Biphenyl is two benzene rings joined by a single bond. The site of substitution for a biphenyl is determined by (1) which phenyl ring is more activated (or less deactivated), and (2) which position on that ring is most reactive, using the fact that a phenyl substituent is activating and ortho, para-directing.


(b) Predict the mononitration products of the following compounds


(iii) <IMAGE>

Verified step by step guidance

1. Identify the structure of biphenyl and recognize that it consists of two benzene rings connected by a single bond.
2. Determine the substituents present on each benzene ring and assess their electronic effects (activating or deactivating).
3. Evaluate which benzene ring is more activated by considering the nature of the substituents and their positions relative to the biphenyl bond.
4. Apply the concept that a phenyl substituent is activating and ortho, para-directing to predict the most reactive positions for nitration on the more activated ring.
5. Predict the mononitration product by adding a nitro group (NO2) to the most reactive position (ortho or para) on the more activated benzene ring.

Key Concepts

Biphenyl Structure

Biphenyl consists of two benzene rings connected by a single bond, which allows for rotation around the bond. This structure influences the reactivity of the compound, as the electronic effects of substituents on one ring can affect the other. Understanding the spatial arrangement and electronic interactions in biphenyl is crucial for predicting substitution patterns.

Electrophilic Aromatic Substitution (EAS)

Electrophilic aromatic substitution is a fundamental reaction in organic chemistry where an electrophile replaces a hydrogen atom on an aromatic ring. The reactivity of the ring is influenced by substituents already present, which can either activate or deactivate the ring towards further substitution. In biphenyl, the position of substitution is determined by the activating effects of substituents and their directing influence.

Ortho/Para Directing Effects

Substituents on an aromatic ring can direct incoming electrophiles to specific positions, typically ortho (adjacent) or para (opposite) to themselves. Activating groups, such as alkyl or -OH, enhance the reactivity of the ring and favor ortho and para positions, while deactivating groups, like -NO2, direct substitution to the meta position. Recognizing these directing effects is essential for predicting the products of nitration in biphenyl.