Phenolates

Structural formula of the phenolate ion

Phenolates (also called phenoxides) are anions, salts, and esters of phenols, containing the phenolate ion. They may be formed by reaction of phenols with strong base.[1]

Properties

Main article: sodium phenoxide

Alkali metal phenolates, such as sodium phenolate hydrolyze in aqueous solution to form basic solutions.[2] At pH = 10, phenol and phenolate are in approximately 1:1 proportions.

The phenoxide anion (aka phenolate) is a strong nucleophile with a comparable to the one of carbanions or tertiary amines.[3] Generally, oxygen attack of phenoxide anions is kinetically favored, while carbon-attack is thermodynamically preferred (see Thermodynamic versus kinetic reaction control). Mixed oxygen/carbon attack and by this a loss of selectivity is usually observed if the reaction rate reaches diffusion control.[4]

Uses

Alkyl aryl ethers can be synthesized through the Williamson ether synthesis by treating sodium phenolate with an alkyl halide:[5]

C₆H₅ONa + CH₃I → C₆H₅OCH₃ + NaI

C₆H₅ONa + (CH₃O)₂SO₂ → C₆H₅OCH₃ + (CH₃O)SO₃Na

Production of salicylic acid

Salicylic acid is produced in the Kolbe–Schmitt reaction between carbon dioxide and sodium phenolate.

See also

• Sodium phenolate

References

1. Smith, Michael B.; March, Jerry (2007), Advanced Organic Chemistry: Reactions, Mechanisms, and Structure (6th ed.), New York: Wiley-Interscience, p. 506, ISBN 978-0-471-72091-1
2. Jakubke, Hans-Dieter; Karcher, Ruth (1999). Lexikon der Chemie in drei Bänden, Band 3. Heidelberg: Spektrum Verlag. p. 14. ISBN 3-8274-0381-2.
3. [1]. Mayr’s Database of Reactivity Parameters. Retrieved July 10, 2019.
4. Mayer, Robert J.; Breugst, Martin; Hampel, Nathalie; Ofial, Armin R.; Mayr, Herbert (2019-06-26). "Ambident Reactivity of Phenolate Anions Revisited: A Quantitative Approach to Phenolate Reactivities". Journal of Organic Chemistry. 84 (14): 8837–8858. doi:10.1021/acs.joc.9b01485. PMID 31241938. S2CID 195696760.
5. Beyer, Hans; Walter, Wolfgang (1984). Organische Chemie. Stuttgart: S. Hirzel Verlag. pp. 463–464. ISBN 3-7776-0406-2.