This document summarizes various mechanisms of electrophilic and nucleophilic addition to alkenes. It discusses factors that determine the stereochemistry of addition, including the use of bridging electrophiles or ion pairing. It also covers addition of halides, protons, water, hydroboration-oxidation, carbon cations, peroxy acids, and nucleophiles. The key factors that determine the stereochemistry and regioselectivity of these addition reactions are discussed.
In organic chemistry, an alkyne is an unsaturated hydrocarbon containing at least one carbon—carbon triple bond. The simplest acyclic alkynes with only one triple bond and no other functional groups form a homologous series with the general chemical formula CₙH₂ₙ−2
In organic chemistry, an alkyne is an unsaturated hydrocarbon containing at least one carbon—carbon triple bond. The simplest acyclic alkynes with only one triple bond and no other functional groups form a homologous series with the general chemical formula CₙH₂ₙ−2
This is the Power Point Presentation for "Electrophilic Addition to Alkenes". This is as per syllabus of University of Mumbai for S.Y. B. Pharmacy students.
Alkenes are a class of hydrocarbons (e.g, containing only carbon and hydrogen) unsaturated compounds with at least one carbon-to-carbon double bond. Another term used to describe alkenes is olefins. Alkenes are more reactive than alkanes due to the presence of the double bond.
These slides include Hell-Volhard-Zelinski reaction introduction and mechanism. The mechanism is full of animation but SlideShare does not allow it. If you need this presentation, contact me.
Basic concepts of chemistry, alkanes, alkenes, alkynes, benzene, their preparation methods, properties and uses are explained. Isomerism in alkanes and alkynes also discussed.
In organic chemistry, an alkene is an unsaturated hydrocarbon that contains at least one carbon–carbon double bond. The words alkene and olefin are often used interchangeably.
Reactions of enolates with carbonyl compoundsvijay291993
Reactions of Enolates with Carbonyl Compounds
Aldol and Claisen condensation reactions
enolates or enols
nucleophillic attack by enols and enolates on carbonyl group
This is the Power Point Presentation for "Electrophilic Addition to Alkenes". This is as per syllabus of University of Mumbai for S.Y. B. Pharmacy students.
Alkenes are a class of hydrocarbons (e.g, containing only carbon and hydrogen) unsaturated compounds with at least one carbon-to-carbon double bond. Another term used to describe alkenes is olefins. Alkenes are more reactive than alkanes due to the presence of the double bond.
These slides include Hell-Volhard-Zelinski reaction introduction and mechanism. The mechanism is full of animation but SlideShare does not allow it. If you need this presentation, contact me.
Basic concepts of chemistry, alkanes, alkenes, alkynes, benzene, their preparation methods, properties and uses are explained. Isomerism in alkanes and alkynes also discussed.
In organic chemistry, an alkene is an unsaturated hydrocarbon that contains at least one carbon–carbon double bond. The words alkene and olefin are often used interchangeably.
Reactions of enolates with carbonyl compoundsvijay291993
Reactions of Enolates with Carbonyl Compounds
Aldol and Claisen condensation reactions
enolates or enols
nucleophillic attack by enols and enolates on carbonyl group
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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.
2. Chemistry of Aliphatic Compounds: Introduction, methods of preparation, physical and chemical properties and pharmaceutical applications of alcohols, aldehydes, ketones, hydrocarbons, ester, ethers, amines, amides and carboxylic acids.
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Electrophillic Addition
1. ch7-sykes-electrophilic-nucleophilic-addition.docx 2016January17 1
1. Mechanism of electrophilic addition
1.1. product maybe syn or anti depending on conditions or reagent
1.1.1. bridging electrophiles will force anti addition
1.1.2. ion pair formation favors syn addition, show on board
1.1.3. free ions give mixture (stablized carbocation or polar solvents)
1.2. Bromination
1.2.1. anti Br2 addition for almost all alkyl (I2 favored)
1.2.2. anti product supports bridged intermediate
1.2.3. ion detected in superacid
1.2.4. for alkyl substituted alkenes, nearly 100% anti
2. ch7-sykes-electrophilic-nucleophilic-addition.docx 2016January17 2
1.2.5. less stereospecific for aromatic substitutents (favored)
?
1.2.6. less stereospecific in polar solvents (favored)
?
