Optical activity arises from compounds lacking symmetry and containing stereogenic centers, such as carbon atoms bonded to four different groups. Chiral compounds exist as non-superimposable mirror images called enantiomers that cannot be separated if they rapidly interconvert through processes like ring flipping. Optical isomers rotate the plane of polarized light in opposite directions.

1. Optical Activity - Chirality
A b t b d d t f diff t ld l d t ti l ti it d i
A carbon atom bonded to four different groups could lead to optical activity and is
called a stereogenic center.
CH3
CH2CH3
HO
H
In general organic compounds, which lack a plane of symmetry are optical active and
are called chiral compounds.
OH OH
OH OH
Achiral Chiral
Optically active compounds exist as enantiomers, which are mirror images of each
other

2. Optical Activity - Chirality
cis-1,2-dichlorocyclohexane
If enantiomers are in equilibrium with each other through ring flipping, one enantiomer
q g g pp g,
cannot be separated from the other.
Cl Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Ring flip 120°

3. Optical Activity - Chirality
Enantiomers
trans-1,2-dichlorocyclohexane
Cl Cl
Cl Cl
Cl Cl
Ring flip
Cl Cl
Cl
Cl