Chemistry · Textbook solutions

Halogen Derivatives

Every solved example, exercise, and miscellaneous question — in the order the textbook teaches them. · 56 questions

10. Halogen Derivatives — worked examples

4 q

Solved Examples

Worked · 4
  1. Solved Ex.10.1
    How will you obtain 1-bromo-1-methylcyclohexane from alkene? Write possible structures of alkene and the reaction involved.
  2. Solved Ex.10.2
    Arrange the following compounds in order of increasing boiling points : bromoform, chloromethane, dibromomethane, bromomethane.
  3. Solved Ex.10.4
    Primary allylic and primary benzylic halides show higher reactivity by SN1\mathrm{S_N1} mechanism than other primary alkyl halides. Explain.
  4. Solved Ex.10.5
    Which of the following two compounds would react faster by SN2\mathrm{S_N2} mechanism and Why ? CH3−CH2−CH2−CH2Cl\mathrm{CH_3-CH_2-CH_2-CH_2Cl} (1-Chlorobutane) and CH3−CHCl−CH2−CH3\mathrm{CH_3-CHCl-CH_2-CH_3} (2-Chlorobutane)

Exercises

52 q

1. Choose the most correct option.

Practice · 10
  1. Choose the most correct option.
    Ex Q.1 (i)
    The correct order of increasing reactivity of C-X bond towards nucleophile in the following compounds is (I) C6H5−X\mathrm{C_6H_5-X} (II) a benzene ring carrying X\mathrm{X}, with a CH3\mathrm{CH_3} group ortho to it and an NO2\mathrm{NO_2} group para to it (III) (CH3)3C−X\mathrm{(CH_3)_3C-X} (IV) (CH3)2CH−X\mathrm{(CH_3)_2CH-X}
    1. A.
      I < II < III < IV
    2. B.
      II < I < III < IV
    3. C.
      III < IV < II < I
    4. D.
      IV < III < I < II
  2. Ex Q.1 (ii)
    CH3−CH=CH2→peroxideHI\mathrm{CH_3-CH=CH_2} \xrightarrow[\text{peroxide}]{\mathrm{HI}} The major product of the above reaction is,
    1. A.
      I−CH2−CH=CH2\mathrm{I-CH_2-CH=CH_2}
    2. B.
      CH3−CH2−CH2I\mathrm{CH_3-CH_2-CH_2I}
    3. C.
      CH3−CHI−CH3\mathrm{CH_3-CHI-CH_3}
    4. D.
      CH3−CHI−CH2OH\mathrm{CH_3-CHI-CH_2OH}
  3. Ex Q.1 (iii)
    Which of the following is likely to undergo racemization during alkaline hydrolysis ? (I) CH3−CHCl−C2H5\mathrm{CH_3-CHCl-C_2H_5} (II) C6H5−CH2Cl\mathrm{C_6H_5-CH_2Cl} (III) C6H5−Cl\mathrm{C_6H_5-Cl} (IV) CH3−CH(CH3)−CH2Cl\mathrm{CH_3-CH(CH_3)-CH_2Cl}
    1. A.
      Only I
    2. B.
      Only II
    3. C.
      II and IV
    4. D.
      Only IV
  4. Ex Q.1 (iv)
    The best method for preparation of alkyl fluorides is
    1. A.
      Finkelstein reaction
    2. B.
      Swartz reaction
    3. C.
      Free radical fluorination
    4. D.
      Sandmeyer's reaction
  5. Ex Q.1 (v)
    Identify the chiral molecule from the following.
    1. A.
      1-Bromobutane
    2. B.
      1,1- Dibromobutane
    3. C.
      2,3- Dibromobutane
    4. D.
      2-Bromobutane
  6. Ex Q.1 (vi)
    An alkyl chloride on Wurtz reaction gives 2,2,5,5-tetramethylhexane. The same alkyl chloride on reduction with zinc-copper couple in alchol give hydrocarbon with molecular formula C5H12\mathrm{C_5H_{12}}. What is the structure of alkyl chloride
    1. A.
      CH3−C(CH3)2−CH2Cl\mathrm{CH_3-C(CH_3)_2-CH_2Cl}
    2. B.
      CH3−CCl(CH3)−CH2CH3\mathrm{CH_3-CCl(CH_3)-CH_2CH_3}
    3. C.
      CH3−CH2−CHCl−CH3\mathrm{CH_3-CH_2-CHCl-CH_3}
    4. D.
      CH3−CH(CH3)−CH(CH3)−CHCl\mathrm{CH_3-CH(CH_3)-CH(CH_3)-CHCl}
  7. Ex Q.1 (vii)
    Butanenitrile may be prepared by heating
    1. A.
      propanol with KCN
    2. B.
      butanol with KCN
    3. C.
      n-butyl chloride with KCN
    4. D.
      n-propyl chloride with KCN
  8. Ex Q.1 (viii)
    Choose the compound from the following that will react fastest by SN1\mathrm{S_N1} mechanism.
    1. A.
      1-iodobutane
    2. B.
      1-iodopropane
    3. C.
      2-iodo-2 methylbutane
    4. D.
      2-iodo-3-methylbutane
  9. Ex Q.1 (ix)
    C6H11−Cl+Mg→etherdryA→H2OB\mathrm{C_6H_{11}-Cl} + \mathrm{Mg} \xrightarrow[\text{ether}]{\text{dry}} \mathrm{A} \xrightarrow{\mathrm{H_2O}} \mathrm{B} (the ring drawn in the book is a plain saturated six-membered ring, i.e. C6H11−\mathrm{C_6H_{11}-} is cyclohexyl) The product 'B' in the above reaction sequence is,
    1. A.
      C6H11−Mg\mathrm{C_6H_{11}-Mg}
    2. B.
      C6H11−Mg−Cl\mathrm{C_6H_{11}-Mg-Cl}
    3. C.
      Cl−C6H10−Mg\mathrm{Cl-C_6H_{10}-Mg} (Cl and Mg on opposite carbons of one cyclohexane ring)
    4. D.
      C6H12\mathrm{C_6H_{12}} (cyclohexane)
  10. Ex Q.1 (x)
    Which of the following is used as source of dichlorocarbene
    1. A.
      tetrachloromethane
    2. B.
      chloroform
    3. C.
      iodoform
    4. D.
      DDT

