This document discusses organic reaction intermediates, specifically carbocations and carbanions. It defines them as positively or negatively charged carbon-containing ions that are formed during chemical reactions and then react further to form final products. The key features, methods of formation, factors affecting stability, and synthetic applications of carbocations and carbanions are described. Inductive effects, resonance effects, and hyperconjugation influence the stability of these intermediates. Carbocations and carbanions are involved in many common organic reaction types such as eliminations, substitutions, additions, and rearrangements.
This document presents information on reactive intermediates. It discusses four main types of reactive intermediates: carbocations, carbanions, free radicals, and carbenes. For each type, it describes examples, structures, factors that influence their stability, and common methods of generation. The document contains 19 slides covering an introduction, the four types of intermediates, conclusions, references, and acknowledgments.
Carbanions are carbon atoms with a negative charge that are formed through various mechanisms. They can be classified based on their formation method such as through heterocyclic cleavage, proton abstraction using a base, decarboxylation, addition of a nucleophile to an alkene, or formation of an organometallic compound. Carbanion stability depends on factors like the electronegativity of the carbon, inductive effects, resonance effects, and attachment to sulfur or phosphorus. Aromatic carbanions and those with electron-withdrawing groups are particularly stable due to resonance delocalization. Carbanions have applications in reactions like the Perkin reaction, Claisen condensation, benzoin condensation,
This document discusses carbanions, which are negatively charged organic species where carbon carries three bond pairs and one lone pair. Carbanions are stabilized through conjugation, resonance effects, field effects, and aromaticity. They are generated through heterolytic bond cleavage or addition of a negative ion to a carbon-carbon multiple bond. As nucleophiles, carbanions undergo reactions such as alpha-halogenation of ketones, additions to carbonyls, nucleophilic acyl substitutions, substitutions with alkyl halides, and Michael additions.
This document discusses carbanions, which are negatively charged carbon-containing species. It describes the structure of carbanions as sp3 hybridized and tetrahedral. Carbanions are stabilized by several factors, including inductive and resonance effects. The stability increases with increased s-character of the carbon atom and delocalization of the negative charge. Carbanions are nucleophilic and can be formed through deprotonation, decarboxylation, metal reduction, or addition to multiple bonds. They have applications in reactions like aldol condensation, Michael addition, Grignard reagents, and the Perkin reaction.
This document summarizes different types of substitution reactions in aliphatic and aromatic compounds. It describes three main types of substitution reactions: free radical substitution, electrophilic substitution, and nucleophilic substitution. Free radical substitution involves radicals and occurs in non-polar solvents. Electrophilic substitution can be aliphatic or aromatic and involves attack by an electrophile. Nucleophilic substitution involves displacement by a nucleophile and can proceed by SN1, SN2, or addition-elimination mechanisms. The document provides examples and details of the mechanisms and factors that influence each type of substitution reaction.
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.
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.
This document discusses organic reaction intermediates, specifically carbocations and carbanions. It defines them as positively or negatively charged carbon-containing ions that are formed during chemical reactions and then react further to form final products. The key features, methods of formation, factors affecting stability, and synthetic applications of carbocations and carbanions are described. Inductive effects, resonance effects, and hyperconjugation influence the stability of these intermediates. Carbocations and carbanions are involved in many common organic reaction types such as eliminations, substitutions, additions, and rearrangements.
This document presents information on reactive intermediates. It discusses four main types of reactive intermediates: carbocations, carbanions, free radicals, and carbenes. For each type, it describes examples, structures, factors that influence their stability, and common methods of generation. The document contains 19 slides covering an introduction, the four types of intermediates, conclusions, references, and acknowledgments.
Carbanions are carbon atoms with a negative charge that are formed through various mechanisms. They can be classified based on their formation method such as through heterocyclic cleavage, proton abstraction using a base, decarboxylation, addition of a nucleophile to an alkene, or formation of an organometallic compound. Carbanion stability depends on factors like the electronegativity of the carbon, inductive effects, resonance effects, and attachment to sulfur or phosphorus. Aromatic carbanions and those with electron-withdrawing groups are particularly stable due to resonance delocalization. Carbanions have applications in reactions like the Perkin reaction, Claisen condensation, benzoin condensation,
This document discusses carbanions, which are negatively charged organic species where carbon carries three bond pairs and one lone pair. Carbanions are stabilized through conjugation, resonance effects, field effects, and aromaticity. They are generated through heterolytic bond cleavage or addition of a negative ion to a carbon-carbon multiple bond. As nucleophiles, carbanions undergo reactions such as alpha-halogenation of ketones, additions to carbonyls, nucleophilic acyl substitutions, substitutions with alkyl halides, and Michael additions.
This document discusses carbanions, which are negatively charged carbon-containing species. It describes the structure of carbanions as sp3 hybridized and tetrahedral. Carbanions are stabilized by several factors, including inductive and resonance effects. The stability increases with increased s-character of the carbon atom and delocalization of the negative charge. Carbanions are nucleophilic and can be formed through deprotonation, decarboxylation, metal reduction, or addition to multiple bonds. They have applications in reactions like aldol condensation, Michael addition, Grignard reagents, and the Perkin reaction.
