Organic ChemistryMain MenuLecture 1: Introduction to Molecular OrbitalsLecture 10: Intermolecular Forces and Intro to ReactivityLecture 11: Alkenes as Nucleophiles ILectures 12 and 13: Alkenes II & IIILecture 14: Benzenes as Nucleophiles ILecture 15 objectives and skillsLecture 2: Molecular Orbitals in Organic StructuresLecture 3: Molecular Orbitals and ResonanceLecture 4: Molecular Orbitals and AromaticityLecture 5: Nomenclature and IR SpectroscopyLecture 6: Stereochemistry ILecture 7: Stereochemistry IILecture 8: Newman and Fisher ProjectionsLecture 9: Conformations and Cyclohexane RingsJulio Terra2fb22914f73f9e5a767bf7fb83987dca0e153e4a
SOLUTION 4.3
12020-02-01T13:23:53-08:00Julio Terra2fb22914f73f9e5a767bf7fb83987dca0e153e4a359921plain2020-02-01T13:23:54-08:00Julio Terra2fb22914f73f9e5a767bf7fb83987dca0e153e4aBoth molecules are technically considered anti-aromatic, due to the presence of an anti-aromatic ring. The main difference between pentalene and heptalene, is that the anti-aromatic ring in heptalene has more flexibility to move out of planarity, thus reducing it to non-aromatic (and increasing its stability relative to pentalene) and allowing it to behave more like a regular alkene.
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1media/kisscc0-atomic-orbital-computer-icons-chemistry-orbitals-5b7136eca13a03.6431040415341462846604.png2020-02-01T13:09:01-08:00Lecture 4: Molecular Orbitals and Aromaticity6image_header2020-02-06T19:04:36-08:00Objectives and Skills
KEY INFORMATION SUMMARY
HERE you can find extra resources to help you with this lecture!
PROBLEMS
Problem 4.1: Benzene Properties
Explain why we cannot use two Kekulé structures (alternating single-double C-C bonds of different lengths) to show benzene resonance. SOLUTION
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 ;)
