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Aromatic compounds

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Question 2

A student reacts methylbenzene with bromine in the presence of an anhydrous iron(III) bromide catalyst to form impure crystals of an organic compound, E.

a.

Describe how the student could recrystallise the impure crystals to obtain a pure sample of E.

[4]
b.

The pure sample of E is analysed to give the following results:

  • Percentage composition by mass: C\text{C}C, 25.56%; H\text{H}H, 1.52%; Br\text{Br}Br, 72.92%.
  • The mass spectrum of E shows a molecular ion peak at m/z=328.7m/z = 328.7m/z=328.7.
  • The 13C{}^{13}\text{C}13C NMR spectrum of E shows a total of 5 peaks: four peaks in the aromatic region (120–150 ppm) and one peak in the aliphatic region (15–25 ppm).

The table below shows directing effects for different groups in the electrophilic substitution of aromatic compounds.

Directing effect2- and 4-directing3-directing
Group−OH-\text{OH}−OH, −CH3-\text{CH}_3−CH3​, −NH2-\text{NH}_2−NH2​, −Br-\text{Br}−Br−NO2-\text{NO}_2−NO2​, −COOH-\text{COOH}−COOH

Analyse all the information to suggest the structure for E. Show all your reasoning.

[7]

Aromatic compounds Questions

  1. A Level
  2. /Chemistry
  3. /Aromatic compounds