This document summarizes different types of substitution reactions in aliphatic and aromatic compounds. It describes three main types of substitution reactions: free radical substitution, electrophilic substitution, and nucleophilic substitution. Free radical substitution involves radicals and occurs in non-polar solvents. Electrophilic substitution can be aliphatic or aromatic and involves attack by an electrophile. Nucleophilic substitution involves displacement by a nucleophile and can proceed by SN1, SN2, or addition-elimination mechanisms. The document provides examples and details of the mechanisms and factors that influence each type of substitution reaction.
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.
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.
more chemistry contents are available
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Organic Synthesis:
The Disconnection Approach
One Group C-C Disconnection of Alcohol and Alkene
This document presents an overview of reaction intermediates from a chemistry department presentation. It defines reactants and products, and describes two types of bond cleavage that can produce intermediates: homolytic, forming radicals, and heterolytic, forming ions. Intermediates are short-lived, highly reactive fragments that react further to form final products. Specific types of intermediates discussed include carbon radicals, carbocations, carbanions, radical ions, carbenes, benzynes. Carbon radicals and carbocations are described in more detail regarding their structure and stability.
FREE RADICALS , CARBENES AND NITRENES.pptxtenzinpalmo3
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.
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
1) α,β-Unsaturated carbonyl compounds contain a carbonyl group and a conjugated carbon-carbon double bond separated by one carbon-carbon single bond.
2) These compounds undergo both electrophilic and nucleophilic addition reactions due to the conjugation between the carbonyl and double bond.
3) Common reactions include the Michael addition, in which a carbanion adds to the β-carbon, and the Diels-Alder reaction, where a conjugated diene adds to form a six-membered ring.
The document discusses various reactive intermediates in chemical reactions:
1. Intermediates are chemical species that are neither the starting reactants nor the final products but appear as transient intermediates in step-wise reactions.
2. Common types of reactive intermediates discussed include carbocations, carbanions, free radicals, carbenes, nitrenes, and arenynes.
3. Specific details are provided about the electronic structure and reactivity of each intermediate.
This presentation describes the concept of Hyperconjugation in simple words, gives definition of hyperconjugation, explains why it is called as 'No bond Resonance' and gives the effects of hyperconjugation on the chemical properties of compounds: alkyl cations and their relative stability, alkyl radicals and their relative stability, alkenes and their relative stability, bond length, anomeric effect and Baker - Nathan effect.
1. Carbenes are neutral molecules containing a divalent carbon atom with two unshared valence electrons. They exist in both singlet and triplet states depending on the electronic spin.
2. Carbenes undergo insertion reactions into X-H and C-C bonds. They also add across double bonds, with singlet carbenes preserving alkene stereochemistry and triplet carbenes losing it.
3. Carbenes are generated by reactions such as α-elimination of halogenated compounds with base or decomposition of diazo compounds. They can rearrange through migrations such as the Wolff or Arndt-Eistert reactions.
The document summarizes aromaticity and related topics for chemistry students. It discusses:
- Benzenoid and non-benzenoid aromatic compounds, including their properties and reactions.
- Resonance structures of benzene and how it follows Huckel's rule for aromaticity.
- Classification of compounds based on aromaticity and examples of antiaromatic compounds.
- Aromatic ions and heterocyclic aromatic compounds like pyrrole, furan and pyridine.
Elimination reactions involve the removal of atoms or groups of atoms from adjacent carbons of a molecule, forming multiple bonds. They are endothermic reactions that occur with heat. There are two main types: alpha elimination removes two ligands from the same atom, while beta elimination removes ligands from adjacent carbons. Elimination mechanisms include E1 (unimolecular), E2 (bimolecular), and E1cb (carbocation intermediate). E1 involves carbocation formation in two steps, E2 is a single-step process, and E1cb forms a carbanion intermediate. The type of mechanism depends on factors like the substrate structure and conditions used.
Addition reactions occur when two reactants combine to form a new product with no leftover atoms. In an addition reaction, new groups are added to the starting material, breaking a pi bond and forming two sigma bonds. Addition reactions involve the addition of electrophiles, radicals, or nucleophiles across multiple bonds such as carbon-carbon double or triple bonds.
The document discusses inductive effect and resonance effect. Inductive effect refers to polarization of a sigma bond due to electron withdrawing or donating groups. Electron withdrawing groups have a negative inductive effect (-I) while electron donating groups have a positive inductive effect (+I). Resonance effect refers to delocalization of pi electrons or a lone pair. Electron withdrawing groups have a negative resonance effect (-R) while electron donating groups have a positive resonance effect (+R). In most cases, resonance effect is stronger than inductive effect. The document provides examples of how these effects influence acidity, reactivity, and stability.
This document discusses organic reactions and mechanisms. It defines key terms like substrate, reagent, products, and mechanism. It describes how factors like inductive and mesomeric effects can influence reactions by altering electron density. It also discusses different types of reaction intermediates that can form, such as carbonium ions, carbanions, free radicals, and carbenes. The document classifies reagents as electrophiles or nucleophiles and describes their behaviors. It explains concepts like activation energy and the transition state that systems must go through for a reaction to occur.
The document discusses functional group interconversions (FGIs) in organic synthesis. It defines FGIs as writing one functional group for another to help with retrosynthetic planning. FGIs are important for identifying suitable disconnections in retrosynthesis when a molecule contains multiple functional groups. The document categorizes common functional groups containing heteroatoms, such as carboxylic acids, aldehydes/ketones, and alcohols/amines. It also discusses methods for oxidizing and reducing functional groups, as well as removing functional groups altogether.
