Arrange the following amines in order of decreasing basicity (most to least)in aqueous solution:
A)IV II I III
B)III II IV I
C)III I II IV
D)II III I IV
E)Cannot be determined from information given

Question

Arrange the following amines in order of decreasing basicity (most to least)in aqueous solution: 
A)IV > II > I > III 
B)III > II > IV > I 
C)III > I > II > IV 
D)II > III > I > IV 
E)Cannot be determined from information given

Quizplus · Accepted Answer

The basicity of amines depends on the availability of lone pair electrons on nitrogen. The more the availability, the higher the basicity will be. 
In compound III, there are two lone pairs of electrons on the nitrogen atom that are readily available for reaction, making it the most basic. 
In compound I, there is only one lone pair of electrons, making it less basic than III. 
In compound II, the nitrogen is part of an aromatic ring, which delocalizes the lone pair of electrons and makes it less available for reaction. 
In compound IV, the nitrogen is part of a tertiary amine, which has an alkyl group bonded to it that reduces the availability of lone pairs, and therefore decreases its basicity even further. Thus, the correct order of basicity is III > I > II > IV.

Arrange the Following Amines in Order of Decreasing Basicity (Most