Chemistry CHEM S-20ab Lecture Notes - Lecture 12: Stereochemistry, Orbiting Solar Observatory, Diol
30 Apr 2018
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Chemistry E-2a: Lecture 8 November 20, 2008
6
Cyclic Ethers and Epoxides
• Draw a curved-arrow mechanism and predict the product of the following reactions:
HO
Br
NaOH
HO
Br NaOH
• The three-membered cyclic ether is given the special name epoxide. Why might this
epoxide exhibit reactivity different from that of the 5-membered ring above?
Reading: Section 11.2
Chemistry S-20ab
Week 3
1
Chemistry E-2a: Lecture 8 November 20, 2008
7
Synthesis of Epoxides With Halohydrins
• Provide complete curved-arrow mechanisms for each step in the following
transformation. Be sure to pay attention to stereochemistry!
Br2 , H2O
OH
Br
(+/–)
NaOH
O
(+/–)
• Explain why the following halohydrin cannot be transformed into an epoxide:
OH
Br
Reading: Section 11.2
Chemistry S-20ab
Week 3
1
Document Summary
Draw a curved-arrow mechanism and predict the product of the following reactions: The three-membered cyclic ether is given the special name epoxide. Provide complete curved-arrow mechanisms for each step in the following transformation. Explain why the following halohydrin cannot be transformed into an epoxide: A much more convenient, one-step synthesis of epoxides from alkenes uses peroxycarboxylic acids, often called peracids. some examples: Draw the curved arrows for the following single-step synthesis of an epoxide from an alkene: Identify the molecular orbitals involved in this reaction. Provide a mechanism and explain why the indicated product is formed selectively in each of the following reactions: mcpba. Provide a mechanism that shows how the following epoxide reacts with the indicated. This reaction is quite useful for synthesis, because it forms a new carbon-carbon bond. Provide a synthetic route for the following transformation: What is the overall stereochemistry of the following transformation? mcpba.
