Nucleophilic substitution
•Download as PPTX, PDF•
4 likes•935 views
nucleophilic substitution..... types of nucleophilic substitution....examples..... stereochemistry of SN1... stereochemistry of SN2... mechanisms
Report
Share
Report
Share
Recommended
Aliphatic Nucleophilic Substitution Reaction
This document discusses aliphatic nucleophilic substitution reactions. It describes the two main mechanisms - SN1 and SN2 reactions. The SN2 reaction is a single step bimolecular process where the nucleophile attacks from the backside, causing inversion of configuration. The rate depends on the concentrations of both the substrate and nucleophile. The SN1 reaction is a two step unimolecular process that involves a carbocation intermediate. It can result in either retention or inversion of configuration, forming a racemic mixture of products. Evidence for the transition states of these reactions is also presented.
Nitrenes slideshare Reactive intermediates
The document discusses nitrenes, which are electron deficient nitrogen species that can exist in singlet or triplet states. It describes various methods for generating nitrenes, such as through the decomposition of azides or oxidation of primary amino groups. The document also outlines several reactions of nitrenes, including their ability to insert into carbon-hydrogen bonds or undergo rearrangement reactions like the Hofmann, Curtius, Lossen, and Schmidt rearrangements.
Determination of reaction mechanisms
1. Reaction mechanisms can be determined through various methods like identifying products, detecting intermediates through isolation, trapping or labeling studies, studying the effects of catalysts and acids, and performing kinetic studies.
2. Isotope labeling and crossover experiments involve using isotopically labeled reactants to determine whether reaction pathways are intra- or intermolecular. Kinetic isotope effects also provide information about which bonds are broken or formed in the rate-determining step.
3. Acid and base catalysis can indicate whether proton transfer is involved in the rate-determining step. General acid catalysis means proton transfer is rate-determining while specific catalysis means it is not.
pericyclic reaction
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.
PERICYCLIC REACTION & WOODWARD HOFFMANN RULES, FMO THEORY
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
Molecular Rearrangements of Organic Reactions pps
This PPT is usefull for aspirants of JEE-IIT, CSIR-NET and UPSC exams in CHEMISTRY section. It is also usefull for grduates and Post graduates students of Indian Universities.
Addition reactions on C-C double bond
1. The document discusses addition reactions of C-C multiple bonds, specifically alkenes and alkynes. It describes various reagents that add across the double or triple bonds, such as hydrogen halides, water, and halogens.
2. Markovnikov's rule is explained, stating that hydrogen adds to the carbon with more hydrogen substituents in alkene additions. Anti-Markovnikov additions are also possible using peroxides.
3. Methods to form alcohols from alkenes like acid-catalyzed hydration and oxymercuration-demercuration are described.
Elimination reaction
1) The document discusses different types of elimination reactions, including E1, E2, and E1cB mechanisms.
2) E1 reactions involve the generation of a carbocation intermediate, while E2 reactions occur in one step without intermediates. E1cB reactions first form a carbanion intermediate before the leaving group departs.
3) The mechanism depends on factors like the substrate, leaving group, solvent, and strength of the base used. Zaitsev's, Hofmann, and Bredt's rules also influence the regiochemistry of double bond formation.
Recommended
Aliphatic Nucleophilic Substitution Reaction
This document discusses aliphatic nucleophilic substitution reactions. It describes the two main mechanisms - SN1 and SN2 reactions. The SN2 reaction is a single step bimolecular process where the nucleophile attacks from the backside, causing inversion of configuration. The rate depends on the concentrations of both the substrate and nucleophile. The SN1 reaction is a two step unimolecular process that involves a carbocation intermediate. It can result in either retention or inversion of configuration, forming a racemic mixture of products. Evidence for the transition states of these reactions is also presented.
Nitrenes slideshare Reactive intermediates
The document discusses nitrenes, which are electron deficient nitrogen species that can exist in singlet or triplet states. It describes various methods for generating nitrenes, such as through the decomposition of azides or oxidation of primary amino groups. The document also outlines several reactions of nitrenes, including their ability to insert into carbon-hydrogen bonds or undergo rearrangement reactions like the Hofmann, Curtius, Lossen, and Schmidt rearrangements.
Determination of reaction mechanisms
1. Reaction mechanisms can be determined through various methods like identifying products, detecting intermediates through isolation, trapping or labeling studies, studying the effects of catalysts and acids, and performing kinetic studies.
2. Isotope labeling and crossover experiments involve using isotopically labeled reactants to determine whether reaction pathways are intra- or intermolecular. Kinetic isotope effects also provide information about which bonds are broken or formed in the rate-determining step.
3. Acid and base catalysis can indicate whether proton transfer is involved in the rate-determining step. General acid catalysis means proton transfer is rate-determining while specific catalysis means it is not.
pericyclic reaction
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.
PERICYCLIC REACTION & WOODWARD HOFFMANN RULES, FMO THEORY
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
Molecular Rearrangements of Organic Reactions pps
This PPT is usefull for aspirants of JEE-IIT, CSIR-NET and UPSC exams in CHEMISTRY section. It is also usefull for grduates and Post graduates students of Indian Universities.
Addition reactions on C-C double bond
1. The document discusses addition reactions of C-C multiple bonds, specifically alkenes and alkynes. It describes various reagents that add across the double or triple bonds, such as hydrogen halides, water, and halogens.
2. Markovnikov's rule is explained, stating that hydrogen adds to the carbon with more hydrogen substituents in alkene additions. Anti-Markovnikov additions are also possible using peroxides.
3. Methods to form alcohols from alkenes like acid-catalyzed hydration and oxymercuration-demercuration are described.
Elimination reaction
1) The document discusses different types of elimination reactions, including E1, E2, and E1cB mechanisms.
2) E1 reactions involve the generation of a carbocation intermediate, while E2 reactions occur in one step without intermediates. E1cB reactions first form a carbanion intermediate before the leaving group departs.
3) The mechanism depends on factors like the substrate, leaving group, solvent, and strength of the base used. Zaitsev's, Hofmann, and Bredt's rules also influence the regiochemistry of double bond formation.
