118K Stereochemistry - Michael Tam(mht347) 3/20/2011...

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Michael Tam(mht347) 3/20/2011 The purpose of this lab was to establish the best reaction mechanism in which Dimethyl Maleate isomerizes into Dimethyl Fumarate via light, or addition of Br 2 . Dimethyl maleate and dimethyl fumarate are geometric isomers of each other. Dimethyl maleate is the cis version of dimethyl fumarate. That being said, we basically are trying to break the double bond in the middle of these two compounds, and rotate it from the cis to the trans conformation. How then, do we make sure only the trans version is formed, instead of the product reversing to form dimethyl maleate again? The answer is simple; the cis isomer isn’t favored in the reaction due to steric hindrance, and therefore we do not need to do anything. Aside from that, how would we tell dimethyl maleate from the fumarate? The two compounds are diastereomers. They have different physical and chemical properties. Dimethyl fumarate, the trans version, is a solid at room temperature as opposed to dimethyl maleate, which is a liquid. Therefore, the trans version should precipitate out when the correct mechanism is established.
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This note was uploaded on 09/25/2011 for the course CH 118K taught by Professor Fjetland during the Spring '08 term at University of Texas at Austin.

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118K Stereochemistry - Michael Tam(mht347) 3/20/2011...

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