Tag: structure, preparation and physical properties of diazonium salts

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Questions Related to structure, preparation and physical properties of diazonium salts

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

Which of the following amines will form stable diazonium salt at 273-283 K? 

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

Aniline (C6H5NH2) is a primary aromatic amine, which reacts with nitrous acid at 273-278 K to form benzenediazonium chloride, which is relatively stable at this temperature due to resonance. Aliphatic amines like C2H5NH2 and C6H5CH2NH2 form highly unstable diazonium salts that decompose immediately, while tertiary aromatic amines like C6H5N(CH3)2 undergo electrophilic aromatic substitution (nitrosation) instead of diazotization.

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

Diazonium salts are used at a very lower temperature because:

  1. they are poisonous at room temperature

  2. they are highly unstable at room temperature

  3. they are highly volatile at room temperature

  4. none of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Diazonium salt is used at very low temperature because of the fact that at the higher temperature they are unstable, as at higher temperature $N _2$ can leave out.

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

Diazonium salts are used:

  1. after storing for a few days after preparation

  2. immediately after its preparation
  3. after storing for $2-3$ hours

  4. difficult to prepare commercially
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Diazonium salts are light sensitive and break down under near UV or violet light.This is why it is used immedietly after being prepared so that it does not loses its properties.

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

What makes diazonium ion one of the best leaving group of organic chemistry? 

  1. Half filled electronic configuration of nitrogen atom

  2. High electronegativity of nitrogen atom

  3. Very high stability of dinitrogen molecule in the atmosphere
  4. Weaker $C-N$ bond
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Diazonium ion is one of best leaving group of organic chemistry because of very high stability of dinitrogen molecule in the atmosphere.

Multiple choice chemistry amines introduction to diazonium salts structure, preparation and physical properties of diazonium salts diazonium salts
What is the molarity of 0.2 N Na2 CO3 solution ?

  1. 0.1M

  2. 0M

  3. 0.4M

  4. 0.2M
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Normality is equal to molarity multiplied by the n-factor. For sodium carbonate (Na2CO3), the n-factor is 2 because it dissociates to release two sodium ions. Thus, a 0.2 N solution has a molarity of 0.2 / 2 = 0.1 M.

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

Diazomethane was photolysed to generate singlet carbine which was treated with cis-2-butene. The main product(s) of the reaction is/are:

  1. cis-1, 2-dimethylcyclopropane

  2. trans-1, 2-dimethylcyclopropane
  3. mixture of $(A)$ and $(B)$

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

Solution:- (A) cis-$1,2$-dimethylcyclopropane

$\underset{\text{Diazomethane}}{C{H} _{2}-\overset{+}{N}={N}^{-}} \xrightarrow[-N \equiv N]{h \nu} \underset{\text{Singlet carbene} \left( \text{Methylene} \right)}{:C{H} _{2}}$
The addition of methylene would yield trans-$1,2$-dimethylcyclopropane from trans-$2$-butene and cis-$1,2$-dimethylcyclopropane from cis-$2$-butene.

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 of $0-5^\circ C$- :

  1. $CH _{3}CH _2N\equiv N\left. \right \} ^\oplus Cl^{-} $
  2. $CH _{3}-C(CH _{3}) _{2}-N\equiv N\left. \right \} ^\oplus Cl^{-} $
  3. $CH _{3}-N\equiv N\left. \right \} ^\oplus Cl^{-} $
  4. $(CH _{3}) _{3}C-N\equiv N\left. \right \} ^\oplus Cl^{-} $
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The diazonium salt  $CH _{3}-N\equiv N\left.  \right } ^\oplus Cl^{-}$ obtained by treatment of methylamine with nitrous acid is relatively stable at $0-5^\circ C$.

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 $\displaystyle 0-5^{\circ}$C?

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

Diazonium salts obtained from aliphatic primary amines are unstable. Those obtained from aromatic primary amines are relatively stable.
Benzene diazonium chloride $(\displaystyle C _{6}H _{5}-N\equiv N \left.  \right }^{\oplus }Cl^{-})$ is obtained from aromatic primary amine. Hence, it is relatively stable.

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

Which of the following statements are correct? 

  1. Aryldiazonium ions are more stable than alkyldiazonium ions.

  2. Electron release from the ortho- and para-positions of the ring stabilises the aryldiazonium ion.
  3. The increased stability of aryldiazonium is due to the great difficulty of forming $\displaystyle { Ar }^{ \oplus }$ as compared to $\displaystyle { R }^{ \oplus }$.

  4. Alkyldiazonium is more stable than aryldiazonium ion.
Reveal answer Fill a bubble to check yourself
A,B,C Correct answer
Multiple choice chemistry amines introduction to diazonium salts structure, preparation and physical properties of diazonium salts diazonium salts

Arrange the following resonating structure according to their contribution towards resonance hybrid?
(a) $CH _2=\overset {\oplus}{N}=\overset {\ominus}{N}$ (b) $\overset {\ominus}{C}H _2-N=\overset {\oplus}{N}:$ (c) $\overset {\oplus}{C}H _2-\underset {. .}{N}=\overset {\ominus}{N}$ (d) $\overset {\ominus}{C}H _2-\overset {\oplus}{N}\equiv \overset {. .}{N}$

  1. a > d > c > b

  2. b > a > c > d

  3. a > c > b > d

  4. d > a > b > c
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
The correct order of the contribution of resonating structure towards resonance hybrid is
$\displaystyle a (CH _2=\overset {\oplus}{N}=\overset {\ominus}{N}) > d (\overset {\ominus}{C}H _2-\overset {\oplus}{N}\equiv \overset {. .}{N}) > c (
\overset {\oplus}{C}H _2-\underset {. .}{N}=\overset {\ominus}{N}
) > b (\overset {\ominus}{C}H _2-N=\overset {\oplus}{N}:)$
a and d have higher contribution as they have less charge separation.
b and c have lower contribution as they have more charge separation.