Question

Arrange the following in increasing order of their basic strength:
$C{H}_{3}N{H}_2\left(I\right),\left(C{H}_3{)}_{2}NH\right(II),(C{H}_3{)}_{3}N\left(III\right),C_6{H}_{5}C{H}_{2}N{H}_2\left(IV\right)$

Answer 1

${CH}_3{NH}_2$, $({CH}_3{)}_{2}NH$, ${(CH}_3{)}_{3}N$, $C_6{H}_5{CH}_2{NH}_2$

The basic strength $\left(III\right)>\left(II\right)>\left(IV\right)>\left(I\right).$

In case of compound $\left(iv\right)$ the inductive effect of phenyl is on the methyl, decreasing it's ability to donate electron density to nitrogen atom. As facility of $1^{\prime },2^{\prime },3^{\prime }$ amines is determine by the tendency of donating electrons and $3^{\prime }$ amines will have the height $+I$ effect due to presence of three methyl group attached to the $N$ atom , leading to greater electron density followed by $2^{\prime }$ and $1^{\prime }$ amine.