2. Do as directed.

Practice · 22
  1. Do as directed. Write IUPAC name of the following compounds
    Ex Q.2 (i-a)
    CH3−CH=C(CH3)−CH(CH3)−Br\mathrm{CH_3-CH=C(CH_3)-CH(CH_3)-Br}
  2. Ex Q.2 (i-b)
    CH3−CH(Cl)−CH(CH3)−CH2−CH3\mathrm{CH_3-CH(Cl)-CH(CH_3)-CH_2-CH_3}
  3. Ex Q.2 (i-c)
    Write the IUPAC name of the substituted cyclohexane whose structure is shown in the figure.
  4. Ex Q.2 (i-d)
    Write the IUPAC name of the substituted benzene whose structure is shown in the figure.
  5. Do as directed. Write structure and IUPAC name of the major product in each of the following reaction.
    Ex Q.2 (ii-a)
    CH3−CH(CH3)−CH2Cl+NaI→Acetone\mathrm{CH_3-CH(CH_3)-CH_2Cl} + \mathrm{NaI} \xrightarrow{\text{Acetone}}
  6. Ex Q.2 (ii-b)
    CH3−CH2Br+SbF3⟶\mathrm{CH_3-CH_2Br} + \mathrm{SbF_3} \longrightarrow
  7. Ex Q.2 (ii-c)
    CH3−CH(CH3)−CH=CH2+HBr→peroxide\mathrm{CH_3-CH(CH_3)-CH=CH_2} + \mathrm{HBr} \xrightarrow{\text{peroxide}}
  8. Ex Q.2 (ii-d)
    C6H11−OH+SOCl2⟶\mathrm{C_6H_{11}-OH} + \mathrm{SOCl_2} \longrightarrow (the ring drawn in the book is a plain saturated six-membered ring, i.e. cyclohexanol)
  9. Ex Q.2 (ii-e)
    C6H5−CH3+Cl2→Fedark\mathrm{C_6H_5-CH_3} + \mathrm{Cl_2} \xrightarrow[\mathrm{Fe}]{\text{dark}}
  10. Do as directed.
    Ex Q.2 (iii)
    Identify chiral molecule/s from the following. a. CH3−CH(OH)−CH2−CH3\mathrm{CH_3-CH(OH)-CH_2-CH_3} b. CH3−CH2−CH(Br)−CH2−CH3\mathrm{CH_3-CH_2-CH(Br)-CH_2-CH_3} c. CH3−CH2−CH2−CH2Br\mathrm{CH_3-CH_2-CH_2-CH_2Br} d. CH3−CH(CH3)−CH3−CH3\mathrm{CH_3-CH(CH_3)-CH_3-CH_3}
  11. Do as directed. Which one compound from the following pairs would undergo SN2\mathrm{S_N2} faster from the?
    Ex Q.2 (iv-a)
    C6H11−CH2Cl\mathrm{C_6H_{11}-CH_2Cl} and C6H11−Cl\mathrm{C_6H_{11}-Cl} (both rings are drawn in the book as plain saturated six-membered rings, i.e. cyclohexyl)
  12. Ex Q.2 (iv-b)
    CH3CH2CH2I\mathrm{CH_3CH_2CH_2I} and CH3CH2CH2Cl\mathrm{CH_3CH_2CH_2Cl}
  13. Do as directed. Complete the following reactions giving major product.
    Ex Q.2 (v-a)
    CH3−CH=CH2→peroxideHBrA→alc. KOHB\mathrm{CH_3-CH=CH_2} \xrightarrow[\text{peroxide}]{\mathrm{HBr}} \mathrm{A} \xrightarrow{\text{alc. KOH}} \mathrm{B}
  14. Ex Q.2 (v-b)
    CH3−CH(OH)−CH3→Red P/Br2A→Ag2O/H2OB\mathrm{CH_3-CH(OH)-CH_3} \xrightarrow{\text{Red } \mathrm{P}/\mathrm{Br_2}} \mathrm{A} \xrightarrow{\mathrm{Ag_2O}/\mathrm{H_2O}} \mathrm{B}
  15. Ex Q.2 (v-c)
    CH3−C(CH3)2−CH2−Cl→Na/dry etherA\mathrm{CH_3-C(CH_3)_2-CH_2-Cl} \xrightarrow{\mathrm{Na}/\text{dry ether}} \mathrm{A}
  16. Ex Q.2 (v-d)
    C6H5−Cl→dry etherMgA\mathrm{C_6H_5-Cl} \xrightarrow[\text{dry ether}]{\mathrm{Mg}} \mathrm{A}
  17. Do as directed. Name the reagent used to bring about the following conversions.
    Ex Q.2 (vi-a)
    Bromoethane to ethoxyethane
  18. Ex Q.2 (vi-b)
    1-Chloropropane to 1 nitropropane
  19. Ex Q.2 (vi-c)
    Ethyl bromide to ethyl isocyanide
  20. Ex Q.2 (vi-d)
    Chlorobenzene to biphenyl
  21. Do as directed.
    Ex Q.2 (vii)
    Arrange the following in the increase order of boiling points a. 1-Bromopropane b. 2- Bromopropane c. 1- Bromobutane d. 1-Bromo-2-methylpropane
  22. Ex Q.2 (viii)
    Match the pairs.
    Column IColumn II
    a. CH3−CH(X)−CH3\mathrm{CH_3-CH(X)-CH_3}i. vinyl halide
    b. CH2=CH−CH2X\mathrm{CH_2=CH-CH_2X}ii. alkyl halide
    c. CH2=CH−X\mathrm{CH_2=CH-X}iii. allyl halide
    iv. benzyl halide
    v. aryl halide

