Real life example 1 Let s look at this series of chloroalcohols, and how fast the chloride gets displaced by an external nucleophile.
|
|
- Oliver Lyons
- 5 years ago
- Views:
Transcription
1 Class 2 Carbocations Last time we talked about neighboring group participation in substitution reactions. I want to start today by talking about a few more real life examples. Real life example 1 Let s look at this series of chloroalcohols, and how fast the chloride gets displaced by an external nucleophile. If the chloride is the same in each case, and that s the part of the molecule that reacts, why is there such a difference in the reaction rate? It must have to do with the length of the alkyl chain. The OH participates in the reaction mechanism to generate a cyclic ether. This step happens before the incoming nucleophile attack. This ring is most favored for the third compound in the series because that forms a 5 membered ring: Why are five membered rings so much more favored than any other ring size? This is really a two part question: Why are five membered rings more favored than small rings? and why are they more favored than large rings? The first part should be obvious to most people the smaller rings (3 and 4 membered) have substantially more ring strain that makes them less favorable. But why should it be easier to form a five membered ring compared to a six membered ring? The answer to this has to do with entropy. The free energy of any reaction relates to the enthalpy of the reaction and its entropy this is the chemical equation: delta G= delta H T delta S S = entropy. Things in nature in general prefer to move towards a system of more disorder, which corresponds to an increase in entropy. When you have an open chain molecule in solution, that molecule has lots of potential rotations and positions that it can assume. This makes the molecule very happy because it is more disordered/ less constrained. When you want to form a ring, you are effectively freezing out some of the motions available to that chain. The bigger the chain, the more it
2 was moving freely before ring formation, and the more difficult it is to form the target ring. This is why it is that much slower to form a six membered ring compared to a five membered ring, even though the stability of six membered rings (once formed) is roughly equivalent to that of a five membered ring. A lot of these cases generated cations as reaction intermediates. I want to talk today in some more detail about carbocations. Carbocations are generated from SN1 reactions, but also from other reactions such as elimination reactions (E1): SN1 reaction: E1 reaction: The stability of carbocations depends on their substitution the more substituted, the more stable. tertiary > secondary > primary > methyl Why does more substitution make carbocations more stable? Because the alkyl groups in general can delocalize the positive charge via a hyperconjugation effect. I don t want to spend too much time talking about hyperconjugation, but I do think I would be remiss as an instructor if we didn t talk about it at all. The Wikipedia definition of hyperconjugation is: In organic chemistry, hyperconjugation is the interaction of the electrons in a sigma bond (usually C H or C C) with an adjacent empty (or partially filled) non bonding p orbital or antibonding π orbital or filled π orbital, to give an extended molecular orbital that increases the stability of the system. NOT THAT ANYBODY HERE SHOULD EVER USE WIKIPEDIA AS A RELIABLE SOURCE. BUT STILL IT CAN BE USEFUL.
3 Basically, this means that sigma bonds can participate in conjugation in the same way that we typically think of double (pi) bonds participating in conjugation. Pi bond conjugation looks something like this: and the positive charge is delocalized over carbons 2 and 4 (numbering the carbons from left to right) Sigma bond conjugation is harder to draw, but basically involves orbital overlap of the bond: What is depicted here are the orbitals on the adjacent carbons being used to delocalize the positive charge of the carbocation. This hyperconjugation is the reason why substituted carbocations are more stable. Primary and methyl cations almost never form because they are so unstable. Those sorts of precursors would undergo SN2or E2 reactions instead. Tertiary halides will almost always form the corresponding tertiary cations. Secondary halides can go either way a secondary carbocation may form, or they may undergo the SN2/E2 reaction pathway. Secondary cations are also highly prone to rearrangements to generate more stable carbocations. In these kinds of rearrangements, some group moves (usually a hydride or an alkyl group) together with its corresponding electrons. We can divide this discussion of carbocation rearrangements into a few sub topics: (1) What things move in the rearrangement? (2) Where can they be in the molecule (i.e. how far away from the positive charge, before they start moving)? (3) What are actual examples of rearrangements? (1) What moves during a rearrangement? Let s start with a simple example of a secondary carbocation: This secondary carbocation can rearrange easily if the hydrogen on the neighboring carbon moves over:
4 The resulting carbocation is more stable because it is tertiary. The hydrogen migrates together with its two electrons which is why it is called a hydride shift, and the charge moves to the carbon from which the hydrogen originated. In theory the alkyl group could also have moved. This however would give a different secondary carbocation, and so we would be no better off than if the rearrangement had not occurred. In the case above, the hydrogen atom moved. Other things can also move in carbocation rearrangements including alkyl groups, vinyl groups, or aryl groups. We can create an ordered list of how apt things are to migrate, called their migratory aptitude, but a lot will depend on the particular reaction conditions. The rough migratory aptitude is: H > 3 o alkyl > 2 o alkyl > 1 o alkyl > methyl although in real life, hydrides and methyl groups are the things that most often end up moving. The reason for this order is that the migrating group develops some degree of positive charge. Certain fragments are better able to stabilize the positive charge (like a hydrogen is not particularly unhappy to be positively charged). Here s an example where the methyl group migrates: (2) Where in the molecule is the rearranged group coming from? Most rearrangements occur via a 1,2 shift which means that the migrating group only moves one carbon. (3) Real world examples: Real world example 1:
5 The carbon 14 labeled secondary tosylate reacts in acetic acid to give predominantly the non rearranged product, and 9% of the rearranged one. The rearrangement product arises through the mechanism shown below: If you have a hard time following this mechanism, then re draw it with all of the implied hydrogens shown, and that will probably clear up some of the confusion. Real world example #2: The first product comes from straight forward substitution of the OH group. But how do we get the second product? It looks like the phenyl group has migrated, which is probably exact what happened. However, the phenyl group likely goes through a three membered ring intermediate during the migration step: I want to move now to a discussion of non classical carbocations which roughly translated means weird carbocations and refers to things with delocalization of the positive charge over single bonds.
