This document discusses various rearrangement reactions including pinacol-pinacolone rearrangement, Favorskii rearrangement, Curtius rearrangement, Beckman rearrangement, and others. It provides mechanisms, requirements, and examples for each reaction. Crossover experiments are described as a way to determine if a reaction proceeds via an intramolecular or intermolecular pathway. Stereochemistry and migratory aptitude are also addressed for several reactions.
The Baeyer-Villiger rearrangement involves the reaction of ketones with peroxy acids, resulting in the conversion of ketones to esters and cyclic ketones to lactones. A typical example is the reaction of acetophenone with perbenzoic acid to produce phenylacetate. The reaction proceeds through an anionotropic rearrangement where a group migrates from carbon to the electron-deficient oxygen. The Baeyer-Villiger rearrangement has applications in synthesizing lactones, anhydrides, and medicinal compounds.
This document summarizes various types of rearrangement reactions in organic chemistry. It describes 15 categories of rearrangements including rearrangements to electron deficient carbons, nitrogens, and oxygens. For each category, 1-2 specific rearrangements are explained in more detail, including their mechanisms. Rearrangements discussed include the Wagner-Meerwein, Pinacol, Benzilic acid, Hofmann, Curtius, Lossen, Beckmann, Baeyer-Villiger, Stevens, Sommelet-Hauser, Wittig, Favorskii, Benzidine, Fries, and Claisen rearrangements. The document was prepared by a student as part of their coursework to provide an overview of
Molecular Rearrangements of Organic Reactions ppsOMPRAKASH1973
This PPT is usefull for aspirants of JEE-IIT, CSIR-NET and UPSC exams in CHEMISTRY section. It is also usefull for grduates and Post graduates students of Indian Universities.
The Neber rearrangement is a base-induced rearrangement of O-acylated ketoximes to the corresponding α-amino ketones. It was discovered in 1926 by Neber and Friedolsheim during their investigation of the Beckmann rearrangement. The Neber rearrangement has since become an important synthetic tool for synthesizing heterocycles that use amino ketones as intermediates. It proceeds through an alkoxide-induced rearrangement of the O-acylated ketoxime to form an α-amino ketone product. There are some limitations in that aldoximes do not undergo the rearrangement and substrates generally require a methylene group in the α-position.
Grignard reagents are organomagnesium compounds formed by the reaction of an organic halide and magnesium. The reaction proceeds through single electron transfers where radicals are converted to carbanions. Grignard reagents are strong nucleophiles similar to organolithium reagents that can form new carbon-carbon bonds. They were analyzed by decomposing ethylmagnesium iodide with sulfuric acid and directing steam through the apparatus to drive off any ethane, proving it did not appreciably dissolve under experimental conditions.
The Baeyer-Villiger oxidation reaction converts cyclic ketones to lactones and acyclic ketones to esters using a peroxy acid as the oxidizing agent. Adolf Baeyer and Victor Villiger first reported this reaction in 1899 using menthone and tetrahydrocarvone. The reaction involves the nucleophilic attack of the peroxy acid on the carbonyl carbon, followed by migration of an alkyl group to the oxygen and formation of the ester or lactone product. This reaction has been modified using hydrogen peroxide as the oxidant and various catalysts. It has applications in synthesizing pharmaceuticals, pheromones, and other fine chemicals.
The document summarizes the Suzuki and Shapiro reactions. The Suzuki reaction involves a palladium-catalyzed cross-coupling between organoboron compounds and organic halides to form carbon-carbon bonds. It proceeds through oxidative addition, transmetallation, and reductive elimination steps. The Shapiro reaction involves the base-catalyzed decomposition of tosyl hydrazones to form olefins. Both reactions have been used in the synthesis of various drugs and natural products.
The Baeyer-Villiger rearrangement involves the reaction of ketones with peroxy acids, resulting in the conversion of ketones to esters and cyclic ketones to lactones. A typical example is the reaction of acetophenone with perbenzoic acid to produce phenylacetate. The reaction proceeds through an anionotropic rearrangement where a group migrates from carbon to the electron-deficient oxygen. The Baeyer-Villiger rearrangement has applications in synthesizing lactones, anhydrides, and medicinal compounds.
This document summarizes various types of rearrangement reactions in organic chemistry. It describes 15 categories of rearrangements including rearrangements to electron deficient carbons, nitrogens, and oxygens. For each category, 1-2 specific rearrangements are explained in more detail, including their mechanisms. Rearrangements discussed include the Wagner-Meerwein, Pinacol, Benzilic acid, Hofmann, Curtius, Lossen, Beckmann, Baeyer-Villiger, Stevens, Sommelet-Hauser, Wittig, Favorskii, Benzidine, Fries, and Claisen rearrangements. The document was prepared by a student as part of their coursework to provide an overview of
Molecular Rearrangements of Organic Reactions ppsOMPRAKASH1973
This PPT is usefull for aspirants of JEE-IIT, CSIR-NET and UPSC exams in CHEMISTRY section. It is also usefull for grduates and Post graduates students of Indian Universities.
The Neber rearrangement is a base-induced rearrangement of O-acylated ketoximes to the corresponding α-amino ketones. It was discovered in 1926 by Neber and Friedolsheim during their investigation of the Beckmann rearrangement. The Neber rearrangement has since become an important synthetic tool for synthesizing heterocycles that use amino ketones as intermediates. It proceeds through an alkoxide-induced rearrangement of the O-acylated ketoxime to form an α-amino ketone product. There are some limitations in that aldoximes do not undergo the rearrangement and substrates generally require a methylene group in the α-position.
