CH 9-2 Phenols.pptVIP

?2012 Wei DONG Nanjing University of Science Technology All Rights Reserved Chapter 9 Phenols Nomenclature Numbering of the ring begins at the hydroxyl-substituted carbon and proceeds in the direction that gives the lower num -ber to the next carbon atom bearing substituent. Substituents are cited in alphabetical order. Naming Priority Acids Esters Aldehydes Ketones Alcohols Amines Alkenes Alkynes Alkanes Ethers Halides  Phenols m-Cresol 5-Chloro-2-methylphenol Carboxyl and acyl groups take precedence over the phenolic hydroxyl in determining the base name.The hydroxyl is trea -ted as a substituent in these cases. p-Hydroxybenzonic acid 2-Hydroxy-4-methlacetophenone Acidity of Phenols Phenols are more acidic than alcohols but less acidic than carboxylic acids. The negative charge in ethoxide ion is localized on oxygen and is stabilized only by solvation forces. The negative charge in phenoxide ion is stabilized both by solvation and by electron delocation into the ring. : : : : : : : : : Ethanol Proton Ethoxide ion Phenol Proton Phenoxide ion On shaking an ether solution of an alcohol and a phenol with dilute sodium hydroxide, the phenol is converted quantitatively to its sodium salt, which is extracted into the aqueous phase. The alcohol remains in the ether phase. Phenol Hydroxide ion Phenoxide ion (weaker base) water (weaker acid) (stronger base) (stronger acid) On shaking an ether solution of a phenol and a carboxylic acid with dilute sodium bicarbonate, the carboxylic acid is converted quantitatively to its sodium salt and extracted into the aqueous phase. The phenol remains in the ether phase. (weaker acid) (weaker base) (stronger base) (stronger acid) Phenol Bicarbonate ion Phenoxide ion Carbonic acid Separation 酸性 由于p-π共轭作用，苯酚酸性（pKa=10）比环己醇（pKa=18）强很多。 吸电基使取代酚的酸性进一步增强。 Substituent Effects On The Acidity of Phenols Alkyl substitution produces negligible changes in acidities, as do weakly electrone