1. The document discusses the conformations of decalin, a fused bicyclic hydrocarbon. Decalin can exist in two conformations - cis and trans.
2. The trans conformation is more stable than the cis conformation by 2.7 kcal/mol. This is because the cis conformation contains unfavorable nonbonded interactions and three gauche interactions between hydrogen atoms.
3. The trans conformation is locked in its structure and cannot undergo ring flipping, unlike the cis conformation which can interconvert between two chair-chair conformations.
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.
The Paternò-Büchi reaction involves the photochemical reaction between a carbonyl compound and an alkene to form an oxetane ring. This reaction was first reported in 1909 by Paternò and Chieffi. Several mechanisms are possible, including those involving a diradical intermediate or photoinduced electron transfer. The reaction shows regioselectivity, site selectivity, and stereoselectivity that depend on factors such as the solvent, substituents on the carbonyl compound or alkene, and temperature. The Paternò-Büchi reaction has been used to synthesize various natural products and allows formation of oxetane rings, which are present in several biologically active compounds.
This document discusses the stereochemistry of allenes, spiranes, and biphenyls. It explains that allenes with different substituents on the terminal carbons can exhibit chirality and enantiomers. Spiranes can also show chirality and optical isomerism if they have different substituents. Biphenyls become chiral when large substituents in the ortho position prevent free rotation of the phenyl rings, leading to atropisomerism with a chiral axis and restricted rotation.
This document discusses classical and nonclassical carbocations. Nonclassical carbocations have charge delocalization from neighboring bonds like C=C pi bonds. The main difference is that classical carbocations have charge localized on one carbon, while nonclassical carbocations have charge delocalized by double or single bonds not in the allylic position. Examples like the norbornyl carbocation are given to show how neighboring double bonds can stabilize and delocalize charge through 3-center bonds. Reaction rates and product stereochemistry provide evidence for nonclassical intermediates. While some challenged this view, most chemists accept nonclassical interpretations of carbocation reactions.
This document is a power point presentation on structure and reactivity given by Dr. Gopinath Shirole. It discusses aromaticity based on Huckel's rule and applies the rule to analyze the aromatic, anti-aromatic, and non-aromatic nature of various monocyclic and polycyclic compounds, including benzenoid and non-benzenoid systems as well as annulenes and fused ring compounds like azulenes. Key aspects of aromaticity like planarity, conjugation, and the (4n+2) rule are explained. A total of 34 examples of different compound classes are presented and determined to be aromatic, anti-aromatic, or non-aromatic according to their π
1. The document discusses the conformations of decalin, a fused bicyclic hydrocarbon. Decalin can exist in two conformations - cis and trans.
2. The trans conformation is more stable than the cis conformation by 2.7 kcal/mol. This is because the cis conformation contains unfavorable nonbonded interactions and three gauche interactions between hydrogen atoms.
3. The trans conformation is locked in its structure and cannot undergo ring flipping, unlike the cis conformation which can interconvert between two chair-chair conformations.
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.
The Paternò-Büchi reaction involves the photochemical reaction between a carbonyl compound and an alkene to form an oxetane ring. This reaction was first reported in 1909 by Paternò and Chieffi. Several mechanisms are possible, including those involving a diradical intermediate or photoinduced electron transfer. The reaction shows regioselectivity, site selectivity, and stereoselectivity that depend on factors such as the solvent, substituents on the carbonyl compound or alkene, and temperature. The Paternò-Büchi reaction has been used to synthesize various natural products and allows formation of oxetane rings, which are present in several biologically active compounds.
This document discusses the stereochemistry of allenes, spiranes, and biphenyls. It explains that allenes with different substituents on the terminal carbons can exhibit chirality and enantiomers. Spiranes can also show chirality and optical isomerism if they have different substituents. Biphenyls become chiral when large substituents in the ortho position prevent free rotation of the phenyl rings, leading to atropisomerism with a chiral axis and restricted rotation.
This document discusses classical and nonclassical carbocations. Nonclassical carbocations have charge delocalization from neighboring bonds like C=C pi bonds. The main difference is that classical carbocations have charge localized on one carbon, while nonclassical carbocations have charge delocalized by double or single bonds not in the allylic position. Examples like the norbornyl carbocation are given to show how neighboring double bonds can stabilize and delocalize charge through 3-center bonds. Reaction rates and product stereochemistry provide evidence for nonclassical intermediates. While some challenged this view, most chemists accept nonclassical interpretations of carbocation reactions.
This document is a power point presentation on structure and reactivity given by Dr. Gopinath Shirole. It discusses aromaticity based on Huckel's rule and applies the rule to analyze the aromatic, anti-aromatic, and non-aromatic nature of various monocyclic and polycyclic compounds, including benzenoid and non-benzenoid systems as well as annulenes and fused ring compounds like azulenes. Key aspects of aromaticity like planarity, conjugation, and the (4n+2) rule are explained. A total of 34 examples of different compound classes are presented and determined to be aromatic, anti-aromatic, or non-aromatic according to their π
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
Prochirality refers to a molecule that can be converted from achiral to chiral. Specifically, an achiral molecule containing a prochiral center can form two chiral isomers upon substitution. Prochiral molecules use the R/S notation to label identical substituents around the prochiral center. For example, the two hydrogens on a prochiral carbon in ethanol are labeled R and S. These hydrogens can be classified as enantiotopic, diastereotopic, or homotopic depending on whether substitution would lead to enantiomers, diastereomers, or no new stereocenter.
