1. Carbenes are neutral molecules containing a divalent carbon atom with six electrons and two substituents. They exist as either singlet or triplet states depending on the electronic spin.
2. Carbenes can be generated through reactions such as α-elimination of halogenated compounds with bases, thermal decomposition of diazo compounds, and metal-catalyzed decomposition of diazo carbonyl compounds.
3. Carbenes undergo several types of reactions including insertion into bonds, addition to multiple bonds, and rearrangements. Notable reactions include C-H and N-H insertions, cyclopropanation of alkenes, and Wolff rearrangement to form ketenes.
A carbene is any neutral carbon species which contains a non-bonding valance pair of electrons.
Contributed by Alison Brown & Nathan Buehler, Undergraduates, University of Utah
A carbene is any neutral carbon species which contains a non-bonding valance pair of electrons.
Contributed by Alison Brown & Nathan Buehler, Undergraduates, University of Utah
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
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
Neighboring group participation, mechanism, groups, consequencesAMIR HASSAN
Neighboring group participation, mechanism, groups, consequences (FROM ORGANIC CHEMISTRY) by AMIR HASSAN OF GOVT. POST GRADUATE COLLAGE MARDAN, KPK, PAKISTAN.
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.
Retrosynthetic analysis, definition, importance, disconnection approach, one group two group disconnection logical and illogical disconnection approach compounds containing two nitrogen atom retrosynthetic analysis of camphor, cartisone, reserpine
more chemistry contents are available
1. pdf file on Termmate: https://www.termmate.com/rabia.aziz
2. YouTube: https://www.youtube.com/channel/UCKxWnNdskGHnZFS0h1QRTEA
3. Facebook: https://web.facebook.com/Chemist.Rabia.Aziz/
4. Blogger: https://chemistry-academy.blogspot.com/
photo redox reactions
Rearrangement to Electron Deficient Carbon
Rearrangement to Electron Deficient Nitrogen
Rearrangement to Electron Deficient Oxygen
Rearrangement to Electron-Rich Carbon
Aromatic Rearrangements
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
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
Neighboring group participation, mechanism, groups, consequencesAMIR HASSAN
Neighboring group participation, mechanism, groups, consequences (FROM ORGANIC CHEMISTRY) by AMIR HASSAN OF GOVT. POST GRADUATE COLLAGE MARDAN, KPK, PAKISTAN.
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.
Retrosynthetic analysis, definition, importance, disconnection approach, one group two group disconnection logical and illogical disconnection approach compounds containing two nitrogen atom retrosynthetic analysis of camphor, cartisone, reserpine
more chemistry contents are available
1. pdf file on Termmate: https://www.termmate.com/rabia.aziz
2. YouTube: https://www.youtube.com/channel/UCKxWnNdskGHnZFS0h1QRTEA
3. Facebook: https://web.facebook.com/Chemist.Rabia.Aziz/
4. Blogger: https://chemistry-academy.blogspot.com/
photo redox reactions
Rearrangement to Electron Deficient Carbon
Rearrangement to Electron Deficient Nitrogen
Rearrangement to Electron Deficient Oxygen
Rearrangement to Electron-Rich Carbon
Aromatic Rearrangements
Introduction to benzene, orbital picture, resonance in benzene, Huckel‟s rule
Reactions of benzene - nitration, sulphonation, halogenation- reactivity, Friedel- Craft‟s alkylation- reactivity, limitations, Friedel-Craft‟s acylation.
Substituents, effect of substituents on reactivity and orientation of mono substituted benzene compounds towards electrophilic substitution reaction.
I hope You all like it. I hope It is very beneficial for you all. I really thought that you all get enough knowledge from this presentation. This presentation is about materials and their classifications. After you read this presentation you knowledge is not as before.
How to Split Bills in the Odoo 17 POS ModuleCeline George
Bills have a main role in point of sale procedure. It will help to track sales, handling payments and giving receipts to customers. Bill splitting also has an important role in POS. For example, If some friends come together for dinner and if they want to divide the bill then it is possible by POS bill splitting. This slide will show how to split bills in odoo 17 POS.