Grignard reagents are organomagnesium compounds formed by the reaction of an organic halide and magnesium. The reaction proceeds through single electron transfers where radicals are converted to carbanions. Grignard reagents are strong nucleophiles similar to organolithium reagents that can form new carbon-carbon bonds. They were analyzed by decomposing ethylmagnesium iodide with sulfuric acid and directing steam through the apparatus to drive off any ethane, proving it did not appreciably dissolve under experimental conditions.
The Baeyer-Villiger oxidation reaction converts cyclic ketones to lactones and acyclic ketones to esters using a peroxy acid as the oxidizing agent. Adolf Baeyer and Victor Villiger first reported this reaction in 1899 using menthone and tetrahydrocarvone. The reaction involves the nucleophilic attack of the peroxy acid on the carbonyl carbon, followed by migration of an alkyl group to the oxygen and formation of the ester or lactone product. This reaction has been modified using hydrogen peroxide as the oxidant and various catalysts. It has applications in synthesizing pharmaceuticals, pheromones, and other fine chemicals.
The document summarizes the Suzuki and Shapiro reactions. The Suzuki reaction involves a palladium-catalyzed cross-coupling between organoboron compounds and organic halides to form carbon-carbon bonds. It proceeds through oxidative addition, transmetallation, and reductive elimination steps. The Shapiro reaction involves the base-catalyzed decomposition of tosyl hydrazones to form olefins. Both reactions have been used in the synthesis of various drugs and natural products.
This document provides an overview of multi-component reactions (MCRs), including their history, advantages over multistep reactions, and examples such as the Passerini reaction, Ugi reaction, Biginelli reaction, and Mannich reaction. MCRs involve more than two starting materials reacting in one pot to form a product containing the majority of atoms from the reactants. They provide an efficient means of generating structural diversity and are important in drug discovery. Some of the earliest and most widely used MCRs are isocyanide-based reactions developed in the early 20th century.
The Mannich reaction involves the condensation of an enolizable carbonyl compound, an amine or ammonia, and formaldehyde to form an aminomethyl derivative known as a Mannich base. Ketones are most commonly used as the carbonyl compound. The reaction proceeds via the generation of an imine intermediate from the carbonyl compound and amine, which then reacts with formaldehyde to form the Mannich base. Mannich bases have applications in synthesizing natural products like alkaloids and building ring systems.
The Suzuki reaction is an organic reaction where an organoboron compound reacts with an organohalide compound to form a carbon-carbon bond. It is catalyzed by palladium and involves three main steps - oxidative addition, transmetalation, and reductive elimination. The Suzuki reaction is widely used in chemical synthesis due to its mild reaction conditions, tolerance of functional groups, and ability to form C-C bonds under aqueous conditions.
The selection rules that determine which electronic transitions are allowed or forbidden in transition metal complexes are the Laporte selection rule and spin selection rule. The Laporte rule forbids transitions that result in no change in orbital angular momentum, while the spin rule forbids transitions that change the overall spin of the complex. These rules can be relaxed by vibronic coupling in octahedral complexes or do not apply in tetrahedral complexes. Orbital contributions to paramagnetic moment only occur when the transition metal d orbitals are asymmetrically occupied, allowing electron circulation between degenerate orbitals.
Sodium borohydride is a reducing agent used in organic synthesis. It is commonly used to reduce carbonyl groups such as aldehydes and ketones to alcohols. The reduction occurs via a two-step mechanism where the borohydride first adds to the carbonyl carbon, then a proton transfers in a second step. Sodium borohydride is a mild reducing agent and selectively reduces carbonyls over other functional groups. It is preferred over lithium aluminum hydride for carbonyl reductions due to its milder and more controlled reactivity in aqueous conditions.
The document summarizes the Brook rearrangement reaction. It was discovered in 1957 by Adrian Brook and involves the migration of a silyl group from carbon to oxygen under basic conditions. The mechanism proceeds through the formation of a pentavalent silicon intermediate. The rearrangement has various applications in synthesis, such as constructing 8-membered rings and chiral silyl ethers. It has been used to synthesize compounds like gamma-amino-beta-hydroxy amides and alpha-hydroxy acid derivatives.
The document discusses electrocyclic reactions, which involve the conversion of a conjugated polyene to an unsaturated cyclic compound with one less carbon-carbon double bond. It notes that these reactions can occur thermally or photochemically, and with high stereoselectivity. It provides examples of electrocyclic reactions involving butadiene and hexatriene, and discusses the correlation between molecular orbital symmetry and the conrotatory or disrotatory nature of the reaction. It also addresses electrocyclic reactions involving reactants with an odd number of atoms, such as cations and anions, as well as photochemical cyclizations.
The Suzuki reaction is a palladium-catalyzed cross-coupling reaction between boronic acids or esters with organic halides, triflates, or other boron-containing compounds. This reaction occurs under basic conditions and leads to the formation of carbon-carbon single bonds, typically between an aryl or vinyl group and another aryl or vinyl group. It is commonly used to synthesize biaryl compounds. The reaction proceeds through oxidative addition, transmetallation, and reductive elimination steps. Key advantages are mild reaction conditions and availability of boronic acids. The Suzuki reaction has applications in synthesizing pharmaceuticals, agrochemicals, and natural products.