Annulenes and Heteroannulenes - Premie FernandesBebeto G
This document discusses annulenes and heteroannulenes. Annulenes are monocyclic conjugated systems represented by the general formula (CH)2m and include benzene and cyclooctatetraene. Heteroannulenes contain one or more heteroatoms in the ring, such as pyridine and thiophene. Aromaticity in these systems is determined by Huckel's rule of (4n+2)π electrons. The document examines various annulene and heteroannulene structures of different ring sizes and whether they obey Huckel's rule and exhibit aromatic, anti-aromatic, or non-aromatic behavior.
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.
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.
Thermal reactions involve absorption or evolution of heat, while photochemical reactions require light to occur. Thermochemical reactions can take place in dark conditions, while photochemical reactions only occur in the presence of light. Temperature significantly affects thermochemical reaction rates, while light intensity mainly influences photochemical reaction rates. The free energy change of a thermochemical reaction is always negative, but a photochemical reaction's free energy change may not be negative. Photochemical reactions involve electronic excitation from light absorption. Excited states can undergo chemical reactions or transfer energy through intersystem crossing to more stable triplet states. Photochemical reactions include photoreduction, photoaddition, and photo-rearrangement reactions of carbonyl compounds and alkenes.
Retrosynthes analysis and disconnection approach ProttayDutta1
Retrosynthetic analysis is a technique used to plan organic syntheses by working backwards from the target molecule. It involves mentally deconstructing the target molecule through sequential disconnections and functional group transformations until commercially available starting materials are reached. Each disconnection produces synthons, which are idealized fragments that represent possible reaction precursors. Common types of disconnections include C-X, C-C, and carbonyl bonds. The goal of retrosynthesis is to simplify the target structure and design multiple possible synthesis routes leading from simple starting materials to the target. It helps chemists discover efficient syntheses by considering the reactivity, selectivity, and availability of materials at each step.
The homolytic cleavage of covalent bonds in carbonyl compound under photochemical conditions known as Norrish Type Reactions
They are divided into two types
Norrish Type I
Norrish Type II reaction
1) Pericyclic reactions proceed in a concerted, one-step process via a cyclic transition state with high stereo selectivity. They include cycloadditions, electrocyclic reactions, and sigmatropic rearrangements.
2) Cycloadditions are classified as (2+2) or (4+2) depending on the number of pi electrons involved. Diels-Alder reactions are a common example of a (4+2) cycloaddition.
3) Electrocyclic reactions involve the formation or breaking of a ring with the generation or loss of a pi bond. They can be analyzed using frontier molecular orbital theory and orbital symmetry correlation diagrams.
The document discusses pericyclic reactions and the Woodward-Hoffmann rules for predicting their stereochemistry. It begins by defining pericyclic reactions as concerted reactions where bonds are formed or broken in a cyclic transition state. It then provides examples of different types of pericyclic reactions, including electrocyclizations, cycloadditions, and sigmatropic rearrangements. The Woodward-Hoffmann theory is explained, showing how it can be used to predict whether a reaction will proceed with antarafacial conrotation or suprafacial disrotation based on whether the reaction is thermally or photochemically induced. Specific examples like cyclobutene formation and the Diels-Alder reaction are analyzed in
The document discusses charge transfer complexes and the different types of charge transfer that can cause color in transition metal complexes. It explains that ligand to metal charge transfer and metal to ligand charge transfer can produce color when pi donor or accepting ligands are present with metals lacking or having low oxidation state d-electrons, respectively. As an example, it describes the metal to ligand charge transfer observed in the spectra of the tris(bipyridine)ruthenium(II) dichloride complex.
The document discusses helicity and chirality in organic chemistry. It explains that helicity arises in molecules with a helical shape, which are inherently chiral. It also describes how overcrowding in molecules like helicenes can lead to helicity. The document then discusses asymmetric synthesis and how existing chiral centers induce asymmetric induction to form diastereomers in unequal amounts. It presents Cram's rule and Prelog's rule as methods to predict the configuration of the predominant diastereomer based on the existing chiral centers.
This document summarizes aromatic nucleophilic substitution reactions. It discusses the SNAr, SN1, and benzyne mechanisms. For SNAr, a strong withdrawing group is needed for reactivity. SN1 is rare for aromatics. In the benzyne mechanism, elimination of H forms benzyne which then adds the nucleophile, producing either ortho or para substituted products. Radiocarbon labeling is used to identify the products. In summary, the document outlines different aromatic nucleophilic substitution reaction mechanisms and factors affecting their reactivity.
This document discusses ligand substitution reactions in octahedral complexes. It describes the main mechanisms of ligand substitution including dissociative (SN1), associative (SN2), and concerted (interchange) pathways. It also discusses hydrolysis reactions and anation reactions as types of ligand substitutions. Specific examples are provided of acid and base hydrolysis in octahedral cobalt complexes, and factors that influence the reaction mechanisms and rates are outlined.
concept of chirality and concept of pro chiralityDiscover for new
This document discusses the concepts of chirality and prochirality. Chirality refers to molecules that have mirror images that are not superimposable, often involving a carbon bonded to four different groups. Prochirality refers to molecules that can be converted from achiral to chiral in a single step. Chirality and prochirality are important concepts in stereochemistry and biochemistry, as most biologically relevant molecules like carbohydrates, proteins, and nucleic acids are chiral.
