CHEM301 F08 CA12A key

CHEM301 F08 CA12A key - CHEM301, Fall 2008 Dr. Ruder 1...

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CHEM301, Fall 2008 Dr. Ruder 1 Class Activity 12A, key Electrophilic Addition Part A: Addition of Oxygen Model 1: Hydration of Alkenes The addition of water to an alkene (hydration) results in formation of an alcohol. Several reagents can be used: these method may vary in the regio- and stereochemistry of the products. 2. H 2 O 2 , HO H 2 SO 4 H 2 O 1. Hg(OAc) 2 , H 2 O 2. NaBH 4 1. BH 3 OH OH OH acid cat. hydration Markovnikov Product, mix of syn and anti oxymercuration Markovnikov Product, anti addition only hydroboration anti-Markovnikov Product, syn addition only H Questions: 1. Of the three products shown in Model 1 which have the same regiochemistry of addition? (ie addition occurred to give the same constitutional isomer). 2. For each reaction determine if the H adds to the least or most substituted carbon of the alkene. Label each product from Model 1 as Markovnikov or anti-Markovnikov. 3. Indicate whether each reaction in Model 1 occurs to give SYN addition, ANTI addition or mixtures. Model 2: Acid Catalyzed Hydration H 2 O OH H + H H H Questions: 4. The mechanism for acid catalyzed hydration is similar to the mechanism for addition of HX as shown below (from class activity 11). + H Cl Cl H H Cl NuΘ E (a). In the addition of HCl, label the nucleophile and the electrophile for both steps. (b). Based on the mechanism shown above, what is the first thing that happens when an alkene is combined with an acid? The electrons in the alkene are donated to form a bond to the acid H+. (c). In the reaction shown in Model 2, what reagents are present? Alkene, H 2 O and H+
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CHEM301, Fall 2008 Dr. Ruder 2 (d). What would you expect to be the first step in the reaction shown in Model 2? The electrons in the alkene reacting with the acid H+. 5. The first step in the mechanism for acid catalyzed hydration is the same as the first step in the addition of HX as shown in question 4 above. (a). Draw the cation obtained on reaction of the alkene with acid, using curved arrows to show electron movement. H
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This note was uploaded on 02/17/2011 for the course CHEM 301 taught by Professor Sahli during the Fall '07 term at VCU.

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CHEM301 F08 CA12A key - CHEM301, Fall 2008 Dr. Ruder 1...

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