3. Give reasons

Practice · 4
  1. Give reasons
    Ex Q.3 (i)
    Haloarenes are less reactive than halo alkanes.
  2. Ex Q.3 (ii)
    Alkyl halides though polar are immiscible with water.
  3. Ex Q.3 (iii)
    Reactions involving Grignard reagent must be carried out under anhydrous condition.
  4. Ex Q.3 (iv)
    Alkyl halides are generally not prepared by free radical halogenation of alkanes.

4. Distinguish between

Practice · 1
  1. Ex Q.4
    Distinguish between - SN1\mathrm{S_N1} and SN2\mathrm{S_N2} mechanism of substitution reaction ?

5. Explain

Practice · 1
  1. Ex Q.5
    Explain - Optical isomerism in 2-chlorobutane.

6. Convert the following.

Practice · 8
  1. Convert the following.
    Ex Q.6 (i)
    Propene to propan-1-ol
  2. Ex Q.6 (ii)
    Benzyl alcohol to benzyl cyanide
  3. Ex Q.6 (iii)
    Ethanol to propane nitrile
  4. Ex Q.6 (iv)
    But-1-ene to n-butyl iodide
  5. Ex Q.6 (v)
    2-Chloropropane to propan-1-ol
  6. Ex Q.6 (vi)
    tert-Butyl bromide to isobutyl bromide
  7. Ex Q.6 (vii)
    p-Nitrochlorobenzene to p-nitrophenol
  8. Ex Q.6 (viii)
    Propene to 1-nitropropane

7. Answer the following

Practice · 6
  1. Answer the following
    Ex Q.7 (i)
    HCl is added to a hydrocarbon 'A' (C4H8)(\mathrm{C_4H_8}) to give a compound 'B' which on hydrolysis with aqueous alkali forms tertiary alcohol 'C' (C4H10O)(\mathrm{C_4H_{10}O}). Identify 'A' , 'B' and 'C'.
  2. Answer the following. Complete the following reaction sequences by writing the structural formulae of the organic compounds 'A', 'B' and 'C' .
    Ex Q.7 (ii-a)
    2-Bromobutane →alc.KOHA→Br2B→NaNH2C\xrightarrow{\text{alc.KOH}} \mathrm{A} \xrightarrow[\mathrm{Br_2}]{} \mathrm{B} \xrightarrow[\mathrm{NaNH_2}]{} \mathrm{C}
  3. Ex Q.7 (ii-b)
    Isopropyl alcohol →PBr3ΔA→NH3 excessB\xrightarrow[\mathrm{PBr_3}]{\Delta} \mathrm{A} \xrightarrow[\mathrm{NH_3}\ \text{excess}]{} \mathrm{B}
  4. Answer the following. Observe the following and answer the questions given below. CH2=CH−X¨:⟷C⊖H2−CH=X⊕:\mathrm{CH_2=CH-\ddot{X}:} \longleftrightarrow \overset{\ominus}{\mathrm{C}}\mathrm{H_2-CH=}\overset{\oplus}{\mathrm{X}}\mathrm{:}
    Ex Q.7 (iii-a)
    Name the type of halogen derivative
  5. Ex Q.7 (iii-b)
    Comment on the bond length of C-X bond in it
  6. Ex Q.7 (iii-c)
    Can react by SN1\mathrm{S_N1} mechanism? Justify your answer.