The document discusses methodology in organic synthesis, including examples of natural products. It describes convergent and divergent synthesis strategies. Convergent synthesis involves coupling molecular fragments through independent synthesis to improve reaction yields compared to linear synthesis. Divergent synthesis starts from a central core and generates a library of compounds through successive additions. Functional group interconversion and addition techniques are discussed to allow for disconnection of target molecules during retrosynthetic analysis.
This document provides an overview of aromatic electrophilic substitution reactions (AES). It defines important terms like arenium ions, electrophiles, nucleophiles and discusses the effects of substituents on reactivity. The mechanisms of common AES reactions like nitration, sulfonation, Friedel-Crafts alkylation and acylation are covered. The document also discusses topics like the mesomeric and inductive effects of substituents, the synthesis of tribromobenzene, and the relative reactivities of benzene and substituted benzenes in bromination. Examples of AES on phenols, xylenes, cresols and other aromatic compounds are provided.
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.
The document discusses carbocations, which are carbon-containing molecules with a positive charge. It defines different types of carbocations based on the groups attached to the charged carbon atom, such as primary, secondary, tertiary, allylic, benzylic, vinyl, and phenyl carbocations. The document also discusses the structure, stability, and rearrangement of carbocations. Carbocations can rearrange into more stable configurations by shifting bonds to form secondary or tertiary carbocations. The stability of carbocations is affected by the number of carbon groups attached, neighboring electron-withdrawing groups, and hybridization of the charged carbon atom.
Semester - I B) Reactive Intermediates by Dr Pramod R Padolepramod padole
The document discusses various reactive intermediates in organic chemistry, focusing on carbocations and carbanions. It defines carbocations as organic ions with a positively charged carbon atom and carbanions as organic ions with a negatively charged carbon atom. It describes their structures, methods of generation, stability orders, and factors affecting stability such as inductive and resonance effects. Carbocations are more stable with electron-donating groups or resonance, while carbanions are more stable with electron-withdrawing groups or resonance. The document also provides examples and practice questions related to these reactive intermediates.
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/
Organic Synthesis:
The Disconnection Approach
One Group C-C Disconnection of Alcohol and Alkene
This document presents an overview of reaction intermediates from a chemistry department presentation. It defines reactants and products, and describes two types of bond cleavage that can produce intermediates: homolytic, forming radicals, and heterolytic, forming ions. Intermediates are short-lived, highly reactive fragments that react further to form final products. Specific types of intermediates discussed include carbon radicals, carbocations, carbanions, radical ions, carbenes, benzynes. Carbon radicals and carbocations are described in more detail regarding their structure and stability.
FREE RADICALS , CARBENES AND NITRENES.pptxtenzinpalmo3
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.
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
1) α,β-Unsaturated carbonyl compounds contain a carbonyl group and a conjugated carbon-carbon double bond separated by one carbon-carbon single bond.
2) These compounds undergo both electrophilic and nucleophilic addition reactions due to the conjugation between the carbonyl and double bond.
3) Common reactions include the Michael addition, in which a carbanion adds to the β-carbon, and the Diels-Alder reaction, where a conjugated diene adds to form a six-membered ring.
The document discusses various reactive intermediates in chemical reactions:
1. Intermediates are chemical species that are neither the starting reactants nor the final products but appear as transient intermediates in step-wise reactions.
2. Common types of reactive intermediates discussed include carbocations, carbanions, free radicals, carbenes, nitrenes, and arenynes.
3. Specific details are provided about the electronic structure and reactivity of each intermediate.
This presentation describes the concept of Hyperconjugation in simple words, gives definition of hyperconjugation, explains why it is called as 'No bond Resonance' and gives the effects of hyperconjugation on the chemical properties of compounds: alkyl cations and their relative stability, alkyl radicals and their relative stability, alkenes and their relative stability, bond length, anomeric effect and Baker - Nathan effect.
1. Carbenes are neutral molecules containing a divalent carbon atom with two unshared valence electrons. They exist in both singlet and triplet states depending on the electronic spin.
2. Carbenes undergo insertion reactions into X-H and C-C bonds. They also add across double bonds, with singlet carbenes preserving alkene stereochemistry and triplet carbenes losing it.
3. Carbenes are generated by reactions such as α-elimination of halogenated compounds with base or decomposition of diazo compounds. They can rearrange through migrations such as the Wolff or Arndt-Eistert reactions.
The document summarizes aromaticity and related topics for chemistry students. It discusses:
- Benzenoid and non-benzenoid aromatic compounds, including their properties and reactions.
- Resonance structures of benzene and how it follows Huckel's rule for aromaticity.
- Classification of compounds based on aromaticity and examples of antiaromatic compounds.
- Aromatic ions and heterocyclic aromatic compounds like pyrrole, furan and pyridine.
Elimination reactions involve the removal of atoms or groups of atoms from adjacent carbons of a molecule, forming multiple bonds. They are endothermic reactions that occur with heat. There are two main types: alpha elimination removes two ligands from the same atom, while beta elimination removes ligands from adjacent carbons. Elimination mechanisms include E1 (unimolecular), E2 (bimolecular), and E1cb (carbocation intermediate). E1 involves carbocation formation in two steps, E2 is a single-step process, and E1cb forms a carbanion intermediate. The type of mechanism depends on factors like the substrate structure and conditions used.
