Elimination reactions

Size: px
Start display at page:

Download "Elimination reactions"

Transcription

1 Chapter 9 Elimination reactions E2 and E1 reactions Competition between S N and E

2 Elimination reactions Ch 9 #2 elimination and/or substitution 2 mechanisms ~ E2 and E1

3 E2: bimolecular elimination rxn bimolecular mechanism ~ concerted Ch 9 #3 no substitution? 1,2-elimination or β-elimination leaving group effect

4 E2: regioselectivity (1) ~ Zaitsev s rule Ch 9 #4 Zaitsev s rule The more substituted alkene product is obtained when a proton is removed from the β-carbon that is bonded to the fewest hydrogens. a product [thermodynamic] control

5 Ch 9 #5 Generally, 1 > 2 (no 3 ) for S N 2 Nu: attacks C 3 > 2 > 1 for E2 (and E1, except 1 ) B: attacks [takes] H

6 E2: regioselectivity (2) ~ resonance Ch 9 #6 Resonance-stabilized alkene [conjugated diene] is more stable. It may not be the more-substituted.

7 E2: regioselectivity (3) ~ steric Ch 9 #7

8 E2: regioselectivity (4) ~ leaving group Ch 9 #8 F is the poorest leaving group. alkene-like TS carbanion-like TS

9 Ch 9 #9 stability of carbanion Effect of leaving group on E2 product Major product of E2 rxn is the more stable alkene. exceptions ~ steric reactant(s), (very) poor leaving group

10 E1: unimolecular elimination reaction Ch 9 #10 unimolecular mechanism no substitution? weak base takes H from sp 3 C? C + accepts e of C: + hyperconjugation

11 E1: reactivity Ch 9 #11 C + stability trend same to SN1 trend same to E2 leaving group effect trend same to S N 2, S N 1, and E2

12 E1: regioselectivity Ch 9 #12 more substituted product ~ Zaitsev s rule

13 E1: C + rearrangement Ch 9 #13

14 Competition betw E2 and E1 Ch 9 #14 E2 is favored by (high concentration of) strong base (like HO, RO ), and in aprotic polar solvent (like DMF, DMSO). E1 is favored by weak base (like H 2 O, ROH), and in protic polar solvent (like H 2 O, ROH). S N 2 is favored by good Nu: in aprotic polar solvent. S N 1 is favored by poor Nu: in protic polar solvent.

15 Stereochemistry of E2 and E1 Ch 9 #15 E2 is an anti-elimination rxn. 4 atoms [H, C, C, X] must be periplanar [coplanar] to form C=C double bond. anti-periplanar (highly) favored over syn-periplanar

16 Ch 9 #16 E2 is stereoselective when 2 β-h s 2 products (stereoselective)

17 Ch 9 #17 when 1 β-h 1 product stereospecific? (2R,3S)?

18 Ch 9 #18 E1 also is stereoselective. 2 β-h s 2 products (stereoselective) 1 β-h s 2 products (stereoselective)

19 Elimination from substituted cx Ch 9 #19 E2 must be anti-periplanar. H and X must be trans-diaxial. E2 of menthyl chloride is slow.

20 Ch 9 #20 + E2 of neomenthyl chloride is rather fast.

21 Ch 9 #21 E1 need not be periplanar. + Cl CH 3 OH CH 3 O 2 S N + 2 E products 1 product

22 Stereochemistry of S N and E Ch 9 #22

23 Kinetic isotope effect Ch 9 #23 k H = 7.1 k D C D stronger than C H (why?) (deuterium) kinetic isotope effect = k H /k D = 7.1 supports E2 (concerted) mechanism, not E1

24 Competition betw S N and E Ch 9 #24 S N 2/E2 is favored by good Nu:/strong B: in aprotic polar solvent. S N 1/E1 is favored by poor Nu:/weak B: in protic polar solvent. X X X S N 2/E favors S N 2 over E2. why? above comparison? just observed.

25 Ch 9 #25 S N 2/E2 (cont d) 2. Steric hindrance favors E2 over S N 2.

26 Ch 9 #26 S N 2/E2 (cont d) 3. Stronger B: [Nu:] favors E2 over S N 2. why? just observed. RCOO ~ a medium base H 3 O + > RCOOH > H 2 O

27 Ch 9 #27 S N 2/E2 (cont d) 4. High temperature favors E2 over S N 2. why? T S

28 Ch 9 #28 S N 2/E2 (cont d) 5. 3 undergoes E2 only.

29 Ch 9 #29 S N 1/E1 hard to control the ratio of S N 1 to E1 no S N 1/E1 for 1 more S N 1 over E1 for 3 why? no S N 2 for 3? just observed.

