Prochirality refers to a molecule that can be converted from achiral to chiral. Specifically, an achiral molecule containing a prochiral center can form two chiral isomers upon substitution. Prochiral molecules use the R/S notation to label identical substituents around the prochiral center. For example, the two hydrogens on a prochiral carbon in ethanol are labeled R and S. These hydrogens can be classified as enantiotopic, diastereotopic, or homotopic depending on whether substitution would lead to enantiomers, diastereomers, or no new stereocenter.
Crown ethers
NOMENCLATURE
GENERAL SYNTHESIS OF CROWN ETHER
AZA CROWN
CRYPTAND
APPLICATIONS
1. SYNTHETIC APPLICTION
Esterification
Saponification
Anhydride formation
Potassium permanganate oxidation
Aromatic substitution reactions
Elimination reactions
Displacement reaction
Generation of carbenes
Superoxide anion
Alkylations – 1. o-alkylations
2. c-alkylations
3. n-alkylations
2. ANALYTICAL APPLICATION
Determination of gold in geological samples
Super critical fluid extraction of trace metal from solid and liquid materials
Application of ionic liquids in analytical chemistry
Oxidation and determination of aldehydes
Crown ethers are used in the laboratory as phase transfer catalyst
OTHER APPLICATION
It is used in photocynation
Resolution of racemic mixture
Benzoin condensation
Hetrocyclisation
Synthesis of furanones
Acetylation of secondary amines in presence of primary amine
Crown ethers
NOMENCLATURE
GENERAL SYNTHESIS OF CROWN ETHER
AZA CROWN
CRYPTAND
APPLICATIONS
1. SYNTHETIC APPLICTION
Esterification
Saponification
Anhydride formation
Potassium permanganate oxidation
Aromatic substitution reactions
Elimination reactions
Displacement reaction
Generation of carbenes
Superoxide anion
Alkylations – 1. o-alkylations
2. c-alkylations
3. n-alkylations
2. ANALYTICAL APPLICATION
Determination of gold in geological samples
Super critical fluid extraction of trace metal from solid and liquid materials
Application of ionic liquids in analytical chemistry
Oxidation and determination of aldehydes
Crown ethers are used in the laboratory as phase transfer catalyst
OTHER APPLICATION
It is used in photocynation
Resolution of racemic mixture
Benzoin condensation
Hetrocyclisation
Synthesis of furanones
Acetylation of secondary amines in presence of primary amine
These are chemical shift reagents and solvent induced shifts have their application in resolving the NMR Spectra of complex structures by inducing shift with respect to reference compound. Thus useful in interpretation of structures of complex organic compounds.
BASIC DISCUSSION ABOUT THE CROWN ETHER AND CRYPTAND. INCLUDING THEIR BACKGROUND,STRUCTURE,NOMENCLATURE,CAVITY SIZE, SELECTIVITY, SYNTHESIS AND APPLICATIONS.
Dynamic Stereochemistry and What role does conformation plays on stereochemistry is being exemplified in this presentation. Useful for the Undergraduate and Postgraduates students of Pharmacy, Pharmaceutical Chemistry and Chemical Sciences
These are chemical shift reagents and solvent induced shifts have their application in resolving the NMR Spectra of complex structures by inducing shift with respect to reference compound. Thus useful in interpretation of structures of complex organic compounds.
BASIC DISCUSSION ABOUT THE CROWN ETHER AND CRYPTAND. INCLUDING THEIR BACKGROUND,STRUCTURE,NOMENCLATURE,CAVITY SIZE, SELECTIVITY, SYNTHESIS AND APPLICATIONS.
Dynamic Stereochemistry and What role does conformation plays on stereochemistry is being exemplified in this presentation. Useful for the Undergraduate and Postgraduates students of Pharmacy, Pharmaceutical Chemistry and Chemical Sciences
Key concepts of Geometrical Isomerism useful for the Undergraduate and Postgraduate students of Pharmacy , Chemistry and Post graduates of Pharmaceutical and Medicinal Chemistry
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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.