Addition reactions occur when two reactants combine to form a new product with no leftover atoms. In an addition reaction, new groups are added to the starting material, breaking a pi bond and forming two sigma bonds. Addition reactions involve the addition of electrophiles, radicals, or nucleophiles across multiple bonds such as carbon-carbon double or triple bonds.
The document discusses inductive effect and resonance effect. Inductive effect refers to polarization of a sigma bond due to electron withdrawing or donating groups. Electron withdrawing groups have a negative inductive effect (-I) while electron donating groups have a positive inductive effect (+I). Resonance effect refers to delocalization of pi electrons or a lone pair. Electron withdrawing groups have a negative resonance effect (-R) while electron donating groups have a positive resonance effect (+R). In most cases, resonance effect is stronger than inductive effect. The document provides examples of how these effects influence acidity, reactivity, and stability.
This document discusses organic reactions and mechanisms. It defines key terms like substrate, reagent, products, and mechanism. It describes how factors like inductive and mesomeric effects can influence reactions by altering electron density. It also discusses different types of reaction intermediates that can form, such as carbonium ions, carbanions, free radicals, and carbenes. The document classifies reagents as electrophiles or nucleophiles and describes their behaviors. It explains concepts like activation energy and the transition state that systems must go through for a reaction to occur.
The document discusses functional group interconversions (FGIs) in organic synthesis. It defines FGIs as writing one functional group for another to help with retrosynthetic planning. FGIs are important for identifying suitable disconnections in retrosynthesis when a molecule contains multiple functional groups. The document categorizes common functional groups containing heteroatoms, such as carboxylic acids, aldehydes/ketones, and alcohols/amines. It also discusses methods for oxidizing and reducing functional groups, as well as removing functional groups altogether.
The document discusses methodology in organic synthesis, including examples of natural products. It describes convergent and divergent synthesis strategies. Convergent synthesis involves coupling molecular fragments through independent synthesis to improve reaction yields compared to linear synthesis. Divergent synthesis starts from a central core and generates a library of compounds through successive additions. Functional group interconversion and addition techniques are discussed to allow for disconnection of target molecules during retrosynthetic analysis.
This document provides an overview of aromatic electrophilic substitution reactions (AES). It defines important terms like arenium ions, electrophiles, nucleophiles and discusses the effects of substituents on reactivity. The mechanisms of common AES reactions like nitration, sulfonation, Friedel-Crafts alkylation and acylation are covered. The document also discusses topics like the mesomeric and inductive effects of substituents, the synthesis of tribromobenzene, and the relative reactivities of benzene and substituted benzenes in bromination. Examples of AES on phenols, xylenes, cresols and other aromatic compounds are provided.
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.
The document discusses carbocations, which are carbon-containing molecules with a positive charge. It defines different types of carbocations based on the groups attached to the charged carbon atom, such as primary, secondary, tertiary, allylic, benzylic, vinyl, and phenyl carbocations. The document also discusses the structure, stability, and rearrangement of carbocations. Carbocations can rearrange into more stable configurations by shifting bonds to form secondary or tertiary carbocations. The stability of carbocations is affected by the number of carbon groups attached, neighboring electron-withdrawing groups, and hybridization of the charged carbon atom.
Semester - I B) Reactive Intermediates by Dr Pramod R Padolepramod padole
The document discusses various reactive intermediates in organic chemistry, focusing on carbocations and carbanions. It defines carbocations as organic ions with a positively charged carbon atom and carbanions as organic ions with a negatively charged carbon atom. It describes their structures, methods of generation, stability orders, and factors affecting stability such as inductive and resonance effects. Carbocations are more stable with electron-donating groups or resonance, while carbanions are more stable with electron-withdrawing groups or resonance. The document also provides examples and practice questions related to these reactive intermediates.
This document discusses various reaction intermediates including carbocations, carbanions, carbenes, free radicals, nitrenes, and nitrenium ions. It provides details on their generation, structure, stability, and common reactions. Carbocations are discussed including factors that stabilize them such as hyperconjugation. The document also covers detection methods for different reaction intermediates including NMR spectroscopy and electron paramagnetic resonance spectroscopy.
Organic intermediates and reaction transformations discusses carbocations, carbanions, and radicals as reactive intermediates in organic reactions. Aromatic systems including heterocycles with various ring sizes are also covered. Two examples of reactions that form useful drugs and dyes are provided. The document focuses on short-lived reactive intermediates and how they are involved in organic transformations.
Organic intermediates and reaction transformations discusses carbocations, carbanions, and radicals as reactive intermediates in organic reactions. Aromatics and heterocycles are examined, specifically discussing their structure and stability. Organic transformations are used to make drugs and dyes by targeting specific disease pathways.
Carbocations are positively charged carbon ions with six electrons. They are planar and sp2 hybridized with bond angles of 120°. Carbocations can form from alkenes and alkyl diazonium salts. Tertiary carbocations are the most stable due to hyperconjugation. Carbocations can undergo addition and elimination reactions. The Wagner-Meerwein rearrangement involves carbocation rearrangement, while the pinacol rearrangement converts vicinal diols to carbonyl compounds.
