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Hydrocarbons: Aromatic (Arenes) formula sheet

Every formula in the Hydrocarbons: Aromatic (Arenes) chapter for JEE Main, with one line on when it applies. Topic 1 is open to everyone; sign in free to read all 11 and download the PDF.

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Benzene and aromaticity

Structure of benzene
1× asked, last 2025
all C–C=139 pm (C–C 154, C=C 133)resonance energy≈3(120)−208≈150 kJ mol−1CX6HX6→Δ3 HX2,  NiCX6HX12\begin{aligned}&\text{all C–C}=139\ \text{pm}\ (\text{C–C }154,\ \text{C=C }133)\\&\text{resonance energy}\approx3(120)-208\approx150\ \text{kJ mol}^{-1}\\&\ce{C6H6 ->[3H2,\ Ni][\Delta] C6H12}\end{aligned}
Planar, all C sp², 6 delocalised π e⁻: substitutes rather than adds. A CX6HX6\ce{C6H6} taking 4 HX2\ce{H2} is not benzene.
Hückel's rule
4× asked, last 2024
cyclic, planar, p orbital on every ring atom(4n+2) π=2, 6, 10: aromatic;4n π: antiaromatic\begin{aligned}&\text{cyclic, planar, p orbital on every ring atom}\\&(4n+2)\,\pi=2,\,6,\,10:\ \text{aromatic};\quad 4n\,\pi:\ \text{antiaromatic}\end{aligned}
Aromatic: CX3HX3X+\ce{C3H3+}, CX5HX5X−\ce{C5H5-}, tropylium, pyrrole, pyridine, COT dianion. Antiaromatic: CX5HX5X+\ce{C5H5+}, cyclobutadiene. COT (tub): non-aromatic.
Preparing benzene
2× asked, last 2025
3 HC≡CH→873 Kred-hot FeCX6HX6CX6HX5OH+Zn→ΔCX6HX6+ZnOCX6HX5COONa+NaOH→ΔCaOCX6HX6+NaX2COX3\begin{aligned}&\ce{3HC#CH ->[\text{red-hot Fe}][873\ K] C6H6}\\&\ce{C6H5OH + Zn ->[\Delta] C6H6 + ZnO}\\&\ce{C6H5COONa + NaOH ->[CaO][\Delta] C6H6 + Na2CO3}\end{aligned}
o = 1,2; m = 1,3; p = 1,4. Toluene, xylenes, cumene, styrene, anisole.

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8 more formulas in 3 topics

Electrophilic aromatic substitution, Directive influence of substituents and Reactions of the side chain. Read the first part free. Sign in free with Google to read the rest and download the PDF.

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Electrophilic aromatic substitution

  • Mechanism2×
  • Halogenation, nitration, sulphonation4×
  • Friedel–Crafts alkylation2×
  • Friedel–Crafts acylation2×

Directive influence of substituents

  • Directors4×
  • Second substitution5×

Reactions of the side chain

  • Side-chain oxidation2×
  • Etard reaction

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