Chapter3自由基卤代
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c. H2N∙, HO∙, H3C∙ The order of increasing reactivity (diminishing selectivity) is: H2N∙ > HO∙ > H3C∙ The nitrogen radical is the most reactive due to resonance stabilization by the lone pair. The oxygen radical is more reactive than the methyl radical due to electronegativity effects.
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1. The document contains 50 multiple choice chemistry questions from an unsolved 2006 past paper.
2. The questions cover a range of chemistry topics including reactions, nomenclature, properties of substances, equilibrium, kinetics, electrochemistry and thermodynamics.
3. Answers to the questions are not provided, as it is an unsolved past paper.
1.5 elimination reaction
This power point presentation summarizes elimination reactions, specifically 1,2 elimination reactions. It defines elimination reactions as reactions where two atoms or groups are removed from a reactant to form an unsaturated product. 1,2 elimination reactions eliminate atoms or groups from the 1 and 2 positions on a molecule. Three possible mechanisms are discussed: E2, E1, and E1cb. Evidence for the E2 mechanism includes kinetic isotope effects, the element effect showing dependence on leaving group ability, and the lack of hydrogen exchange. The Saytzeff rule and factors influencing its application, like stability and transition state crowding, are also covered.
Organic mechanisms
The document summarizes various organic reaction mechanisms including:
1) Free radical substitution, electrophilic addition, nucleophilic substitution, elimination, addition-elimination, electrophilic substitution, esterification, alkaline hydrolysis, nucleophilic addition.
2) Specific mechanisms are described for hydration of alkenes, addition polymerization, bromination of alkenes, nucleophilic substitution, elimination, dehydration, esterification.
3) The formation of polymers like polyamides, polyesters through reactions of dibasic acids and diamines or diols are summarized.
Chapter13炔烃
1) Alkynes contain a carbon-carbon triple bond and are named with the suffix -yne. Common alkynes include ethyne and 1-pentyne.
2) The triple bond is more energetic than double bonds, making alkynes more reactive. Alkynes undergo characteristic reactions like electrophilic additions and hydroboration-oxidation.
3) Common methods to prepare alkynes involve elimination reactions of dihaloalkanes or the alkylation of alkynyl metals like lithium acetylides with alkyl halides.
hesses low.pptx
1) Hess's law states that the total enthalpy change of a chemical reaction is independent of the pathway as long as the initial and final states are the same.
2) The enthalpy change for a reaction can be calculated by adding the enthalpy changes of formation of the products and subtracting the enthalpy changes of formation of the reactants.
3) Examples are provided to demonstrate calculating enthalpy changes of reactions using Hess's law and standard enthalpy of formation values.
What are hydrocarbons and it's study material in pdf
Hydrocarbons, the fundamental compounds of organic chemistry, are composed of hydrogen and carbon atoms. The diverse world of hydrocarbons is neatly categorized based on their structure and the type of bonds they contain. In Class 11, students delve into the classification of hydrocarbons, exploring alkanes, alkenes, alkynes, and aromatic compounds.
hydrocarbons class 11 ncert pdf download
In Class 11 Chemistry, hydrocarbons serve as a fundamental topic within organic chemistry. Hydrocarbons are organic compounds composed exclusively of carbon and hydrogen atoms. The class primarily focuses on four major types of hydrocarbons: alkanes, alkenes, alkynes, and aromatic hydrocarbons.
For more information, visit- www.vavaclasses.com
Hydrogenation (3)
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.
Organic chemistry reaction mechanisms
1) The document discusses various organic chemistry reaction mechanisms including SN1, SN2, addition and substitution reactions.
2) It provides step-by-step explanations of the mechanisms of reactions such as hydrolysis of ethers with HI, addition of Grignard reagents to carbonyls, and acid-catalyzed dehydration of alcohols.
3) Limiting factors for different reaction mechanisms are discussed, such as steric hindrance preventing SN2 in tertiary halides and stability of carbocation intermediates determining SN1 rates.
