E.Amitai Halevi

Orbital Symmetry and Reaction Mechanism

The OCAMS View

• Broschiertes Buch

Produktbeschreibung

Criteria of orbital symmetry conservation had a profound influence on mechanistic thinking in organic chemistry and are still commonly applied today. The author presents a coherent set of operational rules for the analysis of scope and reliability. It is written from the viewpoint of Orbital Correspondence Analysis in Maximum Symmetry (OCAMS). Its advantage lies in its provision of a coherent overview of the relation between symmetry and mechanism. For reasons of consistency, the book remains within the framework of molecular orbital theory.

Produktdetails

• Verlag: Springer / Springer Berlin Heidelberg / Springer, Berlin
• Artikelnr. des Verlages: 978-3-642-83570-4
• Softcover reprint of the original 1st ed. 1992
• Seitenzahl: 340
• Erscheinungstermin: 20. September 2012
• Englisch
• Abmessung: 235mm x 155mm x 19mm
• Gewicht: 522g
• ISBN-13: 9783642835704
• ISBN-10: 3642835708
• Artikelnr.: 37035938

Autorenporträt

Modern mechanistic thinking in organic chemistry is still influenced by the publication of Woodward and Hoffmann "Conservation of orbital symmetry" in 1965. The author explains the foundation of these rules coherently. He outlines the scope and limitations of the model with respect to recent experimental research. The book is written for students in chemistry.