30 Ch 9 #30

31 Using S N in synthesis Ch 9 #31 Williamson (ether) synthesis S N 2 preparation of RO need very strong base for alcohol need less strong base for phenol

32 Ch 9 #32 Williamson (ether) synthesis (cont d) Substrate [RX] should be 1. no S N, no ether (b) is (much) better (a) gives E2 product also S N 1 (using ROH) for 2 or 3 substrate

33 Ch 9 #33 alkynes from acetylide ion S N 2 Substrate [RX] better be 1.

34 Using E in synthesis Ch 9 #34 preparation of alkene E2(/S N 2) rather than E1(/S N 1) 2 better, more hindered better more E2 by using t-buo instead of OH, high temperature

35 Ch 9 #35 preparation of alkyne from dihalides need very strong base ( NH 2 > OH) vinyl halide from alkene

36 Designing synthesis II Ex 1> pka of HCN = 9.1 Ch 9 #36 direct hydrocyanation? possible, using catalyst using S N /E Ex 2> CN ~ stronger B: than Br, weaker B: than OH S N 2 over E2 (or maybe S N 1/E1) E2, no S N 2 anti-markovnikov, syn

37 Ch 9 #37 Ex 3> E2, no S N 2 Ex 4> not BH 3 not BH 3 S N 2 (low E2)

Dehydrohalogenation of Alkyl Halides E2 and E1 Reactions in Detail

Dehydrohalogenation of Alkyl Halides E2 and E1 Reactions in Detail Dehydrohalogenation of Alkyl Halides E2 and E1 Reactions in Detail b-elimination Reactions Overview dehydration of alcohols: X = H; Y = OH dehydrohalogenation of alkyl halides: X = H; Y = Br, etc. X C

More information

Reactions of Alkyl Halides with Nucleophiles and Bases a substitution reaction

Reactions of Alkyl Halides with Nucleophiles and Bases a substitution reaction Reactions of Alkyl Halides with Nucleophiles and Bases a substitution reaction Nucleophilic substitution and base induced elimination are among most widely occurring and versatile reaction types in organic

More information

Walden discovered a series of reactions that could interconvert (-)-malic acid and (+)-malic acid.

Walden discovered a series of reactions that could interconvert (-)-malic acid and (+)-malic acid. Chapter 11: Reactions of alkyl halides: nucleophilic substitutions and eliminations Alkyl halides are polarized in the C-X bond, making carbon δ+ (electrophilic). A nucleophilecan attack this carbon, displacing

More information

Basic Organic Chemistry Course code : CHEM (Pre-requisites : CHEM 11122)

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 information

Substitution and Elimination reactions

Substitution and Elimination reactions PART 3 Substitution and Elimination reactions Chapter 8. Substitution reactions of RX 9. Elimination reactions of RX 10. Substit n/elimin n of other comp ds 11. Organometallic comp ds 12. Radical reactions

More information

Chapter 8 Alkyl Halides and Elimination Reactions

Chapter 8 Alkyl Halides and Elimination Reactions Organic Chemistry, Second Edition Janice Gorzynski Smith University of Hawai i Chapter 8 Alkyl Halides and Elimination Reactions Prepared by Rabi Ann Musah State University of New York at Albany Copyright

More information

Nucleophilic Substitution and Elimination

Nucleophilic 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 information

Chapter 9. Nucleophilic Substitution and ß-Elimination

Chapter 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 information

Essential Organic Chemistry. Chapter 9

Essential Organic Chemistry. Chapter 9 Essential Organic Chemistry Paula Yurkanis Bruice Chapter 9 Substitution and Elimination Reactions of Alkyl Halides 9.1 How Alkyl Halides React Substitution Reactions One group takes the place of another.