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Dr. R. S. Shinde B.Sc. I Sem-I Organic chemistry (1) (1).ppt
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What are hydrocarbons and it's study material in pdf
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Chapter22取代苯化学
1) Benzylic radicals are reactive intermediates in the α-halogenation of alkylbenzenes. Benzylic halogenation proceeds without use of a catalyst like FeBr3 and involves benzylic cation and SN2 reaction mechanisms.
2) Phenol synthesis can occur through three mechanisms - nucleophilic aromatic substitution when electron-withdrawing groups are present, elimination-addition via highly reactive benzyne intermediates under harsh conditions, or using arenediazonium salts with super-leaving nitrogen groups.
3) Phenols are weakly acidic due to resonance stabilization of the phenoxide anion. They undergo electrophilic aromatic substitution and other reactions like ether and ester formation. O
Chapter23克莱森缩合
This document discusses ester enolates and the Claisen condensation reaction. The Claisen condensation involves the deprotonation of a 3-oxoalkanoate to form an ester enolate, which then undergoes nucleophilic addition and elimination to form a β-ketoester product. The acidic hydrogens of β-ketoesters make them readily enolizable and allow the reaction to be driven to completion. Ester enolates can undergo reactions like alkylation, Michael addition, and the Robinson annulation. Methods for synthesizing α-hydroxycarbonyls involve the use of masked alkanoyl anions like 1,3-dithiane derivatives or a catalytic
Chapter21胺及其衍生物
This document discusses amines and their derivatives. It covers their roles in medicines, amino acids, proteins, alkaloids, and industrial materials. Primary, secondary, and tertiary amines are introduced. Amines are basic due to their ability to accept protons. Their structures can be chiral. Common reactions include alkylation, reduction of nitriles, and reductive amination. The Mannich reaction forms β-aminocarbonyl compounds from iminium ions. Reaction with nitrous acid can form N-nitrosamines. Diazomethane is used to form esters and generate carbenes.
Chapter20羧酸衍生物
This document discusses the reactivity of various carboxylic acid derivatives including alkanoyl halides, anhydrides, esters, amides, and alkanenitriles. It compares their relative reactivities and describes common reaction mechanisms. Alkanoyl halides are the most reactive and undergo nucleophilic substitution reactions. Anhydrides and esters undergo similar reactions but are less reactive. Amides have lower acidity than esters due to resonance and undergo hydrolysis or reduction. Alkanenitriles undergo hydrolysis to carboxylic acids or reactions with organometallic reagents to form ketones or aldehydes.
Chapter19羧酸
Carboxylic acids contain the carboxyl group (-COOH). They are named as alkanoic acids in IUPAC nomenclature by replacing the -e ending of the parent alkane with -oic acid. Carboxylic acids are planar due to resonance and undergo hydrogen bonding to form dimers. They are relatively acidic due to the inductively withdrawing carbonyl carbon and resonance stabilization of the carboxylate ion. Common reactions of carboxylic acids include oxidation to form acids, carbonation to introduce the carboxyl group, nitrile hydrolysis to form acids, and reactions to form derivatives like acid halides, anhydrides, esters, and amides.
Chapter18烯醇结构不饱和醛酮
- α-Hydrogens in carbonyl compounds are acidic and can be deprotonated to form enolates using bases like KH or LDA.
- Enolates are nucleophilic and can undergo reactions like alkylation, halogenation, and aldol condensation. They tautomerize between keto and enol forms.
- α,β-Unsaturated carbonyls undergo conjugate additions and other reactions characteristic of alkenes and carbonyl groups. They can rearrange between β,γ and α,β isomers with acid or base catalysis.
