Dolbier HW Solutions 590

Dolbier HW Solutions 590 - directly conjugated to it and...

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Picric acid (2,4,6-trinitrophenol) is a stronger acid by far than 2,4,6-trimethylphenol. All three nitro groups participate in resonance stabilization of the picrate anion. ( b ) Stabilization of a phenoxide anion is most effective when electron-withdrawing groups are present at the ortho and para positions, because it is these carbons that bear most of the nega- tive charge in phenoxide anion. 2,6-Dichlorophenol is therefore expected to be (and is) a stronger acid than 3,5-dichloro- phenol. ( c ) The same principle is at work here as in part ( b ). A nitro group para to the phenol oxygen is
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Unformatted text preview: directly conjugated to it and stabilizes the anion better than one at the meta position. OH NO 2 4-Nitrophenol, stronger acid ( K a 5 1.0 3 10 2 8 , p K a 5 7.2) OH NO 2 3-Nitrophenol, weaker acid ( K a 5 4.1 3 10 2 9 , p K a 5 8.4) OH Cl Cl 3,5-Dichlorophenol, less acidic ( K a 5 6.5 3 10 2 9 , p K a 5 8.2) OH Cl Cl 2,6-Dichlorophenol, more acidic ( K a 5 1.6 3 10 2 7 , p K a 5 6.8) O 2 2 O 2 O 2 O N 1 N 1 O O O 2 2 O O 2 O N 1 O 2 N 1 N 1 O O O 2 2 O O 2 O N 1 2 O N 1 N 1 O O O 2 2 O O 2 N 1 O O 2 2 N 1 N 1 O O O 2 2 O O 2 N 1 O O 684 PHENOLS...
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