‹ Back to the paper
Answer the following.
Illustrate the following reactions with an example in each case: Coupling reaction Balz-Schiemann…
Illustrate the following reactions with an example in each case:
(a)[1.0]
Coupling reaction
(b)[1.0]
Balz-Schiemann reaction
Answer
Answer (a)
Official answer keyEquation: $\mathrm{C_{6}H_{5}N_{2}Cl} + \mathrm{C_{6}H_{5}OH} \xrightarrow{\text{alkali}\text{,}\text{ }\text{273-278}\text{ }\text{K}} \mathrm{C_{6}H_{5}N_{2}C_{6}H_{4}OH} + \mathrm{HCl}$
Product: 4-hydroxyazobenzene
Coupling reaction: benzenediazonium chloride couples with phenol in mildly alkaline medium to give p-hydroxyazobenzene (an azo dye).
Answer (b)
Official answer keyEquations: $\mathrm{C_{6}H_{5}N_{2}Cl} + \mathrm{HBF_{4}} \xrightarrow{\text{273-278}\text{ }\text{K}} \mathrm{C_{6}H_{5}N_{2}BF_{4}} + \mathrm{HCl}$ $\mathrm{C_{6}H_{5}N_{2}BF_{4}} \xrightarrow{\text{heat}} \mathrm{C_{6}H_{5}F} + \mathrm{BF_{3}} + \mathrm{N_{2}}$
Product: fluorobenzene
Balz-Schiemann reaction: benzenediazonium chloride with fluoroboric acid gives benzenediazonium tetrafluoroborate, which on heating gives fluorobenzene.
From ISC 2027 Specimen Chemistry Paper 1, question 9(i).