H menh co2h purpose of the problem a contrast between

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Unformatted text preview: he alkoxide ion (pKa of ROH about 15). This carboxylate anion cannot be protonated in basic solution and is not attacked by methoxide ion. 7 Solutions for Chapter 10 – Nucleophilic Substitution at the Carbonyl Group O O O O O O × no futher reaction OMe OMe OMe O O OMe O In acid solution the first reaction is similar, though the tetrahedral intermediate is neutral, and the carboxyl is still the better leaving group. The second esterification is now all right because methanol can attack the protonated carboxylic acid and water can be driven out after a second protonation. The second step is an equilibrium, with water and methanol about equal as leaving groups, but methanol is present in large excess as the solvent and drives the equilibrium across. We have omitted proton transfer steps. O O O OH OH O O O HO O OH OMe OMe OMe OMe O O PROBLEM 7 Suggest mechanisms for these reactions, explaining why these particular products are formed. O dilute O O H2O Ph Cl in acetone Me Ph O Ph 1. NaOH N 100° C O 2. H MeNH CO2H Purpose of the problem A contrast between very reactive (acid chloride), less reactive (anhydride) and unreactive (...
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This document was uploaded on 02/10/2014.

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