1) The chapter discusses various reactions of aromatic compounds including electrophilic aromatic substitution, nucleophilic aromatic substitution, and Friedel-Crafts reactions. 2) Key mechanisms covered include the step-by-step processes for bromination of benzene, nitration, sulfonation, and the Friedel-Crafts alkylation. 3) The effects of different substituents on the reactivity and orientation of substitution reactions are explained in detail.
This document provides an overview of electrophoresis. It discusses how electrophoresis works, where charged particles migrate through a solution under the influence of an electric field. It describes factors that affect electrophoresis like the charge, size, and shape of samples as well as the electric field strength, buffer composition, ionic strength, and pH. It also summarizes different electrophoresis techniques like moving boundary electrophoresis, SDS-PAGE, and agarose gel electrophoresis. SDS-PAGE is commonly used to separate proteins by size, while agarose gel electrophoresis separates DNA fragments.
Chromatography is a technique used to separate chemical mixtures by exploiting differences in how components partition between a stationary and mobile phase. There are various types including adsorption, partition, ion exchange, and affinity chromatography. The document provides details on the basic principles, mechanisms, phases used, instrumentation, and common techniques like column chromatography, paper chromatography, thin layer chromatography, and gas chromatography.
This document provides an overview of fluorimetry. It defines fluorimetry as the measurement of fluorescence with a spectrofluorimeter. Fluorescence occurs when a substance emits light after absorbing radiation. Factors that affect fluorescence include the nature of the molecule, substituents, concentration, oxygen, pH, temperature, and viscosity. The instrumentation involves a light source, filters, sample cells, and detectors like photomultiplier tubes. Applications of fluorimetry include determining inorganic substances, using fluorescent indicators, developing fluorescent reagents, organic analysis, pharmaceutical analysis, and liquid chromatography.
described about optical activity, specific rotation, angle of rotation and circular dichroism and differences between ORD and CD and applications of ORD AND CD,
- Glucose biosensors are analytical devices used for diabetes management that integrate a biological recognition element (e.g. glucose oxidase) with a transducer to convert glucose detection into a measurable signal.
- Advantages of glucose biosensors over laboratory tests include allowing for routine, wireless, home-based glucose monitoring without relying on laboratory resources.
- Glucose biosensors work by catalyzing the oxidation of glucose and detection of the resulting hydrogen peroxide production through electrochemical transducers.
Photochemical reactions are chemical reactions initiated by the absorption of light energy. These reactions involve an organic molecule absorbing a photon which causes electronic excitation from a lower to a higher orbital. The excited molecule may then undergo various chemical reactions, including photoaddition, photocycloaddition, and photo-oxidation reactions. Photochemical reactions differ from thermochemical reactions in their requirement of light to initiate the reaction.
Determine the composition of the fe3+(jobs method)Mithil Fal Desai
In Job's method, the variation in concentration of the reactants is performed which can reveal the empirical formula of a complex. The method is employed to find the formula of the compound formed by reacting two or more chemical species. The absorption is recorded against different wavelengths and wavelength having maximum absorption is selected. The intensity of solutions with different stoichiometric ratios of the reactants is measured. The highest observed intensity reveals the maximum amount of compound formed. In this experiment, the Fe3+ and salicylic acid are reacted and the wavelength at which the complex absorbs strongly is selected. The absorbance of the different stoichiometric ration of Fe3+ and salicylic acid at a selected wavelength is determined. The maximum absorbance of the solution of the stoichiometric ratio reveals the empirical formula of the complex as the maximum amount of coloured complex is formed.
This document provides an overview of electrophoresis techniques presented by Miss Sayanti Sau. It discusses the basic principles of electrophoresis and defines different types including zone electrophoresis techniques like paper, gel, thin layer, and cellulose acetate electrophoresis. It also covers moving boundary electrophoresis techniques such as capillary electrophoresis, isotachophoresis, and isoelectric focusing. Details are provided on gel electrophoresis methods including agarose, polyacrylamide, and SDS-PAGE. Applications and advantages of various electrophoresis techniques are highlighted.
This document provides an overview of electrophoresis. It discusses how electrophoresis works, where charged particles migrate through a solution under the influence of an electric field. It describes factors that affect electrophoresis like the charge, size, and shape of samples as well as the electric field strength, buffer composition, ionic strength, and pH. It also summarizes different electrophoresis techniques like moving boundary electrophoresis, SDS-PAGE, and agarose gel electrophoresis. SDS-PAGE is commonly used to separate proteins by size, while agarose gel electrophoresis separates DNA fragments.
Chromatography is a technique used to separate chemical mixtures by exploiting differences in how components partition between a stationary and mobile phase. There are various types including adsorption, partition, ion exchange, and affinity chromatography. The document provides details on the basic principles, mechanisms, phases used, instrumentation, and common techniques like column chromatography, paper chromatography, thin layer chromatography, and gas chromatography.
This document provides an overview of fluorimetry. It defines fluorimetry as the measurement of fluorescence with a spectrofluorimeter. Fluorescence occurs when a substance emits light after absorbing radiation. Factors that affect fluorescence include the nature of the molecule, substituents, concentration, oxygen, pH, temperature, and viscosity. The instrumentation involves a light source, filters, sample cells, and detectors like photomultiplier tubes. Applications of fluorimetry include determining inorganic substances, using fluorescent indicators, developing fluorescent reagents, organic analysis, pharmaceutical analysis, and liquid chromatography.
described about optical activity, specific rotation, angle of rotation and circular dichroism and differences between ORD and CD and applications of ORD AND CD,
- Glucose biosensors are analytical devices used for diabetes management that integrate a biological recognition element (e.g. glucose oxidase) with a transducer to convert glucose detection into a measurable signal.
- Advantages of glucose biosensors over laboratory tests include allowing for routine, wireless, home-based glucose monitoring without relying on laboratory resources.