6 Norbornyl carbocation Consider the following case: If you start with either isomer of brosylate and treat it with acetic acid, you end up with the same isomer of acetate product. What is going on here? I ll give you some other information about this case: 1. The exo brosylate is 350 times more reactive than the endo isomer. 2. Chiral starting materials give racemic products. It turns out that the exo brosylate is the unusual case. What you actually form is a non classiccal carbocation, due to the assistance of the C1 C6 single bond: The mechanism is that a C C single bond that is anti periplanar to the leaving group breaks, and forms a new bond to the carbon with the leaving group. This bond formation occurs at the same time that the leaving group is being kicked off: Anti periplanar refers to two substituents that are in the same plane, but are also anti to each other. I know that doesn t make so much sense, so let s look at an example: In this particular example, the H and the LG are anti periplanar to each other. The bonds that connect them are all in the same plane, and the two groups are on opposite sides of the single bond ( anti ).
7 Oftentimes, two things have to be in an anti periplanar relationship in order for elimination to occur, or for their bonds to communicate with each other. This is because an anti periplanar stereochemical relationship maximizes the overlap of the orbitals that exists. So that is what you are looking for in the norbornyl case which one has a bond from the carbon to the leaving group that has an anti periplanar relationship to another bond on the molecule it is the EXO ISOMER! I ve redrawn the exo isomer with the two anti periplanar bonds highlighted. Now, as the brosylate leaves, a non classical carbocation forms: This intermediate has a positive charge delocalized over three carbon atoms. The acetate can add to either side of the ring, because they are both chemically equivalent, to give identical acetate products: Note that even though the positive charge is delocalized over three carbon atoms, you can only add to two of them i.e. nothing adds to the bridgehead position. Why not? This is your take home question for today. This intermediate is achiral (plane of symmetry). The fact that either starting material gives an exo acetate product is merely because you generate a carbocation, which gets substituted with acetate to give the most stable product. This was the first example of a non classical carbocation (first published in 1949). Since then, there have been many more examples of non classical carbocations.
Basic Organic Chemistry Course code : CHEM (Pre-requisites : CHEM 11122)
Basic Organic Chemistry Course code : CHEM 12162 (Pre-requisites : CHEM 11122) Chapter 01 Mechanistic Aspects of S N2,S N1, E 2 & E 1 Reactions Dr. Dinesh R. Pandithavidana Office: B1 222/3 Phone: (+94)777-745-720
More informationNucleophilic Substitution and Elimination
Nucleophilic Substitution and Elimination Alkyl halides react with a nucleophile in one of two ways. Either they eliminate an X to form an alkene, or they undergo a substitution with the nucleophile, Nu,
More informationSome Arrow-Pushing Guidelines (Section 1.14) 1. Arrows follow electron movement.