Chapter17醛和酮
Aldehydes and ketones contain a carbonyl group consisting of a carbon double-bonded to an oxygen. Chapter 17 discusses the properties, nomenclature, synthesis, and reactions of aldehydes and ketones. Key reactions include nucleophilic additions to the carbonyl carbon to form alcohols, such as hydration to form geminal diols or addition of alcohols or amines. Other reactions include oxidations of alcohols to form aldehydes or ketones, and reductions of aldehydes or ketones using reagents such as sodium borohydride or lithium aluminum hydride.
Chapter16苯亲电反应
1. The document discusses the effects of substituents on the reactivity and regiochemistry of electrophilic aromatic substitution (EAS) on benzene derivatives.
2. Substituents can be either activating or deactivating through inductive or resonance effects. Activating groups direct EAS to the ortho- and para- positions, while deactivating groups direct to the meta- position.
3. Strategies are provided to control the regiochemistry of EAS through changing substituents, protecting functional groups, reversible blocking, and considering resonance in polycyclic systems like naphthalene.
Chapter15苯和芳香性
Michael Faraday discovered benzene in 1825 through the pyrolysis of whale oil. It is a colorless liquid with a boiling point around 80°C that is very unreactive. Kekulé proposed its cyclic, hexagonal structure in 1865. Benzene and its derivatives are called arenes. The benzene ring confers additional stability and reactivity due to aromaticity. Electrophilic aromatic substitution reactions occur on benzene and substituted benzenes, including halogenation, nitration, and sulfonation.
Chapter14离域π系统
1) Conjugated double bonds stabilize compounds through resonance and delocalization of pi electrons. This leads to increased stability and reactivity compared to isolated double bonds.
2) Allylic positions adjacent to double bonds exhibit increased reactivity due to stabilization of allylic radicals and cations by resonance. This leads to faster substitution and elimination reactions.
3) Conjugated systems undergo characteristic pericyclic reactions like the Diels-Alder reaction and electrocyclic reactions that involve concerted bonding changes across the pi system. These reactions allow for controlled synthesis of cyclic compounds.
Chapter24碳水化合物
1. Carbohydrates are produced through photosynthesis and stored as glucose. They are hydrated carbon compounds that occur naturally as nucleic acids, fibers, starches, sugars, and other biological molecules.
2. The simplest carbohydrates are monosaccharides or simple sugars. They can form oligomers by ether bridges to create disaccharides, trisaccharides, and higher saccharides. Common monosaccharides include glucose, fructose, and ribose.
3. Carbohydrates can be identified and their structures determined through techniques like sugar extensions, degradations, oxidations, reductions, and recognizing stereochemical relationships between reaction products. This allows deduction of carbohydrate configurations and identities.
Chapter10核磁共振光谱
1. Nuclear magnetic resonance (NMR) spectroscopy provides information about atomic nuclei and the chemical environment around them by applying a strong magnetic field and radio waves.
2. NMR spectra contain peaks that represent different atomic nuclei. The position and splitting of these peaks provides information about the number and type of neighboring atoms.
3. Advanced NMR techniques such as 2D NMR, 13C NMR, and MRI can provide additional structural information and are used in applications such as medical imaging.
Chapter9醇的反应
1. The document discusses reactions of alcohols including deprotonation, protonation, oxidation, and formation of esters and ethers.
2. Specific reactions covered include deprotonation of primary, secondary, and tertiary alcohols using various bases, carbocation rearrangements during SN1 reactions, and formation of ethers through SN2 and SN1 reactions of alcohols.
3. Ethers can be synthesized from alcohols through Williamson ether synthesis and cyclic ethers can be formed through an intramolecular version of this reaction.
Chapter8醇
This document discusses alcohols (compounds containing an -OH functional group). It covers alcohol nomenclature, properties, synthesis, and metabolism.
Alcohols are named based on the parent alkane chain containing the -OH group. They exhibit hydrogen bonding which increases their melting/boiling points and water solubility. Common synthesis methods include SN1/SN2 reactions of alcohols, reduction of carbonyls using NaBH4 or LiAlH4, and reactions of organometallics like Grignard reagents with carbonyls. Ethanol is metabolized in the body through oxidation reactions and excretion primarily through the lungs and urine. Adverse effects of alcohol abuse include
Chapter7亲核取代消除
1. The document discusses mechanisms of substitution and elimination reactions for alkyl halides, including SN1, SN2, E1 and E2.