More information

Dr. Anand Gupta Mr Mahesh Kapil

Dr. Anand Gupta Mr Mahesh Kapil Dr. Anand Gupta Mr Mahesh Kapil 09356511518 09888711209 anandu71@yahoo.com mkapil_foru@yahoo.com Preparation of Haloalkanes From Alkanes Alkenes Alcohols Carboxylic Acids (Hundsdicker Reaction) Halide

More information

CHAPTER 7. Further Reactions of Haloalkanes: Unimolecular Substitution and Pathways of Elimination

CHAPTER 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 information

+ + CH 11: Substitution and Elimination Substitution reactions

+ + CH 11: Substitution and Elimination Substitution reactions C 11: Substitution and Elimination Substitution reactions Things to sort out: Nucleophile Electrophile -- > substrate Leaving Group S N 2 S N 1 E 1 E 2 Analysis Scheme Kinetics Reaction profile Substrates

More information

Organic Reactions Susbstitution S N. Dr. Sapna Gupta

Organic Reactions Susbstitution S N. Dr. Sapna Gupta Organic Reactions Susbstitution S N 2 Dr. Sapna Gupta Kinetics of Nucleophilic Reaction Rate law is order of reaction 0 order is when rate of reaction is unaffected by change in concentration of the reactants

More information

Chapter 11, Part 1: Polar substitution reactions involving alkyl halides

Chapter 11, Part 1: Polar substitution reactions involving alkyl halides hapter 11, Part 1: Polar substitution reactions involving alkyl halides Overview: The nature of alkyl halides and other groups with electrophilic sp 3 hybridized leads them to react with nucleophiles and

More information

Elimination Reactions. Chapter 6 1

Elimination Reactions. Chapter 6 1 Elimination Reactions Chapter 6 1 E1 Mechanism Step 1: halide ion leaves, forming a carbocation. Step 2: Base abstracts H + from adjacent carbon forming the double bond. Chapter 6 2 E1 Energy Diagram E1:

More information

10. Organohalides. Based on McMurry s Organic Chemistry, 7 th edition

10. 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 information

1. Radical Substitution on Alkanes. 2. Radical Substitution with Alkenes. 3. Electrophilic Addition

1. Radical Substitution on Alkanes. 2. Radical Substitution with Alkenes. 3. Electrophilic Addition 1. Radical Substitution on Alkanes Only Cl and Br are useful at the laboratory level. Alkane reactivity: tertiary > secondary > primary > methyl Numbers below products give their relative yield. Relative

More information

Additions to the Carbonyl Groups

Additions to the Carbonyl Groups Chapter 18 Additions to the Carbonyl Groups Nucleophilic substitution (S N 2andS N 1) reaction occurs at sp3 hybridized carbons with electronegative leaving groups Why? The carbon is electrophilic! Addition

More information

Classes of Alkenes. Alkenes and Alkynes. Saturated compounds (alkanes): Have the maximum number of hydrogen atoms attached to each carbon atom.

Classes 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 information

C 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 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 information

REACTION AND SYNTHESIS REVIEW

REACTION AND SYNTHESIS REVIEW REACTION AND SYNTHESIS REVIEW A STUDENT SHOULD BE ABLE TO PREDICT PRODUCTS, IDENTIFY REACTANTS, GIVE REACTION CONDITIONS, PROPOSE SYNTHESES, AND PROPOSE MECHANISMS (AS LISTED BELOW). REVIEW THE MECHANISM

More information

Organic Chemistry CHM 314 Dr. Laurie S. Starkey, Cal Poly Pomona Alkyl Halides: Substitution Reactions - Chapter 6 (Wade)

Organic 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 information

Organic Reactions Susbstitution S N. Dr. Sapna Gupta

Organic Reactions Susbstitution S N. Dr. Sapna Gupta Organic Reactions Susbstitution S N 2 Dr. Sapna Gupta Kinetics of Nucleophilic Reaction Rate law is order of reaction 0 order is when rate of reaction is unaffected by change in concentration of the reactants

More information

Chapter 8 Outline: Alkenes: Structure and Preparation via β-elimination

Chapter 8 Outline: Alkenes: Structure and Preparation via β-elimination Chapter 8 Outline: Alkenes: Structure and Preparation via β-elimination 1. What is β elimination? 2. Alkenes: structure, steroisomerism and stability 3. Elimination Reactions o E2 Mechanism o E1 Mechanism

More information

Elimination Reactions The E2 Mechanism

Elimination Reactions The E2 Mechanism Elimination Reactions The E2 Mechanism The E2 Mechanism X X- B: B- δ- B:- δ+ R 1 δ- R 2 δ+ X δ- The E2 Mechanism R 3 R 4 transition state Free energy (G) Eact B:- B R 1 R 2 X R 1 R 2 R 3 R 4 R 4 R 3 X:-