This document discusses sigmatropic rearrangements, a type of pericyclic reaction involving intramolecular migration of an atom or group across a conjugated pi system. It defines sigmatropic rearrangements and explains that they can occur through thermal or photochemical processes. The document categorizes different types of sigmatropic rearrangements such as Cope, Claisen, and [2,3] rearrangements. It provides examples of these reactions and discusses factors that determine reaction stereochemistry such as suprafacial versus antrafacial migration. The document also references several organic chemistry textbooks for further information on sigmatropic rearrangement mechanisms and applications.
This document provides an overview of 2D NMR spectroscopy techniques, specifically HETCOR. It discusses the principles behind 2D NMR, describing how it plots data in two frequency axes rather than one, providing more information about a molecule's structure. It then explains the four periods that occur in a 2D NMR experiment: preparation, evolution, mixing, and detection. The document focuses on HETCOR, describing it as a heteronuclear experiment that provides correlations between different nuclei like protons and carbons. Examples of HETCOR spectra are provided to show how they indicate couplings between protons and the carbons they are attached to. Related techniques like HSQC and HMBC are also briefly described.
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.
Cyclohexane exists in different conformations viz chair, boat, twist boat and half chair. These conformations possess different energies. Therefore they differ in energy.
An outline of stereochemistry in simple terms.
I wish it will be understandable and useful.
Just go through it and enjoy learning.
Rejoice in learning friends.
This document discusses the topicity of ligands and faces in stereochemistry. It begins by introducing the concepts of homotopic and heterotopic ligands and faces. Ligands or faces are considered homotopic if substitution or addition of a reagent to them results in the same product. They can also be considered homotopic if a symmetry operation allows them to be exchanged. The document provides numerous examples to illustrate these criteria for determining if ligands or faces are homotopic. It focuses on symmetry operations like C2 and C3 axes that allow the exchange of positions of ligands and faces.
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
Prochirality refers to a molecule that can be converted from achiral to chiral. Specifically, an achiral molecule containing a prochiral center can form two chiral isomers upon substitution. Prochiral molecules use the R/S notation to label identical substituents around the prochiral center. For example, the two hydrogens on a prochiral carbon in ethanol are labeled R and S. These hydrogens can be classified as enantiotopic, diastereotopic, or homotopic depending on whether substitution would lead to enantiomers, diastereomers, or no new stereocenter.
Annulenes and Heteroannulenes - Premie FernandesBebeto G
This document discusses annulenes and heteroannulenes. Annulenes are monocyclic conjugated systems represented by the general formula (CH)2m and include benzene and cyclooctatetraene. Heteroannulenes contain one or more heteroatoms in the ring, such as pyridine and thiophene. Aromaticity in these systems is determined by Huckel's rule of (4n+2)π electrons. The document examines various annulene and heteroannulene structures of different ring sizes and whether they obey Huckel's rule and exhibit aromatic, anti-aromatic, or non-aromatic behavior.
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.
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.
Thermal reactions involve absorption or evolution of heat, while photochemical reactions require light to occur. Thermochemical reactions can take place in dark conditions, while photochemical reactions only occur in the presence of light. Temperature significantly affects thermochemical reaction rates, while light intensity mainly influences photochemical reaction rates. The free energy change of a thermochemical reaction is always negative, but a photochemical reaction's free energy change may not be negative. Photochemical reactions involve electronic excitation from light absorption. Excited states can undergo chemical reactions or transfer energy through intersystem crossing to more stable triplet states. Photochemical reactions include photoreduction, photoaddition, and photo-rearrangement reactions of carbonyl compounds and alkenes.
Retrosynthes analysis and disconnection approach ProttayDutta1
Retrosynthetic analysis is a technique used to plan organic syntheses by working backwards from the target molecule. It involves mentally deconstructing the target molecule through sequential disconnections and functional group transformations until commercially available starting materials are reached. Each disconnection produces synthons, which are idealized fragments that represent possible reaction precursors. Common types of disconnections include C-X, C-C, and carbonyl bonds. The goal of retrosynthesis is to simplify the target structure and design multiple possible synthesis routes leading from simple starting materials to the target. It helps chemists discover efficient syntheses by considering the reactivity, selectivity, and availability of materials at each step.
The homolytic cleavage of covalent bonds in carbonyl compound under photochemical conditions known as Norrish Type Reactions
They are divided into two types
Norrish Type I
Norrish Type II reaction
1) Pericyclic reactions proceed in a concerted, one-step process via a cyclic transition state with high stereo selectivity. They include cycloadditions, electrocyclic reactions, and sigmatropic rearrangements.
2) Cycloadditions are classified as (2+2) or (4+2) depending on the number of pi electrons involved. Diels-Alder reactions are a common example of a (4+2) cycloaddition.
3) Electrocyclic reactions involve the formation or breaking of a ring with the generation or loss of a pi bond. They can be analyzed using frontier molecular orbital theory and orbital symmetry correlation diagrams.
The document discusses pericyclic reactions and the Woodward-Hoffmann rules for predicting their stereochemistry. It begins by defining pericyclic reactions as concerted reactions where bonds are formed or broken in a cyclic transition state. It then provides examples of different types of pericyclic reactions, including electrocyclizations, cycloadditions, and sigmatropic rearrangements. The Woodward-Hoffmann theory is explained, showing how it can be used to predict whether a reaction will proceed with antarafacial conrotation or suprafacial disrotation based on whether the reaction is thermally or photochemically induced. Specific examples like cyclobutene formation and the Diels-Alder reaction are analyzed in
The document discusses charge transfer complexes and the different types of charge transfer that can cause color in transition metal complexes. It explains that ligand to metal charge transfer and metal to ligand charge transfer can produce color when pi donor or accepting ligands are present with metals lacking or having low oxidation state d-electrons, respectively. As an example, it describes the metal to ligand charge transfer observed in the spectra of the tris(bipyridine)ruthenium(II) dichloride complex.