2. Key factors that determine the reaction mechanism are the structure of the alkyl halide (primary, secondary, tertiary), the nucleophilicity and basicity of the reaction conditions, and temperature.
3. SN1 proceeds through a carbocation intermediate and gives racemic products. SN2 is stereospecific. E1 and E2 are elimination reactions favored by strong bases and high temperatures.
Chapter6卤代烷亲核取代
This document summarizes key aspects of nucleophilic substitution reactions of haloalkanes. It discusses the polarization of the C-X bond, with X (the leaving group) being electrophilic and carbon being polarized partially positively. The ability of a substituent to be a good leaving group (L) or nucleophile (Nu) depends on trends in electronegativity, bond strength, and orbital size down the periodic table. Steric effects are also important, with bulky groups hindering frontside attack. Solvent effects influence nucleophilicity, with protic solvents enhancing nucleophiles through hydrogen bonding.
Chapter5立体异构
This document discusses stereoisomerism, including constitutional isomers, stereoisomers, and image-mirror image stereoisomers. It provides examples of enantiomers from the bromination of butane and defines terms like stereocenter, chiral, and achiral. The document also covers assigning R/S configuration using Cahn-Ingold-Prelog rules and Fischer projections, and discusses how multiple stereocenters give rise to different stereoisomers like diastereomers and meso compounds.
Chapter4环烷烃
1. The document discusses various types of cyclic hydrocarbons including cycloalkanes, bicyclic compounds, and polyhedral hydrocarbons. Cycloalkanes experience different types of strain due to bond angles and eclipsing interactions.
2. Conformational analysis is used to determine the relative stability of different conformers. Substituted cyclohexanes prefer the lowest energy conformations, though large substituents can lock conformations.
3. Medium rings and polycyclic compounds experience additional transannular strain. Exotic polyhedral hydrocarbons have been synthesized though they are highly strained.
Chapter1绪论
This document provides an overview of organic chemistry concepts including bonding, functional groups, and reactions. It begins with Lewis structures which use octet rules to distribute valence electrons between atoms to form single, double or triple bonds in order to achieve noble gas configurations. Resonance forms are discussed which show that molecules may be represented by multiple equivalent structures. The document then discusses how molecular shape is controlled by valence electron repulsion. Basic reactions like substitution and elimination are also mentioned.
Chapter26氨基酸肽蛋白质以及核酸
This document discusses amino acids, peptides, and proteins. It begins by defining amino acids as α-amino acids with the general formula RCH(NH2)COOH. Amino acids condense to form peptides and proteins through peptide bonds. Peptides and proteins have primary, secondary, tertiary, and quaternary levels of structure that determine their shape and function. The document also discusses various methods for synthesizing and sequencing amino acids and proteins.
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Madhya Pradesh, the "Heart of India," boasts a rich tapestry of culture and heritage, from ancient dynasties to modern developments. Explore its land records, historical landmarks, and vibrant traditions. From agricultural expanses to urban growth, Madhya Pradesh offers a unique blend of the ancient and modern.
Fabular Frames and the Four Ratio Problem
Digital, interactive art showing the struggle of a society in providing for its present population while also saving planetary resources for future generations. Spread across several frames, the art is actually the rendering of real and speculative data. The stereographic projections change shape in response to prompts and provocations. Visitors interact with the model through speculative statements about how to increase savings across communities, regions, ecosystems and environments. Their fabulations combined with random noise, i.e. factors beyond control, have a dramatic effect on the societal transition. Things get better. Things get worse. The aim is to give visitors a new grasp and feel of the ongoing struggles in democracies around the world.
