Predict the major products formed when benzene reacts (just once) with the following reagents.
(i) iodine + HNO₃

검증된 단계별 안내

Step 1: Recognize the type of reaction. This is an electrophilic aromatic substitution (EAS) reaction, where benzene reacts with iodine (I₂) in the presence of nitric acid (HNO₃) to form a substituted benzene derivative.

Step 2: Understand the role of HNO₃. Nitric acid acts as an oxidizing agent in this reaction, converting iodine (I₂) into the electrophilic species I⁺ (iodonium ion), which is necessary for the substitution reaction.

Step 3: Identify the electrophile. The electrophile in this reaction is the iodonium ion (I⁺), which will attack the benzene ring.

Step 4: Describe the mechanism. The benzene ring donates a pair of π-electrons to the electrophile (I⁺), forming a sigma complex (also called an arenium ion). This intermediate is stabilized by resonance.

Step 5: Regenerate aromaticity. A proton (H⁺) is removed from the sigma complex by a base (often H₂O or NO₃⁻), restoring the aromaticity of the benzene ring and yielding the final product, iodobenzene (C₆H₅I).

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Electrophilic Aromatic Substitution

Electrophilic aromatic substitution (EAS) is a fundamental reaction mechanism in organic chemistry where an electrophile replaces a hydrogen atom on an aromatic ring. In this process, the aromatic system retains its stability and aromaticity, which is crucial for understanding how benzene reacts with various reagents. The reaction typically involves the formation of a sigma complex, followed by deprotonation to restore the aromatic character.

Iodination of Aromatic Compounds

Iodination of aromatic compounds involves the introduction of iodine into the aromatic ring, often facilitated by a Lewis acid catalyst. In the presence of nitric acid (HNO3), iodine can generate an electrophilic species that can react with benzene. This reaction is significant as it demonstrates how halogens can be introduced into aromatic systems, impacting their reactivity and properties.

Nitration and its Role in Electrophilic Reactions

Nitration is the process of introducing a nitro group (-NO2) into an aromatic compound, typically using a mixture of concentrated nitric acid and sulfuric acid. In the context of the given reaction, HNO3 can act as a source of the nitronium ion (NO2+), which is a potent electrophile. Understanding nitration is essential for predicting the products of reactions involving benzene and other electrophiles, as it influences the regioselectivity of subsequent substitutions.

Predict the major products formed when benzene reacts (just once) with the following reagents. (i) iodine + HNO3