Lindemann theory
The Lindemann-Hinshelwood mechanism explains how first-order unimolecular gas-phase reactions can occur through collisions. It proposes that: (1) A reactant molecule A becomes energized through a collision with another A molecule, forming the excited species A*. (2) A* then either loses its excess energy through another collision or undergoes unimolecular decay to form products P. (3) If the unimolecular decay is the slowest step, the overall reaction appears first-order. The mechanism predicts a transition to second-order kinetics at low pressures when bimolecular collisions become rate-determining.
Wolf rearrangement
The document discusses carbenes, which are molecules containing a neutral carbon atom with two unshared valence electrons. Carbenes can be classified as singlets or triplets based on their electronic structure. The document also describes the Wolff rearrangement, where α-diazoketones lose nitrogen to form reactive ketenes. Some applications of the Wolff rearrangement include the synthesis of carboxylic acid analogues, acid amides from carboxylic acids, and esters from carboxylic acids.
Electrophilic addition reaction
Electrophilic additions involve reactions of alkenes where the pi electrons in the double bond attack an electrophile. There are several types of additions including addition of HX, halogens, water, alcohols, and hydroboration. The mechanism typically involves formation of a carbocation intermediate that is then attacked by the nucleophile. Addition occurs regioselectively according to Markovnikov's rule, favoring the most stable carbocation. Exceptions include free radical additions, which give the anti-Markovnikov product. Oxymercuration-demercuration and hydroboration allow for Markovnikov addition without rearrangements.
Organic reaction mechanism
The document discusses different types of substitution reactions including nucleophilic substitution, electrophilic substitution, and free radical substitution. It provides details on the mechanisms, kinetics, stereochemistry and factors affecting the rate of nucleophilic substitution reactions SN1 and SN2. SN1 follows a unimolecular mechanism involving a carbocation intermediate while SN2 follows a bimolecular mechanism with a single concerted transition state. The document also discusses electrophilic aromatic substitution reactions and addition and elimination reactions of alkenes and alkynes.
Addition to c=c multi bonds
The document discusses addition reactions to carbon-carbon multiple bonds. It describes four types of addition reactions: electrophilic addition, nucleophilic addition, free radical addition, and addition to conjugated systems. The mechanisms and stereochemistry of each reaction type are explained. Factors that influence the reactivity of different substrate types towards each reaction pathway are also covered.
Ligand substitution reactions
Classification Of Mechanisms, Ligand Substitution In Octahedral Complexes Without Breaking Metal-ligand Bond, Substitution Reaction In Square Planar Complexes, Factors Which Affect The Rate Of Substitution, Trans Effect (Labilizing Effect), Theories and applications Of Trans Effect
E2 reaction
1. The document outlines different elimination reaction mechanisms including E2, E1, and E1cb.
2. It discusses the regiochemistry and stereochemistry of elimination reactions and how Zaytzeff's rule and Hofmann's rule apply.
3. The key differences between the E2, E1, and E1cb mechanisms are described along with factors that determine whether substitution or elimination will occur for a given reaction.
Presentation apc
This document discusses addition reactions to carbon-carbon multiple bonds and carbon-heteroatom multiple bonds. It covers electrophilic, nucleophilic, and free radical addition to alkenes and alkynes. It also discusses addition reactions to carbonyl compounds, nitriles, imines, and sulfonyl chlorides. Reaction mechanisms, orientation, stereochemistry, and factors affecting reactivity are explained for various addition reactions. Important reactions like hydroboration, hydrohalogenation, hydration, oxidation, and reductions are also summarized.
Ligand substitution reactions
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.
Oxidative addition
Oxidative addition is a process where a metal complex increases its oxidation state and coordination number by addition of two ligands. It is the reverse of reductive elimination. It requires the metal to have available orbitals and be in a lower oxidation state. There are four mechanisms for oxidative addition: concerted, SN2, radical, and ionic. Oxidative addition and reductive elimination are important steps in many catalytic cycles in organometallic chemistry and homogeneous catalysis.
Substitution reactions
Nucleophilic substitution reactions involve a nucleophile reacting with an alkyl halide substrate by replacing the halogen leaving group. There are two types of nucleophilic substitution reactions: SN1 and SN2. In an SN1 reaction, the alkyl halide first undergoes heterolysis to form a carbocation intermediate which the nucleophile then attacks. The rate depends only on the concentration of the alkyl halide. In contrast, an SN2 reaction is a concerted bimolecular process where the nucleophile attacks the alkyl halide as the C-X bond breaks. The rate depends on both the concentrations of the alkyl halide and nucleophile.
Photochemistry of Alkene
Photochemistry of alkenes can produce various reaction types upon irradiation with light, including isomerization, cyclization, and rearrangement. Isomerization reactions can involve direct cis-trans isomerization of alkenes or can be sensitized using triplet photosensitizers. Cyclization reactions are either concerted or proceed through a biradical intermediate. Rearrangement reactions of 1,4-dienes follow a D-π-methane rearrangement through a concerted 1,2-shift, while 1,5-dienes undergo a stereospecific [3,3] sigmatropic Cope rearrangement through a cyclic transition state.
Electrophilic substitution reaction.pptx
Electrophilic substitution reactions involve an electrophile replacing a functional group, typically a hydrogen atom, on an organic compound. There are two main types: electrophilic aromatic substitutions, where the electrophile replaces an atom in an aromatic ring, and electrophilic aliphatic substitutions, where the electrophile replaces a group on an aliphatic compound. Both proceed by a three step mechanism of electrophile generation, carbocation formation, and proton removal to restore aromaticity.
Reaction intermediates
Reaction intermediates such as carbocation, carbanion, free radicals, carbene, nitrene and ylides were discussed.
4. Wilkinson's Catalyst
General characteristics, application and mechanism of Wilkinson's catalyst is discussed in the lecture.
chelotropic reactions
The document discusses cheletropic reactions, which involve the concerted formation or breaking of two sigma bonds at a single atom. It provides examples of reactions involving sulfur dioxide and carbene additions to alkenes to form cyclopropanes. It also discusses theoretical analyses, kinetics, thermodynamics, solvent effects, and orbital symmetry considerations for these types of pericyclic reactions.