Stunning art in the small multiples format brings out the spatiotemporal nature of societal transitions, against backdrop issues such as energy, housing, waste, farmland and forest. In each frame we see hopeful and frightful interplays between spending and saving. Problems emerge when one of the two parts of the existential anaglyph rapidly shrinks like Arctic ice, as factors cross thresholds. Ecological wealth and intergenerational equity areFour at stake. Not enough spending could mean economic stress, social unrest and political conflict. Not enough saving and there will be climate breakdown and ‘bankruptcy’. So where does speculative design start and the gambling and betting end? Behind each fabular frame is a four ratio problem. Each ratio reflects the level of sacrifice and self-restraint a society is willing to accept, against promises of prosperity and freedom. Some values seem to stabilise a frame while others cause collapse. Get the ratios right and we can have it all. Get them wrong and things get more desperate.
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3:国家专业人才认证中心颁发入库证书
4:这个认证书并且可以归档倒地方
5:凡事获得留信网入网的信息将会逐步更新到个人身份内，将在公安局网内查询个人身份证信息后，同步读取人才网入库信息
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"Does Foreign Direct Investment Negatively Affect Preservation of Culture in the Global South? Case Studies in Thailand and Cambodia."
Do elements of globalization, such as Foreign Direct Investment (FDI), negatively affect the ability of countries in the Global South to preserve their culture? This research aims to answer this question by employing a cross-sectional comparative case study analysis utilizing methods of difference. Thailand and Cambodia are compared as they are in the same region and have a similar culture. The metric of difference between Thailand and Cambodia is their ability to preserve their culture. This ability is operationalized by their respective attitudes towards FDI; Thailand imposes stringent regulations and limitations on FDI while Cambodia does not hesitate to accept most FDI and imposes fewer limitations. The evidence from this study suggests that FDI from globally influential countries with high gross domestic products (GDPs) (e.g. China, U.S.) challenges the ability of countries with lower GDPs (e.g. Cambodia) to protect their culture. Furthermore, the ability, or lack thereof, of the receiving countries to protect their culture is amplified by the existence and implementation of restrictive FDI policies imposed by their governments.
My study abroad in Bali, Indonesia, inspired this research topic as I noticed how globalization is changing the culture of its people. I learned their language and way of life which helped me understand the beauty and importance of cultural preservation. I believe we could all benefit from learning new perspectives as they could help us ideate solutions to contemporary issues and empathize with others.
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Ponzi schemes, a notorious form of financial fraud, have plagued America’s investment landscape for decades. Named after Charles Ponzi, who orchestrated one of the most infamous schemes in the early 20th century, these fraudulent operations promise high returns with little or no risk, only to collapse and leave investors with significant losses. This article explores the nature of Ponzi schemes, notable cases in American history, their impact on victims, and measures to prevent falling prey to such scams.
Understanding Ponzi Schemes
A Ponzi scheme is an investment scam where returns are paid to earlier investors using the capital from newer investors, rather than from legitimate profit earned. The scheme relies on a constant influx of new investments to continue paying the promised returns. Eventually, when the flow of new money slows down or stops, the scheme collapses, leaving the majority of investors with substantial financial losses.
Historical Context: Charles Ponzi and His Legacy
Charles Ponzi is the namesake of this deceptive practice. In the 1920s, Ponzi promised investors in Boston a 50% return within 45 days or 100% return in 90 days through arbitrage of international reply coupons. Initially, he paid returns as promised, not from profits, but from the investments of new participants. When his scheme unraveled, it resulted in losses exceeding $20 million (equivalent to about $270 million today).
Notable American Ponzi Schemes
1. Bernie Madoff: Perhaps the most notorious Ponzi scheme in recent history, Bernie Madoff’s fraud involved $65 billion. Madoff, a well-respected figure in the financial industry, promised steady, high returns through a secretive investment strategy. His scheme lasted for decades before collapsing in 2008, devastating thousands of investors, including individuals, charities, and institutional clients.
