توضیحات
دانلود پاورپوينت جامع وکامل درباره شیمی پیشرفته ارگانیک ADVANCEDORGANIC CHEMISTRY
459 اسلاید
چکيده محتواي فايل:
Table of Contents:
Chapter 1: Chemical Approach to Chemical Bonding
Chapter 9: Aromaticity
Chapter 2: Stereochemical Principles
Chapter 3: Conformational, Steric, and Stereo Electronic
Effects
Chapter 4: Study and Description of Organic Reaction
Mechanisms
Chapter 5: Nucleophilic Substitution
Chapter 6: Polar Addition and Elimination Reactions
Chapter 7: Carbanions and Other Nucleophilic Carbon
Species
Chapter 1
Chemical Approach to Chemical Bonding
Introduction
Organic Chemistry Main Areas:
a) Structure: Description of bonding in organic molecules and the methods for determining, analyzing, and predicting molecular structure.
b) Dynamics: Study of physical properties and chemical transformations of molecules.
c) Synthesis: Those activities which are directed toward finding methods which convert existing substances into different compounds.
1-1 Valance Bond Approach to Chemical Bonding
1916: G. N. Lewis: sharing of electron pairs between atoms
1927: mansoori & London: Quantum mechanics treatment of H2 molecule; Beginning of Valance Bond Theory (VBT)
Central Feature of VBT: Exchange (resonance) of electrons between two nuclei.
The Actual molecule is the hybrid of the “Canonical Forms”
Complex Molecules Lead to Complex Wave Functions
Linus Pauling’s Key Idea:
1) Hybridization Theory
2) Resonance Theory
Hybrid orbitals are highly directed than s and p orbitals and hence:
More effective Overlap
Stronger bonds
Angle Strain in three and four-membered rings
C-C bonds: decreased s character (17%)
increased p character (83%)
C-H bonds: increased s character (33%)
decreased p character (67%)
Resonance Theory (Different Lewis Structure for a Molecule)
Elements of Resonance Theory for Qualitative Application:
- The actual molecule is combination of ALL Lewis structures.
- Maximum number of valance electrons around each atom (e.g. 2 for H atom and 8 for first row elements)
- Stable structures that approximate the actual molecule have following features:
a) maximum number of covalent bonds:
b) minimum separation of unlike charges
c) Placement of negative charge on the most electronegative atom or reverse
The Use of Resonance Concept:
- Relative Acidity of Isobutene and Acetone:
-
- Stability of Allyl Cation:
- a,b-Unsaturated Compounds
Structural Features of a,b-Unsaturated Compounds:
1690 cm-1 vs. 1730 cm-1 for saturated compounds)
b) b-carbon atom is less shielded (lower electron density) than for simple alkenes (13C-NMR)
c) Increased reactivity of C=C vs. simple alkenes toward nuclephies.
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