The Knoevenagel condensation reaction involves the nucleophilic addition of an active hydrogen compound to a carbonyl group, followed by a dehydration reaction to form an α,β-unsaturated enone. It is a modification of the aldol condensation and uses an active methylene compound and an aldehyde or ketone in the presence of a weak base such as pyridine. With malonic acid derivatives, the reaction product can undergo decarboxylation to form trans-2,4-pentadienoic acid. The Knoevenagel reaction is widely used in the synthesis of conjugated enones for various reactions.
The McMurry coupling reaction is a versatile titanium-mediated process for forming carbon-carbon bonds via the reductive coupling of carbonyl compounds to produce alkenes. Key features of the reaction include the use of low-valent titanium complexes to couple aldehydes and ketones, most commonly prepared by reducing TiCl3 with Zn-Cu. The reaction can form sterically hindered and strained alkenes in high yields. While it lacks stereoselectivity, the McMurry coupling has been used in the synthesis of many natural products due to its ability to form carbon-carbon bonds and macrocyclic rings.
Penicillin, one of the first and still one of the most widely used antibiotic agents, is derived from the penicillium mold. In 1928 Scottish bacteriologist alexander fleming in a contaminated green mold penicillium notatum. He isolated the mold, grew it in a fluid medium, and found that it produced a substance capable of killing many of the common bacteria that infect humans. Australian pathologist howard florey and British biochemist ernst Boris chain isolated and purified penicillin in the late 1930s, and by 1941 an injectable form of the drug was available for therapeutic use.
Penicillin's are beta lactam antibiotics and characterized by three fundamental structural requirements
The fused beta-lactam and thiazolidine ring structure.
free carboxylic acid group.
And one or more substituted acylamino side chain.
Penam nucleus: 7-oxo-l-thia-4-azabicyclo [3.2.0] heptane
Absolute configuration: 3-S, 5-R, 6-R.
Instrumental methods of characterization:
FTIR
MASS
C13-NMR
1H-NMR
FTIR: -
Penicillin G molecule and its IR spectra in D2 O and in DMSO. Spectra are characterized by the presence of three intense bands.
β- lactam CO stretching observe at 1761 cm-1 in D2O and 1762 cm-1 in DMSO solution.
Amide group is observe at 1640 cm-1 in D2O and 1674 cm-1 in DMSO solution.
Asymmetric stretching of carboxylate group is observe at 1601 cm-1 in D20 and 1615 cm-1 in DMSO solution.
A large red shift of amide , out of the frequency window, is observed upon proton exchange in DMSO.
Collision-Induced Dissociation (CID) technique
MASS:-
A high-resolution, hybrid tandem mass spectrometer was used to obtain CID spectra. The CID spectra were acquired by:
Mass selecting the precursor ions using the first mass spectrometer.
Injecting the ions into the first quadrupole (collision cell) where they undergo CID.
Mass-analyzing the fragment ions produced using the second quadrupole.
Argon was used as the collision gas, and the pressure in the collision cell was adjusted to attenuate the precursor ion intensity to 20-50% of the original intensity. The collision energy of the ions ranged from 160 to 180 eV. The mass spectra shown abundant fragmentations at m/z 160 and m/z 176 that were reported to arise from cleavage of the β-lactam ring.
protonated benzyl penicillin exhibits abundant fragment ions at m/z 160, m/z 176, m/z 217, m/z 128, and m/z 289. The most abundant CID fragment at m/z 160 and the molecular ion peak was observed at m/z 334.
C13-NMR: -
The four sp3 ring carbons give rise to resonances in the decreasing chemical shift order C-3, C-5, C-2 and C-6.
Chemical shift for C-2 is 64.9 ppm and the substituents attached with it are α-methyl 27.0 ppm and β-methyl 31.4 ppm. Chemical shift for C-3 is 73.6 ppm and 174.5 ppm for carboxylate functions (reflecting the smaller de-shielding influence of COOH over that of COO-). The chemic shift for C-5 is 67.2 ppm. The chemic shift for C-6 is 58.4 ppm.
The lactam group shows its chemical shift at 175.0 ppm
Amino group
The document summarizes two organic reactions: the Dieckmann reaction and ozonolysis reaction. The Dieckmann reaction involves the intramolecular condensation of diesters in the presence of a strong base to form β-keto esters via a 5-exo-trig cyclization. It is used to synthesize cyclopentane and cyclohexane derivatives. Ozonolysis involves the cleavage of unsaturated bonds like alkenes and alkynes with ozone to form carbonyl groups. It can be used to oxidize alkenes into alcohols, aldehydes, ketones or carboxylic acids and is useful for structure elucidation of unknown compounds containing carbon-carbon double bonds.
The Mitsunobu reaction allows the conversion of alcohols to various functional groups using trialkyl/triaryl phosphine and dialkyl azodicarboxylate reagents. It proceeds via an oxidation-reduction mechanism. Common applications include esterification, etherification, and N-alkylation reactions. Recent advances have focused on replacing conventional reagents to improve selectivity and yields. The Mitsunobu reaction has been widely used in the synthesis of natural products and pharmaceuticals.
