dehydration-091020132031-phpapp01

dehydration-091020132031-phpapp01 - Dehydration of...

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Dehydration of Dehydration of 2 2 - - methylcyclohexanol methylcyclohexanol
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Dehydration Reactions Dehydration Reactions ± Alcohol dehydration is an acid catalyzed reaction, which can be performed by strong, concentrated mineral acids such as sulfuric acid (H 2 SO 4 ) and phosphoric acid (H 3 PO 4 ).
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Alcohol dehydration proceeds by an elimination mechanism called E1 . OH H-O-PO 3 H 2 O-H CH 3 CH 3 H + + H CH 3 H secondary carbocation CH 3 H + CH 3 CH 3 tertiary carbocation carbocation rearrangement O-PO 3 H 2 O-PO 3 H 2 O-PO 3 H 2 rate determining step minor product major product 1 st step - Protonation changes the very poor leaving group ( - OH) into a good leaving group (H 2 O). 2 nd step - Water departs, leaving behind a carbocation. This step is the rate determining step (rds) . 3 rd step - The base H 2 PO 4 - removes a proton from the carbon adjacent to the positively charged carbon, forming an alkene and regenerating the acid catalyst H 3 PO 4 . oxonium ion
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This note was uploaded on 11/25/2011 for the course CHEM 52705 taught by Professor Santon during the Spring '11 term at University of Texas.

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dehydration-091020132031-phpapp01 - Dehydration of...

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