Perspectives in Theoretical Stereochemistry

ISBN-13: 9783540133919 / Angielski / Miękka / 1984 / 253 str.

I. Ugi; J. Dugundij; R. Kopp

Opis

Stereochemistry is the part of chemistry that relates observable prop- erties of chemical compounds to the structure of their molecules, i. e. the relative spatial arrangement of their constituent atoms. In classical stereochemistry, the spatial arrangements relevant for interpreting and predicting a given chemical property are customarily described by geometric features/ symmetries in some suitably chosen rigid model of the molecule The solution of stereochemical problems involving single molecular species is the danain of the geometry based approaches, such as the methods of classical stereochemistry, molecular mechanics and quantum chemistry. The molecules of a pure chemical compound form generally an ensemble of molecular individuals that differ in geometry and energy. Thus it is generally impossible to represent a chemical compund adequately by the geo- metry of a rigid molecular model. In modern stereochemistry it is often necessary to analyze molecular relation within ensembles and families of stereoisomers and permutation isomers, including molecules whose geometric features are changing with time. Accordingly, there is definitely a need for new types of ideas, concepts, theories and techniques that are usable beyond the scope of customary methodology. This is why the present text was written.

Spis treści

I. The Permutational Approach to Stereochemistry.- I The Description of Molecular Structure.- 1. The classical Description of rigid Molecules.- 2. Nonrigid Molecules.- 3. Definition of Chemical Identity, Stereoisomerism, and Chemical Chirality.- References.- II The Chemical Identity Group.- 1. Families of Permutation Isomers.- 2. The Chemical Identity Group.- 3. Role of the Chemical Identity Group in Stereochemistry.- 4. Racemate Group.- 5. Isomerizations.- References.- III The Asymmetric Carbon Atom revisited.- 1. Chemical Identity Group of the Asymmetric Carbon Atom.- 2. Geometrical Interpretation of the Asymmetric Carbon Atom.- 3. Contrast of the Geometrical and Permutational Interpretations.- References.- II. The Mathematical Theory of the Chemical Identity Group.- IV Families of Permutation Isomers.- 1. Permutation Isomers.- 2. The Fundamental Theorem on Molecules with all Ligands Chemically Distinguishable.- 3. The Chemical Identity Group of an Isomer.- 4. The Chemical Identity Group of a Set of Permutation Isomers.- 5. Involution Families and Racemate Groups.- References.- V Reaction Schemes.- 1. Partitions and Coverings in SymL.- 2. Ligand Substitution; Chemically Equivalent Ligands.- 3. Ligand-preserving Isomerizations and Reaction Schemes.- 4. Musher Modes and Permutational Isomerizations.- References.- VI Structure of the Chemical Identity Group.- The Pattern of a Molecule and its Enveloping Group.- 1. The Enveloping Group.- 2. Decompositions of the Chemical Identity and Racemate Groups.- 3. Conformationally flexible Polycentric Molecules.- 4. The Chemical Identity Group of Conformationally Flexible Molecules.- References.- III. Application of the Theory of the Chemical Identity Group to Actual Current Stereochemical Problems.- VII Examples, Illustrations and Applications.- 1. The Chemical Identity Group of a Molecule with a rigid Skeleton.- 2. Permutational Isomerizations of flexible Pentacoordinate Molecules.- 2.1 Berry Pseudorotation.- 2.2 Turnstile Rotation.- 2.3 Double Turnstile Rotation (TR2).- 2.4 The Graphs of Berry Pseudorotation and Turnstile Rotation..- 3. Sigmatropic 1.5-Hydrogen Shift.- 4. Con formationall y flexible Molecules.- 5. Bullvalene.- 6. The Stereoisomers of Trihydroxyglutaric Acid.- 7. SN2 and related Processes.- References.- VIII A Unified Nomenclature and Chemical Documentation System.- 1. Desirable Features of a Chemical Documentation System.- 2. Some Remarks on Traditional Nomenclature and Documentation.- 3. Representation of the Constitutional Aspect of Molecules.- 4. Representation of the Stereochemical Features of Molecules.- 4.1 Molecular Sceleton and Set of Ligands.- 5. Indexing Rules and Algorithms for Ligands.- 5.1 The CIP Rules.- 5.2 The CANONical Ligand Indices.- 6. The Reference Isomer.- 6.1 Skeletal Classes and their Reference Isomer.- 6.2 Choice of Reference Isomers.- 6.3 Ordering and Selection Rules for Sets of Permutations.- 6.4 Chiral Reference System.- 7. Permutational Descriptors.- 7.1 Permutation Isomers with chemically distinguishable Ligands.- 7.2 Molecules with some Indistinguishable Ligands.- References.- 1. Subgroups.- 2. Cosets.- 3. Normal Subgroups.- 4. Conjugates.- 5. Homomorphism.- 6. Direct and Semidirect Products.- 7. Permutations.- 8. Burnside-Frobenius Theorem.- 9. Generalized Wreath Products.- 10. Primitive and Imprimitive Actions.- References.- Index ..