Sodium phenoxide (sodium phenolate) is an
organic compound
In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. Th ...
with the formula NaOC
6H
5. It is a white crystalline solid. Its anion, phenoxide, also known as phenolate, is the
conjugate base
A conjugate acid, within the Brønsted–Lowry acid–base theory, is a chemical compound formed when an acid donates a proton () to a base—in other words, it is a base with a hydrogen ion added to it, as in the reverse reaction it loses a ...
of
phenol
Phenol (also called carbolic acid) is an aromatic organic compound with the molecular formula . It is a white crystalline solid that is volatile. The molecule consists of a phenyl group () bonded to a hydroxy group (). Mildly acidic, it r ...
. It is used as a precursor to many other organic compounds, such as aryl
ether
In organic chemistry, ethers are a class of compounds that contain an ether group—an oxygen atom connected to two alkyl or aryl groups. They have the general formula , where R and R′ represent the alkyl or aryl groups. Ethers can again ...
s.
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:
:NaOCH
3 + HOC
6H
5 → NaOC
6H
5 + HOCH
3
Sodium phenoxide can also be produced by the "alkaline fusion" of
benzenesulfonic acid, whereby the sulfonate groups are displaced by hydroxide:
:C
6H
5SO
3Na + 2 NaOH → C
6H
5ONa + Na
2SO
3
This route once was the principal industrial route to phenol.
Structure
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
A cubane-type cluster is an arrangement of atoms in a molecular structure that forms a cube. In the idealized case, the eight vertices are symmetry equivalent and the species has Oh symmetry. Such a structure is illustrated by the hydrocarbon ...
aOPhsub>4(
HMPA)
4.
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
Salicylic acid is an organic compound with the formula HOC6H4CO2H. A colorless, bitter-tasting solid, it is a precursor to and a metabolite of aspirin (acetylsalicylic acid). It is a plant hormone, and has been listed by the EPA Toxic Substa ...
. In general however, electrophiles irreversibly attack the oxygen center in phenoxide.
500px, center, The Kolbe–Schmitt reaction.
References
External links
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Phenolates
Organic sodium salts