- Glucose biosensors work by catalyzing the oxidation of glucose and detection of the resulting hydrogen peroxide production through electrochemical transducers.
Photochemical reactions are chemical reactions initiated by the absorption of light energy. These reactions involve an organic molecule absorbing a photon which causes electronic excitation from a lower to a higher orbital. The excited molecule may then undergo various chemical reactions, including photoaddition, photocycloaddition, and photo-oxidation reactions. Photochemical reactions differ from thermochemical reactions in their requirement of light to initiate the reaction.
Determine the composition of the fe3+(jobs method)Mithil Fal Desai
In Job's method, the variation in concentration of the reactants is performed which can reveal the empirical formula of a complex. The method is employed to find the formula of the compound formed by reacting two or more chemical species. The absorption is recorded against different wavelengths and wavelength having maximum absorption is selected. The intensity of solutions with different stoichiometric ratios of the reactants is measured. The highest observed intensity reveals the maximum amount of compound formed. In this experiment, the Fe3+ and salicylic acid are reacted and the wavelength at which the complex absorbs strongly is selected. The absorbance of the different stoichiometric ration of Fe3+ and salicylic acid at a selected wavelength is determined. The maximum absorbance of the solution of the stoichiometric ratio reveals the empirical formula of the complex as the maximum amount of coloured complex is formed.
This document provides an overview of electrophoresis techniques presented by Miss Sayanti Sau. It discusses the basic principles of electrophoresis and defines different types including zone electrophoresis techniques like paper, gel, thin layer, and cellulose acetate electrophoresis. It also covers moving boundary electrophoresis techniques such as capillary electrophoresis, isotachophoresis, and isoelectric focusing. Details are provided on gel electrophoresis methods including agarose, polyacrylamide, and SDS-PAGE. Applications and advantages of various electrophoresis techniques are highlighted.
Xanthine oxidase is an enzyme that generates reactive oxygen species by catalyzing the oxidation of hypoxanthine to xanthine and further catalyzing the oxidation of xanthine to uric acid. It plays an important role in purine catabolism in humans. The protein is a homodimer with three domains - an N-terminal FeS cluster domain, an FAD-binding domain, and a molybdenum cofactor domain. It can exist as xanthine dehydrogenase or be converted to xanthine oxidase via oxidation or proteolysis.
Benzilic acid rearrangement. The benzilic acid rearrangement is formally the 1,2-rearrangement of 1,2-diketones to form α-hydroxy–carboxylic acids using a base. This reaction receives its name from the reaction of benzil with potassium hydroxide to form benzilic acid.
Isoelectric focusing is a technique used to separate proteins based on their isoelectric point. It involves creating an immobilized pH gradient using carrier ampholytes within an acrylamide gel. When an electric current is applied, proteins will migrate within the gel until they reach the point where they carry no net charge and stop, allowing separation based on subtle differences in pI. The key steps are preparation of the IEF gel, addition of ampholytes to generate the pH gradient, running electrophoresis to allow protein migration, and staining to visualize the separated protein bands.
Aldol Condensation || with Mechanism || Aldehyde Chemical Rxn| ALDOL Reactio...Anjali Bhardwaj
Aldol Condensation reaction in Aldehydes
You can watch this lecture video on youtube
https://youtu.be/bnQn7LunefE
Subscribe the channel
Follow at twitter:@LifeHobbies
Follow at Instagram:anlifehobbies
This document discusses SDS-PAGE (sodium dodecyl sulphate- polyacrylamide gel electrophoresis), the most widely used method for analyzing protein mixtures. SDS-PAGE separates proteins based on their size. The sample is treated with SDS and beta-mercaptoethanol to denature and negatively charge the proteins. Proteins then migrate through a stacking gel and separating gel based on their charge and size. SDS-PAGE is useful for protein purification, determining molecular weight, and identifying disulfide bonds.
Pyrrole is a colorless, volatile, aromatic 5-membered heterocyclic compound with the formula C4H4NH. It is more reactive than benzene towards electrophilic aromatic substitution due to resonance structures that stabilize positive intermediates. Pyrrole can be synthesized by treating furan with ammonia in the presence of an acid catalyst or by heating acetylene and ammonia. Substitutions occur preferentially at the 2-position carbon.
- Hard and soft acids and bases (HSAB) can be classified based on their polarizability - hard species have tightly held electron clouds while soft species have loosely held, easily polarized electron clouds.
- Hard acids prefer to interact with hard bases that have donor atoms like N, O, F, while soft acids prefer soft bases with donor atoms like P, S, Se, Cl, Br.
- Examples of hard acids are H+, Li+, Na+, K+ and hard bases are OH-, F-. Soft acids include Cu+, Ag+, Au+ and soft bases include S2-, Se2-.
This document discusses elimination reactions, specifically E1 and E2 reactions. It explains that E1 reactions proceed through a carbocation intermediate and involve a two-step mechanism, while E2 reactions are concerted and involve both the alkyl halide and base in a single step. It also describes factors that influence the reactivity and selectivity of elimination reactions, such as substrate structure, the nature of the leaving group and base, and conformational effects.
N-bromosuccinimide (NBS) is a white powder or crystals that is a convenient source of bromine for radical substitution and electrophilic addition reactions. It is more easily handled than bromine. NBS can be used to brominate alkenes, allylic and benzylic positions, carbonyl compounds, aromatic compounds, and perform Hofmann rearrangements. Side reactions include formation of α-bromoketones, dibromo compounds, and conjugates of succinimide. NBS is commercially available but can also be prepared by adding sodium hydroxide and bromine to an ice water solution of succinimide.
assignment ion exchange chromatography Faruk Hossen
Ion exchange chromatography separates ions based on their charge. The column contains resin beads that exchange one type of ion for another. Cation exchange resins contain negatively charged groups that bind positively charged cations, while anion exchange resins contain positively charged groups that bind negatively charged anions. Samples are loaded onto the column and different ions elute at different rates depending on their interaction with the charged resin. Ion exchange chromatography is useful for desalting samples and separating mixtures of biological or inorganic ions.
