Formation and reaction of carbenes, nitrenes & free radicals
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Carbenes, nitrenes, and free radicals can be formed through various reactions. Carbenes are formed through alpha-elimination reactions of halogenated compounds with bases or through catalyzed decomposition of diazo carbonyl compounds. Carbenes undergo insertion, addition, and rearrangement reactions. Nitrenes are formed through protolytic, thermal, or base-catalyzed elimination reactions or from sulfinylamines via pyrolysis. Nitrenes can insert into carbon-hydrogen bonds. Free radicals are generated through thermolysis or photolysis of organic peroxides and azo compounds and undergo substitution and chain reactions.
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FREE RADICALS , CARBENES AND NITRENES.pptx
This document discusses free radicals, carbenes, and nitrenes. It defines each type of species, describes their characteristics such as electronic structure and stability. The document outlines different types for each species and methods for their formation and synthetic applications. Free radicals form through bond homolysis and vary in stability based on alkyl substituents. Carbenes are divalent carbon species that exist as singlet or triplet forms with different hybridizations. Nitrenes are analogous to carbenes but with nitrogen and vary in stability and spin state. Examples of formation and trapping methods are provided along with sample synthetic reactions for each reactive intermediate.
Nitrenes - Bebeto . G
Nitrenes are nitrogen analogues of carbenes that contain no charge and are highly reactive and electrophilic. They exist in both singlet and triplet states, with the triplet state being more stable due to the presence of unpaired electrons. Nitrenes can be generated from acyl and alkyl azides, from sulphinylamine, or through insertion reactions. Important reactions involving nitrenes include the Beckmann rearrangement, Hofmann bromamide reaction, Curtius rearrangement, Lossen rearrangement, and Schmidt rearrangement.
DISCONNECTION-retrosynthesis.pptx
An approach for designing organic synthesis which involves breaking down of target molecule into available starting material by imaginary breaking of bonds (disconnection) and/or by functional group interconversion is known as disconnection approach or retrosynthesis or synthesis backward.
The C-X disconnection approach is mainly applicable to a carbon chain attached to any of the heteroatoms like O, N, or S. Here, a bond joins the heteroatom (X) to the rest of the molecule like a C-O, C-N, or C-S group. This point is good point to initiate a disconnection. This is called a ‘One-group’ C-X disconnection as one would need to identify only one functional group like ester, ether, amide etc. to make the disconnection.
How to choose a disconnection?
These are the few general strategy which are important points introduced which apply to the whole of synthetic design rather than one particular area. The main choice is between the various disconnection, even such a simple disconnection as the following alcohol can be disconnected.
We want to get back to simple starting materials and we shall do if we disconnect the bond which are:
Towards the middle of the molecule thereby breaking into two reasonably equal halves rather than chopping off one or two carbon atoms from the end and,
At a branch as this is more likely to give straight chain fragments and these are more likely to be available.
Disconnections very often take place immediately adjacent to, or very close to functional groups in the target molecule. This is pretty much inevitable, given that functionality almost invariably arises from the forward reaction.
A simple example is the weedkiller propanil used on rice fields. Amide disconnection gives amine obviously made from o-dichlorobenzene by nitration and reduction. All positions around the ring in o-dichlorobenzene are about the same electronically but steric hindrance will lead to dichloronitrobenzene being the major product
This compound was needed for some research into the mechanisms of rearrangements. We can disconnect on either side of the ether oxygen atom, but (b) is much better because (a) does not correspond to a reliable reaction: it might be hard to control selective alkylation of the primary hydroxyl group in the presence of the secondary one.
The disconnections we have made so far have all been of C–O, C–N, or C–S bonds, but, of course, the most important reactions in organic synthesis are those that form C–C bonds. We can analyze C–C disconnections in much the same way as we’ve analyzed C–X disconnections.
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Nitrenes are nitrogen analogues of carbenes that contain no charge and are highly reactive and electrophilic. They exist in both singlet and triplet states, with the triplet state being more stable due to the presence of unpaired electrons. Nitrenes can be generated from acyl and alkyl azides, from sulphinylamine, or through insertion reactions. Important reactions involving nitrenes include the Beckmann rearrangement, Hofmann bromamide reaction, Curtius rearrangement, Lossen rearrangement, and Schmidt rearrangement.
