CHEM 421
Physical Organic and Theoretical Chemistry
Instructor
Galina Orlova Office: PSC-3026 Tel: 867-5237 gorlova@stfx.ca
Supplementary Text: “Perspectives on Structure and Mechanism in Organic Chemistry”, by F.A. Carroll, Brooks/Cole.
Supplementary Text: ”Modern Physical Organic Chemistry”, Eric V. Anslyn, Dennis A. Dougherty, University Science Books.
Supplementary Text: “Introduction to Computational Chemistry”, by Frank Jensen, Wiley (ISBN 0-471-98425-6). In the library (1).
Supplementary Text: ‘Exploring Chemistry with Electronic Structure Methods’, Gaussian Inc. Available in the Computational Chemistry Lab.
I. Concepts and Models in Organic Chemistry
- Qualitative models and concepts to describe molecular geometry and bonding
Quantum numbers and atomic orbitals; electron configurations and electronic diagrams; Lewis structures; formal charges vs. real charges; VSEPR; hybridization; molecular orbital model of bonding; polar covalent bonding; bond dipole, molecular dipoles; resonance; polarizability.
II. Qualitative Theories
-Qualitative molecular orbital theory, orbital mixing, Walsh diagrams (AH2 AH3, AH4)
- Aromaticity and anti-aromaticity. Stabilization due to formation of aromatic structures.
III. Quantitative Theories: Electronic Structure Methods
1. Introductory quantum mechanics:
The nature of wave function; the Schrödinger equation; the Hamiltonian; the nature of chemical bonding
2. Solving the Schrödinger equation:
Born-Oppenheimer approximation; potential energy surface (PES), minima and saddle points (transition states) self-consistent field (SCF) theory; Slater determinant; Variation principle; Hartree-Fock; SCF techniques; basis sets. Semi-empirical methods: AM1 and PM3
3. Density functional theory (DFT)
electron correlation effects, electron density; Kohn-Sham approximation; exchange-correlation functional; Generalized gradient approximation (GGA, i.e. BLYP); Hybrid DFT (i.e. B3LYP).
4. Computational Chemistry software: Gaussian03; GaussView03. Predicting geometries (geometry optimization), IR and NMR spectra, and electronic energies. Thermochemistry in G03: zero point vibrational energy corrections, enthalpies, Gibbs energies.
IV. Reactive Intermediates: Structure and Stabilities
Bonding and structure of reactive intermediates. Radicals, carbocations, carboanions; radicals, radical cations, carbenes. Stabilization via hyperconjugation and resonance structures. Thermodynamic and kinetic stabilities.
V. Kinetic and thermodynamic control.
Basic concepts. Illustrations: formation of enolate anions from unsymmetrical ketones.
VI. Conformational Analysis and Molecular Mechanics
1. Molecular conformation. Group Increments and strain energy. Anti- and Gauche- conformers. Geminal repulsion in tetrasubstituted ethane. Stereochemistry of electron pairs. Gauche effect. Hyperconjugation. Conformational analysis of cyclic systems. Three types of strain. Conformations of cyclohexane. 1,3-diaxial interaction, A-factors. 1,2 dimethylcyclohexane and 1,3 dimethylcyclohexane. Tetrahydrofuran: anomeric effect (hyperconjugation). Stereoelectronic effects. Substituted alkenes. Secondary orbital interaction. Allylic strain. Highly strained molecules.
2. Force Fields Method (molecular mechanics).
Basic concepts. Energy terms (Estr, Ebend , Etors EvDW, Eel, Ecross). Validation of force field. Advantages and limitations of force filed methods.
VII. Thermal Pericyclic Reactions.
Orbital symmetry diagrams, state correlation diagrams, frontier molecular orbital (FMO) theory, aromatic transition state theory, the generalized orbital symmetry rule.
Evaluation Quizzes (2) 20%
December exam 35%
Laboratory 25%
Assignments 10%
Res. Project 10%
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100%