More information

Elimination Reactions The E2 Mechanism

Elimination Reactions The E2 Mechanism Elimination Reactions The E2 Mechanism The E2 Mechanism X B: δ- B:- δ+ R 1 C δ- R 2 C δ+ X δ- The E2 Mechanism R 3 R 4 transition state Free energy (G) Eact B:- B R 1 R 2 C C X R 1 R 2 R 3 R 4 R 4 R 3

More information

c. 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 -

c. 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 information

Glendale Community College Chemistry 105 Exam. 3 Lecture Notes Chapters 6 & 7

Glendale 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 information

11. Reactions of Alkyl Halides: Nucleophilic Substitutions and Eliminations

11. 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 information

Chapter 6 Ionic Reactions-Nucleophilic Substitution and Elimination Reactions of Alkyl Halides"

Chapter 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 information

Chapter 11: Nucleophilic Substitution and Elimination Walden Inversion

Chapter 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 information

Chapter 8. Substitution reactions of Alkyl Halides

Chapter 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 information

Preparation 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 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 information

Chem 251 Fall Learning Objectives

Chem 251 Fall Learning Objectives Learning Objectives Chapter 8 (last semester) 1. Write an electron-pushing mechanism for an SN2 reaction between an alkyl halide and a nucleophile. 2. Describe the rate law and relative rate of reaction

More information

Alkyl Halides. Alkyl halides are a class of compounds where a halogen atom or atoms are bound to an sp 3 orbital of an alkyl group.

Alkyl Halides. Alkyl halides are a class of compounds where a halogen atom or atoms are bound to an sp 3 orbital of an alkyl group. Alkyl Halides Alkyl halides are a class of compounds where a halogen atom or atoms are bound to an sp 3 orbital of an alkyl group. CHCl 3 (Chloroform: organic solvent) CF 2 Cl 2 (Freon-12: refrigerant

More information

S N 1 Displacement Reactions

S 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 information

Organic Chemistry The Functional Group Approach. Organic Chemistry The Functional Group Approach

Organic Chemistry The Functional Group Approach. Organic Chemistry The Functional Group Approach Organic Chemistry The Functional Group Approach OH Br alkane (no F.G.) alcohol halide alkene non-polar (grease, fats) O NH alkyne aromatic aldehyde/ketone imine linear flat Organic Chemistry The Functional

More information

Chapter 4. Reactions of alkenes. Addition reactions Carbocations Selectivity of reactions

Chapter 4. Reactions of alkenes. Addition reactions Carbocations Selectivity of reactions Chapter 4 Reactions of alkenes Addition reactions Carbocations Selectivity of reactions Prob 47 p192. Give the reagents that would be required (including catalyst). Ch 4 #2 Electrophilic addition Ch 4

More information

ORGANIC - CLUTCH CH. 8 - ELIMINATION REACTIONS.

ORGANIC - CLUTCH CH. 8 - ELIMINATION REACTIONS. !! www.clutchprep.com CONCEPT: THE E2 MECHANISM A strong nucleophile reacts with an inaccessible leaving group to produce beta-elimination in one-step. E2 Properties (Circle One) Nucleophile = Strong /

More information

OChem 1 Mechanism Flashcards. Dr. Peter Norris, 2018

OChem 1 Mechanism Flashcards. Dr. Peter Norris, 2018 OChem 1 Mechanism Flashcards Dr. Peter Norris, 2018 Mechanism Basics Chemical change involves bonds forming and breaking; a mechanism describes those changes using curved arrows to describe the electrons

More information

REACTIONS OF HALOALKANES - SUBSTITUTION AND ELIMINATION

REACTIONS 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 information

8.8 Unimolecular Nucleophilic Substitution S N 1

8.8 Unimolecular Nucleophilic Substitution S N 1 8.8 Unimolecular Nucleophilic Substitution S N 1 A question. Tertiary alkyl halides are very unreactive in substitutions that proceed by the S N 2 mechanism. Do they undergo nucleophilic substitution at

More information

Chapter 7 Substitution Reactions 7.1 Introduction to Substitution Reactions Substitution Reactions: two reactants exchange parts to give new products

