112AL+Lecture10 (1) - Some Chemistry of -Pinene Oxide 1....

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Some Chemistry of α -Pinene Oxide 2. Impact of ring strain upon the reactivity of α -pinene and α -pinene oxide 3. A new TLC visualization technique (DNP staining) used in this lab 4. A brief introduction to mass spectrometry 1. The structure of α -pinene and the synthesis of α -pinene oxide
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Synthesis of α -Pinene Oxide 1. Sterics explain why oxygen is only introduced only from the back face 2. Will learn about mechanism of reaction in class (reaction is favorable because the weak O-O single bond is broken in the transformation) Ring strain dominates the chemistry of α -pinene and α -pinene oxide (a four-membered ring has ~26 kcal/mole strain energy)!
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Ring Strain Drives Unexpected Chemistry: Case 1 Release of ring strain (4- to 5-membered ring ~20 kcal/mol) over- comes the greater stability of a 3° relative to a 2° cation (~16 kcal/mol)
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Ring Strain Drives Unexpected Chemistry: Case 2 • When a good nucleophile is not present to trap the 2° cation, ring opening to the more stable 3° cation occurs • Silica gel (TLC) and clay are non-nucleophilic and mildly acidic
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Chemistry of α -Pinene versus a-Pinene Oxide Protonation of oxygen results in a good leaving group
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This note was uploaded on 03/31/2010 for the course CHEM 112 taught by Professor Cheng during the Spring '10 term at École Normale Supérieure.

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112AL+Lecture10 (1) - Some Chemistry of -Pinene Oxide 1....

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