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CH1012
Polarimeter
CHIRAL MOLECULES
L-Alanine
2
                1
3
• When you put
a chiral molecule
in solution and
shine plane polarized
light thru it the light
is rotated by ar 
- the specific rotation.
• One isomer rotates
+ar the other -ar .
• This is the only physical property that differs
between optical isomers.
Only the S form
is observed
in natural amino
acids. (20 AAs)