This document discusses biosensors, which are integrated devices that use a biological recognition element to detect analytes. It describes the key components of biosensors - the analyte, biological detection element, and transducer that converts the biological response into a measurable signal. Different types of biosensors are covered, including calorimetric, optical, resonant, piezoelectric, ion-sensitive, and electrochemical biosensors. Specific examples are provided, such as using an enzyme electrode to detect glucose or a quartz crystal microbalance biosensor coated with antibodies to detect Salmonella bacteria. The document highlights advantages of biosensors like specificity, speed, simplicity, and continuous monitoring capabilities.
This document discusses electrolytic solutions and electrochemistry. It begins by defining electrochemistry as the study of chemical reactions involving electron transfer between an electrode and electrolyte. It then discusses different types of solutions, distinguishing between electrolytic and non-electrolytic solutions. Electrolytic solutions contain ions and are electrically conductive. The document also discusses the differences between electronic and electrolytic conductors, and how conductivity is affected by various factors like temperature, concentration, and ion size. It introduces concepts like equivalent conductance, molar conductance, activity, and activity coefficients. In summary, the document provides an overview of key concepts relating to electrolytic solutions and electrochemistry.
Experimental Methods in Chemical Kinetics - Amina LuthfaBebeto G
Chemical kinetics is the study of rates of chemical reactions. It explains how quickly reactions occur and the factors that influence reaction rates. Various experimental methods are used to study reaction rates, including slow methods like gas evolution and dilatometry, and fast methods like NMR, mass spectrometry, and flow techniques. Reaction rates are determined by withdrawing aliquots from the reaction mixture at time intervals and analyzing for changes in concentration.
Vibrational frequencies can shift from normal values due to several factors:
1) Coupled vibrations occur when bond vibrations interact, causing asymmetric and symmetric stretches at different frequencies than isolated bonds.
2) Fermi resonance involves coupling between fundamental and overtone vibrations, splitting peaks between the two modes.
3) Hydrogen bonding lowers frequencies as it strengthens interactions between donor and acceptor groups. Stronger bonding yields greater shifts to lower frequencies.
4) Electronic effects like induction, mesomerism, and field effects influence frequencies by strengthening or weakening bonds.
A sensor that integrates a biological element with a physiochemical transducer to produce an electronic signal proportional to a single analyte which is then conveyed to a detector.
Based on the reactivity with Tollen’s, Benedict’s or Fehling’s reagent, carbohydrates are classified as;
Reducing sugars
Carbohydrates that can reduce Tollen’s, Benedict’s or Fehling’s reagents are called reducing sugars (sugar with free aldehyde or ketone group). All monosaccharides and most of the disaccharides are reducing sugars. Some examples are Maltose and Lactose.
Non-reducing sugars
Carbohydrates that cannot reduce Tollen’s, Benedict’s or Fehling’s reagents are called non-reducing sugars. Sucrose is a non-reducing sugar.
Electrophilic substitution reactions involve replacing a hydrogen atom in an aromatic ring with an electrophilic group. Nitration replaces hydrogen with a nitro group using nitric and sulfuric acid. Halogenation uses a halogen and Lewis acid. Sulphonation uses fuming sulfuric acid and oleum. Friedel-Crafts alkylation and acylation use an alkyl or acyl halide with aluminum chloride to add those groups. The mechanism involves generating an electrophile, forming a carbocation intermediate, and removing a proton. Ortho and para directing groups increase electron density, favoring substitution at those positions, while meta directing groups decrease electron density, favoring meta position. Polynuclear hydrocarbons from
This document summarizes key concepts from Chapter 17 of Organic Chemistry 8th Edition by L.G. Wade Jr. regarding electrophilic aromatic substitution reactions. It discusses the mechanisms of bromination, chlorination, nitration, sulfonation and other reactions of benzene and substituted benzenes. The effects of different substituents on the reactivity and product distribution are explained, with alkyl groups and methoxy groups shown to be activating while nitro groups strongly deactivate the ring.
Xanthine oxidase is an enzyme that generates reactive oxygen species by catalyzing the oxidation of hypoxanthine to xanthine and further catalyzing the oxidation of xanthine to uric acid. It plays an important role in purine catabolism in humans. The protein is a homodimer with three domains - an N-terminal FeS cluster domain, an FAD-binding domain, and a molybdenum cofactor domain. It can exist as xanthine dehydrogenase or be converted to xanthine oxidase via oxidation or proteolysis.
Benzilic acid rearrangement. The benzilic acid rearrangement is formally the 1,2-rearrangement of 1,2-diketones to form α-hydroxy–carboxylic acids using a base. This reaction receives its name from the reaction of benzil with potassium hydroxide to form benzilic acid.
Isoelectric focusing is a technique used to separate proteins based on their isoelectric point. It involves creating an immobilized pH gradient using carrier ampholytes within an acrylamide gel. When an electric current is applied, proteins will migrate within the gel until they reach the point where they carry no net charge and stop, allowing separation based on subtle differences in pI. The key steps are preparation of the IEF gel, addition of ampholytes to generate the pH gradient, running electrophoresis to allow protein migration, and staining to visualize the separated protein bands.
Aldol Condensation || with Mechanism || Aldehyde Chemical Rxn| ALDOL Reactio...Anjali Bhardwaj
Aldol Condensation reaction in Aldehydes
You can watch this lecture video on youtube
https://youtu.be/bnQn7LunefE
Subscribe the channel
Follow at twitter:@LifeHobbies
Follow at Instagram:anlifehobbies
This document discusses SDS-PAGE (sodium dodecyl sulphate- polyacrylamide gel electrophoresis), the most widely used method for analyzing protein mixtures. SDS-PAGE separates proteins based on their size. The sample is treated with SDS and beta-mercaptoethanol to denature and negatively charge the proteins. Proteins then migrate through a stacking gel and separating gel based on their charge and size. SDS-PAGE is useful for protein purification, determining molecular weight, and identifying disulfide bonds.
