Summary of "HÓA 11-CHƯƠNG 4- LÝ THUYẾT ARENE"

Main Ideas and Concepts

Definition of Arenes (Aromatic Hydrocarbons):
Arenes, also known as aromatic hydrocarbons, are hydrocarbons that contain one or more Benzene rings in their molecular structure. The term "aromatic" does not necessarily imply a fragrant smell; it refers to the special properties of these compounds.
Structure of Benzene:
Benzene is represented as a regular hexagonal ring with alternating double bonds, where each vertex represents a carbon atom bonded to a hydrogen atom. The carbon atoms are sp² hybridized, leading to bond angles of 120 degrees and a coplanar structure.
Molecular Formula:
The general molecular formula for Arenes is CₙH₂ₙ₋₆, where n is greater than or equal to 6. For example:
- C₆H₆ (Benzene)
- C₇H₈ (Toluene)
- C₈H₁₀ (Xylenes)
Degree of Unsaturation:
The degree of unsaturation (K) for Benzene is 4, indicating the presence of three double bonds and one ring.
Structural Isomers:
Arenes can exhibit structural isomerism, including carbon chain isomers and positional isomers on the Benzene ring (ortho, meta, para positions).
Naming Conventions:
The naming of Arenes follows specific rules based on the position of substituents on the Benzene ring. Common names include:
- Benzene
- Toluene
- Xylene
- Cumene
Physical Properties:
Arenes are typically colorless, flammable liquids with varying odors. They are generally insoluble in water but soluble in organic solvents.
Chemical Properties:
Arenes undergo substitution reactions, which can be classified into:
- Intra-cyclic Substitution: Occurs with iron powder or FeBr₃ as a catalyst, favoring ortho or para positions.
- Extra-cyclic Substitution: Occurs under UV light, substituting outside the ring.
Arenes can also participate in addition reactions, particularly with hydrogen, leading to the saturation of the Benzene ring.
Reactions with Potassium Permanganate:
Benzene does not react with KMnO₄ under normal conditions, but alkyl-substituted benzenes can react under hot, concentrated conditions, leading to the formation of carboxylic acids.
Preparation and Applications:
Arenes can be prepared through reforming reactions and have various applications, including use as fuels, dyes, and in the production of explosives like TNT.

Detailed Instructions/Methodology

To Draw Benzene:
Draw a regular hexagon. Indicate alternating double bonds or represent them with a circle inside the hexagon.
To Determine Degree of Unsaturation:
Use the formula K = 2n + 2 - H/2, where H is the number of hydrogens in the molecular formula.
To Name Arenes:
Identify the main chain (Benzene) and the substituents. Number the positions to give the lowest possible numbers to substituents. Use prefixes (ortho, meta, para) for positional isomers.
To Predict Reaction Products:
For substitution reactions with alkyl groups, expect products at ortho or para positions. For reactions involving nitro groups, expect meta substitution.