Sodium phenoxide ( sodium phenolate) is an organic compound with the formula NaOC6H5. It is a white crystalline solid. Its anion, phenoxide, also known as phenolate, is the conjugate base of phenol. It is used as a precursor to many other organic compounds, such as aryl .
Synthesis and structure
Most commonly, solutions of sodium phenoxide are produced by treating phenol with sodium hydroxide.
Anhydrous derivatives can be prepared by combining phenol and sodium. A related, updated procedure uses sodium methoxide instead of sodium hydroxide:
- NaOCH3 + HOC6H5 → NaOC6H5 + HOCH3
Sodium phenoxide can also be produced by the "alkaline fusion" of benzenesulfonic acid, whereby the sulfonate groups are displaced by hydroxide:
- C6H5SO3Na + 2 NaOH → C6H5OH + Na2SO3
This route once was the principal industrial route to phenol.
Structure
Like other sodium
, solid sodium phenoxide adopts a complex structure involving multiple Na-O bonds. Solvent-free material is polymeric, each Na center being bound to three oxygen ligands
hapticity. Adducts of sodium phenoxide are molecular, such as the cubane-type cluster NaOPh
4(
HMPA)
4.
[Michael Kunert, Eckhard Dinjus, Maria Nauck, Joachim Sieler "Structure and Reactivity of Sodium Phenoxide - Following the Course of the Kolbe-Schmitt Reaction" Chemische Berichte 1997 Volume 130, Issue 10, pages 1461–1465. ]
Reactions
Sodium phenoxide is a moderately strong base. Acidification gives phenol:
- PhOH ⇌ PhO− + H+ (K = 10−10)
The acid-base behavior is complicated by
homoassociation, reflecting the association of phenol and phenoxide.
Sodium phenoxide reacts with alkylating agents to afford alkyl phenyl ethers:[
]
- NaOC6H5 + RBr → ROC6H5 + NaBr
The conversion is an extension of the Williamson ether synthesis. With acylating agents, one obtains phenyl esters:
- NaOC6H5 + RC(O)Cl → RCO2C6H5 + NaCl
Sodium phenoxide is susceptible to certain types of electrophilic aromatic substitutions. For example, it reacts with carbon dioxide to form 2-hydroxybenzoate, the conjugate base of salicylic acid. In general however, electrophiles irreversibly attack the oxygen center in phenoxide.
- .]]
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