BSc V SEM B Electrochemistry 1.pptx
4.2 - Debye-Huckel’s theory of Strong Electrolytes - Onsagar equation (No derivation) -Verification and Limitations Wien effect, Falkenhagen effect.
DIELS- ALDER REACTION
The document discusses the Diels-Alder reaction, which involves a diene reacting with a dienophile to form a six-membered ring. Key characteristics include versatility, stereoselectivity, and reversibility. The mechanism involves overlap of the HOMO of the diene and LUMO of the dienophile. The stereochemistry of products is governed by the cis principle and endo rule. Variations include retro Diels-Alder reactions and cycloadditions involving allyl cations/anions.
Nucleophilic Substitution reaction (SN1 reaction)
Attack of nucleophile at a saturated carbon atom bearing substituent, known as leaving group results in Substitution reaction.
The group that is displaced (leaving group) carries its bonding electrons.
The new bond is formed between nucleophile and the carbon using the electrons supplied by the nucleophilic agent.
The compound on which substitution takes place is called “substrate.”
The substrate consists of two parts, alkyl group and leaving group.
Rearrangement Reactions vikram choudhary
The presentation discusses rearrangement reactions, which involve the migration of an atom or group within a molecule to form a structural isomer. It defines rearrangement and provides examples of types including those to electron deficient carbons, nitrogens, and oxygens, as well as electron-rich carbons and aromatic systems. Mechanisms are presented for rearrangements involving migration to various electron-withdrawing or -releasing centers.
First Order and Second Order Kinetics
A first-order reaction can be defined as a chemical reaction in which the reaction rate is linearly dependent on the concentration of only one reactant.
A second kind of second-order reaction has a reaction rate that is proportional to the product of the concentrations of two reactants
Nucleophilic substitution reaction
Nucleophiles and bimolecular nucleophilic substitution reaction mechanism, rate, stereochemistry, steric hindrance
More Related Content
What's hot
Lindemann theory
The Lindemann-Hinshelwood mechanism explains how first-order unimolecular gas-phase reactions can occur through collisions. It proposes that: (1) A reactant molecule A becomes energized through a collision with another A molecule, forming the excited species A*. (2) A* then either loses its excess energy through another collision or undergoes unimolecular decay to form products P. (3) If the unimolecular decay is the slowest step, the overall reaction appears first-order. The mechanism predicts a transition to second-order kinetics at low pressures when bimolecular collisions become rate-determining.
Wolf rearrangement
The document discusses carbenes, which are molecules containing a neutral carbon atom with two unshared valence electrons. Carbenes can be classified as singlets or triplets based on their electronic structure. The document also describes the Wolff rearrangement, where α-diazoketones lose nitrogen to form reactive ketenes. Some applications of the Wolff rearrangement include the synthesis of carboxylic acid analogues, acid amides from carboxylic acids, and esters from carboxylic acids.
Electrophilic addition reaction
Electrophilic additions involve reactions of alkenes where the pi electrons in the double bond attack an electrophile. There are several types of additions including addition of HX, halogens, water, alcohols, and hydroboration. The mechanism typically involves formation of a carbocation intermediate that is then attacked by the nucleophile. Addition occurs regioselectively according to Markovnikov's rule, favoring the most stable carbocation. Exceptions include free radical additions, which give the anti-Markovnikov product. Oxymercuration-demercuration and hydroboration allow for Markovnikov addition without rearrangements.
Organic reaction mechanism
The document discusses different types of substitution reactions including nucleophilic substitution, electrophilic substitution, and free radical substitution. It provides details on the mechanisms, kinetics, stereochemistry and factors affecting the rate of nucleophilic substitution reactions SN1 and SN2. SN1 follows a unimolecular mechanism involving a carbocation intermediate while SN2 follows a bimolecular mechanism with a single concerted transition state. The document also discusses electrophilic aromatic substitution reactions and addition and elimination reactions of alkenes and alkynes.
Addition to c=c multi bonds
The document discusses addition reactions to carbon-carbon multiple bonds. It describes four types of addition reactions: electrophilic addition, nucleophilic addition, free radical addition, and addition to conjugated systems. The mechanisms and stereochemistry of each reaction type are explained. Factors that influence the reactivity of different substrate types towards each reaction pathway are also covered.
Ligand substitution reactions
Classification Of Mechanisms, Ligand Substitution In Octahedral Complexes Without Breaking Metal-ligand Bond, Substitution Reaction In Square Planar Complexes, Factors Which Affect The Rate Of Substitution, Trans Effect (Labilizing Effect), Theories and applications Of Trans Effect
E2 reaction
1. The document outlines different elimination reaction mechanisms including E2, E1, and E1cb.
2. It discusses the regiochemistry and stereochemistry of elimination reactions and how Zaytzeff's rule and Hofmann's rule apply.
3. The key differences between the E2, E1, and E1cb mechanisms are described along with factors that determine whether substitution or elimination will occur for a given reaction.
Presentation apc
This document discusses addition reactions to carbon-carbon multiple bonds and carbon-heteroatom multiple bonds. It covers electrophilic, nucleophilic, and free radical addition to alkenes and alkynes. It also discusses addition reactions to carbonyl compounds, nitriles, imines, and sulfonyl chlorides. Reaction mechanisms, orientation, stereochemistry, and factors affecting reactivity are explained for various addition reactions. Important reactions like hydroboration, hydrohalogenation, hydration, oxidation, and reductions are also summarized.
Ligand substitution reactions
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.
Oxidative addition
Oxidative addition is a process where a metal complex increases its oxidation state and coordination number by addition of two ligands. It is the reverse of reductive elimination. It requires the metal to have available orbitals and be in a lower oxidation state. There are four mechanisms for oxidative addition: concerted, SN2, radical, and ionic. Oxidative addition and reductive elimination are important steps in many catalytic cycles in organometallic chemistry and homogeneous catalysis.
