CHEM302 S09 CA1B key

CHEM302 S09 CA1B key - CHEM302, Spring 2009 Dr. Ruder 1...

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Dr. Ruder 1 Class Activity 1B Alcohols: Versatile Reagents Part B: Reactions of Alcohols as Nucleophiles and Electrophiles. Model 1: Alcohols as Nucleophiles Alcohols can act as nucleophiles in their neutral form (ROH) or after being converted to the alkoxide (RO-). Williamson Ether Synthesis + CH 3 O Na Br CH 3 O + NaBr CH 3 OH Na o alcohol alkoxide Eq. 1. Fischer Esterification O H 3 C OH + HO H 2 SO 4 heat O H 3 C O + H 2 O Eq. 2 Questions: 1. (a) . Would you expect the neutral alcohol CH 3 OH or the alkoxide CH 3 O- to be the stronger nucleophile? Explain why. The alkoxide is the stronger nucleophile. Since nucleophiles donate electrons, the species with a negative charge will more readily be able to donate electrons. (b). In Eq. 1 above what species acts as the nucleophile in the substitution reaction? Label the nucleophile and the electrophile for each reagent in Eq. 1. see above . (c). In Eq. 2 of Model 1, what species acts as the nucleophile in the first step? Label the nucleophile and the electrophile for each reagent in Eq. 2. see above 2. (a). Draw curved arrows to show electron movement for the Williamson Ether Synthesis (Eq. 1). see above (b). If the alkyl halide was tertiary (2-bromo-2-methylpropane), what competing reaction would occur on reaction with the alkoxide? Draw the product and indicate what role the alkoxide plays in this reaction (nucleophile, electrophile, acid, base). Elimination would occur when a tertiary alkyl halide is combined with a base like the alkoxide. 3. (a). Draw curved arrows to show electron movement for the Fischer Esterification (Eq. 2). see above
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CHEM302 S09 CA1B key - CHEM302, Spring 2009 Dr. Ruder 1...

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