2. Allen Stanford: Through his company, Stanford Financial Group, Allen Stanford orchestrated a $7 billion Ponzi scheme, luring investors with fraudulent certificates of deposit issued by his offshore bank. Stanford promised high returns and lavish lifestyle benefits to his investors, which ultimately led to a 110-year prison sentence for the financier in 2012.
3. Tom Petters: In a scheme that lasted more than a decade, Tom Petters ran a $3.65 billion Ponzi scheme, using his company, Petters Group Worldwide. He claimed to buy and sell consumer electronics, but in reality, he used new investments to pay off old debts and fund his extravagant lifestyle. Petters was convicted in 2009 and sentenced to 50 years in prison.
4. Eric Dalius and Saivian: Eric Dalius, a prominent figure behind Saivian, a cashback program promising high returns, is under scrutiny for allegedly orchestrating a Ponzi scheme. Saivian enticed investors with promises of up to 20% cash back on everyday purchases. However, investigations suggest that the returns were paid using new investments rather than legitimate profits. The collapse of Saivian l
KYC Compliance: A Cornerstone of Global Crypto Regulatory Frameworks
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快速制作美国迈阿密大学牛津分校毕业证文凭证书英文原版一模一样
原版一模一样【微信：741003700 】【美国迈阿密大学牛津分校毕业证文凭证书】【微信：741003700 】学位证，留信认证（真实可查，永久存档）offer、雅思、外壳等材料/诚信可靠,可直接看成品样本，帮您解决无法毕业带来的各种难题！外壳，原版制作，诚信可靠，可直接看成品样本。行业标杆！精益求精，诚心合作，真诚制作！多年品质 ,按需精细制作，24小时接单,全套进口原装设备。十五年致力于帮助留学生解决难题，包您满意。
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留信网认证的作用:
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4:这个认证书并且可以归档倒地方
5:凡事获得留信网入网的信息将会逐步更新到个人身份内，将在公安局网内查询个人身份证信息后，同步读取人才网入库信息
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Chapter3自由基卤代
- 1. Chapter 3: Radical Halogenation O O O O N
- 3. Radical Halogenation and Bond Strength Reactions require bond breaking and bond making Bond strengths: Homolytic cleavage radicals ∆H = DHº = Bond dissociation energy (kcal mol-1) This process contrasts with heterolytic cleavage A B A B + - + A B A· B+ e.g. H OH, DHº = +119, yet: H2O + H2O H3O + OH easy + - ·
- 4. H H H H+ DHº = +104 kcal mol-1 To functionalize alkanes, we need to break C H A 1-minute problem: DHº = ? The simplest bond dissociation: A. Same as H–H B. Larger C. Smaller
- 5. We expect C H to be less than for H2. But: Are all C–H bonds the same ? DHº s decrease along the series: CH4 > Rprim―H > Rsec―H > Rtert―H No! Primary Secondary Tertiary
- 6. CH3 H DHº = +105 kcal mol-1
- 8. Calculate feasibility of a reaction: CH3–OH + H–I CH3–I + H–OH ΔH° = ??
- 9. CH3–OH + H–I CH3–I + H–OH 93 71 57 119 164 – 176 = –12 kcal mol-1
- 11. Remember BH3! Why do we see such a trend? R is sp2-hybridized. Substitution stabilizes the radical. How?
- 12. Hyperconjugation p-Orbital (with single e) overlaps with bonding molecular orbital of neighboring C-H (or any other) bond. C C H C C Hyperconjugation
- 13. Hyperconjugation Potential Energy Diagram C H Hyperconjugation E C H bond p-Orbital MO picture of sp3 1s(H) Net stabilization: 3e Bonding MO Antibonding MO
- 14. Hyperconjugation
- 15. Radical Halogenation: Methane and Chlorine (kcal mol-1) CH3 H + Cl Cl CH3 Cl + H Cl Exothermic, but needs heat (∆) and/or light to start. 105 58 ∆Hº = -25 85 103 hv, ∆ CCl4 Mechanism 1. Initiation: Cl2 2 Cl ∆Hº = +58 “light the match” hv or ∆
- 16. How does the Cl–Cl bond break? Thermally: Vibrational energy gets sufficiently large to cause bond breaking. Photochemically: Absorption of photon causes excitation of bonding electron to antibonding molecular orbital.