Pyrrole is a colorless, volatile, aromatic 5-membered heterocyclic compound with the formula C4H4NH. It is more reactive than benzene towards electrophilic aromatic substitution due to resonance structures that stabilize positive intermediates. Pyrrole can be synthesized by treating furan with ammonia in the presence of an acid catalyst or by heating acetylene and ammonia. Substitutions occur preferentially at the 2-position carbon.
- Hard and soft acids and bases (HSAB) can be classified based on their polarizability - hard species have tightly held electron clouds while soft species have loosely held, easily polarized electron clouds.
- Hard acids prefer to interact with hard bases that have donor atoms like N, O, F, while soft acids prefer soft bases with donor atoms like P, S, Se, Cl, Br.
- Examples of hard acids are H+, Li+, Na+, K+ and hard bases are OH-, F-. Soft acids include Cu+, Ag+, Au+ and soft bases include S2-, Se2-.
This document discusses elimination reactions, specifically E1 and E2 reactions. It explains that E1 reactions proceed through a carbocation intermediate and involve a two-step mechanism, while E2 reactions are concerted and involve both the alkyl halide and base in a single step. It also describes factors that influence the reactivity and selectivity of elimination reactions, such as substrate structure, the nature of the leaving group and base, and conformational effects.
N-bromosuccinimide (NBS) is a white powder or crystals that is a convenient source of bromine for radical substitution and electrophilic addition reactions. It is more easily handled than bromine. NBS can be used to brominate alkenes, allylic and benzylic positions, carbonyl compounds, aromatic compounds, and perform Hofmann rearrangements. Side reactions include formation of α-bromoketones, dibromo compounds, and conjugates of succinimide. NBS is commercially available but can also be prepared by adding sodium hydroxide and bromine to an ice water solution of succinimide.
assignment ion exchange chromatography Faruk Hossen
Ion exchange chromatography separates ions based on their charge. The column contains resin beads that exchange one type of ion for another. Cation exchange resins contain negatively charged groups that bind positively charged cations, while anion exchange resins contain positively charged groups that bind negatively charged anions. Samples are loaded onto the column and different ions elute at different rates depending on their interaction with the charged resin. Ion exchange chromatography is useful for desalting samples and separating mixtures of biological or inorganic ions.
This document discusses biosensors, which are integrated devices that use a biological recognition element to detect analytes. It describes the key components of biosensors - the analyte, biological detection element, and transducer that converts the biological response into a measurable signal. Different types of biosensors are covered, including calorimetric, optical, resonant, piezoelectric, ion-sensitive, and electrochemical biosensors. Specific examples are provided, such as using an enzyme electrode to detect glucose or a quartz crystal microbalance biosensor coated with antibodies to detect Salmonella bacteria. The document highlights advantages of biosensors like specificity, speed, simplicity, and continuous monitoring capabilities.
This document discusses electrolytic solutions and electrochemistry. It begins by defining electrochemistry as the study of chemical reactions involving electron transfer between an electrode and electrolyte. It then discusses different types of solutions, distinguishing between electrolytic and non-electrolytic solutions. Electrolytic solutions contain ions and are electrically conductive. The document also discusses the differences between electronic and electrolytic conductors, and how conductivity is affected by various factors like temperature, concentration, and ion size. It introduces concepts like equivalent conductance, molar conductance, activity, and activity coefficients. In summary, the document provides an overview of key concepts relating to electrolytic solutions and electrochemistry.
Experimental Methods in Chemical Kinetics - Amina LuthfaBebeto G
Chemical kinetics is the study of rates of chemical reactions. It explains how quickly reactions occur and the factors that influence reaction rates. Various experimental methods are used to study reaction rates, including slow methods like gas evolution and dilatometry, and fast methods like NMR, mass spectrometry, and flow techniques. Reaction rates are determined by withdrawing aliquots from the reaction mixture at time intervals and analyzing for changes in concentration.
Vibrational frequencies can shift from normal values due to several factors:
1) Coupled vibrations occur when bond vibrations interact, causing asymmetric and symmetric stretches at different frequencies than isolated bonds.
2) Fermi resonance involves coupling between fundamental and overtone vibrations, splitting peaks between the two modes.
3) Hydrogen bonding lowers frequencies as it strengthens interactions between donor and acceptor groups. Stronger bonding yields greater shifts to lower frequencies.
4) Electronic effects like induction, mesomerism, and field effects influence frequencies by strengthening or weakening bonds.
A sensor that integrates a biological element with a physiochemical transducer to produce an electronic signal proportional to a single analyte which is then conveyed to a detector.
Based on the reactivity with Tollen’s, Benedict’s or Fehling’s reagent, carbohydrates are classified as;
Reducing sugars
Carbohydrates that can reduce Tollen’s, Benedict’s or Fehling’s reagents are called reducing sugars (sugar with free aldehyde or ketone group). All monosaccharides and most of the disaccharides are reducing sugars. Some examples are Maltose and Lactose.
Non-reducing sugars
Carbohydrates that cannot reduce Tollen’s, Benedict’s or Fehling’s reagents are called non-reducing sugars. Sucrose is a non-reducing sugar.
Electrophilic substitution reactions involve replacing a hydrogen atom in an aromatic ring with an electrophilic group. Nitration replaces hydrogen with a nitro group using nitric and sulfuric acid. Halogenation uses a halogen and Lewis acid. Sulphonation uses fuming sulfuric acid and oleum. Friedel-Crafts alkylation and acylation use an alkyl or acyl halide with aluminum chloride to add those groups. The mechanism involves generating an electrophile, forming a carbocation intermediate, and removing a proton. Ortho and para directing groups increase electron density, favoring substitution at those positions, while meta directing groups decrease electron density, favoring meta position. Polynuclear hydrocarbons from
This document summarizes key concepts from Chapter 17 of Organic Chemistry 8th Edition by L.G. Wade Jr. regarding electrophilic aromatic substitution reactions. It discusses the mechanisms of bromination, chlorination, nitration, sulfonation and other reactions of benzene and substituted benzenes. The effects of different substituents on the reactivity and product distribution are explained, with alkyl groups and methoxy groups shown to be activating while nitro groups strongly deactivate the ring.