The Mannich reaction involves the condensation of an enolizable carbonyl compound, an aldehyde such as formaldehyde, and an amine to form a β-amino carbonyl compound known as a Mannich base. The reaction proceeds via the initial addition of the amine to the aldehyde to form an iminium ion intermediate, which then reacts with the enol form of the carbonyl compound to eliminate a proton and form the Mannich base product. While versatile building blocks in organic synthesis, the Mannich reaction has limitations in terms of substrate scope and control of regio- and stereoselectivity. Examples of applications include the synthesis of tropinone, a precursor of atropine, as well
Katsuki Sharpless Asymmetric Epoxidation and its Synthetic ApplicationsKeshav Singh
The Sharpless epoxidation reaction allows for the asymmetric epoxidation of allylic alcohols. It uses tert-butyl hydroperoxide as the oxidizing agent, titanium tetra isopropoxide as the catalyst, and a chiral tartrate ester ligand such as diethyl tartrate. The tartrate ligand provides chirality and controls the face selectivity of the epoxidation reaction. The Sharpless epoxidation has been widely used in the synthesis of pharmaceuticals, natural products, and other chemicals.
This document discusses retrosynthetic analysis and disconnection strategies for planning the synthesis of drug molecules. It defines key terms like retrosynthesis, synthons, and functional group interconversions. It provides guidelines for disconnecting different types of bonds and functional groups in a molecule, including C-X, C-C, and multiple bonds/groups. The goal is to break down the target molecule into stable and readily available starting materials by applying principles of retrosynthetic analysis.
The document discusses the Wagner-Meerwein rearrangement, a reaction first observed in 1899 where a carbocation is generated followed by a [1,2]-shift of an adjacent carbon-carbon bond to form a new carbocation. This reaction was not fully understood until 1922 when its ionic nature was revealed. The rearrangement involves the migration of hydrogen, alkyl, or aryl groups between carbocations and can involve multiple consecutive shifts. It can be initiated through various means to generate the initial carbocation and the migrating group retains its stereochemistry.
The document discusses two approaches towards synthesizing graphene nanoribbons (GNRs): the ceramidonine approach and the Perkin approach using cyclodehydrogenation. The ceramidonine approach allowed synthesis of some electron acceptor-type, soluble tetraazaarene ribbons but had difficulties with cyclization reactions and incorporation of solubilizing chains. The document then discusses using the Perkin reaction to synthesize diacrylate monomers, followed by cyclodehydrogenation with DDQ/MeSO3H to form polycyclic aromatic ribbons. Sixteen different diacrylate monomers were synthesized and subjected to cyclodehydrogenation conditions, yielding several cyclized ribbon products.
The document outlines the key objectives and topics to be covered in a unit on haloalkanes and haloarenes. The objectives include naming halo compounds using IUPAC nomenclature, describing their preparation methods and reactions, understanding how structure relates to reactivity, and highlighting their applications and environmental effects. The unit will cover introduction/classification/nomenclature, physical properties, preparation methods, chemical properties including SN1 and SN2 reactions, optical isomerism, and polyhalogen compounds.
This document provides an overview of multi-component reactions (MCRs), including their history, advantages over multistep reactions, and examples such as the Passerini reaction, Ugi reaction, Biginelli reaction, and Mannich reaction. MCRs involve more than two starting materials reacting in one pot to form a product containing the majority of atoms from the reactants. They provide an efficient means of generating structural diversity and are important in drug discovery. Some of the earliest and most widely used MCRs are isocyanide-based reactions developed in the early 20th century.
The Mannich reaction involves the condensation of an enolizable carbonyl compound, an amine or ammonia, and formaldehyde to form an aminomethyl derivative known as a Mannich base. Ketones are most commonly used as the carbonyl compound. The reaction proceeds via the generation of an imine intermediate from the carbonyl compound and amine, which then reacts with formaldehyde to form the Mannich base. Mannich bases have applications in synthesizing natural products like alkaloids and building ring systems.
The Suzuki reaction is an organic reaction where an organoboron compound reacts with an organohalide compound to form a carbon-carbon bond. It is catalyzed by palladium and involves three main steps - oxidative addition, transmetalation, and reductive elimination. The Suzuki reaction is widely used in chemical synthesis due to its mild reaction conditions, tolerance of functional groups, and ability to form C-C bonds under aqueous conditions.
The selection rules that determine which electronic transitions are allowed or forbidden in transition metal complexes are the Laporte selection rule and spin selection rule. The Laporte rule forbids transitions that result in no change in orbital angular momentum, while the spin rule forbids transitions that change the overall spin of the complex. These rules can be relaxed by vibronic coupling in octahedral complexes or do not apply in tetrahedral complexes. Orbital contributions to paramagnetic moment only occur when the transition metal d orbitals are asymmetrically occupied, allowing electron circulation between degenerate orbitals.
Sodium borohydride is a reducing agent used in organic synthesis. It is commonly used to reduce carbonyl groups such as aldehydes and ketones to alcohols. The reduction occurs via a two-step mechanism where the borohydride first adds to the carbonyl carbon, then a proton transfers in a second step. Sodium borohydride is a mild reducing agent and selectively reduces carbonyls over other functional groups. It is preferred over lithium aluminum hydride for carbonyl reductions due to its milder and more controlled reactivity in aqueous conditions.
The document summarizes the Brook rearrangement reaction. It was discovered in 1957 by Adrian Brook and involves the migration of a silyl group from carbon to oxygen under basic conditions. The mechanism proceeds through the formation of a pentavalent silicon intermediate. The rearrangement has various applications in synthesis, such as constructing 8-membered rings and chiral silyl ethers. It has been used to synthesize compounds like gamma-amino-beta-hydroxy amides and alpha-hydroxy acid derivatives.
