Toluene
Toluene is an aromatic hydrocarbon with the molecular formula C₆H₅CH₃.
It consists of a benzene ring (C₆H₅) substituted with a methyl group (–CH₃).
Toluene is also known as methylbenzene, and it is one of the simplest derivatives of benzene.
🔬 Molecular Structure and Bonding
● The benzene ring contains six carbon atoms, each sp² hybridized, forming a planar
hexagonal ring with delocalized π electrons — just like in benzene.
● The methyl group (CH₃) is attached to one of the carbon atoms on the ring via a sigma
(σ) bond.
● The carbon in the methyl group is sp³ hybridized and forms three σ bonds with
hydrogen atoms and one with the ring carbon.
The C–C bond between the methyl group and the benzene ring is slightly shorter
than a regular single bond due to hyperconjugation and partial π-overlap.
📐 Geometry and Shape
● The benzene ring is planar with bond angles of 120°.
● The methyl group rotates freely above and below the ring plane.
● Toluene is overall a nonpolar molecule, but the methyl group slightly increases its
electron density compared to benzene.
⚗️ Chemical Properties and Reactivity
Toluene behaves very similarly to benzene but is more reactive in electrophilic substitution
reactions due to the electron-donating effect of the methyl group.
🧪 Key Reactions:
1. Electrophilic Aromatic Substitution (EAS)
The methyl group is an activating group, making the ring more reactive.
It directs substituents to the ortho and para positions.
○ Nitration → o-/p-nitrotoluene
○ Halogenation → o-/p-chlorotoluene
○ Sulfonation → o-/p-toluenesulfonic acid
2. Side-chain Halogenation
Under UV light, the methyl group undergoes free radical halogenation:
→ Toluene + Cl₂ (hv) → Benzyl chloride, Benzal chloride, etc.
3. Oxidation
The methyl group can be oxidized (e.g., with KMnO₄ or HNO₃) to form benzoic acid
(C₆H₅COOH).
🌡️ Physical Properties
Property Value
Appearance Colorless liquid
Odor Sweet, paint-like smell
Boiling Point ~111 °C
Melting Point –95 °C
Density 0.87 g/cm³
Solubility Insoluble in water, miscible with organic solvents
Flammability Highly flammable
🧴 Uses of Toluene
1. Solvent
○ Widely used in paints, thinners, glues, varnishes, and cleaning agents.
○ Excellent at dissolving nonpolar substances.
2. Chemical Feedstock
○ Used in the manufacture of benzene, benzoic acid, trinitrotoluene (TNT), and
other important chemicals.
3. Fuel Additive
○ Used as an octane booster in gasoline blends.
4. Polymer Industry
○ Precursor for polystyrene, polyurethane foams, and other plastics.
🧠 Fun Fact
● Toluene is naturally found in crude oil and in small amounts in tolu tree resin, after
which it is named.
● Because it can affect the nervous system, prolonged exposure to toluene fumes can
be harmful—always use in well-ventilated areas!
📚 Quick Summary
Feature Description
Formula C₆H₅CH₃ (methylbenzene)
Functional Group Methyl group on benzene ring
Hybridization sp² (ring) + sp³ (methyl carbon)
Reactivity More reactive than benzene (ortho/para
directing)
Key Uses Solvent, fuel additive, TNT production