Chapter 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 information

How alkyl halides react

How alkyl halides react Chapter 10 1 How alkyl halides react δ+ δ- RCH 2 -X X= halogen X = higher EN C = lower EN This polar carbon-halogen bond causes alkyl halide to undergo S N and elimination reaction. 2 The mechanism of

More information

C h a p t e r E i g h t: Alkenes: Structure and Preparation via Elimination Reactions. 5-Androstene, the parent alkene for most anabolic steroids

C h a p t e r E i g h t: Alkenes: Structure and Preparation via Elimination Reactions. 5-Androstene, the parent alkene for most anabolic steroids C h a p t e r E i g h t: Alkenes: Structure and Preparation via Elimination Reactions 5-Androstene, the parent alkene for most anabolic steroids CHM 321: Summary of Important Concepts YConcepts for Chapter

More information

Elimination Reactions:

Elimination Reactions: Elimination Reactions: These are just reverse of addition reactions. These involve the removal of atoms or group of atoms from a molecule. Elimination reactions are generally endothermic and take place

More information

OChem 1 Mechanism Flashcards. Dr. Peter Norris, 2015

OChem 1 Mechanism Flashcards. Dr. Peter Norris, 2015 OChem 1 Mechanism Flashcards Dr. Peter Norris, 2015 Mechanism Basics Chemical change involves bonds forming and breaking; a mechanism describes those changes using curved arrows to describe the electrons

More information

Sn1 or Sn2 Reactions: A Guide to Deciding Which Reaction is Occurring

Sn1 or Sn2 Reactions: A Guide to Deciding Which Reaction is Occurring Sn1 or Sn2 Reactions: A Guide to Deciding Which Reaction is Occurring The following is a discussion of the approach you should use in order to determine if a chemical reaction occurs via a Sn1 or Sn2 mechanism.

More information

Chapter 8: Nucleophilic Substitution 8.1: Functional Group Transformation By Nucleophilic Substitution

Chapter 8: Nucleophilic Substitution 8.1: Functional Group Transformation By Nucleophilic Substitution hapter 8: Nucleophilic Substitution 8.1: Functional Group Transformation By Nucleophilic Substitution Nu: = l,, I Nu - Nucleophiles are Lewis bases (electron-pair donor) Nucleophiles are often negatively

More information

Chapter 5. Nucleophilic aliphatic substitution mechanism. by G.DEEPA

Chapter 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 information

Reaction mechanism 1/17/19. HCl. HCl. 3 radical can form here. Br 2. hint!

Reaction mechanism 1/17/19. HCl. HCl. 3 radical can form here. Br 2. hint! If the reagents or reaction conditions favor radicals, then it is likely to be a radical reaction. Look for hints like peroxide, AIBN, NBS, hn (UV light). 3 radical can form here Reaction mechanism How

More information

Homework problems Chapters 6 and Give the curved-arrow formalism for the following reaction: CH 3 OH + H 2 C CH +

Homework 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 information

Structure and Preparation of Alkenes: Elimination Reactions

Structure 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 information

CONCERTED sp 2 H. HO Et

CONCERTED 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 information

ORGANIC - EGE 5E CH. 7 - NUCLEOPHILIC SUBSTITUTION AND ELIMINATION REACTIONS

ORGANIC - 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 information

Chapter 7 Alkenes and Alkynes I: Properties and Synthesis Elimination Reactions of Alkyl Halides"

Chapter 7 Alkenes and Alkynes I: Properties and Synthesis Elimination Reactions of Alkyl Halides Chapter 7 Alkenes and Alkynes I: Properties and Synthesis Elimination Reactions of Alkyl Halides The (E)-(Z) System for Designating Alkene Diastereomers The Cahn-Ingold-Prelog convention is used to assign

More information

Elimination Reactions Heating an alkyl halide with a strong base causes elimination of a. molecule of HX

Elimination 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 information

Only five of the molecules below may be prepared as the sole product of allylic halogenation of the respective alkene. Circle those five.

Only five of the molecules below may be prepared as the sole product of allylic halogenation of the respective alkene. Circle those five. Chem 232 D. J. Wardrop wardropd@uic.edu Problem Set 6 Answers Question 1. nly five of the molecules below may be prepared as the sole product of allylic halogenation of the respective alkene. Circle those

More information

7. Haloalkanes (text )

7. 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 information

Chapter 8: Alkene Structure and Preparation via Elimination Reactions

Chapter 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 information

2/26/18. Practice Questions. Practice Questions B F. How many steps are there in this reaction?