Chem 350 Jasperse Ch. 1 Notes 1 Note: The headers and associated chapters don t actually jive with the textbook we are using this summer. But otherwise this highlights a lot of the chemistry from Organic
More informationChapter 8. Substitution reactions of Alkyl Halides
Chapter 8. Substitution reactions of Alkyl Halides There are two types of possible reaction in organic compounds in which sp 3 carbon is bonded to an electronegative atom or group (ex, halides) 1. Substitution
More informationS N 1 Displacement Reactions
S N 1 Displacement Reactions Tertiary alkyl halides cannot undergo S N 2 reactions because of the severe steric hindrance blocking a backside approach of the nucleophile. They can, however, react via an
More informationPAPER No. 5:Organic Chemistry-2(Reaction Mechanism-1) MODULE No. 6: Generation, Structure, Stability and Reactivity of Carbocations
Subject Chemistry Paper No and Title Module No and Title Module Tag Paper No. 5: Organic Chemistry-II (Reaction Mechanism-1) Generation, Structure, Stability and Reactivity of Carbocations CHE_P5_M6 TABLE
More informationNuggets of Knowledge for Chapter 17 Dienes and Aromaticity Chem 2320
Nuggets of Knowledge for Chapter 17 Dienes and Aromaticity Chem 2320 I. Isolated, cumulated, and conjugated dienes A diene is any compound with two or C=C's is a diene. Compounds containing more than two
More informationLearning Guide for Chapter 17 - Dienes
Learning Guide for Chapter 17 - Dienes I. Isolated, conjugated, and cumulated dienes II. Reactions involving allylic cations or radicals III. Diels-Alder Reactions IV. Aromaticity I. Isolated, Conjugated,
More information7. Haloalkanes (text )
2009, Department of hemistry, The University of Western Ontario 7.1 7. aloalkanes (text 7.1 7.10) A. Structure and Nomenclature Like hydrogen, the halogens have a valence of one. Thus, a halogen atom can
More informationConjugated Systems, Orbital Symmetry and UV Spectroscopy
Conjugated Systems, Orbital Symmetry and UV Spectroscopy Introduction There are several possible arrangements for a molecule which contains two double bonds (diene): Isolated: (two or more single bonds
More informationAlso called an olefin but alkene is better General formula C n H 2n (if one alkene present) Can act as weak nucleophiles
Alkenes - Structure, Stability, Nomenclature Also called an olefin but alkene is better General formula C n H 2n (if one alkene present) unsaturated - contain fewer than maximum H's possible per C Can
More informationChapter 15: Conjugated Systems, Orbital Symmetry, and UV Spectroscopy
Chapter 15: Conjugated Systems, Orbital Symmetry, and UV Spectroscopy Conjugated unsaturated systems have a p orbital on a carbon adjacent to a double bond The p orbital can come from another double (e.g.
More informationChapter 6 Chemical Reactivity and Mechanisms
Chapter 6 Chemical Reactivity and Mechanisms 6.1 Enthalpy Enthalpy (ΔH or q) is the heat energy exchange between the reaction and its surroundings at constant pressure Breaking a bond requires the system
More informationChapter 5. Nucleophilic aliphatic substitution mechanism. by G.DEEPA
Chapter 5 Nucleophilic aliphatic substitution mechanism by G.DEEPA 1 Introduction The polarity of a carbon halogen bond leads to the carbon having a partial positive charge In alkyl halides this polarity
More informationThere are several possible arrangements for a molecule which contains two double bonds (diene): 1. Isolated: (two or more single bonds between them)
1 Chapter 15: Conjugation and Reactions of Dienes I. Introduction to Conjugation There are several possible arrangements for a molecule which contains two double bonds (diene): 1. Isolated: (two or more
More informationLoudon Chapter 15 Review: Dienes and Aromaticity Jacquie Richardson, CU Boulder Last updated 1/28/2019
This chapter looks at the behavior of carbon-carbon double bonds when several of them are in the same molecule. There are several possible ways they can be grouped. Conjugated dienes have a continuous
More information1. Root of name depends on longest chain of C containing the double bond; ends in "ene"
Alkenes (β-carotene, an antioxidant pigment) n 2n (acyclic) n 2n-2 (cyclic) R R R R Key features sp 2 -hybridized carbons, 120 o bond angles σ + π bonding between = planar geometry around = "unsaturated"
More informationUnderstanding the basics. Mechanisms 5/24/11
Understanding the basics Mechanisms Some Basic rgo I Reactions Mechanisms are the most mind-boggling part of organic chemistry. Students, generally speaking, have spent their time memorizing their way
More informationREARRANGEMENTS NOTES Mechanistic Aspects of Rearrangements
- 1 - REARRANGEMENTS NOTES Mechanistic Aspects of Rearrangements Nature of the Rearrangement It can vary from being truly stepwise to migration occurring in concert with initial ionisation. These two situations
More informationWeek 11 Problem Set (Solutions) 4/24, 4/25, 4/26
Week 11 Problem Set (Solutions) 4/24, 4/25, 4/26 Concepts Covered Alkynes Oxidation Alcohols Reactions/Reagents Deprotonation of Alcohols/Alkynes Jones Oxidation (Cr 2 O 7 ) Dess-Martin Periodinane (DMP)
More informationChapter 6: Organic Halogen Compounds; Substitution and Elimination Reactions
Chapter 6: Organic Halogen Compounds; Substitution and Elimination Reactions Halogen compounds are important for several reasons. Simple alkyl and aryl halides, especially chlorides and bromides, are versatile
More informationB X A X. In this case the star denotes a chiral center.
Lecture 13 Chirality III October 29, 2013 We can also access chiral molecules through the use of something called chiral auxiliaries, which basically is a chiral attachment that you add to your molecule
More informationAcid-Base -Bronsted-Lowry model: -Lewis model: -The more equilibrium lies to the right = More [H 3 O + ] = Higher K a = Lower pk a = Stronger acid
Revision Hybridisation -The valence electrons of a Carbon atom sit in 1s 2 2s 2 2p 2 orbitals that are different in energy. It has 2 x 2s electrons + 2 x 2p electrons are available to form 4 covalent bonds.