The document discusses electrocyclic reactions, which involve the conversion of a conjugated polyene to an unsaturated cyclic compound with one less carbon-carbon double bond. It notes that these reactions can occur thermally or photochemically, and with high stereoselectivity. It provides examples of electrocyclic reactions involving butadiene and hexatriene, and discusses the correlation between molecular orbital symmetry and the conrotatory or disrotatory nature of the reaction. It also addresses electrocyclic reactions involving reactants with an odd number of atoms, such as cations and anions, as well as photochemical cyclizations.
The Suzuki reaction is a palladium-catalyzed cross-coupling reaction between boronic acids or esters with organic halides, triflates, or other boron-containing compounds. This reaction occurs under basic conditions and leads to the formation of carbon-carbon single bonds, typically between an aryl or vinyl group and another aryl or vinyl group. It is commonly used to synthesize biaryl compounds. The reaction proceeds through oxidative addition, transmetallation, and reductive elimination steps. Key advantages are mild reaction conditions and availability of boronic acids. The Suzuki reaction has applications in synthesizing pharmaceuticals, agrochemicals, and natural products.
The Knoevenagel condensation reaction involves the nucleophilic addition of an active hydrogen compound to a carbonyl group, followed by a dehydration reaction to form an α,β-unsaturated enone. It is a modification of the aldol condensation and uses an active methylene compound and an aldehyde or ketone in the presence of a weak base such as pyridine. With malonic acid derivatives, the reaction product can undergo decarboxylation to form trans-2,4-pentadienoic acid. The Knoevenagel reaction is widely used in the synthesis of conjugated enones for various reactions.
The McMurry coupling reaction is a versatile titanium-mediated process for forming carbon-carbon bonds via the reductive coupling of carbonyl compounds to produce alkenes. Key features of the reaction include the use of low-valent titanium complexes to couple aldehydes and ketones, most commonly prepared by reducing TiCl3 with Zn-Cu. The reaction can form sterically hindered and strained alkenes in high yields. While it lacks stereoselectivity, the McMurry coupling has been used in the synthesis of many natural products due to its ability to form carbon-carbon bonds and macrocyclic rings.
Penicillin, one of the first and still one of the most widely used antibiotic agents, is derived from the penicillium mold. In 1928 Scottish bacteriologist alexander fleming in a contaminated green mold penicillium notatum. He isolated the mold, grew it in a fluid medium, and found that it produced a substance capable of killing many of the common bacteria that infect humans. Australian pathologist howard florey and British biochemist ernst Boris chain isolated and purified penicillin in the late 1930s, and by 1941 an injectable form of the drug was available for therapeutic use.
Penicillin's are beta lactam antibiotics and characterized by three fundamental structural requirements
The fused beta-lactam and thiazolidine ring structure.
free carboxylic acid group.
And one or more substituted acylamino side chain.
Penam nucleus: 7-oxo-l-thia-4-azabicyclo [3.2.0] heptane
Absolute configuration: 3-S, 5-R, 6-R.
Instrumental methods of characterization:
FTIR
MASS
C13-NMR
1H-NMR
FTIR: -
Penicillin G molecule and its IR spectra in D2 O and in DMSO. Spectra are characterized by the presence of three intense bands.
β- lactam CO stretching observe at 1761 cm-1 in D2O and 1762 cm-1 in DMSO solution.
Amide group is observe at 1640 cm-1 in D2O and 1674 cm-1 in DMSO solution.
Asymmetric stretching of carboxylate group is observe at 1601 cm-1 in D20 and 1615 cm-1 in DMSO solution.
A large red shift of amide , out of the frequency window, is observed upon proton exchange in DMSO.
Collision-Induced Dissociation (CID) technique
MASS:-
A high-resolution, hybrid tandem mass spectrometer was used to obtain CID spectra. The CID spectra were acquired by:
Mass selecting the precursor ions using the first mass spectrometer.
Injecting the ions into the first quadrupole (collision cell) where they undergo CID.
Mass-analyzing the fragment ions produced using the second quadrupole.
Argon was used as the collision gas, and the pressure in the collision cell was adjusted to attenuate the precursor ion intensity to 20-50% of the original intensity. The collision energy of the ions ranged from 160 to 180 eV. The mass spectra shown abundant fragmentations at m/z 160 and m/z 176 that were reported to arise from cleavage of the β-lactam ring.
protonated benzyl penicillin exhibits abundant fragment ions at m/z 160, m/z 176, m/z 217, m/z 128, and m/z 289. The most abundant CID fragment at m/z 160 and the molecular ion peak was observed at m/z 334.
C13-NMR: -
The four sp3 ring carbons give rise to resonances in the decreasing chemical shift order C-3, C-5, C-2 and C-6.
Chemical shift for C-2 is 64.9 ppm and the substituents attached with it are α-methyl 27.0 ppm and β-methyl 31.4 ppm. Chemical shift for C-3 is 73.6 ppm and 174.5 ppm for carboxylate functions (reflecting the smaller de-shielding influence of COOH over that of COO-). The chemic shift for C-5 is 67.2 ppm. The chemic shift for C-6 is 58.4 ppm.
The lactam group shows its chemical shift at 175.0 ppm
Amino group
The document summarizes two organic reactions: the Dieckmann reaction and ozonolysis reaction. The Dieckmann reaction involves the intramolecular condensation of diesters in the presence of a strong base to form β-keto esters via a 5-exo-trig cyclization. It is used to synthesize cyclopentane and cyclohexane derivatives. Ozonolysis involves the cleavage of unsaturated bonds like alkenes and alkynes with ozone to form carbonyl groups. It can be used to oxidize alkenes into alcohols, aldehydes, ketones or carboxylic acids and is useful for structure elucidation of unknown compounds containing carbon-carbon double bonds.