2/26/18. Practice Questions. Practice Questions B F. How many steps are there in this reaction? Practice Questions Practice Questions D B F C E A G How many steps are there in this reaction? 1 Practice Questions D B F C E A G What is the highest-energy transitions state? Practice Questions D B F

More information

PAPER No. 5: REACTION MECHANISM MODULE No. 2: Types of Organic Reaction Mechanisms

PAPER 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 information

Classes of Halides. Chapter 6 Alkyl Halides: Nucleophilic Substitution and Elimination. Polarity and Reactivity. Classes of Alkyl Halides

Classes of Halides. Chapter 6 Alkyl Halides: Nucleophilic Substitution and Elimination. Polarity and Reactivity. Classes of Alkyl Halides rganic hemistry, 5 th Edition L. G. Wade, Jr. hapter 6 Alkyl alides: Nucleophilic Substitution and Elimination lasses of alides Alkyl: alogen, X, is directly bonded to sp 3 carbon. Vinyl: X is bonded to

More information

1/4/2011. Chapter 18 Aldehydes and Ketones Reaction at the -carbon of carbonyl compounds

1/4/2011. Chapter 18 Aldehydes and Ketones Reaction at the -carbon of carbonyl compounds Chapter 18 Aldehydes and Ketones Reaction at the -carbon of carbonyl compounds The Acidity of the Hydrogens of Carbonyl Compounds: Enolate Anions Hydrogens on carbons to carbonyls are unusually acidic

More information

1-What is substitution reaction? 2-What are can Nucleophilic Substitution Reaction? 3- SN1 reaction. 4-SN2 reaction 5- mechanisms of SN1&SN2

1-What is substitution reaction? 2-What are can Nucleophilic Substitution Reaction? 3- SN1 reaction. 4-SN2 reaction 5- mechanisms of SN1&SN2 1-What is substitution reaction? 2-What are can Nucleophilic Substitution eaction? 3- SN1 reaction. 4-SN2 reaction 5- mechanisms of SN1&SN2 1- SUBSTITUTION EACTIONS 1-Substitution eaction In this type

More information

CHEM 263 Oct 25, stronger base stronger acid weaker acid weaker base

CHEM 263 Oct 25, stronger base stronger acid weaker acid weaker base CEM 263 ct 25, 2016 Reactions and Synthesis (Preparation) of R- Breaking the - Bond of R- with Metals R + Li 0 or Na 0 or K 0 metal R Li + 1/2 2 alkoxide Breaking the - Bond of R- by Acid-Base Reaction

More information

Chapter 6: Organic Halogen Compounds; Substitution and Elimination Reactions

Chapter 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 information

Acid-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

Acid-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 information

Alcohols, Ethers, & Epoxides

Alcohols, 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 information

Chapter 8: Alkene Structure and Preparation via Elimination Reactions

Chapter 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 information

CHEM Lecture 7

CHEM Lecture 7 CEM 494 Special Topics in Chemistry Illinois at Chicago CEM 494 - Lecture 7 Prof. Duncan Wardrop ctober 22, 2012 CEM 494 Special Topics in Chemistry Illinois at Chicago Preparation of Alkenes Elimination

More information

Objective 11. Apply Reactivity Principles to Substitution and Elimination Reactions: compare size and strength of nucleophile to predict major product

Objective 11. Apply Reactivity Principles to Substitution and Elimination Reactions: compare size and strength of nucleophile to predict major product Objective 11 Apply Reactivity Principles to Substitution and Elimination Reactions: compare size and strength of nucleophile to predict major product Given Reactants ----> Predict Products How to figure

More information

UCF - ORGANIC CHEMISTRY 1 - PROF. DAOUDI UCF PROF. DAOUDI EXAM 3 REVIEW.

UCF - ORGANIC CHEMISTRY 1 - PROF. DAOUDI UCF PROF. DAOUDI EXAM 3 REVIEW. UCF PROF. DAOUDI EXAM 3 REVIEW www.clutchprep.com 1 PRACTICE: Identify the most stable and the least stable alkene PRACTICE: Create the full arrow pushing mechanism which shows all intermediates and all

More information

Chem 3719 Example Exams. Chemistry 3719 Practice Exams

Chem 3719 Example Exams. Chemistry 3719 Practice Exams Chem 3719 Example Exams Chemistry 3719 Practice Exams Fall 2018 Chemistry 3719, Fall 2017 Exam 1 Student Name: Y Number: This exam is worth 100 points out of a total of 700 points for Chemistry 3719/3719L.