More informationMethyl > primary > secondary >> tertiary
Lecture 1 Notes September 6, 2012 Welcome to CHM 427. For some of you, this will be the last organic chemistry class that you will ever take. So I see it as my personal mission to make sure that you know
More informationAlcohols: Contain a hydroxy group( OH) bonded to an sp 2 or sp 3 hybridized
Lecture Notes hem 51B S. King hapter 9 Alcohols, Ethers, and Epoxides I. Introduction Alcohols, ether, and epoxides are 3 functional groups that contain σ-bonds. Alcohols: ontain a hydroxy group( ) bonded
More informationORGANIC - EGE 5E CH. 7 - NUCLEOPHILIC SUBSTITUTION AND ELIMINATION REACTIONS
!! www.clutchprep.com CONCEPT: INTRODUCTION TO SUBSTITUTION Previously, we discussed the various ways that acids could react with bases: Recall that in these mechanisms, electrons always travel from density
More informationChapter 17 Reactions of Aromatic Compounds
Chapter 17 Reactions of Aromatic Compounds Electrophilic Aromatic Substitution o General reaction - an electrophile replaces a hydrogen Electrons of pi system attack strong electrophile, generating resonancestabilized
More informationChapter 11: Nucleophilic Substitution and Elimination Walden Inversion
hapter 11: Nucleophilic Substitution and Elimination Walden Inversion (S)-(-) Malic acid [a] D = -2.3 Ag 2, 2 Pl 5 l Ag 2, 2 ()-2-hlorosuccinic acid l (-)-2-hlorosuccinic acid Pl 5 ()-() Malic acid [a]
More informationBSc. II 3 rd Semester. Submitted By Dr. Sangita Nohria Associate Professor PGGCG-11 Chandigarh 1
BSc. II 3 rd Semester Submitted By Dr. Sangita Nohria Associate Professor PGGCG-11 Chandigarh 1 Introduction to Alkyl Halides Alkyl halides are organic molecules containing a halogen atom bonded to an
More informationCHAPTER 7. Further Reactions of Haloalkanes: Unimolecular Substitution and Pathways of Elimination
CHAPTER 7 Further Reactions of Haloalkanes: Unimolecular Substitution and Pathways of Elimination 7-1 Solvolysis of Tertiary and Secondary Haloalkanes The rate of S N 2 reactions decrease dramatically
More informationSubstitution Reactions
Substitution Reactions Substitution reactions are reactions in which a nucleophile displaces an atom or group of atoms (the leaving group) from a tetrahedral carbon atom. onsider the following general
More information11. Reactions of Alkyl Halides: Nucleophilic Substitutions and Eliminations
11. Reactions of Alkyl Halides: Nucleophilic Substitutions and Eliminations Based on McMurry s Organic Chemistry, 6 th edition 2003 Ronald Kluger Department of Chemistry University of Toronto Alkyl Halides
More informationLoudon Chapter 17 Review: Allylic/Benzylic Reactivity
Chapter 17 is all about reactions that happen at the position one away from an aromatic ring, or one away from a double bond. These are called the benzylic and allylic positions respectively. Benzyl and
More informationLearning Guide for Chapter 10 - Alkyl Halides II
Learning Guide for Chapter 10 - Alkyl Halides II I. Elimination Reactions of Alkyl Halides Introduction Mechanisms Beta hydrogens, constitutional isomers, and stereoisomers E2 vs E1 Strong and Weak Bases
More informationCHE1502. Tutorial letter 201/1/2016. General Chemistry 1B. Semester 1. Department of Chemistry CHE1502/201/1/2016
CE1502/201/1/2016 Tutorial letter 201/1/2016 General Chemistry 1B CE1502 Semester 1 Department of Chemistry This tutorial letter contains the answers to the questions in assignment 1. FIRST SEMESTER: KEY
More informationLECTURE #13 Tues., Oct.18, Midterm exam: Tues.Oct.25 during class Ch.1, , 7.10, 2, Sections
CEM 221 section 01 LECTURE #13 Tues., Oct.18, 2005 Midterm exam: Tues.Oct.25 during class Ch.1, 7.2-7.5, 7.10, 2, 3.1-3.5 ASSGNED READNGS: TODAY S CLASS: Sections 4.1 4.6 NEXT CLASS: rest of Ch.4 http://artsandscience.concordia.ca/facstaff/p-r/rogers
More informationL substrate (Leaving group,l)
Aliphatic Nucleophilic Substitution Nu + Nucleophile L substrate (Leaving group,l) conditions products Nucleophiles are chemical species that react with centers of positive ionic character. When the center
More informationDAMIETTA UNIVERSITY. Energy Diagram of One-Step Exothermic Reaction
DAMIETTA UNIVERSITY CHEM-103: BASIC ORGANIC CHEMISTRY LECTURE 5 Dr Ali El-Agamey 1 Energy Diagram of One-Step Exothermic Reaction The vertical axis in this graph represents the potential energy. The transition
More informationChapter 9. Nucleophilic Substitution and ß-Elimination
Chapter 9 Nucleophilic Substitution and ß-Elimination Nucleophilic Substitution Nucleophile: From the Greek meaning nucleus loving. A molecule or ion that donates a pair of electrons to another atom or
More informationChapter 6 Ionic Reactions-Nucleophilic Substitution and Elimination Reactions of Alkyl Halides"
Chapter 6 Ionic Reactions-Nucleophilic Substitution and Elimination Reactions of Alkyl Halides" t Introduction" The polarity of a carbon-halogen bond leads to the carbon having a partial positive charge"