The document discusses helicity and chirality in organic chemistry. It explains that helicity arises in molecules with a helical shape, which are inherently chiral. It also describes how overcrowding in molecules like helicenes can lead to helicity. The document then discusses asymmetric synthesis and how existing chiral centers induce asymmetric induction to form diastereomers in unequal amounts. It presents Cram's rule and Prelog's rule as methods to predict the configuration of the predominant diastereomer based on the existing chiral centers.
This document summarizes aromatic nucleophilic substitution reactions. It discusses the SNAr, SN1, and benzyne mechanisms. For SNAr, a strong withdrawing group is needed for reactivity. SN1 is rare for aromatics. In the benzyne mechanism, elimination of H forms benzyne which then adds the nucleophile, producing either ortho or para substituted products. Radiocarbon labeling is used to identify the products. In summary, the document outlines different aromatic nucleophilic substitution reaction mechanisms and factors affecting their reactivity.
This document discusses ligand substitution reactions in octahedral complexes. It describes the main mechanisms of ligand substitution including dissociative (SN1), associative (SN2), and concerted (interchange) pathways. It also discusses hydrolysis reactions and anation reactions as types of ligand substitutions. Specific examples are provided of acid and base hydrolysis in octahedral cobalt complexes, and factors that influence the reaction mechanisms and rates are outlined.
concept of chirality and concept of pro chiralityDiscover for new
This document discusses the concepts of chirality and prochirality. Chirality refers to molecules that have mirror images that are not superimposable, often involving a carbon bonded to four different groups. Prochirality refers to molecules that can be converted from achiral to chiral in a single step. Chirality and prochirality are important concepts in stereochemistry and biochemistry, as most biologically relevant molecules like carbohydrates, proteins, and nucleic acids are chiral.
This document discusses sigmatropic rearrangements, a type of pericyclic reaction involving intramolecular migration of an atom or group across a conjugated pi system. It defines sigmatropic rearrangements and explains that they can occur through thermal or photochemical processes. The document categorizes different types of sigmatropic rearrangements such as Cope, Claisen, and [2,3] rearrangements. It provides examples of these reactions and discusses factors that determine reaction stereochemistry such as suprafacial versus antrafacial migration. The document also references several organic chemistry textbooks for further information on sigmatropic rearrangement mechanisms and applications.
This document provides an overview of 2D NMR spectroscopy techniques, specifically HETCOR. It discusses the principles behind 2D NMR, describing how it plots data in two frequency axes rather than one, providing more information about a molecule's structure. It then explains the four periods that occur in a 2D NMR experiment: preparation, evolution, mixing, and detection. The document focuses on HETCOR, describing it as a heteronuclear experiment that provides correlations between different nuclei like protons and carbons. Examples of HETCOR spectra are provided to show how they indicate couplings between protons and the carbons they are attached to. Related techniques like HSQC and HMBC are also briefly described.
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.
Cyclohexane exists in different conformations viz chair, boat, twist boat and half chair. These conformations possess different energies. Therefore they differ in energy.
An outline of stereochemistry in simple terms.
I wish it will be understandable and useful.
Just go through it and enjoy learning.
Rejoice in learning friends.
This document discusses the topicity of ligands and faces in stereochemistry. It begins by introducing the concepts of homotopic and heterotopic ligands and faces. Ligands or faces are considered homotopic if substitution or addition of a reagent to them results in the same product. They can also be considered homotopic if a symmetry operation allows them to be exchanged. The document provides numerous examples to illustrate these criteria for determining if ligands or faces are homotopic. It focuses on symmetry operations like C2 and C3 axes that allow the exchange of positions of ligands and faces.
Key concepts of Geometrical Isomerism useful for the Undergraduate and Postgraduate students of Pharmacy , Chemistry and Post graduates of Pharmaceutical and Medicinal Chemistry
This document discusses the topicity of ligands and faces in stereochemistry. It defines homotopic and heterotopic ligands and faces, and describes two criteria - substitution/addition and symmetry - for determining if ligands or faces are homotopic. Homotopic ligands can be interchanged without changing the structure, while heterotopic ligands lead to different structures upon substitution or addition. Symmetry operations like Cn axes may also indicate homotopic relationships. Examples are provided to illustrate homotopic and heterotopic ligands and faces.
This document provides an overview of stereochemistry concepts including:
- Stereoisomers such as configurational, conformational, geometrical, optical isomers and relationships between them.
- Rules for assigning R/S and E/Z descriptors using the Cahn-Ingold-Prelog priority system to name stereoisomers.
- Cis-trans nomenclature for geometrical isomers and its limitations.
- Fischer's D-L notation for distinguishing carbohydrates and amino acid enantiomers and determining configurations.
- Meso compounds which are achiral despite having multiple stereocenters due to an internal plane of symmetry.
The document provides information about geometrical isomerism including definitions, examples, and methods of determination. It defines geometrical isomerism as arising from restricted rotation around a double bond that leads to different spatial arrangements of atoms. Common types of geometrical isomers include cis-trans, E-Z, and syn-anti. Methods for determining configurations include cyclization reactions, conversion to compounds of known configuration, differences in physical properties, and use of stereoselective or stereospecific reactions.
1. Hybridization is a model that explains how atoms combine orbitals to form bonds in molecules. It involves mixing atomic orbitals of similar energies to form new hybrid orbitals used in bonding.
