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Standard XII

Chemistry

Amines as Bases

Point out the...

Question

Point out the correct decreasing order of $p K_{b}$ values of following amines:
$C_{2} H_{5} N H_{2}$ , $C_{6} H_{5} N H C H_{3},$ $(C_{2} H_{5})_{2} N H$ and $C_{6} H_{5} N H_{2}$

(C_{2} H_{5})_{2} N H > C_{2} H_{5} N H_{2} > C_{6} H_{5} N H C H_{3} > C_{6} H_{5} N H_{2}

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(C_{2} H_{5})_{2} N H > C_{6} H_{5} N H C H_{3} > C_{6} H_{5} N H_{2} > C_{2} H_{5} N H_{2}

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C_{6} H_{5} N H_{2} > C_{6} H_{5} N H C H_{3} > C_{2} H_{5} N H_{2} > (C_{2} H_{5})_{2} N H

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C_{2} H_{5} N H_{2} > (C_{2} H_{5})_{2} N H > C_{6} H_{5} N H C H_{3} > C_{6} H_{5} N H_{2}

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Solution

The correct option is C $C_{6} H_{5} N H_{2} > C_{6} H_{5} N H C H_{3} > C_{2} H_{5} N H_{2} > (C_{2} H_{5})_{2} N H$
The lesser the value of $p K_{b}$ the weaker the base.
Electron withdrawing groups like benzene decreases the basicity and increases the $p K_{b}$ of amines and the alkyl groups (electron releasing groups) increases the basicity and decreases the $p K_{b}$ value
So the correct order of $p K_{b}$ is $C_{6} H_{5} N H_{2} > C_{6} H_{5} N H C H_{3} > C_{2} H_{5} - N H_{2} > (C_{2} H_{5})_{2} N H$
Hence option C is correct.

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Similar questions

Arrange the following:

(i) In the decreasing order of the $p K_{b}$ values
$C_{2} H_{5} N H_{2}, C_{6} H_{5} N H C H_{3}, (C_{2} H_{5})_{2} N H$ and $C_{6} H_{5} N H_{2}$

(ii) In increasing order of basic strength:
$C_{6} H_{5} N H_{2}, C_{6} H_{5} N (C H_{3})_{2}, (C_{6} H_{5})_{2} N H a n d C H_{3} N H_{2}$

(iii) In increasing order of basic strength:
(a) Aniline, p-nitroaniline and p-toluidine
(b) $C_{6} H_{5} N H_{2}, C_{6} H_{5} N H C H_{3}, C_{6} H_{5} C H_{2} N H_{2}$

(iv) In decreasing order of basic strength in gas phase :

$C_{2} H_{5} N H_{2}, (C_{2} H_{5})_{2} N H, (C_{2} H_{5})_{3} N a n d N H_{3}$

(v) In increasing order of boiling point:

$C_{2} H_{5} O H, (C H_{3})_{2} N H, C_{2} H_{5} N H_{2} .$

(vi) In increasing order of solubility in water :

$C_{6} H_{5} N H_{2}, (C_{2} H_{5})_{2} N H, C_{2} H_{5} N H_{2} .$

Q. Arrange the following
(i) In decreasing order of the

p K_{b}

values:

C_{2} H_{5} N H_{2}, C_{6} H_{5} N H C H_{3}, (C_{2} H_{5})_{2} N H

and

C_{6} H_{5} N H_{2}

(ii) In increasing order of basic strength:

C_{6} H_{5} N H_{2}, C_{6} H_{5} N (C H_{3})_{2}, (C_{2} H_{5})_{2} N H

and

C H_{3} N H_{2}

(iii) In increasing order of basic strength:
(a) Aniline, p-nitroaniline and p-toluidine

Q. Arrange the following in the increasing order of their

p K_{b}

values.

C_{6} H_{5} N H_{2}, C_{2} H_{5} N H_{2}, C_{6} H_{5} N H C H_{3}

Q. Arrange the following in decreasing order of their basic strength:

C_{6} H_{5} N H_{2}, C_{2} H_{5} N H_{2}, (C_{2} H_{5})_{2} N H, N H_{3}

Arrange the following in increasing order of their basic strength:

(i) C₂H₅NH₂, C₆H₅NH₂, NH₃, C₆H₅CH₂NH₂ and (C₂H₅)₂NH

(ii) C₂H₅NH₂, (C₂H₅)₂NH, (C₂H₅)₃N, C₆H₅NH₂

(iii) CH₃NH₂, (CH₃)₂NH, (CH₃)₃N, C₆H₅NH₂, C₆H₅CH₂NH₂.

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Point out the correct decreasing order of pKb values of following amines:C2H5NH2 , C6H5NHCH3, (C2H5)2NH and C6H5NH2

Point out the correct decreasing order of $p K_{b}$ values of following amines:
$C_{2} H_{5} N H_{2}$ , $C_{6} H_{5} N H C H_{3},$ $(C_{2} H_{5})_{2} N H$ and $C_{6} H_{5} N H_{2}$