Electrophilic substitution reactions involve replacing a hydrogen atom in an aromatic ring with an electrophilic group such as nitro, halogen, sulfonic acid or alkyl/acyl groups. This is done using electrophiles generated in situ with a Lewis acid catalyst. It proceeds by generation of an electrophile, formation of a carbocation intermediate through attack on the aromatic ring, and removal of a proton. Ortho/para directing groups activate the ring towards substitution at those positions, while meta directing groups deactivate the ring at ortho/para positions. Polynuclear aromatic hydrocarbons with more than two fused benzene rings can be carcinogenic if inhaled from incomplete combustion.
I hope You all like it. I hope It is very beneficial for you all. I really thought that you all get enough knowledge from this presentation. This presentation is about materials and their classifications. After you read this presentation you knowledge is not as before.
The document discusses electrophilic aromatic substitution reactions. It explains that electrophiles are attracted to the pi electron clouds above and below aromatic rings. Electrophilic substitution proceeds through a sigma complex intermediate followed by loss of a proton. The position of substitution is directed by substituents on the ring, which can activate or deactivate the ring. Activating groups like alkyl groups stabilize ortho-para sigma complexes, while deactivating groups like nitro withdraw electron density and stabilize meta complexes. Halogen substituents also direct ortho-para but deactivate the ring. Multiple substituents have combined effects on reactivity and regioselectivity.
Introduction to benzene, orbital picture, resonance in benzene, Huckel‟s rule
Reactions of benzene - nitration, sulphonation, halogenation- reactivity, Friedel- Craft‟s alkylation- reactivity, limitations, Friedel-Craft‟s acylation.
Substituents, effect of substituents on reactivity and orientation of mono substituted benzene compounds towards electrophilic substitution reaction.
I hope You all like it. I hope It is very beneficial for you all. I really thought that you all get enough knowledge from this presentation. This presentation is about materials and their classifications. After you read this presentation you knowledge is not as before.
The document discusses the concept of umpolung in organic chemistry, which is the reversal of polarity of a functional group through chemical modification. Specifically, it describes strategies for temporarily modifying carbonyl groups so that the carbon behaves as a nucleophile rather than an electrophile. Several methods are presented for generating equivalents of formyl and acyl anions, including using derivatives of 1,3-dithianes, nitroalkanes, cyanohydrins, enolethers, and lithium acetylides, which allow the "umpolung" of carbonyl reactivity and new disconnection pathways in retrosynthesis. An example of using a dithiane approach in the synthesis of the antibiotic vermic
The document discusses electrophilic aromatic substitution reactions of benzene and its derivatives. Key points include:
1) Benzene undergoes electrophilic substitution reactions that retain the aromatic ring structure. Common substitutions include halogenation, nitration, sulfonation, and Friedel-Crafts alkylation/acylation.
2) Electrophilic reactants are polarized by Lewis acids to attack the benzene π-system. Substitution occurs via a short-lived carbocation intermediate.
3) The electronic effects of substituents on the benzene ring determine the reaction orientation (ortho, meta, para). Activating groups donate electron density while deactivating groups withdraw electron density
Benzene is a colorless liquid with a sweet odor that is found naturally in crude oil and gasoline. Michael Faraday first isolated benzene in 1825 from illuminating gas. Benzene's stability is due to its resonance structure containing alternating single and double bonds. The main electrophilic aromatic substitution reactions of benzene are halogenation, nitration, sulfonation, and Friedel-Crafts acylation and alkylation. Activating groups like -OH increase the rate of substitution at the ortho and para positions by increasing electron density on the ring, while deactivating groups like -NO2 direct substitution to the meta position. Alkylbenzene side chains can undergo halogenation and
1) Heterolytic and homolytic bond fission can result in the formation of short-lived reaction intermediates called carbocations.
2) Carbocations are positively charged carbon ions that are electrophilic and undergo three reaction types: capture a nucleophile, lose a proton to form a pi bond, or rearrange.
3) Carbocation stability increases with increased substitution and the presence of electron donating groups, double bonds, or heteroatoms which delocalize the positive charge. Carbocations are key intermediates in SN1, E1, and rearrangement reactions.
1. Electrophilic aromatic substitution is the characteristic reaction of benzene rings. A hydrogen atom is replaced by an electrophile through a two-step mechanism involving a resonance-stabilized cyclohexadienyl carbocation intermediate.
2. Substituents on benzene rings activate or deactivate the ring towards electrophilic aromatic substitution by influencing the stability of the carbocation intermediate. Electron-donating groups activate the ring while electron-withdrawing groups deactivate it.
3. The identity of existing substituents determines the orientation of new substituents, favoring either ortho/para or meta positions in electrophilic aromatic substitution.
To study the properties, nomenclature and the physical as well chemical reactions of aliphatic and alkyl benzene. Might as well as the usage of benzene in our daily life routine
The document discusses electrophilic aromatic substitution reactions. It explains that benzene's pi electrons are available to electrophilic reagents seeking to attack the ring. The methyl group activates the benzene ring by stabilizing developing positive charge through its inductive effect, making reactions faster. Nitro groups deactivate the ring by intensifying positive charge. The position of substitution is directed by any substituent's ability to stabilize the intermediate carbocation through resonance structures.