1.3. substituent effects - electron donation and delocalization accelates
1.4. Chlorination
1.4.1. similar to bromination but bridged species less stable
1.4.2. more syn formation
1.5. Fluorination – to violent
1.6. Iodination - product unstable
1.7. Mixed halogenations: BrCl > BrBr > ICl > IBr > I-I: order?
1.7.1. Least electronegative atom adds
1.7.2. Faster for more electron deficient electrophile and more electronegative leaving group
2. HX addition: Markovnikov's rule: what is it?
2.1. HI, HBr, HCl, H2SO4, H2O, ROH, RSH, RCOOH all add to alkenes in acid conditions
2.2. H+ does not bridge
2.3. AdE2 bimolecular stepwise addition: RDS is H+ addition
2.4. Markovnikov addition is preferred- proton adds to least substuted carbon (form most stable
cation
3. ch7-sykes-electrophilic-nucleophilic-addition.docx 2016January17 3
2.5. Carbon cation rearrangements can occur
2.6. HX adds H+ in non-polar solvents
2.7. Protonated solvent adds in protic solvent, i.e. H3O+
2.8. HI > HBr > HCl >> HF
2.9. Concerted addition, AdE3, termolecular concerted addition, reverse of E2
2.9.1. break bond, make 2 bonds
2.9.2. addition is anti, favored for unreaction olefins, (unstable cation formation)
2.9.3. mechanism favored when solvent participates (HBr in HOAc)
2.10. Stepwise addition(AdE2) is favored by strong acids (CF3SO3H in HOAc)
3. Hydration
3.1. Acid catalyzed
4. ch7-sykes-electrophilic-nucleophilic-addition.docx 2016January17 4
3.2. Reverse of dehydration of alcohols
3.3. Need strong acid with poor nucleophile/conjugate base,HBr/water?
3.4. Dilute sulfuric acid common, concentrated sulfuric acid for reverse
4. Hydroboration-oxidation – convert alkene to alcohol (water addition – hydration)
4.1. Hydroborane – equilibrium with diborane
4.1.1. BH3 has empty orbital and BH bond is polar (H more electronegative)
4.1.2. B accepts electrons! BH3 is a Lewis acid and hydride donor?
4.1.3. Only 4 electrons total in two bridge, low barrier for dissociation
4.2. Borane addition to C=C
4.2.1. Boron accepts electrons
4.2.2. attaches to least substituted carbon (Markovnikov)
4.2.3. H migration to electron deficient center
4.2.4. often concerted- no C-C rotation, stereochemistry is preserved
4.2.5. Two more equivalents of hydride: trialkylborane
4.3. Hydro oxidation- transfer to oxygen
4.3.1. Trialkylborane, equivalent to carbon cation without charge
4.3.2. Hydroperoxide anion very good nucleophile, adds to electron deficient center
5. ch7-sykes-electrophilic-nucleophilic-addition.docx 2016January17 5
4.3.3. R migration to electron deficient O center
4.4. Base hydrolysis
4.4.1. Hydroxide adds to alkyl borate
4.4.2. Form tetrahedral intermediate from trigonal intermediate common process
4.4.3. substitution of OR by OH, addition-elimination, not an SN2
4.4.4. three equivalent of alcohols
4.5. why not just use regular water addition?
4.5.1. Avoid rearrangement of cations
4.5.2. Stereospecific – retain stereochemistry during addition and migrations
4.5.3. Complementary regeochemistry to acid catalyzed hydration- anti-Markovnikov
4.5.4. H. C. Brown
5. Carbon cation addition to alkene
5.1.1. Dimer/trimer/polymerization
5.1.2. Potonate electrons/cation adds to electrons
5.1.3. Further addition can occur but steric inhibition slowes down reaction
5.1.4. Dissociation of proton forms new alkene
6. ch7-sykes-electrophilic-nucleophilic-addition.docx 2016January17 6
5.1.5. Hydrogenation yields isooctane: 100 % octane rating
6. Oxidative hydroxylation- skip Osmium tetroxide and permanganate
6.1. Peracid is self activating, electron deficient center
6.2. Oxygen adds to both carbons simultaneously, form epoxide
6.3. No rotation about CC bond, preserve stereochemistry
6.4. Similar chemistry to bromonium but epoxide is stable product
6.5. Acid or base catalyzed hydrolysis yields diol: anti addition
6.6. Asymmetric epoxides have different products for acid and base catalyzed reactions
6.6.1. Base conditions favor nucleophile attack least substituted carbon (question)
6.6.2. Acid conditions create positive charge at more substituted carbon
7. ch7-sykes-electrophilic-nucleophilic-addition.docx 2016January17 7
7. Skip Hydrogenation and Ozonolysis (later in cycloaddition)
8. Addition to dienes
8.1. 1,2 versus 1,4 addition (aprotic v. protic)
8.2. HCl addition
8.2.1. at – 60 oC 75% 1,2 addition, 20-25% 1,4 addition
8.2.2. 20 oC? 25% 1,2 addition, 75% 1,4 addition
8.2.3. Ion pairing keeps Cl from roaming and 1,2 is favored
8.2.4. Higher temperature 1,4 is favored
8.2.5. Heating pure 1,2 or 1,4 get the same mixture at high temperature, why?
9. Skip Diels Alder (chapter 12)
10. Nucleophilic addition
10.1. Electron withdrawing group stabilze negative charge
10.2. Michael reaction with carbon nulceophiles
10.2.1. 1,2 addition favored for more reactive group without steric hindrance
10.2.2. 1,4 addition favored for strerically unhindered 4 position if 2 position is blocked?