Predict the mononitration products of the following compounds.
d. p-methoxybenzoic acid

Verified step by step guidance

1. Identify the functional groups present in the compound. p-Methoxybenzoic acid contains a methoxy group (-OCH₃) and a carboxylic acid group (-COOH) attached to a benzene ring. The methoxy group is an electron-donating group (activating), while the carboxylic acid group is an electron-withdrawing group (deactivating).
2. Determine the directing effects of the substituents. The methoxy group is an ortho/para-directing group, meaning it directs incoming electrophiles to the ortho and para positions relative to itself. The carboxylic acid group is a meta-directing group, meaning it directs incoming electrophiles to the meta position relative to itself.
3. Analyze the combined effects of the substituents. Since the methoxy group is para to the carboxylic acid group, the positions influenced by each substituent will overlap. The methoxy group will strongly activate the para position relative to itself (which is also the meta position relative to the carboxylic acid group).
4. Consider the reaction conditions. Mononitration involves the introduction of a nitro group (-NO₂) to the benzene ring using a nitrating mixture (HNO₃ and H₂SO₄). The nitro group will preferentially add to the most activated position, which is the para position relative to the methoxy group.
5. Predict the product. The nitro group will be added to the para position relative to the methoxy group, resulting in 4-methoxy-3-nitrobenzoic acid as the mononitration product.

Key Concepts

Electrophilic Aromatic Substitution

Electrophilic aromatic substitution (EAS) is a fundamental reaction in organic chemistry where an electrophile replaces a hydrogen atom on an aromatic ring. This process is crucial for understanding how substituents on the ring influence the reactivity and orientation of further substitutions, such as nitration.

Activating and Deactivating Groups

Substituents on an aromatic ring can either activate or deactivate the ring towards electrophilic substitution. Activating groups, like methoxy (-OCH3), increase electron density and direct incoming electrophiles to ortho and para positions, while deactivating groups reduce reactivity and typically direct electrophiles to the meta position.

Nitration Reaction

Nitration is a specific type of electrophilic aromatic substitution where a nitro group (-NO2) is introduced into an aromatic compound. The reaction typically involves the use of a nitrating mixture, such as concentrated nitric acid and sulfuric acid, and the position of nitration is influenced by the nature of existing substituents on the aromatic ring.