More informationChemistry 2000 Lecture 18: Reactions of organic compounds
hemistry 2000 Lecture 18: Reactions of organic compounds Marc R. Roussel March 6, 2018 Marc R. Roussel Reactions of organic compounds March 6, 2018 1 / 27 Reactions of organic compounds Organic chemists
More informationHomework problems Chapters 6 and Give the curved-arrow formalism for the following reaction: CH 3 OH + H 2 C CH +
omework problems hapters 6 and 7 1. Give the curved-arrow formalism for the following reaction: : 3 - : 2 : 3 2-3 3 2. In each of the following sets, arrange the compounds in order of decreasing pka and
More informationDepartment of Chemistry SUNY/Oneonta. Chem Organic Chemistry I. Examination #4 - December 9, 2002 ANSWERS
INSTRUCTINS Department of Chemistry SUNY/neonta Chem 221 - rganic Chemistry I Examination #4 - December 9, 2002 ANSWERS This examination is in multiple choice format; the questions are in this Exam Booklet
More information1. What are the respective hybridizations of the atoms numbered 1 to 4 in this compound?
EM 331: hapter 1/2: Structures (Atoms, Molecules, Bonding) 1. What are the respective hybridizations of the atoms numbered 1 to 4 in this compound? N 2 N 2 N 1 2 3 4 2. What hybrid orbitals are used to
More information10. Organohalides. Based on McMurry s Organic Chemistry, 7 th edition
10. Organohalides Based on McMurry s Organic Chemistry, 7 th edition What Is an Alkyl Halide An organic compound containing at least one carbonhalogen bond (C-X) X (F, Cl, Br, I) replaces H Can contain
More information1. What are the respective hybridizations of the atoms numbered 1 to 4 in this compound?
CEM 331: Chapter 1/2: Structures (Atoms, Molecules, Bonding) 1. What are the respective hybridizations of the atoms numbered 1 to 4 in this compound? N C 2 C N C 2 C N 1 2 3 4 1: three sigma bonds and
More informationPreparation of Alkyl Halides, R-X. Reaction of alkanes with Cl 2 & Br 2 (F 2 is too reactive, I 2 is unreactive): R + X X 2.
Preparation of Alkyl alides, R-X Reaction of alkanes with Cl 2 & Br 2 (F 2 is too reactive, I 2 is unreactive): UV R + X 2 R X or heat + X This mechanism involves a free radical chain reaction. A chain
More informationCHAPTER 8 HW SOLUTIONS: ELIMINATIONS REACTIONS
APTER 8 W SLUTNS: ELMNATNS REATNS S-TRANS SMERSM 1. Use a discussion and drawing of orbitals to help explain why it is generally easy to rotate around single bonds at room temperature, while it is difficult
More informationHomework - Review of Chem 2310
omework - Review of Chem 2310 Chapter 1 - Atoms and Molecules Name 1. What is organic chemistry? 2. Why is there an entire one year course devoted to the study of organic compounds? 3. Give 4 examples
More informationStructure and Preparation of Alkenes: Elimination Reactions
Structure and Preparation of Alkenes: Elimination Reactions Alkene Nomenclature First identify the longest continuous chain that includes the double bond. Replace the -ane ending of the corresponding unbranched
More informationAlcohols, Ethers, & Epoxides
Alcohols, Ethers, & Epoxides Alcohols Structure and Bonding Enols and Phenols Compounds having a hydroxy group on a sp 2 hybridized carbon enols and phenols undergo different reactions than alcohols. Chapter
More informationChapter 6. Chemical Reactivity and Reaction Mechanisms
hapter 6 hemical Reactivity and Reaction Mechanisms hemical Reactivity Enthalpy A simple chemical reaction can be broken down into bond creating and bond breaking components: A-B + Y-Z A-Y + B-Z A-B A
More informationOrganic Chemistry CHM 314 Dr. Laurie S. Starkey, Cal Poly Pomona Alkyl Halides: Substitution Reactions - Chapter 6 (Wade)
rganic Chemistry CM 314 Dr. Laurie S. Starkey, Cal Poly Pomona Alkyl alides: Substitution Reactions - Chapter 6 (Wade) Chapter utline I. Intro to RX (6-1 - 6-7) II. Substitution Reactions A) S N 2 (6-8,
More informationc. Cl H Page 1 of 7 major P (E > Z and more substituted over less substituted alkene) LG must be axial are the same Cl -
CEM 109A 1. Predict the products of the following reactions (a-c E2, d-f E1 KEY focuses only on elimination products, in most cases there will also be substitution products.) a. - LG must be axial - are
More informationSTEREOCHEMISTRY AND STEREOELECTRONICS NOTES
- 1 - STEREOCHEMISTRY AND STEREOELECTRONICS NOTES Stereochemistry in Organic Molecules Conventions used in drawing molecules Also, Fischer projections can sometimes be useful for acyclic molecules with
More informationADDITION OF HYDROGEN HALIDES TO CONJUGATED DIENES A. 1,2- and 1,4-Additions 700 CHAPTER 15 DIENES, RESONANCE, AND AROMATICITY
700 CAPTER 15 DIENES, RESONANCE, AND AROMATICITY 15.18 Give the structures of the starting materials that would yield each of the compounds below in Diels Alder reactions. Pay careful attention to stereochemistry,
More informationWeek 4. Even harder stuff!
