Phloroglucinol

Phloroglucinol
IUPAC name[hide] Benzene-1,3,5-triol
Other names[hide] phloroglucine, 1,3,5-trihydroxybenzene, 1,3,5-benzenetriol, or cyclohexane-1,3,5-trione
Identifiers
CAS number	108-73-6 Y
PubChem	359
RTECS number	UX1050000
SMILES [show] Oc1c(O)cccc1
Properties
Molecular formula	C6H6O3
Molar mass	126.11 g/mol
Exact mass	126.031694
Appearance	white solid
Melting point	218-220 °C
Solubility in water	1 g/100 mL
Hazards
EU classification	Harmful (Xn)
Y(what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Phloroglucinol is a benzenetriol. It is an organic compound that is used in the synthesis of pharmaceuticals and explosives. This molecule exists in two forms, or tautomers, 1,3,5-trihydroxybenzene, which has phenol-like, and 1,3,5-cyclohexanetrione (phloroglucin), which has ketone-like character. These two tautomers are in equilibrium. Phloroglucinol is a useful intermediate because it is polyfunctional.

From water, phloroglucinol crystallizes as the dihydrate, which has a melting point of 116-117 °C, but the anhydrous form melts much higher, at 218-220 °C. It does not boil intact, but it does sublime.

Contents 1 Isolation, synthesis, and reactions 2 Natural occurrence 3 Metabolism 4 Applications

Isolation, synthesis, and reactions

Phloroglucinol was originally isolated from bark of fruit trees. It is synthesized via a number of processes, but representative is the following route from trinitrobenzene:^[1]

The synthesis is noteworthy because ordinary aniline derivatives are unreactive toward hydroxide. Because the triaminobenzene also exists as its imine tautomer, it is susceptible to hydrolysis.
The compound behaves like a ketone in its reaction with hydroxylamine, forming the tris(oxime). But it behaves also like a triphenol (K_a1 = 3.56 × 10⁻⁹, K_a2 1.32×10⁻⁹), as the three hydroxyl groups can be methylated to give 1,3,5-trimethoxybenzene.^[1]

Natural occurrence

Phloroglucinols occur naturally in certain plant species. For example, they (and sometimes their acyl dervatives) are present in the fronds of the coastal woodfern, Dryopteris arguta.^[2] Brown algae also produce phloroglucinol derivatives^[3][4] known as phlorotannins.^[5]

Metabolism

Phloretin hydrolase uses phloretin and water to produce phloretate and phloroglucinol.

Applications

Phloroglucinol is mainly used as a coupling agent in printing. It links diazo dyes to give a fast black.
It is useful for the industrial synthesis of pharmaceuticals^[6] and explosives.^[7] It is also used as a treatment for gallstones, spasmodic pain and other related gastrointestinal disorders.^[8][9][10] It has a non-specific spasmolytic action on the vessels, bronchi, intestine, ureters and gall bladder, and is used for treating disorders of these organs.