This document provides an introduction to organic reaction mechanisms, focusing on carbanions. It defines carbanions as anions with a negative charge on a carbon atom. Carbanions are formed through heterolytic bond cleavage, removing a proton or other group from a carbon. They are stabilized through various effects, including induction, s-character of the carbon hybrid orbital, resonance, and aromaticity in some cyclic carbanions. Carbanions act as nucleophiles and undergo addition, substitution, and rearrangement reactions. Their configuration depends on conjugation, with unconjugated carbanions being pyramidal and conjugated ones having planar geometry.
This document discusses reaction intermediates in organic chemistry reactions. It defines reaction intermediates as transient species that exist between reactants and products but cannot be isolated. The main types of reaction intermediates discussed are:
1) Free radicals which have unpaired electrons and are reactive species
2) Carbonium ions which are carbocations with a positively charged carbon atom
3) Factors that influence the stability of carbonium ions such as substituents, conjugation, and resonance structures
Hydrocarbons are organic compounds composed of carbon and hydrogen. They can be classified as saturated, unsaturated, or aromatic based on the presence of carbon-carbon double or triple bonds or aromatic rings. Saturated hydrocarbons contain only single bonds and include alkanes such as methane and propane. Unsaturated hydrocarbons contain double or triple bonds and include alkenes like ethene and alkynes like ethyne. Aromatic hydrocarbons contain aromatic rings, with benzene being the simplest example. Alkanes undergo substitution and combustion reactions. They can also be synthesized from unsaturated hydrocarbons through hydrogenation or from carboxylic acids via decarboxylation.
Alkanes are saturated hydrocarbons that contain only carbon-carbon single bonds. They have the general formula CnH2n+2. Alkanes can be represented by structural formulas that show the specific arrangement of atoms in the molecule. Structural isomers are possible for alkanes with five or more carbons. Alkanes are prepared through hydrogenation of alkenes and alkynes, decarboxylation of fatty acids, and reduction of alkyl halides. They undergo halogenation reactions to form alkyl halides. Physical properties like boiling point increase with increasing molecular size and branching decreases boiling point.
1) The document introduces cycloalkanes, alkenes, and alkynes including their nomenclature, conformations, and cis-trans isomerism.
2) Cyclohexane can exist in chair conformations and ring flipping interconverts between these conformations. Substituted cyclohexanes prefer the equatorial position to avoid 1,3-diaxial interactions.
3) Alkenes and alkynes are named based on parent chain and location of multiple bonds. Cis-trans isomers exist for cycloalkanes and alkenes when two substituents are on the same or opposite sides of the ring or double bond.
This document discusses the classification and properties of hydrocarbons. It describes three main categories of hydrocarbons: saturated hydrocarbons, unsaturated hydrocarbons, and aromatic hydrocarbons. Saturated hydrocarbons contain only single carbon-carbon bonds and include alkanes such as methane. Unsaturated hydrocarbons contain double or triple carbon-carbon bonds and include alkenes and alkynes. Aromatic hydrocarbons contain benzene rings. The document provides examples like propane and propene to illustrate these different types of hydrocarbons.
This document discusses various types of organic reaction intermediates. It explains that reaction intermediates are transient chemical species that are formed in one step of a reaction mechanism and consumed in a subsequent step. Common types of intermediates discussed include radicals, carbocations, and carbanions. The document compares the stability of primary, secondary, and tertiary carbocations and carbanions based on factors like inductive effects, hybridization, and resonance. It also provides examples and structures of different organic reaction intermediates.
Alkanes are saturated hydrocarbons whose carbon-carbon bonds are single bonds. The general formula for alkanes is CnH2n+2. The first ten alkanes are methane, ethane, propane, butane, pentane, hexane, heptane, octane, nonane and decane. Alkanes undergo combustion reactions and halogenation reactions when exposed to halogens like chlorine in the presence of UV light or heat. Haloalkanes are named according to IUPAC rules by identifying the parent alkane, halogen prefix, and halogen position number.
A carbanion is an ion with a negatively charged carbon atom. The most stable carbanions have six electrons in the valence shell of the carbon atom. Carbanions are important in organic chemistry because they can act as nucleophiles, which means they can donate electrons to other molecules. Carbanions are also important in biochemistry because they can be used to transfer electrons between molecules
1) Heterolytic and homolytic bond fission can result in the formation of short-lived reaction intermediates called carbocations.
2) Carbocations are positively charged carbon ions that are electrophilic and undergo three reaction types: capture a nucleophile, lose a proton to form a pi bond, or rearrange.
3) Carbocation stability increases with increased substitution and the presence of electron donating groups, double bonds, or heteroatoms which delocalize the positive charge. Carbocations are key intermediates in SN1, E1, and rearrangement reactions.
Carbanions are negatively charged carbon species with three bonds and a lone pair of electrons, making the carbon atom negatively charged. Carbanions have played an important role in organic synthesis reactions for over 100 years. While usually transient intermediates, certain conditions can produce stable carbanions. The geometry of carbanions depends on hybridization and conjugation - sp3 carbanions are trigonal pyramidal while conjugated carbanions are planar. Carbanions are stabilized by conjugation, field effects, aromaticity, and nonadjacent pi bonds.
