Organic Chemistry Multiple Choice Questions on “Benzene Diazonium Chloride – 1”.
1. What is the general formula of Diazonium salt?
a) RN2+X–
b) RN+
c) RXI
d) RN2+HSO–2
Answer: a
Clarification: Diazonium compounds or diazonium salts are a group of organic compounds sharing a common functional group R−N2+X– where R can be any organic group, such as an alkyl or an aryl, and X is an inorganic or organic anion, such as a halogen.
2. What is the known name of the given reaction?
C6H5N+2 + CuCl → C6H5Cl + N2 + Cu+
a) Gattermanns reaction
b) Sandmeyers reaction
c) Dehydrogenation reaction
d) Esterification reaction
Answer: b
Clarification: Benzene diazonium chloride heated with cuprous chloride or cuprous bromide respectively dissolved in HCl or HBr yield chlorobenzene or Bromobenzene, respectively.
3. What is the known name of the given reaction?
C6H5N+2 + CuX → C6H5X + N2 + Cu+
a) Gattermanns reaction
b) Sandmeyers reaction
c) Dehydrogenation reaction
d) Esterification reaction
Answer: a
Clarification: In the Gatterman reaction, benzene diazonium chloride is warmed with copper powder and HCl or HBr to produce chlorobenzene and bromobenzene respectively.
4. What is the known name of the given reaction?
[C6H5N+2]Cl− + C6H6 → C6H5−C6H5 + N2 + HCl
a) Gattermanns reaction
b) Sandmeyers reaction
c) Gomberg–Bachmann reaction
d) Esterification reaction
Answer: c
Clarification: The aryl group can be coupled to another using aryldiazonium salts. For example, treatment of benzene diazonium chloride with benzene (an aromatic compound) in the presence of sodium hydroxide gives diphenyl. This reaction is known as the Gomberg–Bachmann reaction.
5. What is the known name of the given reaction?
[C6H5N+2]BF−4 → C6H5F + BF3 + N2
a) Gattermanns reaction
b) Sandmeyers reaction
c) Dehydrogenation reaction
d) Balz-Schiemann reaction
Answer: d
Clarification: Fluorobenzene is produced by thermal decomposition of benzene diazonium fluoroborate. The conversion is called the Balz-Schiemann reaction.
6. What is the known name of the given reaction?
[C6H5N+2]Cl− + ArCH=CHCO2H → ArC=C−C6H5 + N2 + CO2 + HCl
a) Gattermanns reaction
b) Sandmeyers reaction
c) Meerwein reaction
d) Balz-Schiemann reaction
Answer: a
Clarification: Benzenediazonium chloride reacts with compounds containing activated double bonds to produces phenylated products. The reaction is called the Meerwein arylation.
7. Benzene diazonium chloride when reacts with hypophosphorus acid produces which of the following compound?
a) Benzene
b) Phenyl phosphate
c) Phenol
d) Phenyl isocyanide
Answer: a
Clarification: Arene diazonium cations are reduced by hypophosphorous acid or sodium stannite gives benzene:
[C6H5N+2]Cl− + H3PO2 + H2O → C6H6 + N2 + H3PO3 + HCl
8. p-amino azo benzene is obtained by treating diazonium chloride with which of the following compound?
a) Benzene
b) Aniline
c) Phenol
d) Benzoic acid
Answer: b
Clarification: p-amino azo benzene is obtained by treating diazonium chloride with aniline. The reactions are specifically acid catalyzed and involve pre‐equilibrium formation of amine and diazonium salt followed by rate‐limiting attack of the diazonium ion at a C‐atom (C‐coupling) to give the corresponding aminoazo compounds.
9. When hypophosphorous acid is treated with diazonium salts, it is reduced to which of the following compound?
a) Arene
b) Methane
c) Ethyl alcohol
d) Amines
Answer: a
Clarification: When hypophosphorous acid is treated with diazonium salts it is reduced to arene. Arene diazonium cations are reduced by hypophosphorous acid or sodium stannite gives benzene:
[C6H5N+2]Cl− + H3PO2 + H2O → C6H6 + N2 + H3PO3 + HCl.
10. Which of the following amine will form stable diazonium salt at 273-283 K?
a) C6H5NH2
b) C6H5N(CH3)2
c) C2H5NH2
d) C6H5CH2NH2
Answer: a
Clarification: Diazonium salts are prepared by treatment of aromatic amines i.e. aniline (C6H5NH2) with nitrous acid and additional acid. Usually the nitrous acid is generated in situ (in the same flask) from sodium nitrite and the excess mineral acid.