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Organic Chemistry

Lecture 4 objectives and skills

Objectives

Determine units of unsaturation for benzene and other cycloalkenes.
Understand the limitations of Kekulé structure of benzene.
Draw resonance structures and interpret MO diagram of benzene p-system.
Recognize cyclic delocalized p-systems.
Apply Huckel’s rule to determine aromatic, anti-aromatic, and non-aromatic classifications for rings (including heterocycles and cation/anonic organic ring structures).
Draw p-system MO diagrams for conjugated ring structures.
Rationalize aromaticity in polycyclic aromatic hydrocarbons (PAHs).

Skills

Critical assessment using abstract concepts
Comparison of fine details
Connection of chemical properties to biochemical properties

This page is referenced by:

Lecture 4: Molecular Orbitals and Aromaticity 6 image_header 2020-02-06T19:04:36-08:00
Objectives and Skills

KEY INFORMATION SUMMARY

HERE you can find extra resources to help you with this lecture!

PROBLEMS

Problem 4.1: Benzene Properties
1. Explain why we cannot use two Kekulé structures (alternating single-double C-C bonds of different lengths) to show benzene resonance. SOLUTION
2. Draw the proper resonance structures for benzene. SOLUTION
If you made some mistakes or want to practice more, review the concepts that gave you trouble and work on this extra problem. If you're good, move to the problem below ;)

Problem 4.2: Aromaticity

Assign the classification of aromatic, anti-aromatic, or non-aromatic to each of the structures below using Hückel’s Rule and check your classifications using the polygon method for p-system MO. SOLUTION

If you made some mistakes or want to practice more, review the concepts that gave you trouble and work on this extra problem. If you're good, move to the problem below ;)

Problem 4.3: Polycyclics and Ring Shapes

Pentalene is unstable, even at -100°C, whereas heptalene can be made and is shown to react like a acyclic alkene. Explain the difference. SOLUTION

If you made some mistakes or want to practice more, review the concepts that gave you trouble and work on this extra problem. If you're good, move to the next lecture ;)