Stereochemistry Flashcards
Define stereoisomers
Compounds with the same molecular connectivity but differ in the spatial arrangement or orientation of their constituent atoms or groups
How do drugs work
They work by interacting with a target , they interact with either the receptors on the surface of the cells, enzymes within the cell or channels in the membrane
They go through the lock and key ,mechanism, where they either
Block the natural substrate or the ligand - these are called ANTAGONISTS
Mimic the natural substrate or the ligand - these are called AGONIST
What are antagonists
These drugs block the natural substrate or ligand
What are agonists
These mimic the natural substrate or ligand to elicit the therapeutic response
What are conformation
Changes in molecular structure due to free rotation about a sigma bond.
A molecule can change from one conformation to another conformation without breaking and reforming bonds
This is not fixed and changes over time
Why do conformation isomers occur
When groups are attached by single sigma bonds this means that they are able to rotate around the bond and then they can take multiple positions, a molecule can take up to an infinite number of different conformations
What is dihedral Angles
An angle between two planes, both which pass through the same bond
The angle between a C-H Bon on the front carbon and a C-H bond on the back carbon is referred to as a dihedral angle
What’s the difference between staggered and eclipsed conformations, and which one has the highest energy
Staggered conformations
This has the lowest energy - making it the most stable
All the dihedral angles are 60 degrees apart- so the distance between the front and back C-H bonds is maximised
Eclipsed conformations
This is highest energy, when the dihedral angles are 0 degrees apart, so the electrons in the front and back C-H bonds are closer together, so they repel making this structure less stable
What is angle strain and what causes it
Angle strain is due to deviation from one or more ideal bond angles, for example cyclopropane has angle strain this is because its C-C-C bond angles are 60 degrees when it should be 109.5 degrees due to the ideal tetrahedral bond angle- because it deviates from it, there is angle strain
What is torsional strain
COME BACK m
Why does cyclo hexane not experience angle strain
A regular hexagon has internal angles of 120 degrees
This deviates from ideal angles of sp3 carbon of 109.5
This would mean that you would expect cyclohexane to experience angle strain but it doesn’t
This is because of ring puckering
- this is when flexible rings can adopt different conformations due to out of plane bending motions, caused by changes in the rotatable ring bonds
