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Chemistry LibreTexts

16: Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy

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  • Learning Objectives

    After reading this chapter and completing ALL the exercises, a student can be able to

    • construct & interpret MO diagrams of ethene, butadiene and allylic systems (refer to section 16.1)
    • recognize reactions that are enhanced by resonance stabilization of the allylic intermediate (refer to section 16.2)
    • predict the products and specify the reagents for electrophilic addition reactions (EAR) of conjugated dienes (refer to section 16.3)
    • specify reaction conditions to promote thermodynamic or kinetic control of the reaction mechanism; correlate these conditions to reaction energy diagrams (section 16.4)
    • predict the products and specify the reagents for bimolecular substitution reactions (SN2) of allylic halides (refer to section 16.5)
    • predict the products of Diels-Alder reactions with stereochemistry, including the orientation of cycloaddition with asymmetrical reagents (refer to sections 16.6 and 16.7)
    • develop mechanisms to explain the observed products of 1,2- & 1,4- addition reactions, including the resonance forms of the stabilized intermediates (refer to section 16.6)
    • use MO theory to predict whether cycloaddition reactions will be thermally or photochemically allowed (refer to section 16.6 and 16.7)
    • recognize the effect of conjugation on UV absorption (refer to section 16.9 and 16.10)
    • use Beer’s Law in UV absorption calculations (refer to section 16.9 and 16.10)
    • explain how light, the conjugation of double bonds, and the stereochemistry of double bonds contribute to visualizing color