Important question answers of haloalkanes and haloarenes class 12th

Q1. Write structures of the following compounds:

(i) 2-Chloro-3-methylpentane

(ii) 1-Chloro-4-ethylcyclohexane

(iii) 4-methyl-3-iodoheptane

(iv) 1,4-Dibromobut-2-ene

(v) 1-Bromo-2-methylbenzene.

(vi) 4-Bromopent-2-ene

(vii) 3-Bromo-2-methylbut-1-ene

(viii) 4-Bromo-3-methylpent-2-ene

(ix) 1-Bromo-2-methylbut-2-ene

(x) 1-Bromobut-2-ene

Q2. Name the following halides according to IUPAC system and classify them as alkyl, allyl, benzyl (primary, secondary, tertiary), vinyl or aryl halides:

(i) (CH3)2CHCH(Cl)CH3

(ii) CH3CH2CH(CH3)CH(C2H5)Cl

(iii) CH3CH2C(CH3)2CH2I

(iv) (CH3)3CCH2CH(Br)C6H5

(v) CH3CH(CH3)CH(Br)CH3

(vi) CH3C(C2H5)2CH2Br

(vii) CH3C(Cl)(C2H5)CH2CH3 

(viii) CH3CH=C(Cl)CH2CH(CH3)2

(ix) CH3CH=CHC(Br)(CH3)2

(x) p-ClC6H4CH2CH(CH3)2

(xi) m-ClCH2C6H4CH2C(CH3)3

(xii) o-Br-C6H4CH(CH3)CH2CH3 

Q3. Which of the products will be a major product in the reaction given below? Explain. 

Q4. Classify the following compounds as primary, secondary and tertiary halides.

(i) 1-Bromobut-2-ene

(ii) 4-Bromopent-2-ene

(iiii) 2-Bromo-2-methylpropane

Q5. Identify the products A and B formed in the following reaction

(a) CH3-CH2-CH=CH-CH3 + HCI → A + B

Q6. A hydrocarbon of molecular mass 72 g mol/l gives a single monochloro derivative and two dichloro derivatives on photo chlorination. Give the structure of the hydrocarbon.(HOTS)

Q7.  Name the alkene which will yield 1-chloro-1-methylcyclohexane by its reaction with HCI. Write the reactions involved.(HOTS)

Q8. Draw the structure of major monohalogen product formed in the following reaction :

Q9. Draw the structure of major monohalogen product in the following reaction :

Q10. A hydrocarbon C5H12 gives only one mono-chlorinatio product. Identify the hydrocarbon.

Q11. Out of which is an example of vinylic halide? 

Q12. Out of which is an example of allylic halide? 

Q13. Out of which is an example of a benzylic halide?

Q14. Complete the following reaction equations : 

Q15. Draw the structure of major monohalo product in each of the following reactions :

Q16. Write the equations for the preparation of 1-bromobutane from :

(i) 1-butanol (ii) but-l-ene

Q4.Give reason:

I, is better leaving group/C—I bond is weaker than C—Br

bond.

Q17. Draw the structures of major monohalo products in each of the following reactions : 

Q18. Haloalkanes, though polar, are insoluble in water.Explain. 

Q19. Arrange the following in increasing order of boiling point:

(i) CH3CH2CH2CH2Br

(ii) (CH3)3.Br

(iii) (CH3)2C.Br

Q20. Identify the chiral molecule in the following pair:

Q21. A hydrocarbon C5H12 gives only one mono-chlorination product. Identify the hydrocarbon.(HOTS).

Q22. Explain why, Alkyl halides, though polar, are immiscible with water.

Q23. Answer the following :

(i) Haloalkanes easily dissolve in organic solvents, why?

(ii) What is known as a racemic mixture? Give an example.

Q24. What is meant by chirality of a compound? Give anx eample.

Q25. Give reason:

(±) 2-Butanol is optically inactive.

Q26. Give reasons :

(a) n-Butyl bromide has higher boiling point than f-butylbromide.

(b) Racemic mixture is optically inactive. 

