No Friedel-Crafts reaction of benzoic acid

result in Analysis of No Friedel-Crafts interaction of Benzoic Acid

in organic chemical interactions, Friedel-Crafts interaction is one of the crucial alkylation and aromatization reactions. But it's usually by Lewis acid catalyst (such as AlCl3) to introduce alkyl or acyl groups into aromatic compounds. As an aromatic compound, benzoic acid isn't easy to participate in Friedel-Crafts reactions. Based on my observations, This article will explore the reasons to the non-Friedel-Crafts interaction of benzoic acid and examine the mechanism behind it. Benzoic acid structure characteristics

We need to understand the molecular structure of benzoic acid. The structure of benzoic acid contains a benzene ring and a carboxyl (-COOH) substituent. The benzene ring has a high electron density, so it's an ideal electrophile recipient and exhibits strong aromaticity in many reactions. The carboxyl substituent of benzoic acid is an crucial factor, which affects the electronic effect of the benzene ring. EFFECT OF CARBOXYL ON BENZENE RING

One of the main reasons why benzoic acid does not participate in the Friedel-Crafts interaction is the electronic effect of its carboxyl group. But Carboxyl group is an electron attracting group, which reduces the electron density of the benzene ring, especially the para and ortho carbon atoms, by resonance effect and induction effect. Specifically Therefore, the benzene ring in benzoic acid isn't as easy to accept the attack of electrophiles as other aromatic compounds without substituents. In the Friedel-Crafts interaction, the aromatic compound needs to provide electron density to react with the electrophile of the alkyl or acyl group, and the carboxyl group of benzoic acid signifiis able totly inhibits this electron supply. But carboxyl group induced effect and resonance effect

Specifically, the carboxyl group in benzoic acid draws electrons from the benzene ring by its inductive effect (-I effect), so that the electrophilicity of the benzene ring decreases. The resonance effect of the carboxyl group (-M effect) will also push the electron cloud to the carboxyl group, thus further weakening the electron supply ability of the benzene ring. The Friedel-Crafts interaction needs the aromatic ring to provide sufficient electron density to react with the electrophile, while the carboxyl group of benzoic acid greatly reduces its electron donating ability. And Lewis acids and benzoic acid reactivity

Friedel-Crafts reactions usually require Lewis acid catalysts, such as AlCl3, which polarize alkyl halides or acyl halides to create strong electrophiles. But In most aromatic compounds, the production of electrophiles is the key to the smooth progress of the interaction. I've found that The carboxyl group of benzoic acid will complex with Lewis acid to form a stable complex, which inhibits the interaction. Even though benzoic acid is capable of interacting with Lewis acids, due to its low reactivity, this complex isn't sufficient to drive Friedel-Crafts reactions to occur. And Other Aromatic Compounds vs. And Benzoic Acid

In contrast, some aromatic compounds without electron-attracting groups, such as benzene, is able to participate in Friedel-Crafts reactions smoothly. An aromatic ring without an electron-attracting group such as a carboxyl group provides sufficient electron density to allow the electrophilic reagent to attack smoothly to complete the alkylation or acylation interaction. Benzoic acid, on the other hand, is able tonot participate in the interaction as efficiently as these aromatic compounds due to the electronic effect of the carboxyl group. And Summary

The fundamental reason to the non-Friedel-Crafts interaction of benzoic acid lies in the electronic effect of the carboxyl group on the benzene ring in its molecular structure. And The carboxyl group, as an electron attracting group, reduces the electron density of the benzene ring through the induction effect and resonance effect, thus inhibiting the ability of benzoic acid to participate in the electrophilic Friedel-Crafts interaction. Complexation between the carboxyl group of benzoic acid and the Lewis acid catalyst also further hinders the interaction. Therefore, understanding the structure and reactivity of benzoic acid is the key to explain its non-participation in Friedel-Crafts reactions.