Substitution reactions
Nucleophilic substitution reactions involve a nucleophile reacting with an alkyl halide substrate by replacing the halogen leaving group. There are two types of nucleophilic substitution reactions: SN1 and SN2. In an SN1 reaction, the alkyl halide first undergoes heterolysis to form a carbocation intermediate which the nucleophile then attacks. The rate depends only on the concentration of the alkyl halide. In contrast, an SN2 reaction is a concerted bimolecular process where the nucleophile attacks the alkyl halide as the C-X bond breaks. The rate depends on both the concentrations of the alkyl halide and nucleophile.
Photochemistry of Alkene
Photochemistry of alkenes can produce various reaction types upon irradiation with light, including isomerization, cyclization, and rearrangement. Isomerization reactions can involve direct cis-trans isomerization of alkenes or can be sensitized using triplet photosensitizers. Cyclization reactions are either concerted or proceed through a biradical intermediate. Rearrangement reactions of 1,4-dienes follow a D-π-methane rearrangement through a concerted 1,2-shift, while 1,5-dienes undergo a stereospecific [3,3] sigmatropic Cope rearrangement through a cyclic transition state.
Electrophilic substitution reaction.pptx
Electrophilic substitution reactions involve an electrophile replacing a functional group, typically a hydrogen atom, on an organic compound. There are two main types: electrophilic aromatic substitutions, where the electrophile replaces an atom in an aromatic ring, and electrophilic aliphatic substitutions, where the electrophile replaces a group on an aliphatic compound. Both proceed by a three step mechanism of electrophile generation, carbocation formation, and proton removal to restore aromaticity.
Reaction intermediates
Reaction intermediates such as carbocation, carbanion, free radicals, carbene, nitrene and ylides were discussed.
4. Wilkinson's Catalyst
General characteristics, application and mechanism of Wilkinson's catalyst is discussed in the lecture.
chelotropic reactions
The document discusses cheletropic reactions, which involve the concerted formation or breaking of two sigma bonds at a single atom. It provides examples of reactions involving sulfur dioxide and carbene additions to alkenes to form cyclopropanes. It also discusses theoretical analyses, kinetics, thermodynamics, solvent effects, and orbital symmetry considerations for these types of pericyclic reactions.
BSc V SEM B Electrochemistry 1.pptx
4.2 - Debye-Huckel’s theory of Strong Electrolytes - Onsagar equation (No derivation) -Verification and Limitations Wien effect, Falkenhagen effect.
DIELS- ALDER REACTION
The document discusses the Diels-Alder reaction, which involves a diene reacting with a dienophile to form a six-membered ring. Key characteristics include versatility, stereoselectivity, and reversibility. The mechanism involves overlap of the HOMO of the diene and LUMO of the dienophile. The stereochemistry of products is governed by the cis principle and endo rule. Variations include retro Diels-Alder reactions and cycloadditions involving allyl cations/anions.
Nucleophilic Substitution reaction (SN1 reaction)
Attack of nucleophile at a saturated carbon atom bearing substituent, known as leaving group results in Substitution reaction.
The group that is displaced (leaving group) carries its bonding electrons.
The new bond is formed between nucleophile and the carbon using the electrons supplied by the nucleophilic agent.
The compound on which substitution takes place is called “substrate.”
The substrate consists of two parts, alkyl group and leaving group.
Rearrangement Reactions vikram choudhary
The presentation discusses rearrangement reactions, which involve the migration of an atom or group within a molecule to form a structural isomer. It defines rearrangement and provides examples of types including those to electron deficient carbons, nitrogens, and oxygens, as well as electron-rich carbons and aromatic systems. Mechanisms are presented for rearrangements involving migration to various electron-withdrawing or -releasing centers.
What's hot (20)
Similar to Nucleophilic substitution
First Order and Second Order Kinetics
A first-order reaction can be defined as a chemical reaction in which the reaction rate is linearly dependent on the concentration of only one reactant.
A second kind of second-order reaction has a reaction rate that is proportional to the product of the concentrations of two reactants
Nucleophilic substitution reaction
Nucleophiles and bimolecular nucleophilic substitution reaction mechanism, rate, stereochemistry, steric hindrance
Substitusi Nukleofilik
1. The document discusses nucleophilic substitution (SN1 and SN2) reactions, where a nucleophile replaces a leaving group on a substrate.
2. It describes factors that determine the rate of these reactions, such as the nucleophilicity of the nucleophile, stability of the leaving group, and structure of the substrate. Tertiary substrates typically undergo SN1 while primary typically undergo SN2.
3. SN1 is a two-step reaction involving a carbocation intermediate, while SN2 is a single-step reaction with inversion of configuration.
soderberg_lecture_6_1.pptx
This document discusses nucleophilic substitution reactions, specifically SN1 and SN2 mechanisms. It defines the key aspects of each mechanism, including:
- SN2 is a concerted, one-step mechanism where nucleophilic attack and bond cleavage occur simultaneously. It results in inversion of configuration.
- SN1 is a two-step mechanism involving a carbocation intermediate. Both enantiomers may be produced. Stereochemistry is not inverted.
- Factors like the nature of the nucleophile and leaving group, carbocation stability, and substrate structure determine whether a reaction will proceed by SN1 or SN2.
Sn2 reaction
The document summarizes key aspects of SN2 reactions including reaction mechanism, kinetics, stereochemistry, and factors that affect the rate of the reaction. It describes the SN2 reaction as a bimolecular nucleophilic substitution where the nucleophile attacks the substrate simultaneously as the leaving group departs, resulting in an inversion of configuration. Rate depends on both the nucleophile and substrate concentrations. The stability of the transition state is affected by substrate structure, nucleophilicity, leaving group ability, solvent properties, and conjugation effects in allylic and benzylic systems. Cyclic substrates and those without available orbital overlap do not undergo SN2 reactions as easily.
Types of Reaction
its ppt about the types of the organic reactions. which include some primary information about types with examples.