Substitution Reactions of Benzene and Other Aroma.pdfajitdoll
Substitution Reactions of Benzene and Other Aromatic Compounds The
remarkable stability of the unsaturated hydrocarbon benzene has been discussed in an earlier
section. The chemical reactivity of benzene contrasts with that of the alkenes in that substitution
reactions occur in preference to addition reactions, as illustrated in the following diagram (some
comparable reactions of cyclohexene are shown in the green box). A demonstration of bromine
substitution and addition reactions is helpful at this point, and a virtual demonstration may be
initiated by clicking here. Many other substitution reactions of benzene have been observed, the
five most useful are listed below (chlorination and bromination are the most common
halogenation reactions). Since the reagents and conditions employed in these reactions are
electrophilic, these reactions are commonly referred to as Electrophilic Aromatic Substitution.
The catalysts and co-reagents serve to generate the strong electrophilic species needed to effect
the initial step of the substitution. The specific electrophile believed to function in each type of
reaction is listed in the right hand column. Reaction Type Typical Equation Electrophile E(+)
Halogenation: C6H6 + Cl2 & heat FeCl3 catalyst ——> C6H5Cl + HCl Chlorobenzene Cl(+) or
Br(+) Nitration: C6H6 + HNO3 & heat H2SO4 catalyst ——> C6H5NO2 + H2O Nitrobenzene
NO2(+) Sulfonation: C6H6 + H2SO4 + SO3 & heat ——> C6H5SO3H + H2O Benzenesulfonic
acid SO3H(+) Alkylation: Friedel-Crafts C6H6 + R-Cl & heat AlCl3 catalyst ——> C6H5-R +
HCl An Arene R(+) Acylation: Friedel-Crafts C6H6 + RCOCl & heat AlCl3 catalyst ——>
C6H5COR + HCl An Aryl Ketone RCO(+) 1. A Mechanism for Electrophilic Substitution
Reactions of Benzene A two-step mechanism has been proposed for these electrophilic
substitution reactions. In the first, slow or rate-determining, step the electrophile forms a sigma-
bond to the benzene ring, generating a positively charged benzenonium intermediate. In the
second, fast step, a proton is removed from this intermediate, yielding a substituted benzene ring.
The following four-part illustration shows this mechanism for the bromination reaction. Also, an
animated diagram may be viewed. Bromination of Benzene - An Example of Electrophilic
Aromatic Substitution There are four stages to this slide show. These may be viewed
repeatedly by continued clicking of the \"Next Slide\" button. To see an animated model of this
reaction using ball&stick models . This mechanism for electrophilic aromatic substitution
should be considered in context with other mechanisms involving carbocation intermediates.
These include SN1 and E1 reactions of alkyl halides, and Brønsted acid addition reactions of
alkenes. To summarize, when carbocation intermediates are formed one can expect them to react
further by one or more of the following modes: 1. The cation may bond to a nucleophile to give
a substitution or addition product. 2. The cation may transfer a proton to a base, g.
Electrophilic aromatic substitution is a reaction where an atom attached to an aromatic system is replaced by an electrophile. The aromatic ring attacks the electrophile, forming a carbocation intermediate. This intermediate is stabilized by resonance. A Lewis base then donates electrons back to the ring, restoring aromaticity. Substituents can activate or deactivate the ring by donating or withdrawing electron density. Activating groups make the reaction more likely and direct substitution to the ortho- and para- positions, while deactivating groups have the opposite effects.
This document discusses various concepts in organic chemistry related to alcohols, phenols, ethers, aldehydes, ketones, carboxylic acids, amines and aromatic compounds. Some key points covered include:
1. The bond angle in alcohols is less than tetrahedral due to repulsion between oxygen's lone pairs. Branched alcohols have lower boiling points than straight-chain alcohols due to decreased intermolecular forces.
2. Phenol is a stronger acid than alcohols due to resonance stabilization of the phenoxide ion. Ethers have lower boiling points than alcohols due to the absence of hydrogen bonding.
3.
Similar to 17 reactionsofaromaticcompounds-wade7th-140409022156-phpapp01 (20)
This document contains a biology passage and 43 multiple choice questions about the passage content. The questions cover topics like DNA base percentages, population graphs of predator-prey relationships, cell structures, aquatic ecosystem oxygen levels, food webs, mercury levels in fish, laboratory processes, human transport systems, and information about a new bird flu virus. For each question, the correct multiple choice answer is provided, along with short explanations for some answers.
This document contains an astronomy homework assignment with multiple choice questions about the phases of the Moon and the scale of planetary orbits. It includes diagrams of the Moon at different positions in its orbit around Earth and asks the student to rank the Moon's appearance in terms of the illuminated area visible from Earth. The homework aims to test the student's understanding of the relative positions of Earth, the Sun and Moon and how this determines what lunar phase we see from Earth.
1) The document describes a ranking task that orders major events in the history of the universe from longest ago to most recent. It then provides context about the "cosmic calendar" that compresses the 14 billion year history of the universe into a single calendar year.
2) On the cosmic calendar, the Big Bang occurred at the start of the year on January 1st, approximately 14 billion years ago.
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2. Chapter 17 2
Electrophilic Aromatic
Substitution
Although benzene’s pi electrons are in a stable aromatic
system, they are available to attack a strong electrophile to give
a carbocation.
This resonance-stabilized carbocation is called a sigma
complex because the electrophile is joined to the benzene ring
by a new sigma bond.
Aromaticity is regained by loss of a proton.
5. Chapter 17 5
Mechanism for the
Bromination of Benzene: Step
1
Before the electrophilic aromatic substitution can take
place, the electrophile must be activated.
A strong Lewis acid catalyst, such as FeBr3, should
be used.
Br Br FeBr3 Br Br FeBr3
+ -
(stronger electrophile than Br2)
6. Chapter 17 6
H
H
H
H
H
H
Br Br FeBr3
H
H
H
H
H
H
Br
+ FeBr4
-
H
H
H
H
H
H
Br
FeBr4
-
Br
H
H
H
H
H
+ FeBr3 + HBr
Step 2: Electrophilic attack and formation of the sigma complex.
Step 3: Loss of a proton to give the products.