The Mitsunobu reaction allows the conversion of alcohols to various functional groups using trialkyl/triaryl phosphine and dialkyl azodicarboxylate reagents. It proceeds via an oxidation-reduction mechanism. Common applications include esterification, etherification, and N-alkylation reactions. Recent advances have focused on replacing conventional reagents to improve selectivity and yields. The Mitsunobu reaction has been widely used in the synthesis of natural products and pharmaceuticals.
The Mannich reaction involves the condensation of an enolizable carbonyl compound, an aldehyde such as formaldehyde, and an amine to form a β-amino carbonyl compound known as a Mannich base. The reaction proceeds via the initial addition of the amine to the aldehyde to form an iminium ion intermediate, which then reacts with the enol form of the carbonyl compound to eliminate a proton and form the Mannich base product. While versatile building blocks in organic synthesis, the Mannich reaction has limitations in terms of substrate scope and control of regio- and stereoselectivity. Examples of applications include the synthesis of tropinone, a precursor of atropine, as well
Katsuki Sharpless Asymmetric Epoxidation and its Synthetic ApplicationsKeshav Singh
The Sharpless epoxidation reaction allows for the asymmetric epoxidation of allylic alcohols. It uses tert-butyl hydroperoxide as the oxidizing agent, titanium tetra isopropoxide as the catalyst, and a chiral tartrate ester ligand such as diethyl tartrate. The tartrate ligand provides chirality and controls the face selectivity of the epoxidation reaction. The Sharpless epoxidation has been widely used in the synthesis of pharmaceuticals, natural products, and other chemicals.
This document discusses retrosynthetic analysis and disconnection strategies for planning the synthesis of drug molecules. It defines key terms like retrosynthesis, synthons, and functional group interconversions. It provides guidelines for disconnecting different types of bonds and functional groups in a molecule, including C-X, C-C, and multiple bonds/groups. The goal is to break down the target molecule into stable and readily available starting materials by applying principles of retrosynthetic analysis.
The document discusses the Wagner-Meerwein rearrangement, a reaction first observed in 1899 where a carbocation is generated followed by a [1,2]-shift of an adjacent carbon-carbon bond to form a new carbocation. This reaction was not fully understood until 1922 when its ionic nature was revealed. The rearrangement involves the migration of hydrogen, alkyl, or aryl groups between carbocations and can involve multiple consecutive shifts. It can be initiated through various means to generate the initial carbocation and the migrating group retains its stereochemistry.
The document discusses two approaches towards synthesizing graphene nanoribbons (GNRs): the ceramidonine approach and the Perkin approach using cyclodehydrogenation. The ceramidonine approach allowed synthesis of some electron acceptor-type, soluble tetraazaarene ribbons but had difficulties with cyclization reactions and incorporation of solubilizing chains. The document then discusses using the Perkin reaction to synthesize diacrylate monomers, followed by cyclodehydrogenation with DDQ/MeSO3H to form polycyclic aromatic ribbons. Sixteen different diacrylate monomers were synthesized and subjected to cyclodehydrogenation conditions, yielding several cyclized ribbon products.
The document outlines the key objectives and topics to be covered in a unit on haloalkanes and haloarenes. The objectives include naming halo compounds using IUPAC nomenclature, describing their preparation methods and reactions, understanding how structure relates to reactivity, and highlighting their applications and environmental effects. The unit will cover introduction/classification/nomenclature, physical properties, preparation methods, chemical properties including SN1 and SN2 reactions, optical isomerism, and polyhalogen compounds.
Deciphering reaction mechanism with intermediate trappingDaniel Morton
This module provides an overview of a tool used to gain information on a reaction mechanism; reactive intermediate trapping.
A reactive intermediate is a short-lived, high-energy, highly reactive molecule. When generated in a chemical reaction, it will quickly convert into a more stable molecule. When their existence is indicated, reactive intermediates can help explain how a chemical reaction takes place.
Contributed by:
Shuangyu Ma & Yiling Bi (Undergraduate Students)
University of Utah
2014
the role of thermodynamics in drug stabilityHassaan Bari
This document provides an overview of the role of thermodynamics in drug stability. It discusses key concepts like entropy, Gibbs free energy, and various theories of reaction rates including collision theory and transition state theory. It also examines how physical factors like crystallization, polymorphism, moisture absorption, temperature, and pH can impact drug stability and degradation over time. Maintaining the appropriate physical state of drugs is important for stability and ensuring the expected quality, purity, and strength of pharmaceutical products during storage.
This powerpoint presentation will cover following aspects:
Kinds of Pericyclic Reactions and Brief details of their kinds
Molecular Orbitals and Orbitals Symmetry
Molecular Orbitals Description
Electrocyclic Reactions
Introduction to Dienes
Introduction to Dienophiles
Photochemical conditions
Ring Closure
Modes of Ring Closure
Diels- Alder Product recognition and Reversibility of Diels Alder Reaction
Conrotatory and Disrotatory arrangements
Cycloadditions in Complete Details
Dimerization , Frontier Orbitals Description, Endo Rule, Stereochemistry, Applications Hoffman's rule and a lot more……
Symmetry is an important concept in science that is commonly observed in nature. It can be described through symmetry operations such as rotations, reflections, and inversions that leave an object in an indistinguishable position. Molecules exhibit different types of symmetry elements including axes of rotation, planes of symmetry, centers of inversion, and improper axes. Understanding molecular symmetry allows classification of molecules and their physical and chemical properties using the mathematical framework of group theory.
