Which statements are correct for the following approximate $p K_{a}$ values of conjugate acids: 2-nitroaniline $- 0.3$ , 3-nitroaniline 2.5, 4-nitroaniline 1.0, aniline 4.6, 4-methylaniline 5.1, 2-methylaniline 4.4?

A2-Nitroaniline is a weaker base than 4-nitroaniline.
B4-Methylaniline is a stronger base than aniline.
C2-Methylaniline is a stronger base than aniline.
D3-Nitroaniline is a stronger base than 4-nitroaniline.

Answer: A, B, D

A higher

p K_{a}

of the conjugate acid means a stronger base. The ortho nitro compound (

- 0.3

) is weaker than the para one (1.0). At meta only the -I effect operates, whereas at para both -I and -R reduce the basicity, so 3-nitroaniline (2.5) is stronger than 4-nitroaniline (1.0). The para methyl compound (5.1) is stronger than aniline (4.6), but 2-methylaniline (4.4) is weaker because of the ortho effect.

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Which statements are correct for the following approximate pKa​ values of conjugate acids: 2-nitroaniline −0.3, 3-nitroaniline 2.5, 4-nitroaniline 1.0, aniline 4.6, 4-methylaniline 5.1, 2-methylaniline 4.4?

Answer: A, B, D

More questions on Basicity of amines

Which statements are correct for the following approximate $p K_{a}$ values of conjugate acids: 2-nitroaniline $- 0.3$ , 3-nitroaniline 2.5, 4-nitroaniline 1.0, aniline 4.6, 4-methylaniline 5.1, 2-methylaniline 4.4?