Substitution reactions
This document summarizes different types of substitution reactions in aliphatic and aromatic compounds. It describes three main types of substitution reactions: free radical substitution, electrophilic substitution, and nucleophilic substitution. Free radical substitution involves radicals and occurs in non-polar solvents. Electrophilic substitution can be aliphatic or aromatic and involves attack by an electrophile. Nucleophilic substitution involves displacement by a nucleophile and can proceed by SN1, SN2, or addition-elimination mechanisms. The document provides examples and details of the mechanisms and factors that influence each type of substitution reaction.
Aliphatic Nucleophilic substitution
1) The document discusses different types of nucleophilic substitution reactions including SN1, SN2, and SNi.
2) The SN1 reaction involves the formation of a carbocation intermediate and follows a two-step mechanism. The rate determining step is the formation of the carbocation.
3) The SN2 reaction is a concerted bimolecular nucleophilic substitution that occurs in one step without an intermediate. It follows second-order kinetics.
Haloalkanes chem.pdf
1. Alkyl halides are organic compounds containing a halogen atom bonded to a carbon. They are classified as primary, secondary, or tertiary based on the number of carbons bonded to the halogenated carbon.
2. Nucleophilic substitution reactions involve three components: an alkyl halide leaving group, a nucleophile, and a solvent. The reaction can proceed by either an SN1 or SN2 mechanism.
3. The type of alkyl halide and nucleophile determine the reaction mechanism and products. Steric effects influence reactivity in SN1 and SN2 reactions.
alkyl halide
The haloalkanes are a group of chemical compounds derived from alkanes containing one or more halogens. They are a subset of the general class of halocarbons, although the distinction is not often made. Haloalkanes are widely used commercially and, consequently, are known under many chemical and commercial names.
Nucleophilic Substitution chemical reaction
A substitution reaction is a chemical reaction during which an atom or one functional group in a chemical compound is replaced by another atom or functional group.
Nucleophilic substitution reactions
Nucleophilic substitution reactions can occur through either an SN1 or SN2 mechanism. The SN1 reaction is a two-step process where the first step is rate-determining and involves formation of a carbocation intermediate. It is a unimolecular reaction that results in loss of configuration. The SN2 reaction is a single concerted step where nucleophilic attack and leaving of the existing group occur simultaneously through a trigonal planar transition state. It results in inversion of configuration. Both mechanisms are affected by factors like the substrate structure, the nucleophile, the leaving group and the solvent used.
Aliphatic nucleophlic substituion- shweta parik
The document discusses various types of aliphatic nucleophilic substitution reactions and their mechanisms. It covers SN2 and SN1 mechanisms in detail, providing evidence that supports each. It also discusses borderline cases where reactions have characteristics of both SN1 and SN2, and other mechanisms like SN1', SNi, SET, and addition-elimination that may occur under different conditions. Specific examples of nucleophilic substitution are discussed at allylic, trigonal, and vinylic carbons that may proceed by different pathways than typical SN1 or SN2 reactions.
aliphatic nuecleophilic reaction saturated c
The document discusses nucleophilic substitution reactions (SN1, SN2, SNi) at sp3 carbons. It explains the key differences between the SN1, SN2 and SNi mechanisms based on their rate equations, stereochemical outcomes, and whether they proceed through a bimolecular transition state (SN2) or a unimolecular carbocation intermediate (SN1). Transition states and reactive intermediates are described. Factors that affect the relative rates of the SN1 and SN2 mechanisms are also discussed, including the nature of the substrate, nucleophile and leaving group, as well as solvent effects.
Reaction Rates.pptx
Chemical reaction engineering deals with designing chemical reactors and optimizing reaction conditions. Reaction rates depend on factors like concentration, temperature, and catalysts. Rate laws express how the reaction rate relates to concentrations raised to specific powers, defining the reaction order. Reaction mechanisms involve elementary reaction steps. Determining the rate law and order involves analyzing concentration changes over time using integrated rate equations or Arrhenius kinetics to study temperature effects. Non-elementary reactions may involve multiple elementary steps occurring in parallel, series, or with reversibility and catalysis.
Nucleophilic substitution type ( Sn1&sn2) mechanism difference between Sn1& s...
Nucleophilic substitution reaction, types, mechanism and difference Sn1&sn2'.
Social media pharmacy notes on goggle , Facebook, Instagram & LinkedIn
E2 reaction by ramkesh chauhan
The document summarizes the E2 elimination reaction.
1) The E2 reaction involves the concerted removal of a β-proton by a base and loss of a halide ion in a single step with no intermediate.
2) It is a second-order reaction that depends on both the base and substrate concentrations. The reaction proceeds through a transition state in which the β-proton and halide leave simultaneously to form an alkene.
3) Factors that increase the rate of the E2 reaction include stronger bases, better leaving groups, more substituted substrates, polar aprotic solvents, and bulky or conjugated substrates. The reaction favors antiperiplanar elimination to form the
pdf alkyl_halides.pdf
Alkyl halides are organic compounds containing one or more carbon-halogen bonds. They can be prepared from alkanes, alkenes, and alcohols using free radical halogenation, addition reactions, or by treating alcohols with reagents like thionyl chloride or phosphorus tribromide. Alkyl halides undergo nucleophilic substitution and elimination reactions. Nucleophilic substitution can proceed by an SN1 or SN2 mechanism depending on the substrate and conditions. The SN1 mechanism involves formation of a carbocation intermediate while SN2 is a concerted bimolecular process. Elimination reactions generate alkene products and compete with substitution. Alkyl halides are versatile
Alkyl halide reactions
1. The document discusses alkyl halide reactions including SN1 and SN2 mechanisms. It describes factors that affect the rates of these reactions such as the substrate, leaving group, nucleophile, and solvent.
2. SN1 is a two-step reaction involving a carbocation intermediate. SN2 is a single-step reaction without an intermediate. SN1 reactions result in racemization while SN2 reactions cause inversion of configuration.
3. Tertiary alkyl halides undergo SN1 reactions most readily due to stable carbocation intermediates. Polar protic solvents favor SN1 while polar aprotic solvents favor SN2.