Molecular rearrangement reactions- Dr. Alka Tangri.pdfRaviansMotivations
This document discusses several types of rearrangement reactions in organic chemistry. It defines rearrangement reactions as reactions where a chemical unit such as an atom, ion, or group of atoms migrates within or between molecules of the same species to form a new product. The document discusses intramolecular and intermolecular rearrangements, and provides examples of anionotropic rearrangements like the pinacol rearrangement and cationotropic rearrangements like the Fries rearrangement. It also provides detailed mechanisms and applications of the pinacol rearrangement and Hoffman rearrangement.
Carbohydrates are aldehyde or ketone compounds that serve multiple roles in life. They store and provide energy through starches like glycogen, make up structural elements like cellulose in plants, and form the backbone of nucleic acids DNA and RNA. Carbohydrates exist as monomers, dimers, and polymers. Glucose is the most abundant monosaccharide and forms cyclic structures in solution. It links to other sugars through glycosidic bonds to create important disaccharides like sucrose and polysaccharides for energy storage.
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Pericyclic reactions involve the formation and breaking of bonds in a concerted cyclic transition state. They can be classified as cycloadditions, electrocyclic reactions, sigmatropic rearrangements, cheletropic reactions, or group transfers. Examples of important pericyclic reactions discussed include the Diels-Alder reaction, 1,3-dipolar cycloadditions, Claisen rearrangement, and electrocyclic ring openings and closings. These reactions are useful in synthesis and occur in biological systems.
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Pericyclic reactions involve the formation or breaking of bonds in a cyclic transition state. They include cycloadditions, electrocyclic reactions, sigmatropic rearrangements, and others. Cycloadditions like the Diels-Alder reaction involve the combination of unsaturated molecules to form a cyclic adduct. The Diels-Alder reaction between a conjugated diene and dienophile forms a cyclohexene ring. Frontier molecular orbital theory can explain the regioselectivity of cycloadditions. Examples of pericyclic reactions include the synthesis of citral via a Claisen rearrangement, Fischer indole synthesis, and Diels-Alder reactions in alkaloid and carbohydrate synthesis.
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1. Dr. Vishnu A. Adole
Mahatma Gandhi Vidyamandir’s
Arts, Science and Commerce
College, Manmad
2. Rearrangement
Reactions
D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 2
This content is made for Undergraduate level as per SPPU, Pune Syllabus
3. Content
1. Introduction
2. Cross-over experiment
3. Pinacol-Pinacolone Rearrangement
4. Favorskii Rearrangement
5. Curtius Rearrangement
6. Beckman Rearrangement
7. Baeyer-Villiger Rearrangement
8. Claisen Rearrangement
D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 3
4. You should know reaction intermediates and transition state
before you start the journey of rearrangement reactions-
1. Carbocation
2. Carbanion
3. Carbene
4. Nitrene
5. Transition state
D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 4
5. INTRODUCTION
Reactions are classified as addition, substitution, elimination, condensation,
rearrangement, pericyclic and redox reactions.
Organic reactions usually end up with the products that are in the line with the most
accepted mechanisms. Consequently, the products are often called as Normal
products.
In many cases, reactions lead to the formation of products by different reaction
pathways. These products are referred as rearranged products or abnormal products.
The rearranged product is sometimes not only the abnormal but also the major one.
This may occur from a plausible rearrangement occurring during the course of
reaction to fulfil the principle of minimum energy T.S. or intermediate.
So, it becomes very important to understand each and every concept involved in the
rearrangement reactions. In rearrangement reactions atoms or group migrates from
one position to another, resulting in reorganization of starting material.
The position from which the group or atom migrates is known as Migration Origin and
the position to which it migrates in rearrangement reaction is known as Migration
Terminus.
D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 5
6. In above case, A is Migration Example- Beckman rearrangement
Example- Beckman Rearrangement
D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 6
7. CROSSOVER EXPERIMENT
In rearrangement reactions, the important thing is to predict whether reaction
proceeds via intramolecular or intermolecular pathway.
The solution for this is crossover experiment.
In crossover experiment, mixture of starting products that differ from each other
only in one characteristic group are subjected to rearrangement reaction and
products are examined.
The product then tells us whether reaction involves intramolecular or
intermolecular pathway.
The intramolecular mechanism would form only normal products whereas
intermolecular mechanism would form normal along with cross products.
D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 7
8. Example- Hoffman Rearrangement
The Hoffman rearrangement of mixture compounds 1 and 2 yields only normal
products 3 and 4 and not cross products 5 and 6. This clearly suggests an
intramolecular reaction pathway for Hoffman rearrangement.
D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 8
10. PINACOL – PINACOLONE REARRANGEMENT
The acid catalyzed transformation of Vicinal diols [1, 2 diols] to ketones or
aldehydes is known as Pinacol - Pinacolone Rearrangement.
General reaction
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11. Mechanism
D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 11
12. Important features
D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 12
13. 1. The rearrangement is intramolecular. The migrating group
starts forming bond with molecular terminus before
departing from molecular origin. This has been confirmed by
crossover experiment. No cross products are isolated in this
rearrangement.
D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 13
14. 2. Stereo electric requirement:
The migrating and leaving group should be trans to each
other.
