L9 - Stereochemistry 2 Flashcards
1
Q
How do you change configurational isomers? what are they?
A
- by breaking bonds
- they are different compounds
2
Q
What is an example of geometric isomers?
A
Trans-but-2-ene (E)
Cis-but-2-ene (Z)
3
Q
when is a molecule chiral?
A
a molecule is chiral if does not have a plane of symmetry within
4
Q
what are enantiomers?
A
mirror images of each other
- have identical physical properties
- they rotate plane polarised light in equal but opposite directions
5
Q
What is - or l?
A
Levorotatory
PPL anti-clockwise
6
Q
what is + or d?
A
dextrotatory
PPL clockwise
7
Q
how do you calculate [alpha]D?
A
observed rotation (alpha) / (path length (dm) x conc (g/mol))
8
Q
what is the [alpha]D for a racemic mixture?
A
0
as it’s 50/50 mixture of 2 enantiomers
9
Q
what is enantiomeric excess (ee)?
A
the excess of one enantiomer over another
10
Q
how do you calculate ee?
A
x-y/x+y
