Week_5.3_PurpleBook_Answers

Week_5.3_PurpleBook_Answers - 127 Acidity of Carboxylic...

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OH O OH O OH O OH O OH O OH O OH O Cl Cl Cl Cl Cl H OH O H 3 C O HO O O OH O Acidity of Carboxylic Acids Cl OH O 1. Match the carboxylic acids below with the list of pKa's at right. Explain your ranking. 0.70 Cl 2.85 O 1.48 2.86 4.05 4.52 O 4.76 2. Explain the observed trend in pKa's for formic acid, acetic acid, and carbonic acid: 3.75 OH O 4.76 O 6.37 pKa: More electron- withdrawing Cl substituents stabilize the carboxylate anion and favor acid dissociation (stronger acid) Closer electron- withdrawing Cl substituents stabilize the carboxylate anion and favor acid dissociation (stronger acid) compared with acetic acid Methyl is a moderate electron donor: electron donation will destabilize the carboxylate anion (compared with formate) and will make acetic acid less acidic. The oxygen is a good electron donor (by resonance) which destabilizes the carboxylate anion even more (compared with acetate) and makes carbonic acid even less acidic. Week 5 127
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More Wittig Mechnisms 1. a) Provide a complete curved-arrow mechanism for all the steps in the following multi-step transformation.
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This note was uploaded on 05/01/2008 for the course CHEM 51 taught by Professor Gribble during the Spring '08 term at Dartmouth.

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Week_5.3_PurpleBook_Answers - 127 Acidity of Carboxylic...

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