Rank each group of compounds from most reactive to least reactive toward electrophilic aromatic substitution:
f. bromobenzene, chlorobenzene, fluorobenzene, iodobenzene

Verified step by step guidance

1. Understand the concept of electrophilic aromatic substitution (EAS): This reaction involves the substitution of a hydrogen atom on an aromatic ring with an electrophile. The reactivity of the aromatic ring depends on the electronic effects of substituents already present on the ring.
2. Analyze the substituents on the benzene ring: In this case, the substituents are halogens (bromine, chlorine, fluorine, and iodine). Halogens are electron-withdrawing groups due to their inductive effect (-I effect) but also have a resonance-donating effect (+R effect) because of their lone pairs.
3. Determine the net effect of halogens on reactivity: The inductive effect (-I) of halogens deactivates the ring by withdrawing electron density, making it less reactive toward EAS. However, the resonance effect (+R) can donate electron density back to the ring, partially counteracting the deactivation. The balance between these effects depends on the halogen's electronegativity and size.
4. Rank the halogens based on their electronegativity and resonance effects: Fluorine is the most electronegative, so its inductive effect dominates, making fluorobenzene the least reactive. Iodine is the least electronegative and has a weaker inductive effect, so its resonance effect is more significant, making iodobenzene the most reactive. Bromine and chlorine fall in between, with bromine being slightly less deactivating than chlorine due to its lower electronegativity.
5. Conclude the ranking: Based on the analysis, the order of reactivity toward electrophilic aromatic substitution is iodobenzene > bromobenzene > chlorobenzene > fluorobenzene.

Key Concepts

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. This process is crucial for understanding the reactivity of aromatic compounds, as the stability of the aromatic system influences how readily it can react with electrophiles.

Halogen Substituents and Their Effects

Halogen substituents (like bromine, chlorine, fluorine, and iodine) on an aromatic ring can either activate or deactivate the ring toward electrophilic substitution. While they are generally deactivating due to their electronegativity, their relative positions in the periodic table affect their reactivity, with larger halogens typically being less electronegative and more polarizable, thus influencing the overall reactivity.

Resonance and Inductive Effects

The resonance and inductive effects of substituents on an aromatic ring play a significant role in determining reactivity. Electron-withdrawing groups decrease electron density on the ring, making it less reactive, while electron-donating groups increase electron density, enhancing reactivity. Understanding these effects is essential for ranking the reactivity of halogenated aromatic compounds.