idea of prochirality

1. What is
Prochirality?
Submitted to:
Dr. Abida
Submitted By:
Sidra
M.Phil. 1st
Semester
Session: 2020-2022
Course: CHM-533- Stereochemistry
Department of Chemistry
The Women University Multan

2.  Term Prochirality:
In stereochemistry, the prochirality meant for prochiral molecule that can be
converted from achiral to chiral molecule. Thus, the achiral specie which can be
changed in to achiral molecule is called prochiral and this conversion
processes known as prochirality.

3.  Notation of prochiral molecule:
Prochiral molecules, prochiral carbon having same substituent are labeled by R and
S notation for labeling of chiral centers. For example in ethanol the 2 hydrogen on
prochiral center is designated as R and S.
Explanation:
Prochiral hydrogen’s can be designated either enantiotopic or
diastereotopic.
Enantiotopic H’s:
If either HR or HS on ethanol were replaced by a deuterium, the two
resulting isomers would be enantiomers (because there are no other
stereo centers anywhere on the molecule). Thus these two hydrogen’s
are enatiotopic.

4. Diasterotopic H’s:
If either of the prochiral hydrogen’s HR or HS is replaced by a
deuterium, a second chiral center is created, and the two resulting
molecules will be diastereomers (one is S,R, one is R,R). Thus, in this
molecule, HR and HS are referred to as diastereotopic hydrogen’s.

5. Homotopic H’s:
Finally, hydrogen’s that can be designated neither enantiotopic nor
diastereotopic are called homotopic. If homotopic hydrogen is replaced
by deuterium, a chiral center is not created. The three hydrogen atoms
on the methyl (CH3) group of ethanol (and on any methyl group) are
homotopic.