Chapter 25: 41 (page 1042)

Rank the compounds in each group in order of increasing basicity.
(a)
(b)

Short Answer

Expert verified

The order of increasing basicity

(a)

(b)

Step by step solution

Trend in basicity

The greater the tendency of nitrogen to donate its electrons, the greater is its basicity.

If a compound containing nitrogen is involved in conjugation, then its ability to donate its lone pair of electrons decreases, making the compound less basic.

Order of increasing basicity

(a)

The nitrogen on indole is the least basic nature because delocalized electron pair on nitrogen.

Delocalized lone pair of indole

$s p^{2}$ hybridized nitrogen is more electronegative than $s p^{3}$ hybridized nitrogen, due to which compound containing $s p^{2}$ hybridized nitrogen is less basic than $s p^{3}$ hybridized one.

N atom hybridization

Hence, the most basic amine is piperidine.

Therefore, the order of increasing basicity is as follows:

order of increasing basicity

(b)

The substituents which are electron-donating in nature, increase the electron density on nitrogen, making them more basic and the substituents that are electron-withdrawing in nature, decrease the electron density on nitrogen, making them less basic.

Among the substituents given, the nitro group is most electron-withdrawing in nature and it decreases the electron density on nitrogen, making it least basic.