- 17. 2. Propagation (“fire”): A radical chain mechanism a. CH4 + Cl CH3 + HCl ∆Hº = +2 b. CH3 + Cl2 CH3Cl + Cl ∆Hº = -27 up! down! [a. + b.]: CH4 + Cl2 CH3Cl + HCl ∆Hº = -25 3. Termination: 2Cl Cl2 CH3 + Cl CH3Cl CH3 + CH3 CH3 CH3 Kills propagation Mech 105 103 58 85 Note: Initiation step does not enter into equation. Only a few Cl∙ needed to convert all of the starting material.
- 18. Orbital Picture of H· Abstraction Fast! Partial radical character δ∙ resembles products
- 19. Potential energy diagram of propagation steps gives picture of the energetic “ups and downs”.
- 20. Lipshutz Trenet
- 21. Other Halogenations of Methane Compare important DH º values: Reactivity: F2 > Cl2 ~ Br2 > I2 won’t go! F2 Cl2 Br2 I2 HF HCl HBr HI F Cl Br I 38 58 46 36 136 103 87 71 110 85 70 57 explodes good ! CH3 X Initiation OK for all Why?
- 22. F2 Cl2 Br2 I2 HF HCl HBr HI F Cl Br I 38 58 46 36 136 103 87 71 110 85 70 57 Won’t go! Endothermic. Remember: CH3--H 105 kcal mol-1 CH3―X
- 23. Reactivity determined in step a. by DHº = H―X. Let’s compare the position of the transition states along reaction coordinate. Hammond Postulate. not far, small δ∙ on C far larger δ∙ on C Early TS fast , exothermic step ( F). Late TS slow , endothermic step ( Br, I).
- 24. Selectivity for Differing C-H Bonds CH3CH2CH3 CH3CH2CH2Cl + CH3CHCH3 Statistical (expected) 3 : 1 Reactivity (expected) Less (prim) More (sec) Found (25 ºC) : 43 : 57 Reactivity per H: 43/6 = 7.2 57/2 = 28.5 1 : 4 CH3 CH2 CH3 CH3 CH3 CH3C H prim, sec, tert Cl -HCl Cl2, hv
- 25. Transition states radical-like; reflect relative stabilities of products For alkanes other than CH4, 1st pro- pagation step is exothermic
- 26. Tertiary? Statistical (expected) 9 : 1 Reactivity (expected) Less (prim) More (tert) Found (25 ºC) 64 : 36 Normalized per H: 64/9 = 7 36/1 = 36 1 : 5 Result: Relative reactivity (selectivity) in chlorinations at 25ºC: Tert : Sec : Prim = ~ 5 : 4 : 1 CH3 CH3 CH3 ClCH2 CH3 CH3 CH3 CH3 CH3C C ClHC H -HCl Cl2, hv +
- 27. Selectivity and Other Halogens (CH3)3CH + F2 FCH2CH + (CH3)3CF 9:1 (CH3)3CH + Br2 (CH3)3CBr only ! statistical !CH3 CH3 “Early TS” (CH3)3CH + F2 FCH2CH + (CH3)3CF 9:1 (CH3)3CH + Br2 (CH3)3CBr only ! “Late TS”
- 28. Just to get a feel for the numbers…….. Selectivities vary extensively with the reagent employed, e.g., ICl, ROCl, R
- 29. Problem Rank H3C∙, H2N∙, and HO∙ in the order of increasing reactivity (diminishing selectivity): a. H3C∙, H2N∙, HO∙ b. H2N∙, H3C∙, HO∙ c. H2N∙, HO∙, H3C∙