Mechanism for the
Bromination of Benzene: Steps
2 and 3
8. Chapter 17 8
Chlorination and Iodination
Chlorination is similar to bromination.
AlCl3 is most often used as catalyst, but
FeCl3 will also work.
Iodination requires an acidic oxidizing
agent, like nitric acid, to produce iodide
cation.
H+
+ HNO3 + ½ I2 I+
+ NO2 + H2O
9. Chapter 17 9
Predict the major product(s) of bromination of p-chloroacetanilide.
The amide group (–NHCOCH3) is a strong activating and directing group because the nitrogen atom
with its nonbonding pair of electrons is bonded to the aromatic ring. The amide group is a stronger
director than the chlorine atom, and substitution occurs mostly at the positions ortho to the amide. Like
an alkoxyl group, the amide is a particularly strong activating group, and the reaction gives some of the
dibrominated product.
Solved Problem 1
Solution
10. Chapter 17 10
Nitration of Benzene
Sulfuric acid acts as a catalyst, allowing the reaction
to be faster and at lower temperatures.
HNO3 and H2SO4 react together to form the
electrophile of the reaction: nitronium ion (NO2
+
).
HNO3
H2SO4
NO2
+ H2O
12. Chapter 17 12
Reduction of the Nitro Group
NO2
Zn, Sn, or Fe
aq. HCl
NH2
Treatment with zinc, tin, or iron in dilute acid
will reduce the nitro to an amino group.
This is the best method for adding an amino
group to the ring.
13. Chapter 17 13
Sulfonation of Benzene
Sulfur trioxide (SO3) is the electrophile in the reaction.
A 7% mixture of SO3 and H2SO4 is commonly referred
to as “fuming sulfuric acid”.
The —SO3H groups is called a sulfonic acid.
SO3H
+ SO3
H2SO4
14. Chapter 17 14
Mechanism of Sulfonation
Benzene attacks sulfur trioxide, forming a sigma
complex.
Loss of a proton on the tetrahedral carbon and
reprotonation of oxygen gives benzenesulfonic acid.
15. Chapter 17 15
Desulfonation Reaction
Sulfonation is reversible.
The sulfonic acid group may be removed
from an aromatic ring by heating in dilute
sulfuric acid.
HSO3H
+ H2O
H+
, heat
+ H2SO4
16. Chapter 17 16
Mechanism of Desulfonation
In the desulfonation reaction, a proton adds
to the ring (the electrophile) and loss of sulfur
trioxide gives back benzene.
17. Chapter 17 17
Nitration of Toluene
Toluene reacts 25 times faster than benzene.
The methyl group is an activator.
The product mix contains mostly ortho and
para substituted molecules.
18. Chapter 17 18
Ortho and Para Substitution
Ortho and para attacks are preferred because their
resonance structures include one tertiary carbocation.
20. Chapter 17 20
Meta Substitution
When substitution occurs at the meta position, the
positive charge is not delocalized onto the tertiary
carbon, and the methyl groups has a smaller effect
on the stability of the sigma complex.
21. Chapter 17 21
Alkyl Group Stabilization
CH2CH3
Br2
FeBr3
CH2CH3
Br
CH2CH3
Br
CH2CH3
Br
+ +
o-bromo
(38%)
m-bromo
(< 1%)
p-bromo
(62%)
Alkyl groups are activating substituents and ortho,
para-directors.
This effect is called the inductive effect because
alkyl groups can donate electron density to the ring
through the sigma bond, making them more active.
22. Chapter 17 22
Substituents with Nonbonding
Electrons
Resonance stabilization is provided by a pi bond between
the —OCH3 substituent and the ring.
23. Chapter 17 23
Meta Attack on Anisole
Resonance forms show that the methoxy
group cannot stabilize the sigma complex in
the meta substitution.
24. Chapter 17 24
Bromination of Anisole
A methoxy group is so strongly activating that
anisole is quickly tribrominated without a
catalyst.
25. Chapter 17 25
The Amino Group
Aniline reacts with bromine water (without a
catalyst) to yield the tribromoaniline.
Sodium bicarbonate is added to neutralize
the HBr that is also formed.
27. Chapter 17 27
Activators and Deactivators
If the substituent on the ring is electron donating, the
ortho and para positions will be activated.
If the group is electron withdrawing, the ortho and
para positions will be deactivated.
28. Chapter 17 28
Nitration of Nitrobenzene
Electrophilic substitution reactions for nitrobenzene
are 100,000 times slower than for benzene.
The product mix contains mostly the meta isomer,
only small amounts of the ortho and para isomers.
29. Chapter 17 29
Ortho Substitution on
Nitrobenzene
The nitro group is a strongly deactivating group when
considering its resonance forms. The nitrogen
always has a formal positive charge.
Ortho or para addition will create an especially
unstable intermediate.
30. Chapter 17 30
Meta Substitution on
Nitrobenzene
Meta substitution will not put the positive
charge on the same carbon that bears the
nitro group.
32. Chapter 17 32
Deactivators and Meta-
Directors
Most electron withdrawing groups are
deactivators and meta-directors.
The atom attached to the aromatic ring has a
positive or partial positive charge.
Electron density is withdrawn inductively
along the sigma bond, so the ring has less
electron density than benzene and thus, it will
be slower to react.
33. Chapter 17 33
Ortho Attack of Acetophenone
In ortho and para substitution of acetophenone, one
of the carbon atoms bearing the positive charge is
the carbon attached to the partial positive carbonyl
carbon.
Since like charges repel, this close proximity of the
two positive charges is especially unstable.
34. Chapter 17 34
Meta Attack on Acetophenone
The meta attack on acetophenone avoids
bearing the positive charge on the carbon
attached to the partial positive carbonyl.
36. Chapter 17 36
Nitration of Chlorobenzene
When chlorobenzene is nitrated the main substitution
products are ortho and para. The meta substitution
product is only obtained in 1% yield.
