Sodium phenoxide Names Preferred IUPAC name Other names Identifiers ChemSpider ECHA InfoCard 100.004.862 UNII Properties C6H5NaO Molar mass 116.09 g/mol Appearance White solid Hazards Occupational safety and health (OHS/OSH): Harmful, Corrosive Flash point Non-flammable Non-flammable
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 ethers.
Most commonly, solutions of sodium phenoxide are produced by treating phenol with sodium hydroxide.[2] Anhydrous derivatives can be prepared by combining phenol and sodium. A related, updated procedure uses sodium methoxide instead of sodium hydroxide:[3]
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.[citation needed]
Like other sodium alkoxides, 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 as well as the phenyl ring. Adducts of sodium phenoxide are molecular, such as the cubane-type cluster [NaOPh]4(HMPA)4.[4]
Sodium phenoxide is a moderately strong base. Acidification gives phenol:[5]
PhOH ⇌ PhO− + H+ (K = 10−10)
The acid-base behavior is complicated by homoassociation, reflecting the association of phenol and phenoxide.[6]
Sodium phenoxide reacts with alkylating agents to afford alkyl phenyl ethers:[2]
NaOC6H5 + RBr → ROC6H5 + NaBr
The conversion is an extension of the Williamson ether synthesis. With acylating agents, one obtains phenyl esters:[citation needed]
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.[citation needed]
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