Tag: introduction to diazonium salts

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Multiple choice chemistry amines introduction to diazonium salts structure, preparation and physical properties of diazonium salts diazonium salts

Which of the following compounds will not undergo azo coupling reaction with benzene diazonium chloride?

  1. Aniline

  2. Phenol

  3. Anisole

  4. Nitrobenzene
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Diazonium cation is weak electrophile and hence it reacts with electron rich compounds containing electron donating groups such as $-OH$, $-NH _2$ and $OCH _3$ groups and not with compounds containing electron withdrawing groups such as $-NO _2$ etc.


Hence,option D is correct.

Multiple choice chemistry amines introduction to diazonium salts structure, preparation and physical properties of diazonium salts diazonium salts

Which of the following diazonium salt is relatively stable at $0-{ 5^0 }^{ }C$?

  1. ${ CH } _{ 3 }-N\equiv N{ \} }^{ \oplus }C{ l }^{ - }$
  2. ${ \left( { CH } _{ 3 } \right) } _{ 2 }CH-N\equiv N{ \} }^{ \oplus }{ Cl }^{ - }$
  3. ${ C } _{ 6 }{ H } _{ 5 }-N\equiv N{ \} }^{ \oplus }{ Cl }^{ - }$
  4. ${ \left( { CH } _{ 3 } \right) } _{ 3 }C-N\equiv N{ \} }^{ \oplus }{ Cl }^{ - }$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The $+I$ effect which stabilizes the ${ N }^{ + }$ion is in the following order ${ C } _{ 6 }{ H } _{ 5 }-<{ CH } _{ 3 }-<{ \left( { CH } _{ 3 } \right)  } _{ 2 }-<{ \left( { CH } _{ 3 } \right)  } _{ 3 }$

$\therefore $ The ${ \left{ { \left( { CH } _{ 3 } \right)  } _{ 3 }C-N\equiv N \right}  }^{ + }{ Cl }^{ - }$ is most stable

Multiple choice chemistry amines introduction to diazonium salts structure, preparation and physical properties of diazonium salts diazonium salts

Which of the following is an Incorrect statement about benzenediazonium chloride?

  1. It is prepared by the reaction of aniline with nitrous acid at 273-278 K

  2. It is a colourless crystalline solid

  3. Alkyl diazonium salts are more stable than arenediazonium salts

  4. Benzene diazonium fluoroborate is water insoluble & stable at room temperature
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Arenediazonium salts are much more stable than alkyl diazonium salts due to the dispersal of the positive charge over the benzene ring via resonance. Alkyl diazonium salts, lacking this resonance stabilization, decompose readily even at low temperatures.

Multiple choice chemistry amines introduction to diazonium salts structure, preparation and physical properties of diazonium salts diazonium salts

For the successful diazotisation of arylamines, how many mole of mineral acid $(HCl \quad or \quad H _2SO _4 )$ are required for each mole of the amine?

  1. 1

  2. 2

  3. 3

  4. 4
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

For successful diazotization, 3 moles of mineral acid are required per mole of amine: 1 mole to convert the amine to its salt, 1 mole to generate nitrous acid from sodium nitrite, and 1 mole to maintain a highly acidic medium to prevent coupling reactions.

Multiple choice chemistry amines introduction to diazonium salts structure, preparation and physical properties of diazonium salts diazonium salts

In an analytical determination of arsenic, a solution containing arsenious acid, $ H _{3}AsO _{4},$ KI and a small amount of starch is electrolysed. The electrolysis produces free $I _{2}$ from $ I^{-}$ ions and the $ I _{2}$ immediately oxidizes the arsenious acid to hydrogen arsenate ion, $ HAsO _{4}^{2-}.$
$ I _{2}+H _{3}AsO _{3}+H _{2}O \rightarrow 2I^{-} + HAsO _{4}^{2-}+4H^{+}$
When the oxidation of arsenic is complete, the free iodine blue colour. If during a particular run, it takes 96.5 s for a current of 10.0 mA to give an end point (indicated by the blue colour),how many g of arsenic are present in the solution. (As = 75)

  1. $ 6.3 \times 10^{-4} g$
  2. $1.26 \times 10^{-4}g$
  3. $ 3.15 \times 10^{-5}g$
  4. $ 6.3 \times 10^{-5}g$
Reveal answer Fill a bubble to check yourself
D Correct answer
Multiple choice chemistry amines introduction to diazonium salts structure, preparation and physical properties of diazonium salts diazonium salts

State, whether the following statements are True or False:
Aniline forms phenol when treated with nitrous acid.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When aniline is treated with nitrous acid (HNO2) at low temperatures (273-278 K), it forms a stable benzenediazonium salt. Only at higher temperatures does the diazonium salt hydrolyze to form phenol. Thus, the direct statement that aniline forms phenol under standard diazotization conditions is false.

Multiple choice chemistry amines introduction to diazonium salts structure, preparation and physical properties of diazonium salts diazonium salts

Which of the following amines form unstable diazonium salt?

  1. ${ C } _{ 6 }{ H } _{ 5 }{ NH } _{ 2 }$
  2. $\left( { C } _{ 2 }{ H } _{ 5 } \right) _{ 2 }NH$
  3. $\left( { C } _{ 2 }{ H } _{ 5 } \right) _{ 3 }N$
  4. ${ CH } _{ 3 }{ NHC } _{ 2 }{ H } _{ 5 }$
Reveal answer Fill a bubble to check yourself
B,C,D Correct answer
Explanation

Only primary aromatic amines form stable arene diazonium salts.
The reaction is as follows:

$C _{6}H _{5}NH _{2} + NaNO _{2} + HCl (0-5^{\circ}C) \rightarrow PhN _{2}^{+}Cl^{-}$

Remain forms the unstable diazonium salt.
So, the correct options are $B$, $C$, $D$

Multiple choice chemistry amines introduction to diazonium salts structure, preparation and physical properties of diazonium salts diazonium salts

Reaction at ${ 0-5 }^{ 0 }C$ between aniline, ${ NaNO } { 2 }$ and HCl is known as___________

  1. Suphonation of benzene

  2. Acylation of aniline

  3. Alkylation of aniline

  4. Diazotisation
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

This is the diazotization reaction.


The reaction goes as follows :
$PhNH _{2} + NaNO _{2} + HCl \rightarrow PhN _{2}^{+} Cl^{-}$

The benzendiazonium salt thus formed acts as a synthetic intermediate and can be used to synthesize a wide variety of substituted benzene compounds.

For example,
$PhN _{2}^{+} Cl^{-} + CuCN \rightarrow PhCN$ (cyanobenzene)
$PhN _{2}^{+} Cl^{-} + CuI (KI) \rightarrow PhI$ (iodobenzene)

Option D is correct.

Multiple choice chemistry amines introduction to diazonium salts structure, preparation and physical properties of diazonium salts diazonium salts

Aniline when treated with $NaNO { 2 }$ and $HCl$ at $0- { 5 }^{ 0 }C$ gives ___________ as a product.

  1. chloroaniline

  2. benzene diazonium chloride

  3. chlorobenzene

  4. dichlorobenzene
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Aniline reacts with sodium nitrite and HCl in cold condition to form benzene diazonium chloride.
$\underset {aniline} {{ C } _{ 6 }{ H } _{ 5 }{ NH } _{ 2 }}\xrightarrow [ { NaNO } _{ 2 } ]{ HCl } \underset {benzene diazonium chloride} {[C _6H _5-N _2^+Cl^-]}$