DISCONNECTION-retrosynthesis.pptx
An approach for designing organic synthesis which involves breaking down of target molecule into available starting material by imaginary breaking of bonds (disconnection) and/or by functional group interconversion is known as disconnection approach or retrosynthesis or synthesis backward.
The C-X disconnection approach is mainly applicable to a carbon chain attached to any of the heteroatoms like O, N, or S. Here, a bond joins the heteroatom (X) to the rest of the molecule like a C-O, C-N, or C-S group. This point is good point to initiate a disconnection. This is called a ‘One-group’ C-X disconnection as one would need to identify only one functional group like ester, ether, amide etc. to make the disconnection.
How to choose a disconnection?
These are the few general strategy which are important points introduced which apply to the whole of synthetic design rather than one particular area. The main choice is between the various disconnection, even such a simple disconnection as the following alcohol can be disconnected.
We want to get back to simple starting materials and we shall do if we disconnect the bond which are:
Towards the middle of the molecule thereby breaking into two reasonably equal halves rather than chopping off one or two carbon atoms from the end and,
At a branch as this is more likely to give straight chain fragments and these are more likely to be available.
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A simple example is the weedkiller propanil used on rice fields. Amide disconnection gives amine obviously made from o-dichlorobenzene by nitration and reduction. All positions around the ring in o-dichlorobenzene are about the same electronically but steric hindrance will lead to dichloronitrobenzene being the major product
This compound was needed for some research into the mechanisms of rearrangements. We can disconnect on either side of the ether oxygen atom, but (b) is much better because (a) does not correspond to a reliable reaction: it might be hard to control selective alkylation of the primary hydroxyl group in the presence of the secondary one.
The disconnections we have made so far have all been of C–O, C–N, or C–S bonds, but, of course, the most important reactions in organic synthesis are those that form C–C bonds. We can analyze C–C disconnections in much the same way as we’ve analyzed C–X disconnections.
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This document summarizes information about haloalkanes and haloarenes. It discusses the formation, classification, properties and reactions of alkyl halides and aryl halides.
Key points include:
1) Haloalkanes are formed by replacing a hydrogen atom in an alkane with a halogen atom. Haloarenes are formed similarly by replacing hydrogen in an aromatic hydrocarbon.
2) Alkyl halides and aryl halides can be classified based on the number of halogen substituents as well as their position on the carbon chain or ring.
3) The physical properties of haloalkanes and haloarenes, such as melting point and boiling point, depend on factors like the
Organic chemistry reactions
The document provides information about various organic chemistry reactions including the Baeyer-Villiger oxidation, Shapiro reaction, Suzuki coupling, ozonolysis, and Michael reaction. It discusses the reaction mechanisms, applications in synthesis, and key steps for each reaction. Examples are given of uses in synthesizing natural products and complex molecules.
Org.chem_Lecture_5_Haloderivatives.pptx
Halohydrocarbons are derivatives of hydrocarbons where one or more hydrogen atoms are replaced by halogen atoms. There are several types including alkyl halides, aryl halides, vinyl halides, and benzyl halides. Halohydrocarbons can undergo nucleophilic substitution and elimination reactions. The reactivity depends on factors like the stability of carbocation intermediates, the nature of the leaving group, and solvent polarity. Vinyl and aryl halides are more resistant to substitution due to conjugation effects.
NUCLEOPHILIC SUBSTITUTION REACTION &.pptx
Nucleophilic substitution reactions are a class of reactions in which an electron rich nucleophile attacks a positively charged electrophile to replace a leaving group. For alginate reactions, the most reactive nucleophile is the C6 carboxylate group
2020_Reaction_of_Carbocations_Carbenes_and_Radicals_ALL.pdf
The document discusses reactions involving carbocation, carbene, and radical intermediates. It covers topics such as carbon-carbon bond formation reactions involving carbocations, rearrangements of carbocations, fragmentation reactions, the structure and reactivity of carbenes, generation of carbenes, addition and insertion reactions of carbenes, generation and reactions of ylides by carbene decomposition, rearrangement reactions of carbenes, and reactions involving nitrene and related intermediates. The document provides detailed mechanistic explanations and examples of many organic reactions that proceed through these reactive intermediate species.