Week 4 Even harder stuff! Focus: SN1 and SN2 Two organic reactions Learn about two basic pathways for how these reactions happen Focus on stereochemistry Focus: SN1 and SN2 You need a couple of things
More informationCourse Goals for CHEM 202
Course Goals for CHEM 202 Students will use their understanding of chemical bonding and energetics to predict and explain changes in enthalpy, entropy, and free energy for a variety of processes and reactions.
More informationChapter 17. Reactions of Aromatic Compounds
Chapter 17 Reactions of Aromatic Compounds Electrophilic Aromatic Substitution Although benzene s pi electrons are in a stable aromatic system, they are available to attack a strong electrophile to give
More informationREACTIONS OF HALOALKANES - SUBSTITUTION AND ELIMINATION
REACTIONS OF HALOALKANES - SUBSTITUTION AND ELIMINATION Haloalkanes (also known as halogenoalkanes and alkyl halides) are organic compounds where one of the hydrogens of an alkane or cycloalkane has been
More informationExam Analysis: Organic Chemistry, Midterm 1
Exam Analysis: Organic Chemistry, Midterm 1 1) TEST BREAK DOWN: There are three independent topics covered in the first midterm, which are hybridization, structure and isomerism, and resonance. The test
More informationC h a p t e r S e v e n : Haloalkanes: Nucleophilc Substitution and Elimination Reactions S N 2
C h a p t e r S e v e n : Haloalkanes: Nucleophilc Substitution and Elimination Reactions S N 2 CHM 321: Summary of Important Concepts Concepts for Chapter 7: Substitution Reactions I. Nomenclature of
More informationIntroduction to Alkenes and Alkynes
Introduction to Alkenes and Alkynes In an alkane, all covalent bonds between carbon were σ (σ bonds are defined as bonds where the electron density is symmetric about the internuclear axis) In an alkene,
More informationCONCERTED sp 2 H. HO Et
Alkyl alides Substitution and Elimination 1 Substitutions (Quick Review) 1.1 SN2 Reactions LB nucleophile "backside attack!" NERTED reaction This is fundamentally just a Lewis acid/base reaction, the Lewis
More informationLoudon Chapter 19 Review: Aldehydes and Ketones CHEM 3331, Jacquie Richardson, Fall Page 1
Loudon Chapter 19 eview: Aldehydes and Ketones CEM 3331, Jacquie ichardson, Fall 2010 - Page 1 Beginning with this chapter, we re looking at a very important functional group: the carbonyl. We ve seen
More informationGlendale Community College Chemistry 105 Exam. 3 Lecture Notes Chapters 6 & 7
Sevada Chamras, Ph.D. Glendale Community College Chemistry 105 Exam. 3 Lecture Notes Chapters 6 & 7 Description: Examples: 3 Major Types of Organic Halides: 1. Alkyl Halides: Chapter 6 (Part 1/2) : Alkyl
More informationChapter 8: Alkene Structure and Preparation via Elimination Reactions
Nature of the pi bond Chapter 8: Alkene Structure and Preparation via Elimination eactions [Sections: 8.1-8.13] C C 3 C C 3 bond length bond strength 2 C C 2 a C=C double bond is stronger than a C C single
More informationChapter 7 Substitution Reactions 7.1 Introduction to Substitution Reactions Substitution Reactions: two reactants exchange parts to give new products
hapter 7 Substitution eactions 7.1 Introduction to Substitution eactions Substitution eactions: two reactants exchange parts to give new products A-B + -D A-D + B- 3 2 + Br 3 2 Br + Elimination eaction:
More informationChapter 10 Radical Reactions"
Chapter 10 Radical Reactions Radicals are intermediates with an unpaired electron H. Cl. Hydrogen radical t Often called free radicals What are radicals? Chlorine radical t Formed by homolytic bond cleavage
More informationClasses of Alkenes. Alkenes and Alkynes. Saturated compounds (alkanes): Have the maximum number of hydrogen atoms attached to each carbon atom.
