Aromatic Compounds & Benzene

⚗️ Aromatic Compounds Benzene

Part 1 of 7 — Aromaticity & Hückel Rule

1. Hückel's rule

planar, cyclic, conjugated, 4n+2 π electrons → aromatic

2. Aromatic compounds are exceptionally stable

Aromatic compounds are exceptionally stable

3. n=0

2 π electrons; n=1: 6 π electrons; n=2: 10 π electrons

4. Benzene

6 π electrons (n=1), aromatic

Concept Check 🎯

Key Concepts Summary

• Hückel's rule: planar, cyclic, conjugated, 4n+2 π electrons → aromatic
• Aromatic compounds are exceptionally stable
• n=0: 2 π electrons; n=1: 6 π electrons; n=2: 10 π electrons
• Benzene: 6 π electrons (n=1), aromatic

Concept Check 🎯

Fill in the Blanks 🔍

Benzene Structure

Part 2 of 7 — Benzene Structure

1. Benzene

six equivalent C-H bonds, all 1.39 Å

2. Two equivalent resonance structures

Two equivalent resonance structures

3. Actual structure is a hybrid (delocalized)

Actual structure is a hybrid (delocalized)

4. Heat of hydrogenation is 150 kJ/mol LESS than expected (resonance energy)

Heat of hydrogenation is 150 kJ/mol LESS than expected (resonance energy)

Concept Check 🎯

Key Concepts Summary

• Benzene: six equivalent C-H bonds, all 1.39 Å
• Two equivalent resonance structures
• Actual structure is a hybrid (delocalized)
• Heat of hydrogenation is 150 kJ/mol LESS than expected (resonance energy)

Concept Check 🎯

Fill in the Blanks 🔍

Nomenclature of Aromatics

Part 3 of 7 — Nomenclature of Aromatics

1. Monosubstituted

toluene (methylbenzene), aniline (aminobenzene)

2. Disubstituted

ortho (1,2), meta (1,3), para (1,4)

3. Common names

phenol, anisole, benzaldehyde, benzoic acid

4. Phenyl group

C₆H₅- ; Benzyl group: C₆H₅CH₂-

Concept Check 🎯

Key Concepts Summary

• Monosubstituted: toluene (methylbenzene), aniline (aminobenzene)
• Disubstituted: ortho (1,2), meta (1,3), para (1,4)
• Common names: phenol, anisole, benzaldehyde, benzoic acid
• Phenyl group: C₆H₅- ; Benzyl group: C₆H₅CH₂-

Concept Check 🎯

Fill in the Blanks 🔍

Properties of Aromatic Compounds

Part 4 of 7 — Properties of Aromatic Compounds

1. Aromatic compounds undergo substitution, not addition

Aromatic compounds undergo substitution, not addition

2. Preserves aromaticity (stable π system)

Preserves aromaticity (stable π system)

3. Higher melting/boiling points due to planarity

Higher melting/boiling points due to planarity

4. Many aromatic compounds have distinctive odors

Many aromatic compounds have distinctive odors

Concept Check 🎯

Key Concepts Summary

• Aromatic compounds undergo substitution, not addition
• Preserves aromaticity (stable π system)
• Higher melting/boiling points due to planarity
• Many aromatic compounds have distinctive odors

Concept Check 🎯

Fill in the Blanks 🔍

Aromatic vs Antiaromatic

Part 5 of 7 — Aromatic vs Antiaromatic

1. Antiaromatic

planar, cyclic, conjugated, 4n π electrons → destabilized

2. Cyclobutadiene (4 π electrons)

antiaromatic, very unstable

3. Nonaromatic

not fully conjugated, not planar

4. Charged species can be aromatic

cyclopentadienyl anion (6 π e⁻)

Concept Check 🎯

Key Concepts Summary

• Antiaromatic: planar, cyclic, conjugated, 4n π electrons → destabilized
• Cyclobutadiene (4 π electrons): antiaromatic, very unstable
• Nonaromatic: not fully conjugated, not planar
• Charged species can be aromatic: cyclopentadienyl anion (6 π e⁻)

Concept Check 🎯

Fill in the Blanks 🔍

Problem-Solving Workshop

Part 6 of 7 — Problem-Solving Workshop

1. Determining aromaticity using Hückel's rule

Determining aromaticity using Hückel's rule

2. Counting π electrons in cyclic systems

Counting π electrons in cyclic systems

3. Naming aromatic compounds

Naming aromatic compounds

4. Comparing aromatic, antiaromatic, and nonaromatic

Comparing aromatic, antiaromatic, and nonaromatic

Concept Check 🎯

Key Concepts Summary

• Determining aromaticity using Hückel's rule
• Counting π electrons in cyclic systems
• Naming aromatic compounds
• Comparing aromatic, antiaromatic, and nonaromatic

Concept Check 🎯

Fill in the Blanks 🔍

Synthesis & Review

Part 7 of 7 — Synthesis & Review

1. Aromaticity is a fundamental concept in organic chemistry

Aromaticity is a fundamental concept in organic chemistry

2. Hückel's rule predicts stability

Hückel's rule predicts stability

3. Aromatic compounds prefer substitution over addition

Aromatic compounds prefer substitution over addition

4. Review

aromaticity and nomenclature

Concept Check 🎯

Key Concepts Summary

• Aromaticity is a fundamental concept in organic chemistry
• Hückel's rule predicts stability
• Aromatic compounds prefer substitution over addition
• Review: aromaticity and nomenclature

Concept Check 🎯

Fill in the Blanks 🔍