CHAPTER 25 CHEM 140B

CHAPTER 25 CHEM 140B - Chapter 25: Heterocycles I....

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Chapter 25: Heterocycles I. Heterocycles A. Cyclic compounds that have at least one heteroatom in the ring B. Two categories non-aromatic and aromatic B.1.Non-aromatic B.1.a. Aza – nitrogen substitution B.1.b. Oxa – oxygen substitution B.1.c. Thia – sulfur substitution B.1.d. Phospha – phosphorous substitution B.2.Aromatic II. Preparation of Furans, Thiophenes, and Pyrroles A. Mechanism B. Furan C. Pyrrole D. Thiophene E. Hydrogenation F. Desulfrization G. Reverse III. Reactivity of Furans, Thiophenes, and Pyrroles A. Major mode of reactivity is electrophilic aromatic substitution B. There are two possible sites of reaction C. C3 is more stable due to three resonance structures D. C2 is less stable due to only two resonance structures E. Electrophilic substitution can happen at both positions 2 & 3 but there is a preference for position 2 F. If position 2 is taken will go to position 3 IV. Pyridine A. Aromatic 6 membered ring with nitrogen inside the ring B. Lone pair on nitrogen don’t participate in aromaticity
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This note was uploaded on 03/27/2012 for the course CHEM 140B CHEM 140B taught by Professor Theodorakis during the Spring '10 term at UCSD.

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CHAPTER 25 CHEM 140B - Chapter 25: Heterocycles I....

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