Chapter07- Alkenes- Reactions and Synthesis

Chapter07- Alkenes- Reactions and Synthesis - 7. Alkenes:...

Info iconThis preview shows pages 1–12. Sign up to view the full content.

View Full Document Right Arrow Icon
7. Alkenes: Reactions and Synthesis Based on McMurry’s Organic Chemistry , 6 th edition ©2003 Ronald Kluger Department of Chemistry University of Toronto
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
McMurry Organic Chemistry 6th edition Chapter 7 2 Diverse Reactions of Alkenes Alkenes react with many electrophiles to give useful products by addition (often through special reagents) alcohols (add H-OH) alkanes (add H-H) halohydrins (add HO-X) dihalides (add X-X) halides (add H-X) diols (add HO-OH) cyclopropane (add :CH 2 )
Background image of page 2
McMurry Organic Chemistry 6th edition Chapter 7 3 7.1 Preparation of Alkenes: A Preview of Elimination Reactions Alkenes are commonly made by elimination of HX from alkyl halide ( dehydrohalogenation ) Uses heat and KOH elimination of H-OH from an alcohol ( dehydration ) require strong acids (sulfuric acid, 50 ºC)
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
McMurry Organic Chemistry 6th edition Chapter 7 4 7.2 Addition of Halogens to Alkenes Bromine and chlorine add to alkenes to give 1,2-dihaldes, an industrially important process F 2 is too reactive and I 2 does not add Cl 2 reacts as Cl + Cl - Br 2 is similar
Background image of page 4
McMurry Organic Chemistry 6th edition Chapter 7 5 Addition of Br 2 to Cyclopentene Addition is exclusively trans +
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
McMurry Organic Chemistry 6th edition Chapter 7 6 Mechanism of Bromine Addition Br + adds to an alkene producing a cyclic ion Bromonium ion, bromine shares charge with carbon Gives trans addition
Background image of page 6
McMurry Organic Chemistry 6th edition Chapter 7 7 Bromonium Ion Mechanism Electrophilic addition of bromine to give a cation is followed by cyclization to give a bromonium ion This bromoniun ion is a reactive electrophile and bromide ion is a good nucleophile
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
McMurry Organic Chemistry 6th edition Chapter 7 8 The Reality of Bromonium Ions Bromonium were postulated more than 60 years ago to expain the stereochemical course of the addition (to give the trans -dibromide from a cyclic alkene Olah showed that bromonium ions are stable in liquid SO 2 with SbF 5 and can be studied directly
Background image of page 8
McMurry Organic Chemistry 6th edition Chapter 7 9 7.3 Halohydrin Formation This is formally the addition of HO-X to an alkene (with + OH as the electrophile) to give a 1,2-halo alcohol, called a halohydrin The actual reagent is the dihalogen (Br 2 or Cl 2 in water in an organic solvent)
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
McMurry Organic Chemistry 6th edition Chapter 7 10 Mechanism of Formation of a Bromohydrin Br 2 forms bromonium ion, then water adds Orientation toward stable C + species Aromatic rings do not react
Background image of page 10
McMurry Organic Chemistry 6th edition Chapter 7 11 An Alternative to Bromine Bromine is a difficult reagent to use for this reaction N-Bromosuccinimide (NBS) produces bromine in organic solvents and is a safer source
Background image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 12
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 10/18/2010 for the course CHE 321 taught by Professor Fowler/sampson during the Fall '08 term at SUNY Stony Brook.

Page1 / 48

Chapter07- Alkenes- Reactions and Synthesis - 7. Alkenes:...

This preview shows document pages 1 - 12. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online