L02outline - I. Review 1,3-dienes contain an uninterrupted...

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I. Review • 1,3-dienes contain an uninterrupted run of four parallel p-orbitals that can mix to form four molecular orbitals • When predicting the molecular orbitals of a contiguous run of orbitals, the outcome must be symmetric or antisymmetric, and energy increases as the number of nodes (phase changes) increases • Extending the length of a π -system reduces the energetic gap between the HOMO and the LUMO • The amount of energy required to promote an electron from the HOMO to the LUMO can be measured with UV-visible spectroscopy • The UV-visible range spans wavelengths of 200 to 800 nm (143 to 36 kcal/mol) • The spectrum measures the extent of absorbance (amount of light intensity reduction) vs wavelength ( λ ) • The absorbance (A) is dictated by the Beer-Lambert law: A = ε lc, in which l is the path length, c is the sample concentration, and e is the extinction coefficient that is a fundamental property of a molecule in a solvent and is related to the efficiency of absorption
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L02outline - I. Review 1,3-dienes contain an uninterrupted...

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