More information

C h a p t e r S e v e n : Substitution Reactions S N 2 O H H H O H H. Br -

C h a p t e r S e v e n : Substitution Reactions S N 2 O H H H O H H. Br - C h a p t e r S e v e n : Substitution Reactions Br Br S N 2 CM 321: Summary of Important Concepts YConcepts for Chapter 7: Substitution Reactions I. Nomenclature of alkyl halides, R X A. Common name:

More information

Alkenes are prepared by the reverse of the electrophilic reactions in the last chapter. That is, they are prepared by elimination reactions.

Alkenes are prepared by the reverse of the electrophilic reactions in the last chapter. That is, they are prepared by elimination reactions. Ch 8 Alkene Reactions and Syntheses Alkenes are prepared by the reverse of the electrophilic reactions in the last chapter. That is, they are prepared by elimination reactions. Dehydrohalogenation - Mechanism

More information

Preparation of alkenes

Preparation of alkenes Lecture 11 אלקנים הכנה ותגובות של אלקנים: הידרוגנציה, סיפוח הידרוהלוגנים )כלל מארקובניקוב(, סיפוח הלוגנים והסטראוכימיה של תוצרי הסיפוח, הידרובורציה, אפוקסידציה, אוזונוליזה. 1 Preparation of alkenes 1.

More information

Organic Chemistry Lecture 2 - Hydrocarbons, Alcohols, Substitutions

Organic Chemistry Lecture 2 - Hydrocarbons, Alcohols, Substitutions ALKANES Water-insoluble, low density C-C single bonds Higher MW -> higher BP, higher MP Branching -> lower BP, higher MP Forms cycloalkanes which can have ring strain Cyclohexane: chair vs. boat configuration

More information

Lecture Notes Chem 51B S. King I. Conjugation

Lecture Notes Chem 51B S. King I. Conjugation Lecture Notes Chem 51B S. King Chapter 16 Conjugation, Resonance, and Dienes I. Conjugation Conjugation occurs whenever p-orbitals can overlap on three or more adjacent atoms. Conjugated systems are more

More information

Double and Triple Bonds. The addition of an electrophile and a

Double and Triple Bonds. The addition of an electrophile and a Chapter 11 Additions to Carbon-Carbon Double and Triple Bonds The addition of an electrophile and a nucleophile to a C-C C double or triple bonds 11.1 The General Mechanism Pi electrons of the double bond

More information

BSc. 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 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 information

1.13 Acid-Base Reactions: Lone-Pair Donors & Acceptors

1.13 Acid-Base Reactions: Lone-Pair Donors & Acceptors 1.13 Acid-Base Reactions: Lone-Pair Donors & Acceptors I, Cl, N 3, 3 P 4 pka 10 to 5 Super strong acids 3 + pka 1.7 RC 2 pka ~ 5 acids Ph pka ~ 10 get 2, R pka ~ 16 weaker RCC (alkynes) pka ~ 26 RN 2 pka

More information

Alkyl Halides and Nucleophilic Subs5tu5on Reac5ons. S N 2 and S N 1 Reac,ons

Alkyl Halides and Nucleophilic Subs5tu5on Reac5ons. S N 2 and S N 1 Reac,ons Alkyl Halides and Nucleophilic Subs5tu5on Reac5ons S N 2 and S N 1 Reac,ons 1 Alkyl Halides The electronega5ve halogen atom in alkyl halides creates a polar C X bond, making the carbon atom electron deficient.

More information

2311A and B Practice Problems to help Prepare for Final from Previous Marder Exams.

2311A and B Practice Problems to help Prepare for Final from Previous Marder Exams. 2311A and B Practice Problems to help Prepare for Final from Previous Marder Exams. Disclaimer.: Use only to help learn what you need to know and don t expect the final to be in the same form. 1 1. Short

More information

The Electrophile. S N 2 and E2 least stable most stable least hindered most hindered. S N 1 and E1. > x > >

The 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 information

Physical Properties: Structure:

Physical 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 information

Chapter 8 I. Nucleophilic Substitution (in( II. Competion with Elimination. Nucleophilic Substitution