Alkenes and Alkynes Saturated compounds (alkanes): ave the maximum number of hydrogen atoms attached to each carbon atom. Unsaturated compounds: ave fewer hydrogen atoms attached to the carbon chain than
More informationLecture Topics: I. Electrophilic Aromatic Substitution (EAS)
Reactions of Aromatic Compounds Reading: Wade chapter 17, sections 17-1- 17-15 Study Problems: 17-44, 17-46, 17-47, 17-48, 17-51, 17-52, 17-53, 17-59, 17-61 Key Concepts and Skills: Predict and propose
More informationCHEM 261 HOME WORK Lecture Topics: MODULE 1: The Basics: Bonding and Molecular Structure Text Sections (N0 1.9, 9-11) Homework: Chapter 1:
CHEM 261 HOME WORK Lecture Topics: MODULE 1: The Basics: Bonding and Molecular Structure Atomic Structure - Valence Electrons Chemical Bonds: The Octet Rule - Ionic bond - Covalent bond How to write Lewis
More informationThe Electrophile. S N 2 and E2 least stable most stable least hindered most hindered. S N 1 and E1. > x > >
The Electrophile 1 Recall that electrophile means electron- loving. When considering substitution and elimination reactions we must consider the carbon attached to the leaving group. Is it a primary, secondary,
More informationChem 341 Jasperse Ch Handouts 1
Chem 341 Jasperse Ch. 5 + 10 Handouts 1 Ch. 5 The Study of Chemical Reactions 5.1 Four general types of chemical reactions 1. Addition reactions 2. Elimination Reactions 3. Substitution Reactions 4. Rearrangement
More informationChapter 7 - Alkenes and Alkynes I
Andrew Rosen Chapter 7 - Alkenes and Alkynes I 7.1 - Introduction - The simplest member of the alkenes has the common name of ethylene while the simplest member of the alkyne family has the common name
More informationReactions SN2 and SN1
Reactions SN2 and SN1 Reactivity: Functional groups can be interconverted using a great variety of reagents. Millions of organic molecules have been synthesized via a series of functional-group interconversions.
More informationCHAPTER 9 HW SOLUTIONS: ALCOHOLS + ETHERS
CAPTER 9 W SLUTNS: ALCLS + ETERS ALCL + ETER NMENCLATURE. Give the UPAC name for each compound. nclude cis/trans or R/S stereochemistry if necessary. Structure C Name -methyl--heptanol -t-butylcyclopentanol
More informationand Ultraviolet Spectroscopy
Organic Chemistry, 7 th Edition L. G. Wade, Jr. Chapter 15 Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy 2010, Prentice all Conjugated Systems Conjugated double bonds are separated
More informationChapter 7 Alkenes; Elimination Reactions
hapter 7 Alkenes; Elimination Reactions Alkenes Alkenes contain a carbon-carbon double bond. They are named as derivatives of alkanes with the suffix -ane changed to -ene. The parent alkane is the longest
More informationElimination Reactions Heating an alkyl halide with a strong base causes elimination of a. molecule of HX
Elimination eactions eating an alkyl halide with a strong base causes elimination of a molecule of X 1. Potassium hydroxide dissolved in ethanol and the sodium salts of alcohols (such as sodium ethoxide)
More informationBenzene and Aromatic Compounds
1 Background Benzene and Aromatic Compounds Benzene (C 6 H 6 ) is the simplest aromatic hydrocarbon (or arene). Benzene has four degrees of unsaturation, making it a highly unsaturated hydrocarbon. Whereas
More informationDepartment of Chemistry SUNY/Oneonta. Chem Organic Chemistry I. Examination #4 - December 7, 1998*
Department of hemistry SUNY/neonta hem 221 - rganic hemistry I Examination #4 - December 7, 1998* INSTRUTINS --- This examination is in multiple choice format; the questions are in this Exam Booklet and
More informationThe Study of Chemical Reactions. Mechanism: The complete, step by step description of exactly which bonds are broken, formed, and in which order.
