Basic Organic Chemistry and Isomerism Flashcards
What are the three types of structural isomer?
- Chain
- Positional
- Functional Group
What are chain isomers?
Have different arrangements of the carbon skeleton. Some are straight chains and the others are branched in different ways.
What are positional isomers?
Positional isomers have the same skeleton and the same atoms or groups of atoms attached. The difference is that the atom or group of atoms is attached to a different carbon atom.
What are functional group isomers?
Have the same atoms arranged into different functional groups.
What are stereoisomers?
Have the same structural formula but a different arrangement of atoms in space.
Why do E/Z isomers exist?
Because double bonds have a fixed position and you cannot rotate the rest of the molecule around it like a single bond.
When do E/Z isomers occur?
When the double bonded carbon atom has two different atoms or groups attached. Then you get and E-isomer and a Z-isomer.
What is an E- isomer?
One that has the highest priority groups across the double bond from each other.
What is a Z-isomer?
One which has the highest priority groups both above or below the double bond.
What is optical isomerism?
Another type of stereoisomerism.
Same structural formula but different arrangement of atoms in space.
Optical isomers have a chiral carbon atom.
What is a chiral (or asymmetric) carbon atom?
A carbon atom with four different groups attached.
What are optical isomers (enantiomers)?
Mirror images of each other- they cannot be superimposed.
Optical isomers are optically active. What does this mean?
They rotate plane-polarised light.
What is plane polarised light?
Normal light vibrates in all directions- some of it vibrates up and down, some of it vibrates side to side. If normal light is passed through a polarising filter it becomes plane polarised, this means all the light is vibrating in the same plane.
What happens when you pass plane polarised light through an optically active mixture?
The molecules interact with the light and rotate the plane of the vibration of the light. The two enantiomers of an optically active molecule will rotate the plane- polarised light in opposite directions- One clockwise and one anticlockwise.
What is a racemic mixture (racemate)?
Contains equal quantities of each enantiomer of an optically active compound.
Don’t show any optical activity- two enantiomers cancel out each others light- rotating effect.
When two molecules react there’s an equal chance of forming each enatiomer.
How do drugs work?
They change the chemical reactions that are taking place in the body. Most drugs do this by binding to an active site- usually by binding to an active site- usually an enzyme or a specific receptor molecule.
A drug must be exactly the right shape to fit into the correct active site.
The other enantiomer might fit into a different enzyme, and might cause harmful side effects or have no effect at all.
What are the benefits of using a racemic mixture as a drug?
No need to separate which reduces the difficulty and cost of production.
What was thalidomide and what were the side effect of thalidomide?
Prescribed to pregnant women for morning sickness- didn’t appear to have any side effects.
Babies began to be born with malformed limbs- thalidomide was shown to be causing these symptoms and use was banned.
What was the problem with thalidomide (chemically).
Two optical isomers had different affects on the body. One is an effective anti-sickness drug, the other causes birth defects.
Even if pure dose given of safe isomer the body will convert some into harmful isomer.
