The Medicine Flashcards
What is a Stereoisomer?
Molecule with that same molecular formula but a different arrangement in space
Why are Geometric Isomers formed?
Due to the restriction around the double bond
What are the different two types of isomers?
Cis - where the high priority groups are on the same side
Trans - where high priority groups are on opposite sides
State the Cahn-Ingold-Prelog rules for E/Z Assignment
Rule One - Dependent on atomic number of atom attached to the carbon
The higher the atomic number, the higher the priority
Rule Two - Compare the atomic number of atoms attached next to these atoms
Rule Three - For double and triple bonds, the atoms connected to them are duplicated or triplicated
When Four different groups are attached to sp3 hybridised carbon atom, it is called…
A Chiral Centre
What is another name for Optical Isomers?
Are they super-imposable?
Another name for optical isomers are Enantiomers
They are not superimposed, therefore they are not the same as its mirror image
How do you determine which Enantiomer is S/R?
Rule One - Dependent on the atomic number of the atom attached directly to the chiral carbon
The higher the atomic number, the higher the priority
Rule Two - Look at the next atoms bonded to the carbon atoms and determine which has the highest atomic number
Rule Three - Look at the Double bonds
How to assign S/R Enantiomer?
It is important for the molecule to be drawn with the 4th priority ligand going backwards (with the dashed line) in the tetrahedral
Having established the priorities you then join the dots from 1st to 2nd to 3rd.
If they go clockwise, then the chiral Centre is of the R configuration, R is from Rectus, Latin for right.
If they go anticlockwise, then the chiral Centre is of the S configuration, S is from Sinister, Latin for left.
How do you calculate Specific Rotation?
The specific optical rotation is the constant number for a molecule
It is dependent on the concentration of the sample (g/ml) and the path length of the sample tube (dm)
The higher the concentration and length of sample tube, the higher the alpha (specific rotation) will be, as the light will have bumped into more molecules
A 100 g/l solution of (R)-1-phenethylamine in a 5cm length polarimeter tube gives a rotation of +1.9° . Calculate the specific rotation.
L = 5 cm = 0.5 dm c = 100 g/l = 0.1 g/ml [a] = +1.9 / (0.5 x 0.1)=+ 38°
What is a Racemic Mixture?
A Racemic mixture has 50% of the enantiomer that rotates the light in a -ve direction and 50% of the enantiomer that rotates the light in a +ve direction
How many possible stereoisomers are there in a molecule with 2 Chiral centres that are not identical?
There are 4 possible stereoisomers
What is a Diastereoisomer?
A Diastereoisomer is a stereoisomer which is not a mirror image of another
What is a Meso Compound?
A meso compound is superimposable on its mirror image, even though the molecule contains chiral centers.
How do you calculate the number of stereoisomers?
If there are n chiral centers in a molecule, there are a maximum of 2n stereoisomers.
Symmetry in the molecule decreases the number of stereoisomers.
