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426 Chapter 22 CHEMISTRY OF BENZENE SUBSTITUENTS: ALKYLBENZENES, PHENOLS, AND BENZENAMINES a H CI :OH CH₂CO₂⁻ Cl Cl Cl OCH₂CO₂H (after acidification) Cl Cl HOOC COOH 53. (a) HOOC COOH (b) The first step oxidizes the benzylic alcohol to an aldehyde. The molecule is then capable of an intramolecular aldol condensation. forming a second six-membered ring that contains an α, ketone. This ketone. in turn. is unusual in that it is a cyclohexadienone, the ketone tautomer of a more stable phenol. Using we have o H o MnO₂ o H CH₃ KOH Tautomerization Aldol OH H H H COOH (c) COOH 54. (c) (The group is very acidic) > (b) > (e) > (f) > (d) > (a). Carboxylic acids are more acidic than most phenols, and electron-withdrawing groups increase the acidity of phenols. CH3 55. (a) product