More practice questions

5. Q5. How many monochloro structural isomers does free radical chlorination of 2-methylpropane, (CH₃)₃CH, give? Name them.

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   Two sets of alike hydrogens: the nine on the three CH₃ groups and the one on the central carbon. So 2 isomers: 1-chloro-2-methylpropane, (CH₃)₂CHCH₂Cl, and 2-chloro-2-methylpropane, (CH₃)₃CCl (reasoned, as in NCERT Example 6.3, page 165).

6. Q6. Complete: (i) CH₃CH₂CH₂OH + SOCl₂ → ? (ii) CH₃CH=CH₂ + Br₂ (in CCl₄) → ?

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   (i) CH₃CH₂CH₂Cl + SO₂ + HCl (1-chloropropane). (ii) CH₃CHBrCH₂Br, 1,2-dibromopropane, a colourless vic-dibromide (NCERT pages 164–165).

7. Q7. What mass of 1-iodobutane (C₄H₉I, 184 g mol⁻¹) can at most be made from 0.040 mol of 1-bromobutane by the Finkelstein reaction?

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   R–Br + NaI → R–I + NaBr: one mole of iodide per mole of bromide, so at most 0.040 mol × 184 g mol⁻¹ = 7.36 g (reasoned from NCERT page 165).

8. Q8. Why is bromine in CCl₄ used to detect a C=C double bond?

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   Bromine adds across the double bond to give a colourless vic-dibromide, so the reddish brown colour of the bromine solution disappears (NCERT page 165). An alkane, with no multiple bond, does not take up bromine this way, so the colour stays (reasoned).