\green{Ques:}}$ Out of SN¹ and SN² which can show racemisation?

$\sf{\green{Ans:}}$ SN¹ will show racemisation because in SN¹ mechanism, 3° carbocation can attack by a nuclephile from both sides which leads to formation of levo or dextro rotatory isomer almost in same proportion and ultimately can provide a racemic mixture.

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2) β- Elimination:

When Haloalkane with β-Hydrogen atom heated in the presence of alcoholic NaOH or KOH then hydrogen will be removed or eliminated from that carbon which contains less number of hydrogen atom. Because it will provide more symmetrical and stable product.

3) Reaction with metals:

a) Grignard Reagent or Organometallic compound

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$\sf{\green{Ques:}}$ Why Grignard Reagent is prepared in anhydrous conditions?

$\sf{\green{Ans:}}$ Because Grignard Reagent can hydrolyse to give alkane.

R-MgX + H-OH → R-H (Alkane) + Mg-X-OH

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b) Wurtz Reaction

c) Fittig Reaction

d) Wurtz Fittig Reaction