Nucleophilic substitutions reactions
This document summarizes various nucleophilic substitution reactions including SN1, SN2, SN1 prime, SN2 prime, and SNi reactions. It describes the key characteristics of SN2 reactions, which proceed through a single transition state with inversion of configuration. Factors that affect SN2 reactivity include the nature of the nucleophile, electrophile, leaving group, and solvent. SN1 reactions involve ionization to a carbocation intermediate and generally give racemic products. Allylic substrates can undergo rearrangement in SN1 or SN2 reactions.
Similar to Nucleophilic substitution (20)
Nucleophilic substitution type ( Sn1&sn2) mechanism difference between Sn1& s...
Nucleophilic substitution type ( Sn1&sn2) mechanism difference between Sn1& s...
More from mahrooshabbasi1
photomultiplier tube and photodiode
photomultiplier tube ,its construction ,it's working....... photodiode ,it's construction and working
Quinine (2)
Quinine is an antimalarial drug extracted from the bark of cinchona trees. It has been used since the 17th century to treat malaria. Quinine works by accumulating in lysosomes and binding to heme to kill malaria parasites. It is absorbed through the GI tract and metabolized in the liver before being excreted by the kidneys. While an effective treatment for malaria, quinine can cause side effects like headaches, ringing in the ears, and low blood pressure.
Beckmann rearrangement
The Beckmann rearrangement is an acid-catalyzed reaction where an oxime is converted to an amide. Specifically, the reaction involves the migration of an acyl group from carbon to nitrogen on the oxime. This rearrangement allows the conversion of ketones and aldehydes to amides. Common catalysts used include sulfuric acid, phosphorus pentachloride, and hydrochloric acid. The reaction proceeds through an oxonium ion intermediate.
Blood donation
Blood donation is the process of transferring blood or blood components from one person to another. There is no substitute for blood, and every three seconds someone needs a blood transfusion. Blood is the most precious gift that can be given to save another person's life. To be eligible to donate blood, males must be at least 17 years old, weigh at least 130 lbs, be at least 5'1" tall, and have a hemoglobin level of at least 11. Some health benefits of donating blood include reducing the risk of heart disease, stimulating the production of new red blood cells, and balancing iron levels in the blood.
First Aid Tips (Terrorism and Earthquake)
During earthquakes or terrorist attacks, it is important to assess the situation and any injured persons. The document provides first aid tips (FATs) for various injuries that may occur, including unconsciousness, cuts, fractures, spinal injuries, nosebleeds, and burns. It emphasizes not moving victims and maintaining an open airway. The first steps are always to check if the person is breathing and conscious before providing first aid according to the specific injury.
Pyrantel
Pyrantel is an anti-helminthic drug developed by Pfizer in the 1960s to treat roundworm, pinworm, hookworm, and other parasitic infections. It works by activating nicotinic cholinergic receptors in the worm's nervous system, causing paralysis and expulsion. Pyrantel is a light yellow to tan powder that is odorless, tasteless, and stable in heat but decomposes in light. It has a chemical formula of C11H14N2S and is administered orally to treat parasitic infections. Common side effects include nausea, diarrhea, dizziness, and headache.
More from mahrooshabbasi1 (6)
Recently uploaded
Pengantar Penggunaan Flutter - Dart programming language1.pptx
Pengantar Penggunaan Flutter - Dart programming language1.pptx
Solutons Maths Escape Room Spatial .pptx
Solutions of Puzzles of Mathematics Escape Room Game in Spatial.io
What is Digital Literacy? A guest blog from Andy McLaughlin, University of Ab...
What is Digital Literacy? A guest blog from Andy McLaughlin, University of Aberdeen
ISO/IEC 27001, ISO/IEC 42001, and GDPR: Best Practices for Implementation and...
Denis is a dynamic and results-driven Chief Information Officer (CIO) with a distinguished career spanning information systems analysis and technical project management. With a proven track record of spearheading the design and delivery of cutting-edge Information Management solutions, he has consistently elevated business operations, streamlined reporting functions, and maximized process efficiency.
Certified as an ISO/IEC 27001: Information Security Management Systems (ISMS) Lead Implementer, Data Protection Officer, and Cyber Risks Analyst, Denis brings a heightened focus on data security, privacy, and cyber resilience to every endeavor.
His expertise extends across a diverse spectrum of reporting, database, and web development applications, underpinned by an exceptional grasp of data storage and virtualization technologies. His proficiency in application testing, database administration, and data cleansing ensures seamless execution of complex projects.
What sets Denis apart is his comprehensive understanding of Business and Systems Analysis technologies, honed through involvement in all phases of the Software Development Lifecycle (SDLC). From meticulous requirements gathering to precise analysis, innovative design, rigorous development, thorough testing, and successful implementation, he has consistently delivered exceptional results.
Throughout his career, he has taken on multifaceted roles, from leading technical project management teams to owning solutions that drive operational excellence. His conscientious and proactive approach is unwavering, whether he is working independently or collaboratively within a team. His ability to connect with colleagues on a personal level underscores his commitment to fostering a harmonious and productive workplace environment.
Date: May 29, 2024
Tags: Information Security, ISO/IEC 27001, ISO/IEC 42001, Artificial Intelligence, GDPR
-------------------------------------------------------------------------------
Find out more about ISO training and certification services
Training: ISO/IEC 27001 Information Security Management System - EN | PECB
ISO/IEC 42001 Artificial Intelligence Management System - EN | PECB
General Data Protection Regulation (GDPR) - Training Courses - EN | PECB
Webinars: https://pecb.com/webinars
Article: https://pecb.com/article
-------------------------------------------------------------------------------
For more information about PECB:
Website: https://pecb.com/
LinkedIn: https://www.linkedin.com/company/pecb/
Facebook: https://www.facebook.com/PECBInternational/
Slideshare: http://www.slideshare.net/PECBCERTIFICATION
ANATOMY AND BIOMECHANICS OF HIP JOINT.pdf
it describes the bony anatomy including the femoral head , acetabulum, labrum . also discusses the capsule , ligaments . muscle that act on the hip joint and the range of motion are outlined. factors affecting hip joint stability and weight transmission through the joint are summarized.
