What Is Fluoroglucinol?
Fluoroglucinol is a naturally occurring organic compound with the chemical formula C6H6O3.
Fluoroglucinol is biosynthesized by bacteria and plants and is present as glycosides in components within various plants. Acyl derivatives are found in the phloem of the fern Dryopteris arguta. Fluoroglucinol can be isolated from brown algae, and a type of tannin, phlorotannin, can be synthesized. Phlorotannin can also be obtained by hydrolysis of phenone derivatives with phloretin hydrolase.
Chemical Properties of Fluoroglucinol
| Chemical formula | C6H6O3 |
| Molecular weight | 126.11 |
| Melting point | 216 – 219°C |
Uses of Fluoroglucinol
Being polyfunctional, fluoroglucinol is useful as an intermediate in organic synthesis. It is mainly used as a synthetic raw material for pharmaceuticals and explosives.
For example, it is used as a synthetic raw material for flopropion. It can also be used as a coupling agent in printing because it quickly turns black when combined with diazo dyes. It shows a color reaction with lignin and is used as an analytical reagent. It is also used in the detection and quantification of pentoses and other compounds (the Torrens reaction), which is called the fluoroglucinol reaction.
Physical Properties of Fluoroglucinol
Fluoroglucinol has a molecular weight of 126.11 and a melting point of 216-219 °C. The melting point of fluoroglucinol dihydrate at ambient pressure is 116-117 °C. Fluoroglucinol is sublimable. It is a weak tribasic acid with the first two pKa of 8.5 and 8.9.
It reacts with hydroxylamine to form an oxime. This is because fluoroglucinol, like enol, exists in equilibrium with the keto tautomer.
Fluoroglucinol also behaves like benzentriol, and methylation of the three hydroxyl groups yields 1,3,5-trimethoxybenzene.
Structure of Fluoroglucinol
Fluoroglucinol, also known as 1,3,5-benzentriol, is a polyphenol with three hydroxy groups substituted on the benzene ring and is a member of the benzenetriols or trihydroxybenzenes.
Fluoroglucinol is in pH-dependent chemical equilibrium. Two tautomers exist: 1,3,5-trihydroxybenzene (phenolic form) and 1,3,5-cyclohexatrione (ketone form). The keto tautomer of the spectroscopically neutral compound is undetectable. However, when deprotonated, the keto tautomer is predominant.
Other Information on Fluoroglucinol
1. Synthesis of Fluoroglucinol
In organic synthesis, the reduction of 1,3,5-trinitrobenzene gives triaminobenzene, which is hydrolyzed by boiling the resulting hydrochloride salt with water. Normal aniline derivatives are inert to hydroxide ions, but triaminobenzene is easily hydrolyzed to an imine form due to its tautomerism.
2. Reaction of Fluoroglucinol
1-(2,4,6-trihydroxyphenyl)ethanone can be synthesized by the Hoesch reaction of fluoroglucinol. The reaction of fluoroglucinol with isovaleroylnitrile in the presence of a zinc chloride catalyst yields leptospermone.
Fluoroglucinol reacts readily with low-temperature aqueous ammonia to form 5-aminoresorcinol (fluoramine). The reaction of fluoroglucinol with phloretic acid yields phloretin in 30% yield.
3. Isomers of Fluoroglucinol
There are three isomers depending on the position of the hydroxy group: 1,2,4-benzenetriol and 1,2,3-benzenetriol. 1,2,4-benzenetriol is also called hydroxyquinol and 1,2,3-benzenetriol is called pyrogallol.