D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 14
15. 3. If migrating atom is chiral, it retains its
configuration. The migrating group starts forming the
bond with migration terminus before it gets completely
detached from the molecular origin. Therefore,
retention of configuration is observed.
D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 15
16. 4. Migratory aptitude
The ease with which particular group migrates in preference to another is known as its
migratory aptitude.
Migratory aptitude amongst aryl and alkyl groups:
The electron donating group at para and meta position increases migratory aptitude
while electron withdrawing groups decrease migratory aptitude. Due to steric
interference of ortho substituent, o-substituted aryls have less migratory aptitude than
para and meta substituted aryls. The migratory aptitude amongst some aryl groups,
D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 16
17. The migratory aptitude amongst the alkyl groups is,
The general migration order is,
D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 17
18. 5. There are two important points about unsymmetrical diols in
pinacol-pinacolone rearrangement.
Protonate that –OH which gives more stable carbocation.
Migrate that group which is having more migratory aptitude i.e.
more electron rich or which is better to provide electron density
more readily. To explain this, let’s consider following two examples
D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 18
19. A B
D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 19
20. A B
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21. D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 21
22. Examples for practice
D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 22
23. D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 23
24. D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 24
25. D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 25
26. D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 26
28. The α-haloketones having at least one α -hydrogen on treatment with base in the
presence of a nucleophile undergo a rearrangement via cyclopropane to give
carboxylic acid and carboxylic acid derivatives is known as Favorskii
rearrangement.
The nucleophiles can be alcohol, water or amines. Very strict requirement for a
Favorskii rearrangement is presence of α -hydrogen at non-halogenated α -
position.
FAVORSKII REARRANGEMENT
General reaction
D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 28
29. Mechanism
D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 29
When R is EWG Major
Minor
30. Important features
D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 30
31. 1. The halogen substituent can be a chlorine, bromine or
iodine and the base is usually an alkoxide or hydroxide.
D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 31
32. 2. Acyclic halo ketones give carboxylic acid derivative whereas cyclic
ketone give cyclic acid derivative with ring contraction.
Example
Compound A (2-chorocyclohexanone) gives compound B when subjected Favorskii
rearrangement with NaOMe / MeOH
A B
D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 32
33. D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 33
34. 3. The reaction is regio-selective when goes through unsymmetrical cyclopropanone
intermediate. The unsymmetrical cyclopropanone opens in two ways leading to the
formation of mixture of two products in unequal amount.
The compound X on treatment with NaOMe/MeOH gives Y and Z .
X Y Z
D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 34
35. D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 35
36. Examples
D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 36
37. D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 37
38. D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 38
40. The thermal decomposition of acyl azide to isocynate is known as Curtius
rearrangement. If the reaction is carried out in the presence of water, alcohol or
amine, the products are amines, carbamates and urea derivatives respectively.
CURTIUS REARRANGEMENT
General reaction
Acyl azide can be prepared by several ways.
The most common reaction is reaction of acid chloride with alkali azide.
D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 40
41. Mechanism
D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 41
42. Examples
D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 42
43. D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 43
44. D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 44
46. The conversion of aldoximes and ketoximes to the corresponding amides is known as
Beckman rearrangement.
BECKMANN REARRANGEMENT
General reaction
D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 46
47. Mechanism
D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 47
48. Stereo chemical aspect
Beckman rearrangement is often used as a method to determine the initial
configuration of oxime. Let’s observe oxime A and B (general structures are given).
The migratory group approaches nitrogen atom from side opposite to leaving group i.e.
the group which is anti to hydroxyl group migrates. Hence, in Beckman rearrangement
migration of the group depends upon its orientation and not on migratory aptitude.
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49. Cyclic ketones give lactams on Beckman rearrangement. Cyclopentanone gives δ-
lactam on Beckman rearrangement
Very important use of this method is a
preparation of very famous polymer nylon-6.
D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 49
50. D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 50
Beckman rearrangement starting from unsymmetrical ketones
Minor
Major
Less stable-Minor
More stable-Minor
51. D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 51
52. D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 52
53. D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 53
54. D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 54
56. BAEYER-VILLIGER REARRANGEMENT (Oxidation)
Baeyer-Villiger rearrangement involves the conversion of acyclic ketones into ester and
cyclic ketones into lactones by using peroxyacids.
General reaction
The overall reaction is
insertion of oxygen atom
between carbonyl group
and the adjacent alkyl or
aryl group.
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57. Mechanism
D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 57
58. The regio-selectivity of oxygen insertion depends upon the migratory aptitude and ability
of that group to stabilize positive charge in the transition state.
The group with more electron density can stabilize positive charge very well and therefore
migrates preferentially. The migratory aptitude of different groups is as follows:
3° alkyl >2° alkyl > phenyl > 1° alkyl > methyl
D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 58
59. Examples
D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 59
60. D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 60
61. D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 61
62. D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 62
63. D R . V I S H N U A . A D O L E , M G V ' S A S C C O L L E G E , M A N M A D 63
65. The thermal [3,3]-sigmatropic rearrangement of allyl-vinyl ethers to the corresponding
γ,δ-unsaturated carbonyl compound is called Claisen rearrangement. When allyl phenyl
ethers are used as reactants, the rearrangement is called as aromatic Claisen
rearrangement.
CLAISEN REARRANGEMENT
General reaction
Aliphatic Claisen rearrangement Aliphatic Claisen rearrangement
Allyl vinyl
ether
g,d-
unstaurated
aldehyde
Allyl phenyl
ether
o-Allyl phenol
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