Chapter 8 I. Nucleophilic Substitution (in( II. Competion with Elimination. Nucleophilic Substitution hapter 8 I. Nucleophilic Substitution (in( depth) II. ompetion with Elimination Nucleophilic Substitution Substrate is a sp3 hybridized carbon atom (cannot be an a vinylic halide or an aryl halide except

More information

LECTURE #14 Thurs., Oct.20, Midterm exam: Tues.Oct.25 during class Ch.1, , 7.10, 2, Sections

LECTURE #14 Thurs., Oct.20, Midterm exam: Tues.Oct.25 during class Ch.1, , 7.10, 2, Sections CHEM 221 section 01 LECTURE #14 Thurs., Oct.20, 2005 Midterm exam: Tues.Oct.25 during class Ch.1, 7.2-7.5, 7.10, 2, 3.1-3.5 ASSIGNED READINGS: TODAY S CLASS: NEXT LECTURE: Sections 4.7-4.10 finish Ch.4,

More information

Chapter 9 Alkynes. Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Chapter 9 Alkynes. Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 9 Alkynes Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9.1 Sources of Alkynes Acetylene Industrial preparation of acetylene is by dehydrogenation of

More information

Chapter 7 - Alkenes and Alkynes I

Chapter 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 information

Loudon Chapter 9 Review: Reactions of Alkyl Halides Jacquie Richardson, CU Boulder Last updated 5/1/2016

Loudon Chapter 9 Review: Reactions of Alkyl Halides Jacquie Richardson, CU Boulder Last updated 5/1/2016 Chapter 9 covers reactions you can do with alkyl halides. For the most part, these break down into two categories: substitution and elimination. Substitution results in replacing the halogen with some

More information

Chapter 11 - Alcohols and Ethers 1

Chapter 11 - Alcohols and Ethers 1 Andrew Rosen Chapter 11 - Alcohols and Ethers 1 11.1 - Structure and Nomenclature - The common naming calls alcohols as alkyl alcohols (eg: methyl alcohol) - The common names of ethers have the groups

More information

9.2 Bimolecular Elimination

9.2 Bimolecular Elimination 314 CAPTE 9 ELIMINATION EACTIONS called carbon 1, then the proton is lost from carbon 2 The reaction is therefore termed a 1,2-elimination (Alternatively, because the carbon attached to the functional

More information

CHEMISTRY. Module No and Title Module-7, Nucleophilic and Free Radical Addition. Reactions of Alkenes

CHEMISTRY. Module No and Title Module-7, Nucleophilic and Free Radical Addition. Reactions of Alkenes Subject Chemistry Paper No and Title Paper-9, Organic Chemistry-III (Reaction Mechanism-2) Module No and Title Module-7, Nucleophilic and Free Radical Addition Module Tag CHE_P9_M7 TABLE OF CONTENTS 1.

More information

1. The Substrate: CH3, 1 o, 2 o, 3 o, Allyl or Benzyl

1. The Substrate: CH3, 1 o, 2 o, 3 o, Allyl or Benzyl Putting it all together: Substitution and elimination reactions are almost always in competition with each other. In order to predict the products of a reaction, it is necessary to determine which mechanisms

More information

Chapter 15: Conjugated Systems, Orbital Symmetry, and UV Spectroscopy

Chapter 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 information

Substitution α to a carbonyl center: Enol and enolate chemistry

Substitution α to a carbonyl center: Enol and enolate chemistry Chapter 11 Organic Reaction Mechanisms, Part 2: Substitutions at Aliphatic Centers and Thermal Isomerizations/Rearrangements 11.1 Tautomerization Substitution α to a carbonyl center: Enol and enolate chemistry

More information

Alkyl Halides React with Nucleophiles and Bases

Alkyl Halides React with Nucleophiles and Bases Chapter 11- Reactions of Alkyl Halides: Nucleophilic Substitutions and Eliminations Ashley Piekarski, Ph.D. Alkyl Halides React with Nucleophiles and Bases Alkyl halides are polarized at the carbon- halide

More information

10. 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 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 information

Department of Chemistry SUNY/Oneonta. Chem Organic Chemistry I

Department of Chemistry SUNY/Oneonta. Chem Organic Chemistry I Department of Chemistry SUNY/Oneonta Chem 221 - Organic Chemistry I Examination #4 - ANSWERS - December 11, 2000 Answer to question #32 corrected 12/13/00, 8:30pm. INSTRUCTIONS This examination is in multiple

More information