37. Chapter 17 37
Halogens Are Deactivators
X
Inductive Effect: Halogens are deactivating
because they are electronegative and can
withdraw electron density from the ring along
the sigma bond.
38. Chapter 17 38
Halogens Are Ortho, Para-
Directors
Resonance Effect: The lone pairs on the
halogen can be used to stabilize the sigma
complex by resonance.
41. Chapter 17 41
Effect of Multiple Substituents
The directing effect of the two (or more)
groups may reinforce each other.
42. Chapter 17 42
Effect of Multiple Substituents
(Continued)
The position in between two groups in
Positions 1 and 3 is hindered for substitution,
and it is less reactive.
43. Chapter 17 43
Effect of Multiple Substituents
(Continued)
OCH3
O2N
Br2
FeBr3
OCH3
O2N
Br
OCH3
O2N
Br
If directing effects oppose each other, the
most powerful activating group has the
dominant influence.
major products obtained
44. Chapter 17 44
Friedel–Crafts Alkylation
Synthesis of alkyl benzenes from alkyl halides
and a Lewis acid, usually AlCl3.
Reactions of alkyl halide with Lewis acid
produces a carbocation, which is the
electrophile.
46. Chapter 17 46
Protonation of Alkenes
An alkene can be protonated by HF.
This weak acid is preferred because the
fluoride ion is a weak nucleophile and will not
attack the carbocation.
47. Chapter 17 47
Alcohols and Lewis Acids
Alcohols can be treated with BF3 to form the
carbocation.
48. Chapter 17 48
Limitations of Friedel–Crafts
Reaction fails if benzene has a substituent
that is more deactivating than halogens.
Rearrangements are possible.
The alkylbenzene product is more reactive
than benzene, so polyalkylation occurs.
50. Chapter 17 50
Devise a synthesis of p-nitro-t-butylbenzene from benzene.
To make p-nitro-t-butylbenzene, we would first use a Friedel–Crafts reaction to make t-butylbenzene.
Nitration gives the correct product. If we were to make nitrobenzene first, the Friedel–Crafts reaction to
add the t-butyl group would fail.
Solved Problem 2
Solution
51. Chapter 17 51
Friedel–Crafts Acylation
Acyl chloride is used in place of alkyl chloride.
The product is a phenyl ketone that is less
reactive than benzene.
52. Chapter 17 52
Mechanism of Acylation
Step 1: Formation of the acylium ion.
Step 2: Electrophilic attack to form the sigma complex.
53. Chapter 17 53
Clemmensen Reduction
The Clemmensen reduction is a way to
convert acylbenzenes to alkylbenzenes by
treatment with aqueous HCl and
amalgamated zinc.
54. Chapter 17 54
Nucleophilic Aromatic
Substitution
A nucleophile replaces a leaving group on the
aromatic ring.
This is an addition–elimination reaction.
Electron-withdrawing substituents activate the
ring for nucleophilic substitution.
55. Chapter 17 55
Mechanism of Nucleophilic
Aromatic Substitution
Step 1: Attack by hydroxide gives a resonance-stabilized complex.
Step 2: Loss of chloride gives the product. Step 3: Excess base deprotonates the product.
56. Chapter 17 56
Activated Positions
Nitro groups ortho and para to the halogen
stabilize the intermediate (and the transition
state leading to it).
Electron-withdrawing groups are essential for
the reaction to occur.
57. Chapter 17 57
Benzyne Reaction: Elimination-
Addition
Reactant is halobenzene with no electron-
withdrawing groups on the ring.
Use a very strong base like NaNH2.
58. Chapter 17 58
Benzyne Mechanism
Sodium amide abstract a proton.
The benzyne intermediate forms when the bromide is
expelled and the electrons on the sp2
orbital adjacent
to it overlap with the empty sp2
orbital of the carbon
that lost the bromide.
Benzynes are very reactive species due to the high
strain of the triple bond.
60. Chapter 17 60
Chlorination of Benzene
Addition to the
benzene ring may
occur with excess of
chlorine under heat
and pressure.
The first Cl2 addition is
difficult, but the next
two moles add rapidly. An insecticide
61. Chapter 17 61
Catalytic Hydrogenation
Elevated heat and pressure is required.
Possible catalysts: Pt, Pd, Ni, Ru, Rh.
Reduction cannot be stopped at an
intermediate stage.
CH3
CH3
Ru, 100°C
1000 psi3H2,
CH3
CH3
62. Chapter 17 62
Birch Reduction
H
H
H
H
H
H
Na or Li
NH3 (l), ROH
H
H
H
H
H
H
H
H
This reaction reduces the aromatic ring to a
nonconjugated 1,4-cyclohexadiene.
The reducing agent is sodium or lithium in a
mixture of liquid ammonia and alcohol.
65. Chapter 17 65
Side-Chain Oxidation
Alkylbenzenes are oxidized to benzoic acid by
heating in basic KMnO4 or heating in Na2Cr2O7/H2SO4.
The benzylic carbon will be oxidized to the carboxylic
acid.
CH2CH3
(or Na2Cr2O7, H2SO4 , heat)
CO2H
KMnO4, NaOH
H2O, 100oC
66. Chapter 17 66
Side-Chain Halogenation
CH2CH3
Br2 or NBS
hν
CHCH3
Br
The benzylic position is the most reactive.
Br2 reacts only at the benzylic position.
Cl2 is not as selective as bromination, so
results in mixtures.
69. Chapter 17 69
SN2 Reactions
Benzylic halides are
100 times more
reactive than
primary halides via
SN2.
The transition state
is stabilized by a
ring.
70. Chapter 17 70
Oxidation of Phenols
Na2Cr2O7
H2SO4
OH
Cl
O
Cl
O
2-chloro-1,4-benzoquinone
Phenol will react with oxidizing agents to produce
quinones.
Quinones are conjugated 1,4-diketones.
This can also happen (slowly) in the presence of air.