The document discusses racemization and resolution of enantiomers. Racemization is the process where an enantiomer converts to a racemic mixture. Resolution separates the enantiomers of a racemic mixture. Various mechanisms of racemization are described, including those involving carbanions, carbonium ions, free radicals, and stable symmetrical intermediates. Methods of resolution discussed include crystallization, formation of diastereomers, chromatography, equilibrium asymmetric transformations, kinetic asymmetric transformations, biochemical transformations, and inclusion compounds.
Biphenyl derivatives & Atropisomerism:Optical activity in Biphenyls, Stereochemistry of biphenyl derivatives, rules and assigning RS configuration to biphenyls
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The Schmidt reaction is an organic reaction in which an azide reacts with a carbonyl derivative, usually a aldehyde, ketone, or carboxylic acid, under acidic conditions to give an amine or amide, with expulsion of nitrogen
Rearrangement to Electron Deficient Carbon
Rearrangement to Electron Deficient Nitrogen
Rearrangement to Electron Deficient Oxygen
Rearrangement to Electron-Rich Carbon
Aromatic Rearrangements
An organic species which has a carbon atom bearing only six electrons in its outermost shell and has a positive charge is called carbocation.
The positively charged carbon of carbocation is sp2 hybridized.
The unhybridized p-orbital remains vacant.
They are highly reactive and act as reaction intermediate.
They are also called carbonium ion.
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PTC IS THE PHASE TRANSFER CATALYSIS HERE TYPES OF PTC ARE DISCUSSED , THEORIES OF CATALYSIS AND MECHANISM OF PTC, ADVANTAGES OF PTC, APPLICATION OF PTC
The Schmidt reaction is an organic reaction in which an azide reacts with a carbonyl derivative, usually a aldehyde, ketone, or carboxylic acid, under acidic conditions to give an amine or amide, with expulsion of nitrogen
Rearrangement to Electron Deficient Carbon
Rearrangement to Electron Deficient Nitrogen
Rearrangement to Electron Deficient Oxygen
Rearrangement to Electron-Rich Carbon
Aromatic Rearrangements
An organic species which has a carbon atom bearing only six electrons in its outermost shell and has a positive charge is called carbocation.
The positively charged carbon of carbocation is sp2 hybridized.
The unhybridized p-orbital remains vacant.
They are highly reactive and act as reaction intermediate.
They are also called carbonium ion.
Cyclohexane exists in different conformations viz chair, boat, twist boat and half chair. These conformations possess different energies. Therefore they differ in energy.
THIS PRESENTATION COVER INTRODUCTION, STRUCTURE, AROMATICITY, RESONANCE, BASICITY, PHYSICAL PROPERTIES, SYNTHESIS, CHEMICAL PROPERTIES AND MEDICAL USES OF PYRIDINE AND PYRIMIDINE
PTC IS THE PHASE TRANSFER CATALYSIS HERE TYPES OF PTC ARE DISCUSSED , THEORIES OF CATALYSIS AND MECHANISM OF PTC, ADVANTAGES OF PTC, APPLICATION OF PTC
Asymmetric synthesis (As per new syllabus of PCI)
Methods of asymmetric synthesis using chiral pool
Chiral auxiliaries and catalytic asymmetric synthesis
Enantiopure seperation
Stereoselective synthesis
Recent advances
References
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The French Revolution, which began in 1789, was a period of radical social and political upheaval in France. It marked the decline of absolute monarchies, the rise of secular and democratic republics, and the eventual rise of Napoleon Bonaparte. This revolutionary period is crucial in understanding the transition from feudalism to modernity in Europe.
For more information, visit-www.vavaclasses.com
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Letter from the Congress of the United States regarding Anti-Semitism sent June 3rd to MIT President Sally Kornbluth, MIT Corp Chair, Mark Gorenberg
Dear Dr. Kornbluth and Mr. Gorenberg,
The US House of Representatives is deeply concerned by ongoing and pervasive acts of antisemitic
harassment and intimidation at the Massachusetts Institute of Technology (MIT). Failing to act decisively to ensure a safe learning environment for all students would be a grave dereliction of your responsibilities as President of MIT and Chair of the MIT Corporation.
This Congress will not stand idly by and allow an environment hostile to Jewish students to persist. The House believes that your institution is in violation of Title VI of the Civil Rights Act, and the inability or
unwillingness to rectify this violation through action requires accountability.
Postsecondary education is a unique opportunity for students to learn and have their ideas and beliefs challenged. However, universities receiving hundreds of millions of federal funds annually have denied
students that opportunity and have been hijacked to become venues for the promotion of terrorism, antisemitic harassment and intimidation, unlawful encampments, and in some cases, assaults and riots.
The House of Representatives will not countenance the use of federal funds to indoctrinate students into hateful, antisemitic, anti-American supporters of terrorism. Investigations into campus antisemitism by the Committee on Education and the Workforce and the Committee on Ways and Means have been expanded into a Congress-wide probe across all relevant jurisdictions to address this national crisis. The undersigned Committees will conduct oversight into the use of federal funds at MIT and its learning environment under authorities granted to each Committee.
• The Committee on Education and the Workforce has been investigating your institution since December 7, 2023. The Committee has broad jurisdiction over postsecondary education, including its compliance with Title VI of the Civil Rights Act, campus safety concerns over disruptions to the learning environment, and the awarding of federal student aid under the Higher Education Act.
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Biological screening of herbal drugs: Introduction and Need for
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2. Introduction
Racemisation is the process when the
enantiomer is converted into racemic
modification
Resolution is the process when a racemic
modification is separated into its
constituent enantiomers.
Racemisation and Resolution are
complementary to each other.
7. Mechanism involving carbonium ions
Recombination of
anion
gives racemic mix.
R
1
R
2
C
R
3
Cl R
2
C
+
R
1
R
3
-Cl-
acid
+/-
carbonium
8. Mechanism involving free radical
Free radical has a near planar structure
and if a chiral centre is converted into a
free radical pair by homolytic cleavage of
a bond, the recombination of pair leads to
racemic product
R
1
R
2
C
R
3
+ Cl
R
2
C
R
1
R
3
Cl
Cl C
R
3
R
1
R
2
12. Methods of resolution
By crystallisation method
Through formation of diastereomers
By chromatography
Through equilibrium asymmetric
transformation
Through kinetic asymmetric
transformation
By biochemical transformation
Through inclusion compounds
15. By chromatography
RESOLUTION IN FOUR WAYS :
FORMATION OF DIASTEREOMERS AND
THEN SEPARATION
DIRECT RESOLUTION USING CHIRAL
STATIONARY PHASE
DIRECT RESOLUTION USING ACHIRAL
MOBILE PHASE
DIRECT RESOLUTION USING ACHIRAL
STATIONARY PHASE MODIFIED BY CHIRAL
REAGENT
16.
17. Resolution through equilibrium
asymmetric transformation
In this, resolution involve 2 steps:
1. Epimerisation of diastereotopic species
2. Precipitation of the predominant epimer
This combination of epimerisation and
precipitation is known as second order
asymmetric transformation.
19. Resolution by biochemical transformation
Chiral reagents are replaced by
microorganisms or enzymes which are
stereoselective in their reactions.
It is mainly used in resolution in amino
acids.
20. Through inclusion compounds
An inclusion compound is a complex in
which one chemical compound (the
"host") forms a cavity in which molecules
of a second "guest" compound are
located.
If the spaces in the host lattice are
enclosed on all sides so that the guest
species is ‘trapped’ as in a cage, the
compound is known as a clathrate.
This method is of little practical use.
