CHEM 3580 Lecture Notes - Lecture 1: Reagent, Alkylation, Hyperconjugation

• School: Cornell University
• Department: Chemistry
• Course: CHEM 3580
• Professor: Tom Ruttledge

Document Summary

Lectures: 2/6/17 2/10/17: chapters 15 and 16 benzene and derivatives: aromatic compounds (continued from review guide #2) Benzene has a special stability that is termed aromaticity and can be depicted as the hybrid of two equally contributing resonance structures. Since the molecule is planar, and the axes of all six p orbitals are parallel, the p orbitals overlap to form a continuous molecular orbital providing additional bonding and additional stability. The empirical resonance energy = 34 kcal/mol compared to ~5 kcal/mol for a conjugated diene: criteria for aromaticity, aromatic compounds contain rings with a cyclic arrangement of p orbitals. Every atom of an aromatic ring has a p orbital. Aromatic rings are planar so orbitals can overlap. The cyclic arrangement of p orbitals in an aromatic compound must contain 4n + 2 electrons (huckel"s rule) where n= any integer. So, an aromatic ring must contain 2, 6, 10 electrons: compounds that are not aromatic and anti-aromaticity.