2. There are several types of hybridization depending on how many orbitals mix, including sp, sp2 and sp3 hybridization. This determines the geometry and bond angles of the molecule.
3. Hybridization also influences bond properties like bond length and bond strength. Polar bonds form when there is a large difference in electronegativity between the atoms, and the overall polarity of a molecule depends on whether individual bond dipoles cancel or reinforce.
Introduction to stereochemistry, Representation of 3D molecules, R/S nomenclature, D-L and M-P convention, Topicity, Prochirality, Allenes, Biphenyls, Spiranes, Hemispirane.
This document provides an overview of stereochemistry. It begins by defining constitutional and stereoisomers. Stereoisomers have the same connectivity but different arrangements in space, and include enantiomers and diastereomers. The document then discusses chiral centers and molecules, and how the presence of a chiral center leads to chirality. It also covers topics such as optical activity, properties of enantiomers and diastereomers, meso compounds, geometric isomers, and resolving racemic mixtures. Resolution methods discussed include conversion to diastereomers and differential absorption chromatography.
The document discusses the Ramachandran plot, which is a plot of the phi (φ) angle versus the psi (ψ) angle of amino acid residues in protein structures. It explains that these two angles are limited by steric constraints from the atoms in the protein backbone. The allowed and disallowed regions in the Ramachandran plot correspond to conformations where backbone atoms are too close or clashing versus conformations where they have sufficient space. Most protein structures fall within the allowed regions, helping explain their stable secondary structures.
This document discusses the limits on rotation in protein backbones and defines the psi (ψ) and phi (φ) angles. It introduces the Ramachandran plot, which maps allowed combinations of ψ and φ angles based on steric constraints. The plot reveals preferred regions that correspond to common secondary structures like alpha helices and beta sheets. Understanding the steric limits on individual amino acid residues provides insight into how proteins fold into their specific three-dimensional shapes.
This document provides an overview of stereochemistry concepts taught in an organic chemistry course. It defines different types of isomerism including structural, stereoisomerism, and tautomerism. It describes geometrical isomerism which can occur in alkenes and cyclic compounds due to restricted bond rotation. The document introduces the E/Z system for naming geometrical isomers based on priority of substituents. It also discusses optical isomerism and defines terms like chiral, enantiomers, and diastereomers.
This document provides an overview of organic chemistry concepts including:
1. Carbon is unique due to its ability to form chains (catenation) and bonds (tetravalency), making it central to organic compounds. Hybridization allows carbon to form different types of bonds to satisfy its valence.
2. Organic compounds can be classified based on their structure as acyclic/aliphatic, cyclic/aromatic, or heterocyclic aromatic. Nomenclature systems like IUPAC provide standardized naming conventions.
3. Key concepts include structural representations showing bonding and 3D orientation, and classification of organic compounds based on functional groups and ring structures. Hybridization explains how carbon satisfies its valence to form
The document discusses how the electronic distribution of a drug molecule influences its biological activity and interactions with target sites. It introduces the Hammett constants which quantify electronic effects of substituents on aromatic rings. Hansch analysis attempts to mathematically relate drug activity to measurable chemical and physical properties using parameters like Hammett constants, molar refractivity, and steric factors. Craig plots provide a visual representation of substituent electronic properties.
Year 2 Organic Chemistry - Mechanism and Stereochemistry Lecture 2University of Warwick
1) The document discusses conformational analysis in organic chemistry, focusing on ethane, butane, and cyclic molecules.
2) In ethane, the staggered conformation is lowest in energy due to orbital overlap between filled and empty orbitals. Butane has several distinct conformations with varying energies.
3) Cyclohexane exhibits angle strain as the bond angles are further from 109 degrees than in a puckered structure. Acyclic molecules can have high energy due to 1,3-strain from consecutive gauche interactions.
Ion-exchange chromatography separates molecules on the basis of charge. The stationary phase contains resin beads with cationic or anionic functional groups that can bind positively or negatively charged molecules. Proteins either bind to the resin based on their net charge or pass through. Elution is achieved by changing pH or adding salts to compete for binding sites on the resin. Modern systems automate ion-exchange chromatography using gradients controlled by multiple pumps and fraction collectors.
Stereochemistry is the study of the three-dimensional structure of molecules. Stereoisomers differ in their spatial arrangement but have the same connectivity and functional groups. The two main classes of isomers are constitutional isomers and stereoisomers. Stereochemistry plays an important role in determining the properties and reactions of organic compounds. Many drugs exhibit different biological effects based on their stereochemistry. Enzymes can also distinguish between stereoisomers.
1) The document discusses various topics in stereochemistry including different types of isomers such as constitutional isomers, stereoisomers, and configurational isomers.
2) It also covers concepts like chirality, optical activity, enantiomers, diastereomers, and resolving racemic mixtures.
3) Examples are provided to illustrate different isomer types as well as conformational analysis using Newman projections and sawhorse diagrams.
1. The document describes several organic reactions and asks questions about determining product structures and rationalizing stereochemical outcomes.
2. Key concepts discussed include: conformational analysis to determine reactivity; Cram chelation control to set stereochemistry; Ireland-Claisen rearrangements maintaining configuration; and using chiral auxiliaries to induce diastereoselectivity through chelation.
3. Rationalizations of stereochemical outcomes involve analyzing transition states, identifying favored conformations, and determining approach selectivity based on steric interactions.
1) The document describes the procedure for synthesizing benzimidazole from o-phenylenediamine and formic acid.
2) Key steps include heating a mixture of o-phenylenediamine and excess formic acid at 100°C for 2 hours, then making the reaction mixture alkaline with sodium hydroxide to precipitate crude benzimidazole.