A review of the growth of the Israel Genealogy Research Association Database Collection for the last 12 months. Our collection is now passed the 3 million mark and still growing. See which archives have contributed the most. See the different types of records we have, and which years have had records added. You can also see what we have for the future.
Main Java[All of the Base Concepts}.docxadhitya5119
This is part 1 of my Java Learning Journey. This Contains Custom methods, classes, constructors, packages, multithreading , try- catch block, finally block and more.
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How to Manage Your Lost Opportunities in Odoo 17 CRMCeline George
Odoo 17 CRM allows us to track why we lose sales opportunities with "Lost Reasons." This helps analyze our sales process and identify areas for improvement. Here's how to configure lost reasons in Odoo 17 CRM
it describes the bony anatomy including the femoral head , acetabulum, labrum . also discusses the capsule , ligaments . muscle that act on the hip joint and the range of motion are outlined. factors affecting hip joint stability and weight transmission through the joint are summarized.
This presentation includes basic of PCOS their pathology and treatment and also Ayurveda correlation of PCOS and Ayurvedic line of treatment mentioned in classics.
BÀI TẬP BỔ TRỢ TIẾNG ANH 8 CẢ NĂM - GLOBAL SUCCESS - NĂM HỌC 2023-2024 (CÓ FI...
Reactive intermediates
1. 1
Late Ku. Durga K. Banmeru Science College,
LONAR DIST. BULDANA (Maharashtra), India.
Section –II
Unit-3
Electronicdisplacements
“Reactive Intermediates”
B. Sc. Ist year Sem-Ist
Subject:- Chemistry
2. 2
Dr. Suryakant B. Borul
(M.Sc., M.Phil., Ph.D.)
Head Of Department
Department of Chemistry
Late Ku. Durga K. Banmeru Science College,
Lonar
Teacher Profile
3. B) Reactive Intermediates
Q.-What are reactive intermediates?
Ans- Definition- “The short lived fragments or species obtained in homolytic or
heterolytic bond fission are called as reactive intermediates.”
Ex. Carbocations, Carbanions and Free radicals.
The organic compounds undergoes heterolytic bond fission gives carbocations
and carbanions.
4. Carbocations (Carbonium ions)
Ans-
“The positively charge carries carbon atoms containing six electrons in its
valence shell is called as carbocation or carbonium ion.”
Examples-
Q.-Explain the terms Carbocations. OR
What is carbocation? How it is formed?
5. Characteristics of Carbocations
It is positive charge carries carbon atom.
Six electrons in its valence shell.
Carbocation carbon is in sp2 hybridization state.
It is planner ion.
It acts as electrophiles.
It attack on electron rich species i.e. on nucleophiles.
It is classified into primary, secondary, tertiary carbocation
Stability order as –
tertiary > secondary > primary > Methyl carbocation
It is product of heterolytic bond fission of organic compounds.
6. Formation of Carbocations
1. Heterolysis of Alkyl Halides-
C
H3 C
CH3
CH3
Br C
H3 C
+
CH3
CH3
Br
-
+
t - Butyl bromide t - Butyl Carbocation
2. Dehydration of Alcohols-
C
H3 CH2 OH + H
+
C
H3 CH2 OH2
+
C
H3 CH2
+
+ O
H2
ethyl alcohol ethyl carbocation
7. 3. Protonation of Alkenes-
C
H2 CH2 + H
+
C
H3 CH2
+
ethy l carbocation
Ethylene
4. Decomposition of Diazo salt-
+
C
H3 N
+
NCl
-
C
H3 N
+
N CH3
+
N2
methyl diazonium chloride Methy l carbocation
8. Stability of Carbocations
Stability of carbocation is influenced by-
A. Inductive effect-
• The electron releasing group i. e. + effect such as alkyl groups stabilize
the carbocation by dispersing the positive charge.
• Maximum number such group alkyl groups attached to positive charge
carbon greater the dispersal of positive charge and increases the stability
of carbocation.
• Thus tertiary carbocation is more stable than secondary carbocation,
which in turn is more stable than primary carbocation.
9. • -I effect due to electron withdrawing groups destabilize the carbocation.
C
H3 C
+
CH3
CH3
C
H3 CH
+
CH3 C
H3 CH2
+
CH3
+
> > >
t - butyl isopropyl ethyl methyl
Tertiary Secondary Primary Methyl
carbocation carbocation carbocation carbocation.
10. B. Resonance-
Q- Explain the stability of Allyl carbocation and n-propyl carbocation.
Ans-
• The carbocation which involved resonance are more stable than those not
involve in resonance.
• In resonance delocalization of positive charge increases the stability of
carbocation.
• Ex.- Allyl carbocation is more stable than n-propyl carbocation, because
allyl carbocation involved in resonance while n-propyl carbocation do not
involve in resonance.
11. C
H3 CH2 CH2
+
No Resonance Occur
n-Propyl carbocation-
Allyl carbocation-
Ex- Benzyl carbocation -
CH2
+
CH
+
CH2
CH
+
CH2
C
H
+
CH2
Benzyl carbocation is stabilized by resonance.
Thus, Allyl carbocation is more stable than n-propyl carbocation.
12. C. Hyperconjugation-
• Allyl group release electrons via hyperconjugation effect increases the
stability of carbocation.