How to Make a Field invisible in Odoo 17Celine George
It is possible to hide or invisible some fields in odoo. Commonly using “invisible” attribute in the field definition to invisible the fields. This slide will show how to make a field invisible in odoo 17.
The Indian economy is classified into different sectors to simplify the analysis and understanding of economic activities. For Class 10, it's essential to grasp the sectors of the Indian economy, understand their characteristics, and recognize their importance. This guide will provide detailed notes on the Sectors of the Indian Economy Class 10, using specific long-tail keywords to enhance comprehension.
For more information, visit-www.vavaclasses.com
How to Create Map Views in the Odoo 17 ERPCeline George
The map views are useful for providing a geographical representation of data. They allow users to visualize and analyze the data in a more intuitive manner.
Model Attribute Check Company Auto PropertyCeline George
In Odoo, the multi-company feature allows you to manage multiple companies within a single Odoo database instance. Each company can have its own configurations while still sharing common resources such as products, customers, and suppliers.
This is a presentation by Dada Robert in a Your Skill Boost masterclass organised by the Excellence Foundation for South Sudan (EFSS) on Saturday, the 25th and Sunday, the 26th of May 2024.
He discussed the concept of quality improvement, emphasizing its applicability to various aspects of life, including personal, project, and program improvements. He defined quality as doing the right thing at the right time in the right way to achieve the best possible results and discussed the concept of the "gap" between what we know and what we do, and how this gap represents the areas we need to improve. He explained the scientific approach to quality improvement, which involves systematic performance analysis, testing and learning, and implementing change ideas. He also highlighted the importance of client focus and a team approach to quality improvement.
Palestine last event orientationfvgnh .pptxRaedMohamed3
An EFL lesson about the current events in Palestine. It is intended to be for intermediate students who wish to increase their listening skills through a short lesson in power point.
The Roman Empire A Historical Colossus.pdfkaushalkr1407
The Roman Empire, a vast and enduring power, stands as one of history's most remarkable civilizations, leaving an indelible imprint on the world. It emerged from the Roman Republic, transitioning into an imperial powerhouse under the leadership of Augustus Caesar in 27 BCE. This transformation marked the beginning of an era defined by unprecedented territorial expansion, architectural marvels, and profound cultural influence.
The empire's roots lie in the city of Rome, founded, according to legend, by Romulus in 753 BCE. Over centuries, Rome evolved from a small settlement to a formidable republic, characterized by a complex political system with elected officials and checks on power. However, internal strife, class conflicts, and military ambitions paved the way for the end of the Republic. Julius Caesar’s dictatorship and subsequent assassination in 44 BCE created a power vacuum, leading to a civil war. Octavian, later Augustus, emerged victorious, heralding the Roman Empire’s birth.
Under Augustus, the empire experienced the Pax Romana, a 200-year period of relative peace and stability. Augustus reformed the military, established efficient administrative systems, and initiated grand construction projects. The empire's borders expanded, encompassing territories from Britain to Egypt and from Spain to the Euphrates. Roman legions, renowned for their discipline and engineering prowess, secured and maintained these vast territories, building roads, fortifications, and cities that facilitated control and integration.
The Roman Empire’s society was hierarchical, with a rigid class system. At the top were the patricians, wealthy elites who held significant political power. Below them were the plebeians, free citizens with limited political influence, and the vast numbers of slaves who formed the backbone of the economy. The family unit was central, governed by the paterfamilias, the male head who held absolute authority.
Culturally, the Romans were eclectic, absorbing and adapting elements from the civilizations they encountered, particularly the Greeks. Roman art, literature, and philosophy reflected this synthesis, creating a rich cultural tapestry. Latin, the Roman language, became the lingua franca of the Western world, influencing numerous modern languages.
Roman architecture and engineering achievements were monumental. They perfected the arch, vault, and dome, constructing enduring structures like the Colosseum, Pantheon, and aqueducts. These engineering marvels not only showcased Roman ingenuity but also served practical purposes, from public entertainment to water supply.
Instructions for Submissions thorugh G- Classroom.pptxJheel Barad
This presentation provides a briefing on how to upload submissions and documents in Google Classroom. It was prepared as part of an orientation for new Sainik School in-service teacher trainees. As a training officer, my goal is to ensure that you are comfortable and proficient with this essential tool for managing assignments and fostering student engagement.