3) Benzimidazole has biological applications as an active component in anthelmintic and antiulcer drugs, and its derivatives also show antimicrobial and anticancer properties.
This document summarizes the synthesis of 7-Hydroxy-4-Methyl Coumarin via the Pechmann condensation reaction of resorcinol and ethyl acetoacetate in the presence of concentrated sulfuric acid. Coumarins are an important class of compounds that are found in plants and have various medical applications such as antimicrobial and antitumor properties. The procedure involves cooling concentrated sulfuric acid to below 5°C and adding a solution of resorcinol and ethyl acetoacetate dropwise, followed by workup to obtain an impure product that is recrystallized from ethanol.
This document summarizes the synthesis of 1-bromo-2-naphthol from 2-naphthol. It involves selectively brominating 2-naphthol using sodium bromide and oxone. 2-Naphthol, sodium bromide, and oxone are ground together and reacted overnight. Ethyl acetate is then used to extract the crude 1-bromo-2-naphthol product, which is a dark brown solid. The theoretical and practical yields are calculated and the percentage yield is reported.
Theories of coordination compounds, CFSE, Bonding in octahedral and tetrahedral complex, color of transition metal complex, magnetic properties, selection rules, Nephelxeuatic effect, angular overlap model
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https://www.etran.rs/2024/en/home-english/
1. C
X
Y
A B
Relation
between
X & Y
TOPICITY
By
Dr. G. Krishnaswamy
Faculty
DOS & R in Organic Chemistry
Tumkur University
Tumakuru
Bottom face
Top face
10/6/2019 1
2. Earlier part of stereochemistry was concentrated on the stereo
center.
(TOPOs in Greek means place)
C
X
Y
A B
Stereo center
*
C
X
Y
A B
Relation
between
X & Y
Now we start to see the relationship between the ligands
attached to stereo center if the attached ligands are
homomorphic in nature.
10/6/2019 2
3. Homomorphic Groups / Ligands / Atoms
The Groups / ligands / atoms which are in isolation look the
same or super imposable mirror images of each other are
called homomorphic groups / ligands / atoms.
C
CH3
CH3
H H Homomorphic
groups
Homomorphic atoms
Homo in greek means same
Morph in greek means form
10/6/2019 3
4. In case of atoms, they must be of same element example two
H’s or two Br atoms.
C
CH3
CH3
HH
H H
Isolated Isolated
Identical and super imposable
If we isolate the two H’s, then they are same and super
imposable to each other hence they are called homomorphic
hydrogen's.
10/6/2019 4
5. In case of groups, they must have same constitution and
configuration. Example two methyl or two Ph groups of same
chirality R or S.
They are called homomorphic groups / ligands / atoms.
TOPICITY can be defined as geometrical or
sterochemical relationship between homorphic groups / ligands
/ atoms and structure of the molecule.
Different types of relationships are possible for homorphic
ligands / groups / atoms.
1. Homo topic (Homo-same; topo-place)
2. Hetero topic (Hetero-different; topo-place)
10/6/2019 5
6. Ligands can not by itself be called homotopic or heterotopic, in
order to use this terminologies a comparison with other
homomorphic ligand or ligands present either in the same
molecule (internal comparison) or in a different molecule
(external comparison) is necessary.
Two criteria are used to decide whether the ligands / groups are
equivalent or not
1. Substitution-addition criteria
2. Symmetry criteria
Are employed to determine the topic relationship of
homomorphic ligands
10/6/2019 6
7. 1. (a) Homo topic ligands
Two or more ligands that are identical when viewed in isolation
but individual replacement of two identical ligands by another
give rise to identical molecule, then they are called homotopic
ligands.
1. Substitution-addition criteria
Two homomorphic ligands are homotopic if substitution
(replacement) of first one and other by different test ligand
leads to homomers or identical product.
10/6/2019 7
8. Br
Br
Ha Hb
Ha D
Hb D
Br
Br
D H
Br
Br
H D
Identical
product
HOMOTOPIC
Hence, Ha & Hb are
homotopic atoms
10/6/2019 8
9. Ha X
Hb X
Identical
productC C C
Hb
HaH
H
C C C
H
XH
H
C C C
X
HH
H
Hence, Ha & Hb are
homotopic atoms
10/6/2019 9
10. Hence, Ha, Hb & Hc are
homotopic atoms
Ha F
Hb F
Identical
products
COOH
Hc
Ha Hb
Hc F
COOH
H
F H
COOH
H
H F
COOH
F
H H
10/6/2019 10
11. Ha D
Identical
products
COOH
Ha OH
Hb D
COOH
D OH
COOH
H OH
HbHO
COOH
HO D
COOH
HO H
COOH
Hence, Ha & Hb are
homotopic atoms
Turn the
molecule 180o in
plane
10/6/2019 11
12. 1. (b) Homo topic faces
Two faces of a pi system or a double bond are homotopic
if addition to either face gives same or identical product.
Bottom face
Top face
Backface
Frontface
OR
10/6/2019 12
16. 2. Symmetry criteria
2. (a) Homo topic ligands
Two homomorphic ligands are homotopic if they can
interchange position by rotation around Cn axis.
HbHa
H3C CH3
C2
HaHb
H3C CH3
180o
rotation
They are identical and hence homotopic ligands10/6/2019 16
18. 2. (b) Homo topic faces
C2
180o
rotationCC
H3C
H
CH3
H
CC
H3C
H
CH3
H
Two faces of pi system are homotopic if they can
interchange face result in same structure by rotation
around C2 axis.