Latha Chemistry ppt.pptx
Aldehydes and ketones contain a carbonyl group (>C=O) and can undergo numerous reactions. In aldehydes, the carbonyl is bonded to one alkyl group and one hydrogen. In ketones, it is bonded to two alkyl groups. Common reactions include reduction to alcohols using LiAlH4 or NaBH4, addition of Grignard reagents, and reactions involving the acidic alpha-hydrogens like benzoin condensation, Cannizzaro reaction, and Clemmenson reduction. Other important reactions are the Wittig reaction, Knoevenagel condensation, Wolf-Kishner reduction, and Baeyer-Villiger oxidation.
Important Name reaction
Name reactions:Clemmensen reduction, Darzens condensation, Diels Alder, Eschweiler-Clarke, Friedel-Crafts, Grinard, HofmanMannich, Michael, Meerwin- Pondorf- Verley, Perkin, Reformatsky, Reimer-Tiemann,, Witting and Wolf-Kishner reduction, Aldol condensation.
ch09_Chem221.ppt
1) Radical reactions involve the cleavage of covalent bonds through homolysis to form reactive radical species with unpaired electrons.
2) Radicals react by pairing their unpaired electrons, such as through hydrogen abstraction. Their reactivity depends on the stability of the radical, which is influenced by factors like molecular structure.
3) Homolytic bond dissociation energies provide a measure of how much energy is required to break a covalent bond and form radicals. These energies can be used to determine the thermodynamics of radical reactions.
Name Reactions part 1 sem iv poc iii
Name Reactions of synthetic importance
Pinacol-Pinacolone, Hofmann, Baeyer-Villiger oxidation, Benzilic acid rearrangement
reaction, Beckmann’s rearrangement and Schmidt rearrangement
S & Suzuki Reaction.pptx
The document summarizes the Suzuki reaction and Shapiro reaction. The Suzuki reaction is a palladium-catalyzed cross-coupling reaction between organoboron compounds and organic halides or triflates that forms carbon-carbon sigma bonds, especially for synthesizing biaryl compounds. It proceeds through oxidative addition, transmetallation, and reductive elimination steps. The Shapiro reaction involves the base-catalyzed decomposition of tosyl hydrazones of aldehydes and ketones into olefins upon reaction with organolithium compounds at -78°C. It proceeds via deprotonation of the tosylhydrazone to form a diazo compound and an alkenyllithium
Shapiro & Suzuki Reaction in powerpointt
The document summarizes the Suzuki reaction and Shapiro reaction. The Suzuki reaction is a palladium-catalyzed cross-coupling reaction between organoboron compounds and organic halides that forms carbon-carbon sigma bonds, particularly for synthesizing biaryl compounds. It proceeds through oxidative addition, transmetallation, and reductive elimination steps. The Shapiro reaction involves the base-catalyzed decomposition of tosyl hydrazones of aldehydes and ketones into olefins upon reaction with organolithium compounds as a base at -78°C. It proceeds through deprotonation of the tosylhydrazone to form a diazo compound and an alkenyllithium intermediate
Generation and sources of free radicals in human.pptx
This document discusses the generation and sources of free radicals in the human body. There are several ways that free radicals are generated, including photolysis (decomposition using light), thermolysis (decomposition using heat), and redox reactions. Specific examples of compounds that generate free radicals through these processes include peroxides, azo compounds, and ketones. Free radicals are also generated through internal biological sources like mitochondria and enzymes, as well as external sources like cigarette smoke, pollution, radiation, and solvents. Physiological stress and disease states can further influence free radical production levels in the body.
Baeyer Villiger Oxidation of Ketones, Cannizzaro Reaction, MPV
The document summarizes several organic chemistry reactions:
1) The Baeyer-Villiger oxidation reaction involves the oxidation of ketones with peroxy acids to form esters through a rearrangement reaction.
2) The Cannizzaro reaction involves the base-induced disproportionation of two aldehyde molecules to form a carboxylic acid and primary alcohol.
3) The Meerwein-Ponndorf-Verley (MPV) reduction uses aluminum isopropoxide catalyst in isopropanol to reduce aldehydes and ketones to the corresponding alcohols through a reversible reaction.
Hsslive-xii-chemistry-Haloalkane and Haloarenes.pdf
1. The document discusses halogen compounds and their synthesis. It describes how halogen atoms can substitute hydrogen atoms in hydrocarbons to form haloalkanes and haloarenes.
