Organic Chemistry, 5th Edition L.G. Wade, Jr Chapter 16 Aromatic Compounds Jo blackburn Richland college, dallas TX Dallas County Community College District c 2003. Prentice hall
Chapter 16 Aromatic Compounds Jo Blackburn Richland College, Dallas, TX Dallas County Community College District © 2003, Prentice Hall Organic Chemistry, 5th Edition L. G. Wade, Jr
Discovery of benzene Isolated in 1825 by Michael Faraday Who determined c h ratio to be 1: 1 Synthesized in 1 8 34 by eilhard Mitscherlich who determined molecular formula to be C6H6 Other related compounds with low C: H ratios had a pleasant smell, so they Were classified as aromatic Chapter 16
Chapter 16 2 Discovery of Benzene • Isolated in 1825 by Michael Faraday who determined C:H ratio to be 1:1. • Synthesized in 1834 by Eilhard Mitscherlich who determined molecular formula to be C6H6 . • Other related compounds with low C:H ratios had a pleasant smell, so they were classified as aromatic. =>
Kekule structure after multiple bonds were suggested,SA Proposed in 1866 by Friedrich Kekule, shortly Failed to explain existence of only one isomer of 1.2-dichlorobenzene H H H H H H Chapter 16
Chapter 16 3 Kekulé Structure • Proposed in 1866 by Friedrich Kekulé, shortly after multiple bonds were suggested. • Failed to explain existence of only one isomer of 1,2-dichlorobenzene. C C C C C C H H H H H H =>
H Resonance structure Each sp hybridized c in the ring has an unhybridized p orbital perpendicular to the ring which overlaps around the ring 1.397A H H 120° H 120° Chapter 16
Chapter 16 4 Resonance Structure Each sp2 hybridized C in the ring has an unhybridized p orbital perpendicular to the ring which overlaps around the ring. =>
Unusual reactions Alkene+ KMnO4>diol (addition) Benzene Kmno,-> no reaction Alkene+ Br2/CCl4>dibromide(addition) Benzene br/ccl-> no reaction With FeCl3 catalyst, Br2 reacts with benzene to form bromobenzene hbr (substitution! ) Double bonds remain > Chapter 16
Chapter 16 5 Unusual Reactions • Alkene + KMnO4 → diol (addition) Benzene + KMnO4 → no reaction. • Alkene + Br2 /CCl4 → dibromide (addition) Benzene + Br2 /CCl4 → no reaction. • With FeCl3 catalyst, Br2 reacts with benzene to form bromobenzene + HBr (substitution!). Double bonds remain. =>