• Greater the number of hyperconjugative structures the greater its stability
of carbocations.
• The decreasing order of stability of allyl carbocation as-
C
H3 C
+
CH3
CH3
C
H3 CH
+
CH3 C
H3 CH2
+
CH3
+
> > >
t - butyl isopropyl ethyl methyl
13. Recations of Carbocations
1. Combination with carbocations-
2. Elimination of Proton-
C
H3 C
CH3
CH3
OH
C
H3 C
+
CH3
CH3
O
H
-
+
t - Buty l alcohol
t - Buty l Carbocation
Nucleophile
+
C
H3 CH2
+
C
H2 CH2 H
+
Ethyl carbocation Ethylene Proton
14. 3. Addition to double bond to produce higher carbocation-
C
H3 C
CH3
CH3
CH2 C
+
CH3
C
H3
C
H3 C
+
CH3
CH3
+
t - Buty l Carbocation
C
H2
CH3
CH3
4. Rearrangement to produce more stable carbocation-
CH2 CH2
+
C
H3 CH
+
C
H3 CH3
( less stable ) ( more stable )
1 2
0 0
15. Carbanion
Ans-
“The negatively charge carries carbon atoms containing eight electrons in
its valence shell is called as carbanion.”
Examples-
Q.-Explain the terms Carbanions. OR
What is carbanion? How it is formed?
C
H3 C
-
CH3
CH3
t - Butyl Carbanion
CH3
-
Methyl carbanion
C
H3 CH2
+
ethyl carbanion
CH2
-
Benzyl carbanion
16. Characteristics of Carbanions
It is negative charge carries carbon atom.
Eight electrons in its valence shell.
Carbanion carbon is in sp3 hybridization state.
It is electron rich center.
It acts as nucleophiles.
It attack on electron deficient species i.e. on electrophiles.
It is classified into primary, secondary, tertiary carbanion
Stability order as –
Methyl > primary > secondary > tertiary carbocation
It is product of heterolytic bond fission of organic compounds.
17. Formation of Carbanion
1. Heterolysis -
C
H3 C
CH3
CH3
Br C
H3 C
+
CH3
CH3
Br
-
+
t - Butyl bromide t - Butyl Carbocation
2. Dehydration of Alcohols-
C
H3 CH2 OH + H
+
C
H3 CH2 OH2
+
C
H3 CH2
+
+ O
H2
ethyl alcohol ethyl carbocation
18. Stability of Carbocations
Stability of carbocation is influenced by-
A. Inductive effect-
• The electron releasing group i. e. + effect such as alkyl groups stabilize
the carbocation by dispersing the positive charge.
• Maximum number such group alkyl groups attached to positive charge
carbon greater the dispersal of positive charge and increases the stability
of carbocation.
• Thus tertiary carbocation is more stable than secondary carbocation,
which in turn is more stable than primary carbocation.
19. • -I effect due to electron withdrawing groups destabilize the carbocation.
C
H3 C
+
CH3
CH3
C
H3 CH
+
CH3 C
H3 CH2
+
CH3
+
> > >
t - butyl isopropyl ethyl methyl
Tertiary Secondary Primary Methyl
carbocation carbocation carbocation carbocation.
20. B. Resonance-
Q- Explain the stability of Allyl carbocation and n-propyl carbocation.
Ans-
• The carbocation which involved resonance are more stable than those not
involve in resonance.
• In resonance delocalization of positive charge increases the stability of
carbocation.
• Ex.- Allyl carbocation is more stable than n-propyl carbocation, because
allyl carbocation involved in resonance while n-propyl carbocation do not
involve in resonance.
21. C
H3 CH2 CH2
+
No Resonance Occur
n-Propyl carbocation-
Allyl carbocation-
Ex- Benzyl carbocation -
CH2
+
CH
+
CH2
CH
+
CH2
C
H
+
CH2
Benzyl carbocation is stabilized by resonance.
Thus, Allyl carbocation is more stable than n-propyl carbocation.
22. C. Hyperconjugation-
• Alkyl group release electrons via hyperconjugation effect increases the
stability of carbocation.
• Greater the number of hyperconjugative structures the greater its stability
of carbocations.
• The decreasing order of stability of alkyl carbocation as-
C
H3 C
+
CH3
CH3
C
H3 CH
+
CH3 C
H3 CH2
+
CH3
+
> > >
t - butyl isopropyl ethyl methyl
23. 1. The tertiary carbocation is more stable than secondary carbocation and
secondary carbocation more stable than primary carbocation.
2. The stability order as –
Tertiary > Secondary > Primary > Methyl
Ex-. t-Butyl > sec-Propyl > Ethyl > Methyl
3. The carbocations which gives maximum structure of hyperconjugation which
are more stable.
24. t-butyl carbocation gives nine hyperconjugative structures
sec-propyl carbocation gives six hyperconjugative structures
4
5
25. ethyl carbocation gives three hyperconjugative structures
Thus t-carbocation is more stable than primary carbocation.