Q26. A solution of KOH hydrolyses CH3CHClCH2CH3 and CH3CH2CH2CH2Cl. Which one of these is more easily hydrolyzed?

Q27. Predict the order of reactivity of four isomeric bromobuta estate in SN1 reaction.

Q28. Which compound in the following pair undergoes faster SN1 reaction and why?

Q29. In the following pair of halogen compounds, which compound will react faster by SN1 mechanism?

Q30. Out of which is more reactive towards SN1 reaction and why?

Q31. Write the structure of an isomer of compound C4H9Br which is most reactive towards SN1 reaction. 

Q32. Which one in the following pairs of substances undergoes SN2 substitution reaction faster and why? 

 

Q33. Which one in the following pairs undergoes SN1 substitution reaction faster and why? 

Q34. Which alkyl halide from the following pair is chiral and undergoes faster SN2 reaction? 

Q35. Out of SN1 and SN2, which reaction occurs with

(a) Inversion of configuration

(b) Racemisation.

Q36. Which compound in each of the following pairs will react faster in SN2 reaction with —OH?

(i) CH3Br or CH3I (ii) (CH3)3 CCl or CH3Cl 

Q37. Which alkyl halide from the following pair is (i) Chiral and (ii) undergoes SN2 reaction faster? 

Q38. Which alkyl halide from the following pair is (i) Chira land (ii) undergoes SN1 reaction faster?

(a) (CH3)2CBr

(b) CH3CH2CHBrCH3

Q39. Rearrange the compounds of each of the following sets in order of reactivity towards SN2 displacement :

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

(ii) l-Bromo-3-methylbutane, 2-Bromo-2-methyl-butane, 3-Bromo-2-methylbutane

(iii) 1-Bromobutane, l-Bromo-2,2-dimethyl-propane, l-Bromo-2-methylbutane.

Q40. Which compound in each of the following pairs will react faster in SN2 reaction with -OH group?

(i) CH3Br or CH3I

(ii) (CH3)3CCl or CH3Cl.

Q41. How would you differentiate between SN1 and SN2mechanisms of substitution reactions? Give one example of each. 

Q42. Draw the structure of major monohalogen product in the following reaction : 

Q43. What happens when CH3 — Br is treated with KCN?

Q44.What happens when ethyl chloride is treated with aqueous KOH?

Q45. Write down Sandmayers reaction.

Q46. Convert Benzyl chloride to benzyl alcohol.

Q47. How will you carry out the following conversions:

(i) 2-Bromopropane to 1-bromopropane.

(ii) Benzene to p-chloronitrobenzene.

Q48.. Write the product of the following reactions: 

Q48. How can the following conversions be carriedout:

(i) Aniline to bromobenzene

(ii) Chlorobenzene to 2-chloroacetophenone

(iii) Chloroethane to butane

Q9. How do you convert:

(i) Chlorobenzene to biphenyl

(ii) Propene to 1-iodopropane

(iii) 2-bromobutane to but-2-ene 

Q49.Write the major product(s) in the following: 

Q50. Write the structural formula of A, B, C and D in the following: 

Q51. Give a chemical test to distinguish between C2H5Br and C6H5Br.

Q52. Haloalkanes undergo nucleophilic substitution whereas Haloarenes undergo electrophilic substitution. Explain. 

Q53. Chlorobenzene is extremely less reactive towards a nucleophilic substitution reaction. Give two reasons for the same.

Q54. Account for the following:

(i) The C – Cl bond length in chlorobenzene is shorter than that in CH3 – Cl.

(ii) Chloroform is stored in closed dark brown bottles

Q55. State one use each of DDT and iodoform.

Q56. Although chlorine is an electron withdrawing group, yet it is ortho-, para-directing in electrophilic aromatic substitution reactions.

Q57. Grignard’s reagents should be prepared under anhydrous conditions. Why?

Q58. The presence of nitro group (-NO2) at o/p positions increases the reactivity of haloarenes towards nucleophilic substitution reactions.