Very Important Questions : Haloalkanes & Haloarenes

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1.Why is sulphuric acid not used during the reaction of alcohols with KI?

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2. Why is sulphuric acid not usedduring the reaction of alcohols with KI?

3. A hydrocarbon C5H10 does not react with chlorine in dark but gives a single monochloro compound C5H9Cl in bright sunlight. Identify the hydrocarbon.

4. Write the equations for the preparationof 1−iodobutane from –

          (i) 1-butanol  (ii) 1-chlorobutane   (iii) but-1-ene.

Video lecture “Haloalkane & Haloarenes-1”

5. What are ambident nucleophiles?Explain with an example.

6. Which compound in each of the following pairs will react faster in SN2 reaction with OH? (i) CH3Br or CH3I   (ii) (CH3)3CCl or CH3Cl

7.Predict all the alkenes that would be formed by dehydrohalogenation of the following halides with sodium ethoxide in ethanol and identify the major alkene

          (i) 1-Bromo-1-methylcyclohexane  (ii) 2-Chloro-2-methylbutane (iii)2,2,3-Trimethyl-3-bromopentane.

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8.How will you bring about thefollowing conversions?

(i) Ethanol tobut-1-yne  (ii) Propene to1-nitropropane  (iii) Tolueneto   

  benzylalcohol  (iv) Propene to propyne (v)Ethanol to ethyl fluoride 

(vi) Bromomethane to propanone (vii)But-1-ene to but-2-ene  (viii)1-Chlorobutane to n-octane  (ix)Benzene to biphenyl.

9. Explain why

(i) the dipole moment of chlorobenzeneis lower than that of cyclohexyl chloride?

(ii) alkyl halides, though polar, areimmiscible with water?

(iii) Grignard reagents should beprepared under anhydrous conditions?

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10. Write the structure of the major organic product in each of the following reactions:

(a) (CH3)3CBr + KOH  =         (b) CH3-CH(Br)CH2CH3 + NaOH =

(c) CH3CH=C(CH3)2 + HBr =

      (a) (CH3)3CBr + KOH         (b) CH3-CH(Br)CH2CH3+ NaOH

      (c) CH3CH=C(CH3)2+ HBr

11. Write the mechanism of thefollowing reaction: n BuBr +KCN         = BuCN

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12. Arrange the compounds of each setin order of reactivity towards SN2 displacement:

(i) 2-Bromo-2-methylbutane,1-Bromopentane, 2-Bromopentane

(ii) 1-Bromo-3-methylbutane,2-Bromo-2-methylbutane, 3-Bromo-2- methylbutane

(iii) 1-Bromobutane,1-Bromo-2,2-dimethylpropane, 1-Bromo-2-methylbutane, 1-Bromo-3-methylbutane.

13. Out of C6H5CH2Cl andC6H5CHClC6H5, which is more easilyhydrolysed by aqueous KOH?

14. p-Dichlorobenzene has higher m.p.and lower solubility than those of o– and m-isomers. Why.

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15. How the following conversions can be carried out?

(i) Ethanol to but-1-yne (iii) 1-Bromopropane to 2-bromopropane (iii) Toluene tobenzyl alcohol (iv) Benzene to 4-bromonitrobenzene (v) Benzylalcohol to 2-phenylethanoic acid (vi) Ethanol to propanenitrile (vii)Aniline to chlorobenzene (viii) 2-Chlorobutane to 3, 4-dimethylhexane(ix)2-Methyl-1-propene to 2-chloro-2-methylpropane (x) Ethyl chloride topropanoic acid (xi) But-1-ene to n-butyliodide (xii)2-Chloropropane to 1-propanol (xiii) Isopropyl alcohol to iodoform (xiv)Chlorobenzene to p-nitrophenol (xv) Benzene to diphenyl

(xvi) Aniline to phenylisocyanide

For 100%success in Board exam.

16. The treatment of alkyl chlorides with aqueous KOH leads to the formation of alcohols but in the presence of alcoholic KOH, alkenes are major products. Explain

17. Primary alkyl halide C4H9Br (a) reacted with alcoholic KOH to give compound (b).Compound (b) is reacted with HBr to give (c) which is an isomer of (a). When (a) is reacted with sodium metal it gives compound (d), C8H18which is different from the compound formed when n-butyl bromide is reacted with sodium. Give the structural formula of (a) and write the equations for all the reactions.

18.What happens when

(i) n-butyl chloride is treated withalcoholic KOH, (ii) bromobenzene is treated with Mg in the presence ofdry ether,(iii) chlorobenzene is subjected to hydrolysis, (iv)ethyl chloride is treated with aqueous KOH,(v) methyl bromide is treated withsodium in the presence of dry ether, (vi) methyl chloride is treatedwith KCN.

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