Chapter wise All Notes of First year Basic Civil Engineering.pptx
Chapter wise All Notes of First year Basic Civil Engineering
Syllabus
Chapter-1
Introduction to objective, scope and outcome the subject
Chapter 2
Introduction: Scope and Specialization of Civil Engineering, Role of civil Engineer in Society, Impact of infrastructural development on economy of country.
Chapter 3
Surveying: Object Principles & Types of Surveying; Site Plans, Plans & Maps; Scales & Unit of different Measurements.
Linear Measurements: Instruments used. Linear Measurement by Tape, Ranging out Survey Lines and overcoming Obstructions; Measurements on sloping ground; Tape corrections, conventional symbols. Angular Measurements: Instruments used; Introduction to Compass Surveying, Bearings and Longitude & Latitude of a Line, Introduction to total station.
Levelling: Instrument used Object of levelling, Methods of levelling in brief, and Contour maps.
Chapter 4
Buildings: Selection of site for Buildings, Layout of Building Plan, Types of buildings, Plinth area, carpet area, floor space index, Introduction to building byelaws, concept of sun light & ventilation. Components of Buildings & their functions, Basic concept of R.C.C., Introduction to types of foundation
Chapter 5
Transportation: Introduction to Transportation Engineering; Traffic and Road Safety: Types and Characteristics of Various Modes of Transportation; Various Road Traffic Signs, Causes of Accidents and Road Safety Measures.
Chapter 6
Environmental Engineering: Environmental Pollution, Environmental Acts and Regulations, Functional Concepts of Ecology, Basics of Species, Biodiversity, Ecosystem, Hydrological Cycle; Chemical Cycles: Carbon, Nitrogen & Phosphorus; Energy Flow in Ecosystems.
Water Pollution: Water Quality standards, Introduction to Treatment & Disposal of Waste Water. Reuse and Saving of Water, Rain Water Harvesting. Solid Waste Management: Classification of Solid Waste, Collection, Transportation and Disposal of Solid. Recycling of Solid Waste: Energy Recovery, Sanitary Landfill, On-Site Sanitation. Air & Noise Pollution: Primary and Secondary air pollutants, Harmful effects of Air Pollution, Control of Air Pollution. . Noise Pollution Harmful Effects of noise pollution, control of noise pollution, Global warming & Climate Change, Ozone depletion, Greenhouse effect
Text Books:
1. Palancharmy, Basic Civil Engineering, McGraw Hill publishers.
2. Satheesh Gopi, Basic Civil Engineering, Pearson Publishers.
3. Ketki Rangwala Dalal, Essentials of Civil Engineering, Charotar Publishing House.
4. BCP, Surveying volume 1
How to Create a More Engaging and Human Online Learning Experience
How to Create a More Engaging and Human Online Learning Experience Wahiba Chair Training & Consulting
Wahiba Chair's Talk at the 2024 Learning Ideas Conference. BÀI TẬP DẠY THÊM TIẾNG ANH LỚP 7 CẢ NĂM FRIENDS PLUS SÁCH CHÂN TRỜI SÁNG TẠO ...
BÀI TẬP DẠY THÊM TIẾNG ANH LỚP 7 CẢ NĂM FRIENDS PLUS SÁCH CHÂN TRỜI SÁNG TẠO ...Nguyen Thanh Tu Collection
https://app.box.com/s/qhtvq32h4ybf9t49ku85x0n3xl4jhr15Bed Making ( Introduction, Purpose, Types, Articles, Scientific principles, N...
Topic : Bed making
Subject : Nursing Foundation
Advanced Java[Extra Concepts, Not Difficult].docx
This is part 2 of my Java Learning Journey. This contains Hashing, ArrayList, LinkedList, Date and Time Classes, Calendar Class and more.
বাংলাদেশ অর্থনৈতিক সমীক্ষা (Economic Review) ২০২৪ UJS App.pdf
বাংলাদেশের অর্থনৈতিক সমীক্ষা ২০২৪ [Bangladesh Economic Review 2024 Bangla.pdf] কম্পিউটার , ট্যাব ও স্মার্ট ফোন ভার্সন সহ সম্পূর্ণ বাংলা ই-বুক বা pdf বই " সুচিপত্র ...বুকমার্ক মেনু 🔖 ও হাইপার লিংক মেনু 📝👆 যুক্ত ..
আমাদের সবার জন্য খুব খুব গুরুত্বপূর্ণ একটি বই ..বিসিএস, ব্যাংক, ইউনিভার্সিটি ভর্তি ও যে কোন প্রতিযোগিতা মূলক পরীক্ষার জন্য এর খুব ইম্পরট্যান্ট একটি বিষয় ...তাছাড়া বাংলাদেশের সাম্প্রতিক যে কোন ডাটা বা তথ্য এই বইতে পাবেন ...
তাই একজন নাগরিক হিসাবে এই তথ্য গুলো আপনার জানা প্রয়োজন ...।
বিসিএস ও ব্যাংক এর লিখিত পরীক্ষা ...+এছাড়া মাধ্যমিক ও উচ্চমাধ্যমিকের স্টুডেন্টদের জন্য অনেক কাজে আসবে ...
Beyond Degrees - Empowering the Workforce in the Context of Skills-First.pptx
Iván Bornacelly, Policy Analyst at the OECD Centre for Skills, OECD, presents at the webinar 'Tackling job market gaps with a skills-first approach' on 12 June 2024
Hindi varnamala | hindi alphabet PPT.pdf
हिंदी वर्णमाला पीपीटी, hindi alphabet PPT presentation, hindi varnamala PPT, Hindi Varnamala pdf, हिंदी स्वर, हिंदी व्यंजन, sikhiye hindi varnmala, dr. mulla adam ali, hindi language and literature, hindi alphabet with drawing, hindi alphabet pdf, hindi varnamala for childrens, hindi language, hindi varnamala practice for kids, https://www.drmullaadamali.com
Recently uploaded (20)
Film vocab for eal 3 students: Australia the movie
Film vocab for eal 3 students: Australia the movie
spot a liar (Haiqa 146).pptx Technical writhing and presentation skills
spot a liar (Haiqa 146).pptx Technical writhing and presentation skills
NEWSPAPERS - QUESTION 1 - REVISION POWERPOINT.pptx
NEWSPAPERS - QUESTION 1 - REVISION POWERPOINT.pptx
Pengantar Penggunaan Flutter - Dart programming language1.pptx
Pengantar Penggunaan Flutter - Dart programming language1.pptx
What is Digital Literacy? A guest blog from Andy McLaughlin, University of Ab...