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
2. CARBENES
Introduction
• A carbene is a molecule containing
neutral carbon atom with a valence of two and two
unshared valence electrons.
•Carbenes are uncharged, electron deficient molecular
species that contain a divalent carbon atom surrounded
by a sextet of electrons, and two substituents.
3. Types of Carbenes
• Carbenes are called singlet or triplet depending on the electronic
spins they possess.
• Triplet carbenes are paramagnetic. The total spin of singlet
carbenes is zero while that of triplet carbenes is one.
• Bond angles are 130-150° for triplet methylene and 100-110° for
singlet methylene.
• Triplet carbenes are generally stable in the gaseous state, while
singlet carbenes occur more often in aqueous media.
4. Structure and bonding
• Singlet carbenes are spin-paired. This molecule adopts an sp2 hybrid
structure.
• Eg- :CH2 :CHPh :CHPh2 :CHR
• Triplet carbenes have two unpaired electrons.
• Most carbenes have a nonlinear triplet ground state, except for those with
nitrogen, oxygen, or sulfur atoms, and halides directly bonded to the divalent
carbon.
• Eg:- :CCl2 :CHCl :C(OMe)2
5. • Singlet state: carbocation-like in nature, trigonal planar
geometry,electrophiliccharacter. . Singlet carbenes generally participate in
cheletropic reactions as either electrophiles or nucleophiles .
• Triplet state: diradical-like in nature, linear geomtry and participate in
stepwise radical additions. Triplet carbenes have to go through an
intermediate with two unpaired electrons whereas singlet carbene can react
in a single concerted step.
6. Cont…..
• Metal carbene complexes have been classified into two broad
classes:
• “Fischer-type” and “Schrocktype”.
7. Fischer Carbenes
• The Fischer-type carbene complexes are low-valent complexes stabilized by
strong -accepting ligands (often CO).
• One or two heteroatoms (O, N, or S) are bonded to the carbine carbon atom
and stabilize it by delocalizing the positive formal charge. The carbene is
formally regarded as a neutral ligand.
• Accordingly, Fischer carbenes are relatively inert, but tend to react as
electrophiles. In general, Fischer carbenes are 18 e–, coordinatively saturated
complexes. Therefore, nucleophilic attack at the metal is not possible.
8. Schrock Carbenes
• The Schrock-type carbene complexes contain an early transition metal
in a formal high oxidation state (often in the d0 electron configuration)
stabilized by strong -donor ligands.
• Most of these complexes have an electron count below 18 and are,
thus, coordinatively unsaturated.
• Therefore, nucleophilic attack at the metal is possible because of the
electron deficiency.
10. Formation of carbenes
• Cabenes are formed by reactions of halogenated compounds
with bases.
1. α elimination of chloroform with base
2. Thermal decomposition of diazo compounds
3. Metal(Rhodium or copper – catalysed decomposition of diazo
carbonylcompound
4. From tosylhydrazones
11. α-elimination of HX or X2 from an organic halide
• α elimination means the eliminations in which both the proton and the leaving
group are located on the same atom.
• A strong base removes an acidic proton adjacent to an electron withdrawing
group to give a carbanion.
• Loss of a leaving group from the carbanion creates a carbene.
• One of the best known elimination reactions occurs when chloroform is treated
with base, forming a dichlorocarbene.
• The more common dehydrogenations (to form alkenes)are called beta(β)
eliminations because the hydrogen and the halogen are lost from adjacent carbon
atoms.
14. Carbene generation via α-elimination under mild non-
basic conditions:
• Thermolysis of sodium trichloroacetate:
• The Simmons-Smith reaction:OH OH
CH2
Zn/Cu
CH2I2 + Zn :CH2 + ZnI2
CH2I2
15. Formation of carbenes from tosylhydrazone
• Tosylhydrazone salts can react with metals to form metal carbenes and used in
cyclopropanations and epoxidations.
• An example of a transition metal-catalyzed cyclopropanation is a synthesis of
tranylcypromine, in which the sodium salt of benzaldehyde tosylhydrazone is
converted to a rhodium metal carbene through the diazo intermediate.
