l6 - Benzene Benzene Very stable molecule hypothetical...

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Benzene Very stable molecule 1.39 Å Perfect hexagon. All angles and all bonds the same length. hypothetical -150.6 kJ mol resonance energy = H 2 /Pd -119.7 kJ mol 119 7 kJ real H 2 /Pd -119.7 kJ mol -359 kJ mol -119.7 kJ mo H 2 /Pd H 2 /Pd -119.7 kJ mo H 2 /Pd -208.4 kJ mol energy mol mol Resonance stabilization 152 kJ/mol Resonance stabilization 15 kJ/mol Kekule Structures Which of these models predicts the shortest carbon-carbon bonds? Only 1865 Br Br Br Br one 1,2 – (A) equilibrium dibromo benzene Br Br Br Br 1920’s (B resonance (B) Ally The 2 electron cation π system is more stable as a ring. It is an aromatic system Allyl Cation Cyclopropenyl Cation Degenerate Energy levels Thought Experiment Ally The 4 electron anion π system is less stable as a ring. It is an antiaromatic system Allyl Anion Cyclopropenyl Anion Degenerate Energy levels Thought Experiment
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C 4 H 4 The 4 electron π system is less stable as a ring. It is an antiaromatic system C 4 H 4 2+ The 2 electron π system is more stable as a ring. It is an aromatic system C 4 H 4 2- The 6 electron π system is more stable as a ring. It is an aromatic system C 6 H 6 S A A S A S C 6 H 6 S A A S A 6 electron system aromatic S http://www.ic.sunysb.edu/Class/orgchem/shmo/ Cyclic π Systems Aromatic 4n + 2 electrons (
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l6 - Benzene Benzene Very stable molecule hypothetical...

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