kapitel 4

Page 1: Isomers and their Effect on Physiological Properties

• Isomers: Compounds with the same molecular formula but different structures.

  • Constitutional Isomers: Differ in the connectivity of their atoms.

    • Example: Ethanol (C2H5OH) and Dimethyl Ether (C2H6O)

  • Stereoisomers: Same connectivity but different spatial arrangement.

    • Types: Conformational isomers (interconvert rapidly) and Configurational isomers (cannot interconvert without breaking covalent bonds).

• Interchanging groups bonded to carbon can significantly alter molecular activity, e.g., Vicks and methamphetamine.

• Constitutional Isomers Examples:

  • 1-chlorobutane and 2-chlorobutane

  • Ethanol and Dimethyl Ether

Page 2: Types of Isomers

• Stereoisomers: Atoms are arranged in the same way but differ in spatial arrangement.

  • Conformational Isomers: Cannot be separated, e.g., staggered and eclipsed forms.

  • Configurational Isomers: Can be separated into distinct compounds.

    • Types: Cis-trans isomers and isomers with asymmetric centers.

• Conformers are different spatial arrangements that can rapidly interconvert.

• Cis-trans Isomers: Result from restricted rotation due to ring structures or double bonds.

Page 3: Cis-Trans Isomers

• Cis Isomer: Substituents on the same side.

• Trans Isomer: Substituents on opposite sides.

• Examples in cyclic structures (e.g., cis-4-methylcyclohexanol, trans-4-methylcyclohexanol).

• Restrictions of Rotation: Based on presence of double bonds impacting isomerism.

Page 4: Configurational Isomers

• Cis-trans isomers are a subset of configurational isomers formed due to restricted rotation about double bonds.

• Cis isomers have similar groups on the same side, while Trans have them on opposite sides.

• Separation: Cis and trans isomers can be separated due to differing physical properties.

Page 5: Vision and Isomerism

• Cis-trans interconversion in vision: Opsin binds to cis-retinal forming rhodopsin.

• Light triggers a change from cis to trans configuration, initiating nerve impulses for vision.

Page 6: The E,Z System of Designation

• E,Z System: Used for alkenes that do not have a hydrogen attached to each sp2 carbon.

• E Isomers: High-priority groups on opposite sides.

• Z Isomers: High-priority groups on the same side.

Page 7: Enantiomers and Chirality

• Chiral Objects: Non-superimposable mirror images.

• Achiral Objects: Superimposable mirror images.

• Chiral Molecules: Must have an asymmetric center (four different groups attached to a carbon).

Page 8: Asymmetric Centers Influence Chirality

• Asymmetric centers lead to chirality; enantiomers are nonsuperimposable.

• Stereochemistry is critical for understanding molecular behavior.

• Chirality in Molecules: Key for understanding biological interactions and drug actions.

Page 9: Enantiomers and Optical Activity

• Enantiomers have different physiological properties affecting drug behavior.

• Optically Active Compounds: Rotate plane-polarized light; achiral compounds do not.

Page 10: Racemic Mixtures

• Racemic Mixtures: Equal amounts of two enantiomers, optically inactive.

• Specific Rotation: Each enantiomer has a characteristic optical activity, measurable using a polarimeter.

• Enantiomeric Excess (ee): Indicates the extent of one enantiomer over the other in mixtures.

Page 11: Diastereomers and Meso Compounds

• Diastereomers: Stereoisomers that aren’t enantiomers (not mirror images).

• Meso Compounds: Have asymmetric centers but are achiral, possessing a plane of symmetry.

Page 12: Identification of Isomers

• Cyclic compounds may also demonstrate chiral properties.

• Enantiomers vs. Diastereomers: Each behave differently with respect to physical and chemical properties.

• Two asymmetric centers supply many isomers, including meso forms.

Page 13: Naming Isomers with Multiple Asymmetric Centers

• Determine configurations for each asymmetric center (R or S).

• R,S Designation: Used systematically to describe orientation around multiple centers.

Page 14: More Complex Isomers and Chirality

• Compounds with multiple asymmetric centers follow systematic nomenclature rules.

• Chiral Molecules resulting from N, P atoms demonstrate chirality, enabling more complex interactions.

• These structures have significant biological implications, especially in drug formulation and efficacy.