Inhaltsangabe

I. Preliminary Survey.- 1. The Woodward-Hoffmann Rules in Perspective.- 1.1 Prolegomenon.- 1.2 The Suprafacial-Antarafacial Dichotom.- 1.2.1 Ground-State Reactions.- 1.2.2 Excited State Reactions.- 1.3 Frontier Electrons and Frontier Orbitals.- 1.3.1 HOMO-LUMO Interactio.- 1.3.2 Superjacent and Subjacent Orbitals.- 1.4 Orbital and Configuration Correlation.- 1.4.1 Frontier Electron Energy.- 1.4.2 Correlation of Electron Configurations.- 1.4.2.1 [4+2]-Cycloaddition and Cycloreversion.- 1.4.2.2 [2+2]-Cycloaddition and Cycloreversion.- 1.5 Problems and Prospects.- 1.5.1 Some Unanswered Questions.- 1.5.2 Where Do We Go From Here?.- 1.6 References.- II. Symmetry and Energy.- 2. Atoms and Atomic Orbitals.- 2.1 Is an Isolated Atom Spherically Symmetrical?.- 2.2 Desymmetrization by an External Field.- 2.2.1 p Orbitals in a Magnetic Field.- 2.2.2 p Orbitals in a Quadrupolar Field.- 2.2.3 Digression: Some Elementary Group Theory.- 2.2.4 The Phase of an Orbital.- 2.2.5 Digression: A Bit More Group Theory.- 2.2.6 Hybridization.- 2.2.7 The Formal Expression of Desymmetrization.- 2.2.7.1 I. Desymmetrization to a Subgroup.- 2.2.7.2 II. Desymmetrization by a Perturbation.- 2.3 Something About d Orbitals.- 2.3.1 Splitting d Orbitals by an External Field.- 2.3.2 A Further Excursion into Group Theory.- 2.3.2.1 Classes and Degenerate Representations.- 2.3.2.2 Invariant Subgroups, Kernels and Co-Kernels.- 2.4 References.- 3. Diatomic Molecules and Their Molecular Orbitals.- 3.1 The Hydrogen Molecule Ion.- 3.1.1 The Symmetry of Ht.- 3.1.2 The Molecular Orbitals of Ht.- 3.2 Homonuclear Diatomic Molecules.- 3.2.1 Mulliken';s Orbital Correlation Diagram.- 3.2.2 The Symmetry of Electron Configurations.- 3.2.3 State Symmetry in Dooh and D2h.- 3.3 Heteronuclear Diatomic Molecules.- 3.3.1 The Non-Crossing Rule..- 3.3.2 Configuration and State Correlatio.- 3.4 Symmetry Coordinates.- 3.4.1 Homonuclear Diatomics.- 3.4.2 Heteronuclear Diatomics.- 3.5 References.- 4. Formation and Deformation of Polyatomic Molecules.- 4.1 Triatomic Molecules.- 4.1.1 Molecular Orbitals and Walsh Diagrams.- 4.1.2 Symmetry Coordinates of a Symmetric Triatomic Linear Molecule.- 4.1.3 Symmetry Coordinates of a Symmetric Non-Linear Triatomic.- 4.2 Linear Tetraatomics and Their Deformation.- 4.3 Dimerization of Methylene and Its Reversal.- 4.3.1 The Dimerization of Methylene.- 4.3.1.1 I. Desymmetrization to a Subgroup.- 4.3.1.2 II. Desymmetrization by a Perturbation.- 4.3.1.3 WH-LHA and OCAMS: A Comparison.- 4.3.2 The Fragmentation of Ethylene.- 4.3.2.1 Bader's Analysis of Molecular Fragmentation.- 4.4 Symmetry Coordinates and Normal Modes.- 4.4.1 Non-Degenerate Vibrations.- 4.4.2 Degenerate Vibrations.- 4.4.3 Reducing Reducible Representations.- 4.4.3.1 The CH-Stretching Coordinates of Ethylene.- 4.4.3.2 The NiF -Stretching Coordinates of NiF~.- 4.5 Motion Along the Reaction Coordinate.- 4.5.1 Distortional and Substitutional Desymmetrization Compared.- 4.5.2 At The Transition State.- 4.6 References.- III. The Classical Thermal Reactions.- 5. Electrocyclic Reactions and Related Rearrangements.- 5.1 Rudimentary Analysis of Polyene Cyclization.- 5.1.1 Cyclization of Butadiene to Cyclobutene.- 5.1.2 cis-1 ,3,5-Hexatriene to 1,3-Cyclohexadiene.- 5.2 More Subtle Considerations.- 5.2.1 Correlation vs. Correspondence.- 5.2.2 The Role of IT-Orbitals.- 5.2.3 Substitutional Desymmetrization: Norcaradiene.- 5.2.4 Local vs. Global Symmetry:.- 5.2.4.1 Bisnorcaradiene.- 5.2.4.2 Cyclooctatetraene +--+ Bicyclooctatriene.- 5.3 "Allowedness" and "Forbiddenness".- 5.3.1 Rearrangement of s-cis-Butadiene to Bicyclobutane.- 5.3.2 The Bond-Bisection Requirement: Benzvalene.- 5.3.3 Genuinely Forbidden Valence Isomerizations.- 5.3.4 Quantifying "Allowedness": Cubane +--+ Cyclooctatetraene.- 5.3.4.1 Analysis in Global Symmetry.- 5.3.4.2 Analysis in Local Symmetry.- 5.3.5 The Bottom Line So Far.- 5.4 References.- 6. Cycloadditions and Cycloreversions: I. [2+2]-Cycloaddition.- 6.1 Addition of Singlet Carbenes to Ethylene.- 6.1.1 The Direct Approach.- 6.1.2 Correcting a Geometrically Unreasonable Approach.- 6.1.2.1 Composite Motions.- 6.2 Concerted [1r2+1r2]-Cycloaddition.- 6.2.1 The [1r2s+1r2sl Approach.- 6.2.1.1 Substitutional Desymmetrization: Dimerization of Silaethylene.