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Substituted Benzenes. p 6 *. p 4 *. p 5 *. p 2. p 3. p 1. Symmetry and selection rules limit actual transitions: ~185 nm ( e ~60,000), “primary band” or “E band” ~204 nm ( e ~8,000), “second primary band” or “K band” ~256 nm ( e ~200), “secondary band” or “B band”. Substituted Benzenes.
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Substituted Benzenes p6* p4* p5* p2 p3 p1 Symmetry and selection rules limit actual transitions: ~185 nm (e~60,000), “primary band” or “E band” ~204 nm (e~8,000), “second primary band” or “K band” ~256 nm (e~200), “secondary band” or “B band”
Substituted Benzenes Pretsch/Buhlmann/Affolter/Badertscher, Structure Determination of Organic Compounds
Substituent Effects on Aromatic Absorption 256 nm band is sensitive to electron density of aromatic ring e units = L mole-1 cm-1 Electron density Red = highestGreen = moderate
pH Effects on Aromatic Absorption Phenoxide ion electrostatic potential map e units = L mole-1 cm-1 Anilinium ion electrostatic potential map
Aromatic Carbonyl Compounds Pretsch/Buhlmann/Affolter/Badertscher, Structure Determination of Organic Compounds
Are you getting the concept? Predict the absorption lmaxfor the enol of 1,2-cyclopentanedione. 202 (base) 12 (b substituent) 35 (a-OH) ----- 249 nm Obs. 247 nm
Common Solvents Pretsch/Buhlmann/Affolter/Badertscher, Structure Determination of Organic Compounds
