Conjugated Systems and UV-Spectroscopy

Conjugated Systems and UV-Spectroscopy -- Section 13 of Organic Chemistry Notes is 19 pages in length (page 13-1 through page 13-19) and covers ALL you'll need to know on the following lecture/book topics:

SECTION 13 – Conjugated Systems and UV-Spectroscopy

13-1 -- Three Classes of Dienes
_· Conjugated Dienes
_· Cumulenes (“Allenes”)
_· Other, Isolated Double Bonds (d.b.’s)
13-1 -- Relative Stabilities of Dienes
_· Heats of Formation (ΔH°f) – Values and Comparisons
13-2 -- Double Bonds of Conjugated Dienes
_· Prefer to be Coplanar
_· “Cisoid” or S-Cis Conformation
_· “Transoid” or S-Trans Conformation
_· Resonance Description
13-4 -- Reactions of Dienes – Summary (3 Main Reactions)
13-4 -- Additions of Electrophiles
_· Markovnikov Addition
_· 1,2-Addition Product vs. 1,4-Addition Product
_· Mechanism of the Reaction
_· Equilibration via an SN1 Mechanism
_· Kinetic Control vs. Thermodynamic Control
13-6 -- Addition of Halogens (X2)
_· Also Gives 1,2-Addition Product and 1,4-Addition Product
_· Mechanism of the Reaction
_· With Br2, Mechanism May Go via a Bromonium Ion Intermediate
13-6 -- The Diels-Alder Reaction (Huge Topic!)
_· General Form of the Reaction
_· The Diene (4e- Component) and the Dienophile (2e- Component)
_· Diene Conformation Must be S-Cis
_· Diels-Alder Reaction is Concerted – All Bonding Changes Occur Simultaneously
_· Formation of 1 New π-Bond and 2 New σ-Bonds
_· Diels-Alder Reaction is Stereospecific
_· Formation of Products that are Enantiomers and/or Meso Compounds
_· Electronic Requirements of the Diels-Alder Reaction
_· The “Endo Effect”
_· Endo Substituents vs. Exo Substituents
13-13 -- Ultraviolet-Visible (UV-Vis) Spectroscopy
_· Excitation of Electrons (e-‘s)
_· Promoting e- from Bonding Molecular Orbital (MO) or Non-Bonding MO
_· Bonding Molecular Orbitals (MO’s) and Antibonding MO’s
_· Non-Bonding MO’s
_· The “Excited State”
_· Lowest-Energy Transitions (the HOMO-LUMO gap, and ΔE)
_· Conjugated π-Systems
_· The Electromagnetic Spectrum and Complimentary Colors
_· A Typical UV-Vis Spectrum
_· Beer’s Law (A = Є . c . b)
_· The Extinction Coefficient (Є) = “Molar Absorptivity”
_· λmax Increases with Increasing Conjugation
_· Delocalization of π-MO’s
_· Systems with Non-Bonding e-‘s and π-Electrons
_· π --> π* Transitions vs. n --> π* Transitions
_· 3 General Rules for λmax
_· What are Chromophores?

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Conjugated Systems and UV-Spectroscopy

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