Acetanilide is less basic than aniline

Acetanilide alkaline lower than aniline cause analysis

Acetanilide (Acetanilide) and aniline (Aniline) are two common organic compounds. They have some significant differences in chemical properties. One of the more common problems is that "acetanilide is less alkaline than aniline". This problem involves their molecular structure, electronic effects and other factors. This article will analyze the causes of this phenomenon in detail.

1. The molecular structure characteristics

In the molecule of aniline, the amino group (-NH2) is directly connected to the benzene ring, and the lone pair electron of the amino group can participate in the conjugated system of the benzene ring, providing electron density and enhancing the basicity of aniline. This allows aniline to more readily accept protons and thus exhibit a stronger basicity.

Acetanilide is different. In the molecular structure of acetanilide, the amino group is attached to the benzene ring through an acetyl group (-COCH3). Acetyl group is a group with electron attraction effect, which pulls part of the electron density from the benzene ring and amino group by resonance effect, thus reducing the electron supply ability of the amino group. The lone pair electron of the amino group becomes less readily involved in proton acceptance, so that the base of acetanilide is relatively low.

2. The electronic effect of acetyl group on amino group

The effect of the acetyl group on the amino group is one of the key reasons why the basicity of acetanilide is lower than that of aniline. The acetyl group reduces the electron cloud density of the amino group by its electronegative attraction effect (-I effect) and resonance effect (-M effect), thereby reducing the basicity of the amino group. Specifically, the electron attraction effect of the acetyl group makes the lone pair electron distribution of the amino group more concentrated, rather than diffusing to the amino group, resulting in a decrease in its ability to accept protons.

In contrast, the amino group of aniline has no similar electron attraction effect, so its amino group can provide more electrons and has stronger basicity. This phenomenon makes acetanilide significantly less basic than aniline.

3. Benzene ring effect

Although both acetanilide and aniline contain a benzene ring in the molecule, the electronic effect of the benzene ring also changes due to the introduction of acetyl groups. The electron attraction effect of the acetyl group reduces the electron density of the benzene ring, which affects the interaction between the benzene ring and the amino group. This effect not only reduces the basicity of the amino group, but may also affect the reactivity of acetanilide in chemical reactions.

In contrast, the benzene ring in aniline can provide more electrons to interact with the amino group because there is no interference of the electron attracting group, which makes the aniline more basic.

4. Conclusion: Acetanilide is less basic than aniline

The reason why the basicity of acetanilide is lower than that of aniline is mainly due to the electron attraction effect and resonance effect of acetyl group, which reduces the electron density of acetanilide amino group, resulting in its weak ability to accept protons. In contrast, the amino group of aniline can maintain strong basicity due to the interference of no electron attracting group. This phenomenon is not only of great significance in chemical reactions, but also provides a theoretical basis for the use of acetanilide in industrial applications.