They are identical and hence it has homotopic face10/6/2019 18
19. H H
H H
O
C2
H H
H H
O
180o
rotation
They are identical and hence it has homotopic face
10/6/2019 19
20. NMR Spectroscopy of Homotopic Hydrogen
If the hydrogen atoms in the molecule are homotopic, then
they are chemically equivalent. Hence they will resonate at
same chemical shift values.
H
C
H
Cl
Cl
C
O
CC
H
H
H
H
H
H
10/6/2019 20
21. SUMMARY
Between homotopic groups and faces no differentiation is
possible either by enzyme or by NMR or by human being
because they are homomers or identical.
Topicity
Substitution-
addition
criteria
Symmetry
criteria
Reactivity
Homotopic
groups and
faces
Homomers /
Identical
Cn or C2
No
differentiation
possible
10/6/2019 21
22. 2. Hetero topic ligands
Two or more ligands that are identical when viewed in
isolation but individual replacement of two identical ligands
by another ligand give rise to two structurally different
(isomeric) molecule, then they are called heterotopic
ligands.
10/6/2019 22
24. Two or more ligands in a molecule that are identical on
individual replacement by another ligand give rise to two
molecule that constitutional isomers of each other, then the
original two ligands are said to be constitutionally
heterotopic ligands.
Constitutionally Hetero topic ligands
10/6/2019 24
27. Stereo chemically heterotopic
Two or more ligands in a molecule that are identical on
individual replacement by another ligand give rise to two
molecule that are enantiomers / super imposable mirror
images of each other, then the original two ligands are said
to be enantiotopic ligands.
Two or more ligands in a molecule that are identical on
individual replacement by another ligand give rise to two
molecule that are diastereomers / non super imposable not
mirror images of each other, then the original two ligands
are said to be diastereotopic ligands.
10/6/2019 27
28. (a) Enantiotopic ligands
1. Substitution-addition criteria
Two homomorphic ligands are enantiotopic if substitution
(replacement) of first one and other by different test ligand
leads to enantiomers.
COOH
C
CH3
Ha Hb
COOH
C
CH3
Br H
COOH
C
CH3
H Br
Ha
Br
Hb
Br
1
2
3
4
1
2
3
4
(S)
(R)
They are
enantiomers and
hence enantiotopic
ligands
10/6/2019 28
29. C CC
(R)(S)
H
Cl
Ha
Hb
Ha Cl Hb Cl
C CC
H
Cl
Cl
H
CC C
H
Cl
Cl
H
1
23
41
23
4
They are enantiomers and hence enantiotopic ligands
10/6/2019 29
30. (R) (S)
OH
O
Hb Ha
Ha D Hb D
OH
O
H D
OH
O
D H
They are enantiomers and hence Ha & Hb are enantiotopic ligands10/6/2019 30
31. (R)(S)
Ha D Hb D
H3C
CH3
Ha
H
Hb
H
H3C
CH3
D
H
H
H
H3C
CH3
H
H
D
H
They are enantiomers and hence Ha & Hb are enantiotopic ligands10/6/2019 31
32. (b) Enantiotopic faces
Two faces of a pi system or a double bond are enantiotopic if
addition to either face gives enantiomeric product.
(R) (S)
O
H
Ph
Top face
Bottom face
H
Ph
Et
OH
H
Ph
OH
Et
EtMgBr EtMgBr
Addition reaction
from either face leads
to formation of
enantiomers and
hence two faces are
enantiotopic
10/6/2019 32
34. Molecules having stereo heterotopic ligands (enantiotopic)
exhibit prostereoisomerism or prochirality
Prochiral molecules are those which are achiral can be
converted into chiral molecule in a single step.
Prostereoisomerism or Prochirality
Prochirality may be the result of substitution reaction of Sp3
carbon substituent (usually hydrogen) with other substituent
results in chiral center.
OR
Prochirality may be the result of addition reaction of an Sp2
carbon to a chiral Sp3 carbon with nucleophile.
10/6/2019 34
35. (R) (S)
Ha Cl Hb Cl
12
3
1
2
3
4
C
CH3
Hb
Ha
4
C
CH3
H
Cl
C
CH3
Cl
H
4th group on wedge bond hence
clock wise "S" configuration
PROCHIRAL
CHIRAL CHIRAL
PROCHIRAL
HYDROGENS
Prochirality may be the result of substitution reaction of Sp3
carbon substituent.
10/6/2019 35
36. Prochirality may be the result of addition reaction of an Sp2
carbon.
(R)(S)
NaBH4
1
2
3
1
2
3
4
CH2H3C
C
H3C
4
View the molecule through C-H bond for assigning the
configuration
PROCHIRAL
CHIRAL CHIRAL
O
C
H
OH
H3C
C
H2
C
OH
H
H3C
C
H2
H3C H3C
NaBH4
10/6/2019 36
37. 2. Symmetry criteria
(a) Enantiotopic ligands
Two homomorphic ligands are enantiotopic if they can
interchangeable through plane of symmetry or center of
inversion or Sn axis.
COOH
Ha OH
Hb OH
COOH
plane of symmetry
10/6/2019 37
39. O
H
Ph
Top face
Bottom face
O
Ph
H
Top face
Bottom face
(b) Enantiotopic faces
Two faces are enantiotopic if they can interchangeable
through plane of symmetry or center of inversion or Sn axis.
Structure is not same upon rotation hence mirror plane
exists.
