organic Chemistry, 5th Edition C--CHun L.G. Wade Jr Chapter 8 Reactions of alkenes Jo blackburn Richland college, dallas TX Dallas County Community College District c 2003. Prentice hall
Chapter 8 Reactions of Alkenes Jo Blackburn Richland College, Dallas, TX Dallas County Community College District © 2003, Prentice Hall Organic Chemistry, 5th Edition L. G. Wade, Jr
Reactivity of C=C C Electrons in pi bond are loosely held Electrophiles are attracted to the pi electrons Carbocation intermediate forms Nucleophile adds to the carbocation Net result is addition to the double bond > Chapter 8
Chapter 8 2 Reactivity of C=C • Electrons in pi bond are loosely held. • Electrophiles are attracted to the pi electrons. • Carbocation intermediate forms. • Nucleophile adds to the carbocation. • Net result is addition to the double bond. =>
Electrophilic Addition C Step 1: Pi electrons attack the electrophile E C+ Step 2: Nucleophile attacks the carbocation E E Nuc -C-C+ t Nuc C-C hapter 8
Chapter 8 3 Electrophilic Addition • Step 1: Pi electrons attack the electrophile. C C + E + C E C + C E C + + Nuc: _ C E C Nuc => • Step 2: Nucleophile attacks the carbocation
Types of Additions f Addition Product Elements Added] H OH ation halogenation H,OJ TX2 an oxidation OH hydrogenation halohydrin formtion [H,I, a reduction [HOXI, an oxidation OH OH hydroxyl at ion HX addition HOOH I. an oxidation HXI oxidative cle C=00= [O,I an oxidation cyclopropanation epoxidat ion CH, O. an oxidation a These are not the reagents used but simply the groups that appear in the product
Chapter 8 4 Types of Additions =>
Addition of HX(1) C Protonation of double bond yields the most stable carbocation Positive charge goes to the carbon that was not protonated CH3 CH3-C-CH-CH3 CH3-C-CH-CH3 Br Br X CH3 CH3-C-CH--CH3 十 > Chapter 8
Chapter 8 5 Addition of HX (1) Protonation of double bond yields the most stable carbocation. Positive charge goes to the carbon that was not protonated. X => + Br _ + + CH3 C CH3 CH CH3 H CH3 C CH3 CH CH3 H H Br CH3 C CH3 CH CH3