- 6.2.2 [1r2s+1r2al-Cycloaddition.- 6.3 Cycloaddition via a Tetramethylene Intermediat.- 6.3.1 The Biradical Mechanism.- 6.3.1.1 Stereochemistry of Biradical Cycloaddition.- 6.3.2 The Zwitterionic Mechanism.- 6.4 Ketene Cycloadditions.- 6.4.1 Diversion: Secondary Isotope Effects.- 6.4.2 Reconciling the Evidence.- 6.4.2.1 Product Stereochemistry.- 6.4.2.2 Substituent, Solvent and Isotope Effects.- 6.5 Apologia.- 6.6 References.- 7. Cycloadditions and Cycloreversions: II. Beyond [2+2].- 7.1 [1r4 + 1r2]-Cycloaddition; Anasymmetrization.- 7.1.1 The Diels-Alder Reaction.- 7.1.1.1 Anasymmetrization.- 7.1.1.2 Changing the Initial Orientation.- 7.2 Reactions Related to [1r4 + 1r2]-Cycloaddition.- 7.2.1 The Homo-Diels-Alder Reaction.- 7.2.2 n > 4 and/or m >2.- 7.2.3 1,3-Dipolar Cycloaddition.- 7.3 More Complex [1r2 +1r2]-Cycloadditions.- 7.3.1 Dimerization of Cyclobutadiene.- 7.3.1.1 The (Non)-Dimerization of CBD to Cubane.- 7.3.1.2 Dimerization of Cylobutadiene to Tricyclooctatriene.- 7.3.2 [2 + 2]-Cycloreversion of o,o'-Benzene-dimer.- 7.3.2.1 Digression on Entropy of Activation.- 7.3.3 Dimerization of Cyclomonoalkenes.- 7.3.3.1 Cyclopropene.- 7.3.3.2 Dimerization of Silacyclopropenes.- 7.4 References.- 8. Degenerate Rearrangements.- 8.1 Correspondence Between Reactant and/or Product and Transition Structure.- 8.1.1 1,2-Rearrangement of Tetraaryldisilenes.- 8.1.2 Digression: Degenerate X- Ion Substitution in CH3X.- 8.2 The Cope Rearrangement.- 8.2.1 Symmetry Analysis of the Cope Rearrangement.- 8.2.2 Rearrangement of Bridged Hexadienes.- 8.3 [l,j]-Sigmatropic Rearrangements.- 8.3.1 [l,j]-Hydrogen Shifts in Non-Cyclic Molecules.- 8.3.1.1 [1,3]-Sigmatropic Rearrangement of Propylene.- 8.3.1.2 [1,5]-Hydrogen Shift in s-cis-Pentadiene.- 8.3.1.3 A Word About [1,7]-Hydrogen Shifts.- 8.3.2 Circumambulatory Rearrangements.- 8.3.2.1 [1,5]-Hydrogen Shift in Cyclopentadiene.- 8.3.2.2 The "Norcaradiene Walk" Rearrangement.- 8.4 Fluxional Isomerization of Cyclobutadiene.- 8.4.1 Correspondence Between Reactant and Product.- 8.4.2 Correspondence Between Anasymmetrized Reactant and Transition Structure.- 8.5 References.- IV. Spin and Photochemistry.- 9. Electron Spin.- 9.1 Spin and Symmetry.- 9.1.1 The Symmetry of Spinning Electrons.- 9.1.1.1 A Single Spinning Electron.- 9.1.1.2 Two Spinning Electrons.- 9.1.2 Space-, Spin- and Overall Symmetry.- 9.1.2.1 Example 1: Rectangular Cyclobutadiene (D2h).- 9.1.2.2 Example 2: Square-Planar Cyclobutadiene (D4h).- 9.1.2.3 Overall Symmetry.- 9.1.2.4 Geminals.- 9.2 Intersystem Crossing..- 9.2.1 Intersystem Crossing of Carbenes.- 9.2.1.1 Spin-Orbit Coupling.- 9.2.1.2 Spin-Vibronic Coupling.- 9.3 Reactive Intersystem Crossing.- 9.3.1 The Arrhenius Parameters of Spin-Non-Conservative Reactions.- 9.3.2 Thermolysis of Diazomethane.- 9.3.3 Thermolysis of Methylenepyrazoline.- 9.3.3.1 The Zwitterion Cascade Mechanism.- 9.3.3.2 Secondary Isotope Effects.- 9.3.4 "Photochemistry Without Light".- 9.3.4.1 Isomerization of Dewar Benzene to Triplet Benzene.- 9.3.4.2 Fragmentation of 1,2-Dioxetanes.- 9.4 References.- 10. Excited State Reactions.- 10.1 The Basic Photophysical Processes.- 10.1.1 Fluorescence: The Azulene Anomaly.- 10.1.2 Stereoselectivity of Photophysical Processes: Bimanes.- 10.1.3 Chemical Sensitization: Singlet Dioxygen.- 10.2 Photofragmentation.- 10.2.1 Photolysis of Cyclobutadiene.- 10.2.2 Photochemical Decomposition of Formaldehyde.- 10.2.2.1 Pathway I: Sl(H2CO) -+ So(H2CO) -+ H2 + CO.- 10.2.2.2 Pathway II: Sl(H2CO) -+ H + HCO.- 10.2.2.3 Sidelight: Coping with the Limitations.- 10.3 Photoisomerization of Benzene.- 10.3.1 Photoisomerization to Benzvalene.- 10.3.2 Photoisomerization to Dewar Benzene.- lO.4 Spin-Non-Conservative Photoisomerization: Naphthvalene.- 10.5 Rydberg Photochemistry: Photolysis of Methane.- 10.6 References.- 11. Into Inorganic Chemistry.- 11.1 Main-Group Elements.- 11.1.1 Ground-State Isomerization: "Berry Pseudorotation".- 11.1.2 The Allotropy of Phosphorus.- 11.1.3 An Excited-State Reaction: Photoextrusion of Silylene.- 11.2 Transition Metals: Isomerization of NiX4.- 11.3 Afterword.- 11.4 References.- A. Character Tables of the More Common Symmetry Point Groups.- B. Kernels and Co-Kernels of Degenerate Irreducible Representations.- C. Group Correlation Tables.