What is Digital Literacy? A guest blog from Andy McLaughlin, University of Ab...
ISO/IEC 27001, ISO/IEC 42001, and GDPR: Best Practices for Implementation and...
ISO/IEC 27001, ISO/IEC 42001, and GDPR: Best Practices for Implementation and...
Chapter wise All Notes of First year Basic Civil Engineering.pptx
Chapter wise All Notes of First year Basic Civil Engineering.pptx
How to Create a More Engaging and Human Online Learning Experience
How to Create a More Engaging and Human Online Learning Experience
BÀI TẬP DẠY THÊM TIẾNG ANH LỚP 7 CẢ NĂM FRIENDS PLUS SÁCH CHÂN TRỜI SÁNG TẠO ...
BÀI TẬP DẠY THÊM TIẾNG ANH LỚP 7 CẢ NĂM FRIENDS PLUS SÁCH CHÂN TRỜI SÁNG TẠO ...
Bed Making ( Introduction, Purpose, Types, Articles, Scientific principles, N...
Bed Making ( Introduction, Purpose, Types, Articles, Scientific principles, N...
বাংলাদেশ অর্থনৈতিক সমীক্ষা (Economic Review) ২০২৪ UJS App.pdf
বাংলাদেশ অর্থনৈতিক সমীক্ষা (Economic Review) ২০২৪ UJS App.pdf
Beyond Degrees - Empowering the Workforce in the Context of Skills-First.pptx
Beyond Degrees - Empowering the Workforce in the Context of Skills-First.pptx
Nucleophilic substitution
- 1. Presented by : Mahroosh
- 2. CONTE NTS TERMS USED SN COMP RISON SN¹ SN² •Mechanis m • Example • Condition • Mechanism • Example
- 3. SUBSTITUTION REACTIONS Substitution : “A chemical reaction during which one functional group in a chemical compound is replaced by another functional group” Nucleophile : “An atom or molecule that donates an electron pair to make a covalent bond” Examples : OH¯ , Cl¯ , RO¨H ,RS¨H , CN ¯etc.
- 4. Definition of SN : “It is the reaction of an electron pair donor (nucleophile) with an electron pair acceptor (electrophile) or simply the leaving group in a substrate is replaced by nucleophile ” General reaction :
- 5. TERMS USED IN SN Substrate : “ Molecule which undergoes SN reaction ” Leaving group (nucleofuge) : “Specie which is being replaced by incoming entering group”
- 6. SN REACTIONS FOR ALIPHATIC COMPOUNDS SN SN²SN¹ (Based on molecularity)
- 7. SN¹ Abbreviation : “unimolecular nucleophilic substitution reaction” S • Substitution N • Nucleophilic 1 • Unimolecular
- 8. SN¹ MECHANISM FORMATION OF CARBOCATION AND ATTACK OF NUCLEOPHILE:
- 9. EXAMPLES
- 10. NECESSARY CONDITIONS FOR SN¹ • Substrate : • Temperature : Temperature α rate of reaction (upto carbocation prodctn) Temperature α bond breaking reaction Temperature α carbocation production
- 11. • Solvent : Polar protic solvent (high polarity, high dielectric) Water Formic acid Alcohols Ammonia
- 12. • Rate determining step : • Rate expression : Rate = k[R – LG] Where : [R – LG] »»» substrate slow
- 13. •Kinetics : 1st order reactions. Rate = k[R – LG]¹ •Molecularity : oUnimolecular (one molecule is involved in RDS) [R –
- 14. • REACTION INTERMEDIATE : o Tertiary carbocation o Single intermediate o Stability of carbocations < <
- 15. • Transition state : “Transition states are potential energy maximums”. • Symbol : [ ]* o Several transition states. ]*[ hhhhhh [ ]*
- 16. • Energy profile diagram :
- 17. RY
- 18. SN² Abbreviation : “bimolecular nucleophilic substitution reaction” S • Substitution N • Nucleophilic 2 • Bimolecular
- 19. SN² MECHANISM
- 20. EXAMPLES
- 21. SN² • Substrate : • Temperature : Temperature α rate of reaction Temperature α bond breaking reaction > > >
- 22. • Solvent :
- 23. • Rate determining step : o Both nucleophile and substrate are involved . • Rate expression : Rate = k[R – LG][Nu] Where : [R – LG] »»» substrate , [Nu] »»» nucleophile
- 24. •Kinetics : o2nd order reaction oRate = k[R – LG]¹[Nu]¹ • Molecularity : oBimolecular (substrate and nucleophile is involved in RDS) [R – [Nu
- 25. • Reaction intermediate : o No reaction intermediate o Single step reaction • Transition state : o Single transition state
- 26. • Energy profile diagram :
- 27. STEREOCHEMISTR Y
- 28. CONCLUSION SN¹ • One molecule in RDS • Molecularity = 1 • Rate α [substrate]¹ • Polar protic solvent • Weak nucleophile • Barrier carbocation stability • 2 steps involved • Mixing of retention and inversion • 1st order kinetics • 2 transition states SN² • Two molecule in RDS • Molecularity = 2 • Rate α [substrate]¹[Nu]¹ • Polar aprotic solvent • Strong nucleophile • Big barrier is steric hindrance • One step involved • Only inversion of configuration • 2nd order kinetics • 1 transition state
- 29. • Which is faster SN¹/SN² ??? SN² will be faster if : Reagent is strong base. Carbon connected to LG is methyl or primary. Solvent is aprotic (DMF , DMSO ) . They need space (for entering into molecule and to push LG).