26. Recations of Carbocations
1. Combination with carbocations-
2. Elimination of Proton-
C
H3 C
CH3
CH3
OH
C
H3 C
+
CH3
CH3
O
H
-
+
t - Buty l alcohol
t - Buty l Carbocation
Nucleophile
+
C
H3 CH2
+
C
H2 CH2 H
+
Ethyl carbocation Ethylene Proton
27. 3. Addition to double bond to produce higher carbocation-
C
H3 C
CH3
CH3
CH2 C
+
CH3
C
H3
C
H3 C
+
CH3
CH3
+
t - Buty l Carbocation
C
H2
CH3
CH3
4. Rearrangement to produce more stable carbocation-
CH2 CH2
+
C
H3 CH
+
C
H3 CH3
( less stable ) ( more stable )
1 2
0 0
28. Carbanion
Ans-
“The negatively charge carries carbon atoms containing eight electrons in
its valence shell is called as carbanion.”
Examples-
Q.-Explain the terms Carbanions. OR
What is carbanion? How it is formed?
C
H3 C
-
CH3
CH3
t - Butyl Carbanion
CH3
-
Methyl carbanion
C
H3 CH2
+
ethyl carbanion
CH2
-
Benzyl carbanion
B) Reactive Intermediates
29. Characteristics of Carbanions
It is negative charge carries carbon atom.
Eight electrons in its valence shell.
Carbanion carbon is in sp3 hybridization state.
It is electron rich center.
It acts as nucleophiles.
It attack on electron deficient species i.e. on electrophiles.
It is classified into primary, secondary, tertiary carbanion
Stability order as –
Methyl > primary > secondary > tertiary carbocation
It is product of heterolytic bond fission of organic compounds.
30. Formation of Carbanion
1. Heterolysis -
2. Abstraction of Proton-
+
Na
C
H Na
+
Sodium Acetylene Acetylide Carbanion
C
-
C
H
CH2 CHO
H
+
O
H
-
+ O
H2
C
H2
-
CHO
2. Decomposition of anion-
O
-
O
C
H3 CH3
-
CO2
+
31. Stability of Carbanion
Stability of carbanion is influenced by-
A. Inductive effect-
• The electron releasing group such as alkyl groups decrease stabilize the
carbanion by intensifying the negative charge.
• The electron withdrawing group i. e. -I effect increase stabilize the
carbanion by dispersal of the negative charge.
• The stability order as –
Methyl > Primary > Secondary > Tertiary
Ex-. Methyl > Ethyl > sec-Propyl > t-Butyl
32. B. Resonance-
• Carbanions stabilized by resonance due to delocalization of the negative
charge.
• Ex.– benzyl carbocation is more stable than ethyl carbanion.
CH2
-
CH
-
CH2
CH
-
CH2
C
H
-
CH2
C
H3 CH2
-
No Resonance
Resonance structures of Benzyl carbanion
33. Reactions of Carbanion
1. Combination with proton or cation -
C
H3 CH2
-
+ H
+
C
H3 CH3
Ethyl carbanion Proton Ethane
2. Additions to multiple bonds to form an anion or new carbanion-
C
H3 C
O
H + C
H2
-
C
O
H C
H3 C
O
-
H
CH2 CH
O
Carbanion New carbanion
34. Free Radicals
Ans-
“The highly reactive odd or unpaired electron containing charge less
species is called as free radical.”
Examples-
Q.-Explain the terms Free Radicals. OR
What is Free Radical? How it is formed?
B) Reactive Intermediates
35. Characteristics of Free radical
It is charge less species.
It carries odd or unpaired electron in its valence shell.
The central carbon atom of free radicals is in sp2 hybridized state.
It is attack on free radicals and combine with free radicals.
It has planer structure.
It is classified into Primary, Secondary, & tertiary free radicals.
Stability order as Tertiary > Secondary > Primary free radicals.
36. Formation of Free Radicals
1. Thermal Decomposition -
C
H3 CH2
C
H3 CH2
Pb
CH2 CH3
CH2 CH3
C
H3 CH2
4 + Pb
i
ii
Tetraethyl lead
Ethyl free radical
H5C6
O
O
O
C6H5
O H5C6 C
O
O C6H5 + CO2
Benzoyl peroxide Phenyl freeradical
Due to heating above molecule undergoes homolysis to form free radicals
37. 2. Photochemical Decomposition -
i
ii
In presence of light compound undergoes homolysis to from free radicals
Cl Cl Cl
2
homolysis
Chlorine free radical
C
H3
C
H3
O C CH2
CH3
+ CH3
Acetyl free radical
methyl free radical
Acetadehyde
38. Stability of Free Radicals
1. Resonance-
• According to resonance theory those molecule gives maximum resonating
structures which are more stable.
• Free radicals get stability by resonance due to delocalization of the
unpaired electron.
• Ex. Allyl free radicals–
Benzyl free radical-
C
H2 CH CH2 C
H2 CH CH2
I II
CH2
CH
CH2
CH
CH2
C
H
CH2
I II III IV
Resonance structures of benzyl free radicals
In above two examples benzyl free radicals more stable than allyl free radicals.
39. 2. Hyperconjugation Effect-
• The alkyl groups are electron releasing groups.
• The presence of alkyl group attached to free radical carbon increases the
stability of free radical.
• Hence the decreasing order of stability of free radical is
• Presence of alkyl group increases the hyperconjugation
structures.
40. Reactions of Free Radicals
1. Combination with other free radicals-
2. Addition to multiple bond to form a new free radicals-
3. Disproportionation-