The Study of Chemical Reactions Mechanism: The complete, step by step description of exactly which bonds are broken, formed, and in which order. Thermodynamics: The study of the energy changes that accompany
More informationCEM 351 2nd EXAM/Version A Friday, October 17, :50 2:40 p.m. Room 138, Chemistry
Name (print) Signature Student # Section Number CEM 351 2nd EXAM/Version A Friday, October 17, 2003 1:50 2:40 p.m. Room 138, Chemistry Ann Swerkey Grade? 1.(20 2.(20. 3.(20 4.(20 5.(20 6.(20 TOTAL 100
More informationCOURSE UNIT DESCRIPTION. Type of the course unit. Mode of delivery Period of delivery Language of instruction Face to face Autumn English
Course unit title Organic Chemistry I Lecturer(s) Dr. Rimantas Vaitkus COURSE UNIT DESCRIPTION Department Dept. Organic Chemistry, Vilnius University Cycle First Type of the course unit Mode of delivery
More information10. Alkyl Halides. What Is an Alkyl Halide. An organic compound containing at least one carbonhalogen
10. Alkyl Halides What Is an Alkyl Halide An organic compound containing at least one carbonhalogen bond (C-X) X (F, Cl, Br, I) replaces H Can contain many C-X bonds Properties and some uses Fire-resistant
More informationChem Lecture 23 Page- 1 -
Chem 230-001 Lecture 23 Page- 1 - ydroboration/ oxidation - acemic trans-2-methylcyclohexanol may be neatly synthesized from 1-methyl- 1-cyclohexene by using a reagent called borane, 3. 0.33 equivs. 3,
More informationCHEMISTRY Topic #3: Addition Reactions of Conjugated Dienes Spring 2017 Dr. Susan Findlay
CEMISTRY 2600 Topic #3: Addition Reactions of Conjugated Dienes Spring 2017 Dr. Susan Findlay Different Kinds of Dienes When a molecule contains multiple π-bonds, their reactivity is dictated in part by
More information75. A This is a Markovnikov addition reaction. In these reactions, the pielectrons in the alkene act as a nucleophile. The strongest electrophile will
71. B SN2 stands for substitution nucleophilic bimolecular. This means that there is a bimolecular rate-determining step. Therefore, the reaction will follow second-order kinetics based on the collision
More informationChemistry 2050 Introduction to Organic Chemistry Fall Semester 2011 Dr. Rainer Glaser
Chemistry 2050 Introduction to Organic Chemistry Fall Semester 2011 Dr. Rainer Glaser Examination #2 Practice Edition Arenes, Stereochemistry, and Organic Halogen Compounds, with Nucleophilic Substitution
More informationChapter 8: Alkene Structure and Preparation via Elimination Reactions
1. Nature of the pi bond Chapter 8: Alkene Structure and Preparation via Elimination eactions [Sections: 8.1-8.13] C C bond length bond strength 3 C C 3 3 C C 3 3 C C 3 3 C 2 C C 2 3 C a C=C double bond
More informationPhysical Properties: Structure:
Nomenclature: Functional group suffix = -ol Functional group prefix = hydroxy- Primary, secondary or tertiary? Alcohols are described as primary (1 o ), secondary (2 o ) or tertiary (3 o ) depending on
More informationChapter 7: Alcohols, Phenols and Thiols
Chapter 7: Alcohols, Phenols and Thiols 45 -Alcohols have the general formula R-OH and are characterized by the presence of a hydroxyl group, -OH. -Phenols have a hydroxyl group attached directly to an
More informationOnce familiar with chiral centers, models, drawings and mental images NOW: Final representation of chiral centers: Fischer Projections
Once familiar with chiral centers, models, drawings and mental images NOW: Final representation of chiral centers: Fischer Projections Fischer Projections are 2-dimensional representations of 3-dimensional
More informationLoudon Chapter 14 Review: Reactions of Alkynes Jacquie Richardson, CU Boulder Last updated 1/16/2018
An alkyne is any molecule with a triple bond between two carbon atoms. This triple bond consists of one σ bond and two π bonds: the σ bond exists on a straight line between carbon atoms, while one π bond
More informationPAPER No. : 5; Organic Chemistry-II MODULE No. : 13; Mixed S N 1 and S N 2 Reactions
Subject Chemistry Paper No and Title Module No and Title Module Tag 5; Organic Chemistry-II 13; Mixed S N 1 and S N 2 Reactions CHE_P5_M13 TABLE OF CONTENTS 1. Learning Outcomes 2. Introduction 3. Nature
More informationPAPER No. 5: REACTION MECHANISM MODULE No. 2: Types of Organic Reaction Mechanisms
Subject Chemistry Paper No and Title Module No and Title Module Tag Paper No. 5:Organic Chemistry-II Module No. 2: Overview of different types of Organic Reaction Mechanisms CHE_P5_M2 TABLE OF CONTENTS
More informationLoudon Ch. 4 Review: Alkene Structure/Reactivity Jacquie Richardson, CU Boulder Last updated 5/30/2017
We already saw in Ch. 1 that π bonds are based on side-on overlap of leftover p orbitals. C atom C=C bond C atom orbital comes from destructive (differentcolor) interference: (note extra node) + 2p 2p
More informationConjugated Systems. With conjugated double bonds resonance structures can be drawn
Conjugated Systems Double bonds in conjugation behave differently than isolated double bonds With conjugated double bonds resonance structures can be drawn With isolated double bonds cannot draw resonance
More informationREACTIONS OF ALCOHOLS Created by: Mohammad Heidarian
Nucleophilic Substitution, β- Elimination, and Oxidation reactions are the main type of reactions associated with alcohols. Nucleophilic Substitution: A reaction in which a nucleophile replaces a leaving
More information