2. Haloalkanes and haloarenes can be prepared by several methods including free radical halogenation of alkanes, halogenation of alkenes, and electrophilic aromatic substitution for arenes.
3. The properties and reactions of haloalkanes and haloarenes are discussed. Important reactions include nucleophilic substitution and elimination reactions.
Reaction of synthetic importance
B.phram
Semester .4
Subject : Organic chemistry - III
Use as reference and also usable for examination prearation.
gtu afflitited phramacy college's student may using this ppt.
Free radicals
Properties, method of formation, stability, applications, types of reaction mechanisms, radical inhibitors, method of detection of free radicals
ch09_Chem221.pdf
1) Radical reactions involve the cleavage of covalent bonds through homolysis, producing highly reactive radical intermediates.
2) Radicals react by pairing their unpaired electrons, such as through hydrogen abstraction. Their relative stabilities follow trends similar to carbocations.
3) Alkanes undergo substitution reactions with halogens like chlorine and bromine via free radical chain mechanisms under thermal or photolytic conditions, producing mixtures of mono- and polyhalogenated products.
Structure and Reactivity of Carbenes
A supplement to Clayden, Greeves, and Warren's Organic Chemistry, Chapter 40. Covers the first half of the chapter.
Reactions intermediate
This document provides an overview of various carbon-based reaction intermediates including carbocations, carbanions, carbenes, free radicals, nitrenes, and nitrenium ions. It discusses their generation, structure, stability, reactions, and detection methods. Key points include that carbocations are positively charged carbon species that react as electrophiles, while carbanions are negatively charged carbon species that react as nucleophiles. Carbenes contain a carbon with six valence electrons in a triplet or singlet state. Free radicals contain one or more unpaired electrons. Nitrenes and nitrenium ions involve a reactive nitrogen species. Detection methods include NMR, EPR, UV-Vis spectroscopy, and trapping reactions.
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Formation and reaction of carbenes, nitrenes & free radicals
- 1. FORMATION AND REACTION OF CARBENES, NITRENES & FREE RADICALS BY- ASHUTOSH KUMAR SINGH M.PHARM 2020 AMRITA SCHOOL OF PHARMACY
- 2. FORMATION OF CARBENES Carbenes are formed by reactions of halogenated compounds with bases. Alpha elimination of chloroform with base Catalysed decomposition of diazo carbonyl compound( By photolytic, thermal, and transitional metal (Rh,Cu)- catalyzed routes.
- 3. Alpha-elimination of HX or X2 from an organic halide • The elimination in which both the proton and the leaving group are located on same atom • Chloroform is treated with base,forming a dichlorocarbene.
- 4. Catalysed decomposition of diazo carbonyl compound
- 6. REACTIONS OF CARBENES Three major classes of carbenes reaction Carbene insertion Carbene addition Carbene rearrangement
- 7. CARBENE INSERTION:- C-H insertion C-C insertion
- 8. CARBENE REARRANGMENT Wolff rearrangement The wolff rearrangement is a reaction in organic chemistry in which an alpha- diazocarbonyl compound is comverted into ketene by loss of dinitrogen with accompanying 1,2-rearrangement.
- 9. GENERATION OF NITRINES :- Like carbenes they are also generated by protolytic, thermal or base catalyzed alpha- elimination reaction. From sulfinylamines:- pyrolysis of sulfinylamine gives nitrenes Eg:-
- 10. REACTION OF NITRENES (a) Insertion:- A nitrene can easily insert into a carbon to hydrogen covalent bond yielding an amine or amide. A singlet nitrene reacts with retention of configuration.
- 11. (b)
- 12. FREE RADICAL Thermolysis or photolysis of organic peroxides and azo compounds generates free radicals.
- 13. Stabilization of free radicals: Resonance effect due to conjugation stabilizes the free radical.
- 14. REACTION OF FREE RADICAL A radical substitution reaction is a reaction which occurs by a free radical mechanism and results in the substitution of one or more of the atoms or groups present in the substrate by different atoms or groups. The initiation step in a radical chain reaction is the step in which a free radical is first produced. A termination step of a radical chain reaction is one in which two radicals react together in some way so that the chain can no longer be propagated.