16. Formation reactions of carbenes
a) R2C N N
+ _
h
or
R C R
(singlet)
+ N2
b) R2C C O
h
or
R C R
(singlet)
+ CO
c) RCHX2 + base R CX2
_ _X
_
R C X
d) RCHX2
+ R'Li
(where X = I & Br)
C
H
R
X
Li
R'X
R C H
(carbenoid)
+ LiX
e) RCHX2
+ R'Li CR
X
Li
X
R'H
R C X
(carbenoid)
+ LiX
(where X = F & Cl)
f) CH2I2
Zn-Cu
ether
I CH2 Zn I (Simmons-Smith reagent)
a carbenoid species that reacts stereospecifically
with alkenes to give cyclopropanes but does not
insert into alkane C-H bonds
17. Reactions of carbenes
• Carbenes are highly electrophilic species.
• Three major classes of carbene reactions.
(1) Carbene insertions
(2) Carbene additions
(3) Carbene rearrangements
21. 1.Carbene insertions
• common type of carbene reactions.
• The order of preference is commonly:
• 1. X–H bonds where X is not carbon
• 2. C–H bond
• 3. C–C bond.
• Insertions may or may not occur in single step.
22. • Carbocation usually react with the HOMO of a molecule.
• It will be much more selective about which HOMOs will do.
• For carbenes ,any HOMO will do a lone pair,a C=C or even a C-H
bond.
23. Type of nucleophile Method of insertion
Insertion in a C-H bond
Insertion in a C=C bond
Insertion in an O-H bond
24. • Simple C-H insertion:
• Carbenes can undergo insertion into a C-H bond.
• These insertion reactions create new bonds at completely
unfunctionalized centres.
25. intramolecular insertion and inter
molecular insertion
• Intramolecular insertion reactions present new synthetic
solutions.
• When an intramolecular insertion is possible, no
intermolecular insertions are seen.
26. Carbenes will also insert into other bonds
• Carbene insertion into an O-H bond
Initial attack on the lone pair of hetero atom
• The mechanism involves addition of the oxygen lone pair into an
empty p-orbital on the carbene, followed by proton transfer to
generate a neutral molecule
27. Carbene insertion into an N-H bond - Merck industrial synthesis of
a β-lactam antibiotic.
A synthesis of the class of compound as carbapenam around a rhodium catalysed
carbene insertion into a N-H bond.
28. 2.Carbene addition
• The stereochemistry of carbene addition to alkenes can be used as a
test of whether the carbene is reacting via the singlet or the triplet
spin state:
29. Addition of singlet and triplet carbenes to alkenes.
• Singlet and triplet carbenes do not demonstrate the
same reactivity
• Triplet carbenes should be considered to be diradicals,
and participate in stepwise radical additions.
• Triplet carbenes have to go through an intermediate
with two unpaired electrons whereas singlet carbene
can react in a single concerted step.
30. Alkenes react with singlet carbene in a concerted fashion - alkene
stereochemistry is preserved in the cyclopropane product:
31. Alkenes react with triplet (i.e. diradical) carbene in a stepwise fashion - the alkene
stereochemistry is lost in the cyclopropane product:
33. • Step 1:
• The reaction mechanism of a Buchner ring expansion begins with
carbene formation from ethyl-diazoacetate generated initially
through photochemical or thermal reactions with extrusion of
nitrogen.
• The generated carbene adds to one of the double bonds of benzene
to form the cyclopropane ring.
35. • Wolff rearrangement
• The Wolff rearrangement is a reaction in organic chemistry in
which an α-diazocarbonyl compound is converted into a ketene by
loss of dinitrogen with accompanying 1,2-rearrangement.
• The Wolff rearrangement yields a ketene as an intermediate
product, which can undergo nucleophilic attack with weakly acidic
nucleophiles such as water, alcohols, and amines, to generate
carboxylic acid derivatives
• The Wolff rearrangement can be induced via
thermolysis,photolysis,or transition metal catalysis.
37. Arndt-eistert reaction
• One important application of this reaction is the chain extension of
acyl chlorides to their homologous esters known as the arndt-eistert
reaction.