Phay002; Stereochemistry

• What is stereochemistry in pharmaceutical chemistry?

  Stereochemistry is a significant concept that involves the three-dimensional arrangement of atoms in drug molecules.
• Why is the stereochemical configuration of a drug molecule important?

  It is key to its ability to interact with a biological target.
• What is the consequence of different stereoisomers in terms of biological activity?

  Different stereoisomers almost always demonstrate completely different biological activities.
• What are biological targets in relation to stereochemistry?

  Biological targets are stereospecific, meaning they interact differently with various stereoisomers.
• What is the relationship between a drug's three-dimensional shape and its pharmacological response?

  The ability of a drug to interact with its biological target is a direct consequence of its three-dimensional shape.
• What are stereoisomers?

  Stereoisomers are isomers that have the same connectivity but a different spatial arrangement of their atoms.
• How do stereoisomers differ from constitutional isomers?

  Stereoisomers have the same connectivity, while constitutional isomers differ in their connectivities.
• What is chirality?

  Chirality is the property of an object that is non-superimposable on its mirror image.
• What is a chiral molecule?

  A chiral molecule is one that is non-superimposable on its mirror image.
• How can you determine if a molecule is chiral?

  A molecule is chiral if it has a tetrahedral sp3-hybridised carbon atom with four different groups bonded to it.
• What distinguishes enantiomers from other types of stereoisomers?

  Enantiomers are non-superimposable mirror images of each other that have OPPOSITE configuration at EVERY chirality centre
• What is a stereogenic centre?

  A stereogenic centre is a carbon atom bonded to four different substituents.
• Why is the methyl group in alanine not a chiral centre?

  The methyl group is not a chiral centre because it does not have four different substituents.
• How can you identify chirality centres in complex molecules?

  You must look for sp3-hybridised carbon atoms bonded to four different substituents.
• What is the significance of a plane of symmetry in a molecule?

  If a molecule has a plane of symmetry, it is achiral as its mirror image will be superimposable.
• What is the general rule for identifying achiral molecules?

  If a molecule has a plane of symmetry, it is achiral.
• What is the importance of stereospecific structural representations?

  Stereospecific representations indicate the 3D arrangement of groups at chirality centres, which is essential for distinguishing enantiomers.
• How do you draw a stereospecific structure for a chiral molecule?

  You must specify the tetrahedral arrangement of the bonds at the chirality centre.
• How can you create the opposite enantiomer of a molecule with one chirality centre?

  You can invert the configuration at the chirality centre by swapping any two substituents.
• What are the key features of stereoisomers and constitutional isomers?

  • Stereoisomers: Same connectivity, different spatial arrangement.
  • Constitutional isomers: Different connectivity, can have different physical and chemical properties.
• What are the structural features that give rise to chirality?

  • Tetrahedral sp3-hybridised carbon atom
  • Four different substituents bonded to it
• What are the substituents of the chirality centre in alanine?

  1. Amino group
  2. Carboxyl group
  3. Methyl group
  4. Hydrogen atom
• What are the substituents of the chirality centre in pseudoephedrine?

  1. Aromatic ring
  2. Hydroxyl group
  3. Hydrogen atom
  4. Carbon atom bonded to nitrogen
• What are the substituents of the chirality centre in tetrahydrocannabinol?

  1. Hydrogen atom
  2. Carbon atom with two methyl groups
  3. Carbon atom with a double bond
  4. Carbon atom with a single bond
• What are the substituents of the chirality centre in hexan-3-ol?

  1. Hydroxyl group (-OH)
  2. Hydrogen atom (-H)
  3. Ethyl group (-CH2CH3)
  4. Propyl group (-CH2CH2CH3)
• What is the significance of the hydroxyl group in the stereospecific representation of hexan-3-ol?

  • Indicates the position of the hydroxyl group in 3D space.
  • Essential for distinguishing between enantiomers.
• What is the role of asterisks in representing chirality centres?

  • Asterisks (*) indicate the presence of chirality centres in molecular structures.
• What is the relationship between carvone and its stereoisomers?

  • Carvone has two stereoisomers that are enantiomers, distinguished by their different odours.
• What is the significance of the structural representation of chiral drugs?

  • It provides clarity on the 3D arrangement of atoms.
  • Essential for understanding drug interactions and effects.
• What is the importance of recognizing chirality in drug design?

  • Chirality can affect the efficacy and safety of drugs.
  • Different enantiomers can have different biological effects.
• What is necessary to describe the arrangement of substituents in three dimensions for stereoisomers?

  A method to describe the configuration of the substituents
• Why do enantiomers require different names?

  Because they are different compounds with the same connectivity
• What is the system used to describe the configuration of a chirality centre?

  The Cahn-Ingold-Prelog system (CIP)
• How does the Cahn-Ingold-Prelog system determine the configuration of a chirality centre?

  By ranking the four substituents bonded to the chirality centre in order of priority
• What is the first step in determining the configuration of lactic acid?

  Identify the four different substituents bonded to the chirality centre
• How do you rank substituents in the Cahn-Ingold-Prelog system?

  By looking at the atoms directly bonded to the chirality centre and ranking them according to atomic number
• What happens if the directly bonded atoms are identical when ranking substituents?

  You move along to the next atom until the first difference is found
• What is the priority order for the substituents in lactic acid?

  OH > CO2H > CH3 > H
• What is the lowest priority substituent in lactic acid?

  Hydrogen
• What should you do if the lowest priority substituent is not at the back?

  You can rotate the other groups until the lowest priority one is at the back