10/6/2019 39
41. NMR Spectroscopy of Enantiotopic Hydrogen
If the hydrogen atoms in the molecule are enantiotopic, then
they are chemically equivalent. Hence they will resonate at
same chemical shift values.
10/6/2019 41
42. SUMMARY
Between enantiotopic groups and faces differentiation is
possible either by enzyme or by NMR in chiral reagent or
catalyst.
Topicity
Substitution-
addition
criteria
Symmetry
criteria
Reactivity
Enantiotopic
groups and
faces
Enantiomers σh or Sn
Differentiatio
n possible
10/6/2019 42
43. (a) Diastereotopic ligands
Substitution-addition criteria
Two homomorphic ligands are diastereotopic if substitution
(replacement) of first one and other by different test ligand
not already attached to the molecule leads to diastereomers
/ non super imposable not mirror images.
10/6/2019 43
44. Substitution of Ha & Hb by Cl leads to formation of trans
and cis products which are diastereomers and hence two
hydrogens are diastereotopic
H3C
C C
H
Hb
Ha
H3C
C C
H
H
Cl
H3C
C C
H
Cl
H
Ha
Cl
Hb
Cl
-CH3 & -Cl
are
Cis
-CH3 & -Cl
are
Trans
10/6/2019 44
45. Ha
Cl
Hb
Cl
-Br & -Cl
are
Trans
-Br & -Cl
are
Cis
Br
H
Ha
Hb
Br
H
Cl
H
Br
H
H
Cl
Substitution of Ha & Hb by Cl leads to formation of trans
and cis products which are diastereomers and hence two
hydrogens are diastereotopic10/6/2019 45
46. Geminal methylene protons adjacent to a stereocenter on
substitution test by other ligands not already present in the
molecule usually leads to diastereomers and are usually
diastereotopic.
O
Hb Ha
Stereo center
Adjacent to a stereo
center hence they are
usually diastereotopic
10/6/2019 46
47. Ha
Cl
Hb
Cl
O
Hb Ha
O
Cl H
O
H Cl
(S)
(R) (R)
(R)
RR SS
RS SR
Enantiomers
Enantiomers
Diastereomers
Diastereomers
Diastereomers
Substitution of Ha
& Hb by Cl leads to
formation of
diastereomers and
hence two
hydrogens are
diastereotopic
10/6/2019 47
48. Ha
D
Hb
D
(S)
(R) (R)
(R)
CH3
H Cl
Hb Ha
Cl
CH3
H Cl
D H
Cl
CH3
H Cl
H D
Cl
(R)
Substitution of Ha
& Hb by D leads to
formation of
diastereomers and
hence two
hydrogens are
diastereotopic
10/6/2019 48
49. (b) Diastereotopic faces
Two faces of a carbonyl group adjacent to a stereo center on
addition reaction leads to diastereomers and possess
diastereotopic face.
Stereo center
CH3
O
H3C H
C6H5
Two faces of a
carbonyl group
adjacent to a stereo
center
10/6/2019 49
50. HCNHCN
(S) (R)
(R)
CH3
O
H3C H
C6H5
Top face
Bottom face
(R)
CH3
OH
H3C H
C6H5
(R)
CH3
CN
H3C H
C6H5
NC HO
Additon of HCN two
face of carbonyl adjcent
to stereo center leads to
formation of
diastereomers and hence
two faces are
diastereotopic.
10/6/2019 50
51. NMR Spectroscopy of Diastereotopic Hydrogen
If the hydrogen atoms in the molecule are diastereotopic,
then they are chemically and magnetically non equivalent.
Hence they will resonate at different chemical shift values.
H
H
HO
H
CH3
Diastereotopic hydrogens
Due to non equivalent nature of protons
it splits into multiplet.
10/6/2019 51
52. SUMMARY
Between diastereotopic groups and faces differentiation is
possible either by enzyme or by reagent or by NMR.
Topicity
Substitution-
addition
criteria
Symmetry
criteria
Reactivity
Diastereotopic
groups and
faces
Diastereomers
Not
applicable
Differentiation
possible
10/6/2019 52
54. Ha
Hb
D
H
H
D
Substitution of Ha & Hb by D
leads to formation of
homomers and hence two
hydrogens are homotopic.
MeO OMe
H H
MeO OMe
D H
MeO OMe
H D
Substitution of H & H by D
leads to formation of
homomers and hence two
hydrogens are homotopic.
10/6/2019 54
55. Substitution of H & H by D
leads to formation of
homomers and hence two
hydrogens are homotopic.
Cl Cl
H H
Cl Cl
D H
Cl Cl
H D
R R
R R
R R
O O
H
Ph CH3
H3C Ph
H
O O
H
Ph CH3
H3C Ph
H
C2
H & H are
interchangeable by C2
rotation and hence two
hydrogens are homotopic.
10/6/2019 55
56. H
H
D
H
H
D
Substitution of H & H by D
leads to formation of homomers
and hence two hydrogens are
homotopic.
H
H
D
H
H
D
Substitution of H & H by D
leads to formation of
enantiomers and hence two
hydrogens are enantiotopic.
10/6/2019 56
57. H H
Cl
D H
Cl
H D
Cl
Substitution of H & H by D
leads to formation of
enantiomers and hence two
hydrogens are enantiotopic.
H
H
D
H
H
D
Exo Endo
Substitution of H & H by D
leads to formation of
diastereomers and hence two
hydrogens are diastereotopic.
10/6/2019 57
58. H
H
D
H
H
D
Substitution of H & H by D
leads to formation of
diastereomers and hence two
hydrogens are diastereotopic.
10/6/2019 58