Amines Test

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Amines Test - 28

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Weekly Quiz Competition

Question 1
1 / -0

Secondary amines can be prepared by:

A
reduction of nitro compounds

B
reduction of amides

C
reduction of isonitriles

D
reduction of nitriles

Solution

Isonitriles on reduction with lithium aluminium hydride $$(LiAlH_4)$$ or catalytic hydrogenation ($$H_2/Ni$$) produce secondary amines.
$$R-NC \xrightarrow{LiAlH_4, H_2/Ni} R-NH-CH_2$$
Question 2
1 / -0

$$C_3H_9N$$ cannot represent:

A
$$1^o$$ amine

B
$$2^o$$ amine

C
$$3^o$$ amine

D
quaternary ammonium salt

Solution

$${C}_{3}{H}_{9}N$$ can not represent a quaternary salt$$.$$ Because it has only three carbon atom$$.$$
Question 3
1 / -0

Which one of the following is aromatic amine?

A

B

C

D
Both $$A$$ and $$B$$

Solution

(A) Aniline is aromatic as it obeys Huckel's rule of aromaticity. It is aromatic.

(B) This is also followed Huckel's rule of aromaticity
$$(4n+2)\pi e^-$$
$$=6\pi e^-(n=1)$$
It is also planar, cyclic and conjugated system.

So both A and B are aromatic amines.

While option C is aliphatic amine since the $$NH_2$$ group attached to aliphatic carbon.

Option D is correct.
Question 4
1 / -0

Basic strength of different alkyl amines depends upon:

A
$$+I$$ effect

B
steric effect

C
solvation effect

D
all of these

Solution

The basic strength of different alkyl amines depends on many factors like:
1) $$+ I$$ effect is the polarization of a sigma bond due to electron donating effect of adjacent groups or atoms.
2) In water, the ammonium salts of primary and secondary amines undergo solvation effects due to hydrogen bonding to a much greater degree than ammonium salts of tertiary amines.
3) steric effect is the effect faced by incoming group or hydrogen by the already present bulky $$-R$$ groups on the Nitrogen atom.
Question 5
1 / -0

Identify $$X,\ Y$$ and $$Z$$ in the given reaction.
$$CH_2 \, =\, CH_2 \xrightarrow [CCl_4]{Br_2} \,X\, \xrightarrow[(2 \, moles)]{NaCN} \, Y \, \xrightarrow {LiAlH_4} \, Z$$

A
$$X \,=\, CH_2BrCH_2Br \, ,\, Y \, =\, CH_3CH_2CH_2CN$$

B
$$X \, =\, CH_2BrCH_2Br \, , \, Y \, =\, CH_3CH_2CN$$

C
$$X\, =\, CH_3CH_2Br \, ,\, Y\, = \, CH_3CH_2CN$$

D
$$X \, =\, CH_2BrCH_2Br \, ,\, Y \,=\, NCCH_2CH_2CN$$

Solution

$$CH_2 = CH_2 \xrightarrow [CCl_4]{Br_2} \underset{(X)}{BrCH_2 - CH_2Br} \xrightarrow {NaCN} \underset {(Y)}{NCCH_2CH_2CN} \xrightarrow {LiAlH_4} \underset{(Z)} {\underset {(1,4-Diaminobutane)}{H_2NCH_2CH_2CH_2CH_2NH_2}}$$
Question 6
1 / -0

Tertiary amines have lowest boiling points amongst isomeric amines because:

A
they have highest molecular mass

B
they do not form hydrogen bonds

C
they are more polar in nature

D
they are most basic in nature

Solution

Primary and secondary amines can form hydrogen bonds whereas tertiary amines fail to do so. Hence, their boiling points are lowest.
Question 7
1 / -0

Which of the following has highest $$pK_b$$ value?

A
$$(CH_3)_3CNH_2$$

B
$$NH_3$$

C
$$(CH_3)_2NH$$

D
$$CH_3NH_2$$

Solution

Higher the basicity, lower is the $$pK_b$$ value.

Since $$NH_3$$ is the weakest base, hence it has highest $$pK_b$$ value.

Option B is correct.
Question 8
1 / -0

Amongst the following, the strongest base in aqueous medium is ____________

A
$$CH_3NH_2$$

B
$$NCCH_2NH_2$$

C
$$(CH_3)_2NH$$

D
$$C_6H_5NHCH_3$$

Solution

In aqueous medium ,$$2^0$$ amine $$(CH_3)_2NH$$ is more basic than $$1^0$$ amine $$(CH_3)NH_2$$.Due to the -I effect of -CN group, $$NCCH_2NH_2$$ is less basic than $$CH_3NH_2$$ and due to the delocalisation of lone pair of electron of N atom in benzene ring. $$C_6H_5NHCH_3$$ is less basic than $$CH_3NH_2$$ and more basic than $$NC-CH_2NH_2$$ .Thus, the strongest base in aqueous medium is $$(CH_3)_2NH$$
Question 9
1 / -0

The correct order of boiling points of the following isomeric amines is:
$$C_4H_9NH_2,(C_2H_5)_2NH,\, C_2H_5N(CH_3)_2$$

A
$$C_2H_5N(CH_3)_2 \, >\, (C_2H_5)_2NH \, >\, C_4H_9NH_2$$

B
$$(C_2H_5)_2NH\, >\, C_2H_5N(CH_3)_2 \,>\, C_4H_9NH_2$$

C
$$C_4H_9NH_2 \, >\, (C_2H_5)_2NH \, >\, C_2H_5N(CH_3)_2$$

D
$$(C_2H_5)_2 NH \, >\, C_4H_9NH_2 \, >\, C_2H_5N(CH_3)_2$$

Solution

Order of Boiling points of amines:
Primary amines ($$RNH_2$$) > Secondary amines ($$R_2NH$$) > Tertiary amines ($$R^{'}NR_2$$).
Intermolecular hydrogen bonding is more in primary amines than that in secondary amines and nil in tertiary amines as there are no hydrogens attached to the nitrogen atom.

$$C_4H_9NH_2 > (C_2H_5)_2NH > C_2H_5N(CH_3)_2$$
Question 10
1 / -0

Which of the following Diazonium salt is stable at room temperature?

A

B

C

D

Solution

Benzenediazonium fluoroborate is the most stable diazonium salt at room temperature. The benzenediazonium cation and fluoroborate anion are of similar size resulting their stability.
option D is correct