Dolbier HW Solutions 418

Dolbier HW Solutions 418 - ( g ) Furan-2-carboxylic acid...

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attached to the carboxyl group in benzoic acid stabilizes benzoate anion better than the cor- responding sp 3 -hybridized carbon stabilizes cyclohexanecarboxylate. Benzoic acid is a stronger acid. ( d ) Its f ve F uorine substituents make the penta F uorophenyl group more electron-withdrawing than an unsubstituted phenyl group. Thus, penta F uorobenzoic acid is a stronger acid than benzoic acid. ( e ) The penta F uorophenyl substituent is electron-withdrawing and increases the acidity of a car- boxyl group to which it is attached. Its electron-withdrawing effect decreases with distance. Penta F uorobenzoic acid is a stronger acid than p -(penta F uorophenyl)benzoic acid. ( f ) The oxygen of the ring exercises an acidifying effect on the carboxyl group. This effect is largest when the oxygen is attached directly to the carbon that bears the carboxyl group. Furan-2-carboxylic acid is thus a stronger acid than furan-3-carboxylic acid.
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Unformatted text preview: ( g ) Furan-2-carboxylic acid has an oxygen attached to the carbon that bears the carboxyl group, whereas pyrrole-2-carboxylic acid has a nitrogen in that position. Oxygen is more Furan-2-carboxylic acid (p K a 3.2) K a 6.9 3 10 2 4 CO 2 H O Furan-3-carboxylic acid (p K a 3.9) K a 1.1 3 10 2 4 CO 2 H O Pentafluorobenzoic acid K a 4.1 3 10 2 4 (p K a 3.4) p-(Pentafluorophenyl)benzoic acid ( K a not measured in water; comparable with benzoic acid in acidity) CO 2 H F F F F F CO 2 H F F F F F Pentafluorobenzoic acid K a 4.1 3 10 2 4 (p K a 3.4) Benzoic acid K a 6.7 3 10 2 5 (p K a 4.2) CO 2 H CO 2 H F F F F F Benzoic acid K a 6.7 3 10 2 5 (p K a 4.2) CO 2 H Cyclohexanecarboxylic acid K a 1.2 3 10 2 5 (p K a 4.9) CO 2 H 512 CARBOXYLIC ACIDS __ __ __...
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This note was uploaded on 09/30/2011 for the course CHM 2210 taught by Professor Reynolds during the Fall '01 term at University of Florida.

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