First slide

Basic Strength

Question

The correct order of the basic strength of methyl substituted amines in aqueous solution is

Moderate

A

${CH}_{3} {NH}_{2} > {({CH}_{3})}_{2} NH > {({CH}_{3})}_{3} N$
B

${({CH}_{3})}_{2} NH > {CH}_{3} {NH}_{2} > {({CH}_{3})}_{3} N$
C

${({CH}_{3})}_{3} N > {CH}_{3} {NH}_{2} > {({CH}_{3})}_{2} NH$
D

${({CH}_{3})}_{3} N > {({CH}_{3})}_{2} NH > {CH}_{3} {NH}_{2}$

Solution

The basicity of amines in aqueous solution depends on the stability of the ammonium cation or conjugate acid formed by accepting a proton from water which in turn depends on the +I -effect of alkyl group, extent of hydrogen bonding and steric factor. All these factors are favourable for $2 °$ amines. Therefore, $2 °$ amines are the strongest bases. If the alkyl group is small i.e., ${CH}_{3}$ then there is no steric hindrance to H-bonding. Thus, the stability due to hydrogen bonding predominates over the stability due to +I -effect of ${CH}_{3}$ group and hence primary amine is a stronger base than $3 °$ amine. Hence, overall decreasing basic strength for methylamines in aqueous solution is
${({CH}_{3})}_{2} NH > {CH}_{3} {NH}_{2} > {({CH}_{3})}_{3} N$

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App