Resorcinol

Resorcinol (or resorcin) is a chemical compound from the dihydroxy phenols. it is the 1,3-isomer of benzenediol. It is also known with a variety of other names, including: m-dihydroxybenzene, 1,3-benzenediol, 1,3-dihydroxybenzene, 3-hydroxyphenol, m-hydroquinone, m-benzenediol, and 3-hydroxycyclohexadien-1-one.

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Nomenclature

Resorcinol is the name recommended by the International Union of Pure and Applied Chemistry (IUPAC) in its 1993 Recommendations for the Nomenclature of Organic Chemistry.^[1]

Production

It is obtained on fusing many resins (galbanum, asafoetida, etc.) with potassium hydroxide, or by the distillation of Brazilwood extract. It may be prepared synthetically by fusing 3-iodophenol, phenol-3-sulfonic acid or benzene-1,3-disulfonic acid with potassium carbonate; by the action of nitrous acid on 3-aminophenol; or by the action of 10% hydrochloric acid on 1,3-diaminobenzene ^[2]. Many ortho- and para-compounds of the aromatic series (for example, the bromophenols, benzene-para-disulfonic acid) also yield resorcinol on fusion with potassium hydroxide.

Properties

Resorcinol crystallizes from benzene as colorless needles which are readily soluble in water, alcohol and ether, but insoluble in chloroform and carbon disulfide. It reduces Fehling's solution, and ammoniacal silver solutions. It does not form a precipitate with lead acetate solution, as the isomeric pyrocatechol does. Iron(III) chloride colors its aqueous solution a dark violet, and bromine water precipitates tribromoresorcin. Sodium amalgam reduces it to dihydroresorcin, which when heated to 150 to 160 °C with concentrated barium hydroxide solution gives γ-acetylbutyric acid (D. Vorlgnder); when fused with potassium hydroxide, resorcinol yields phloroglucin, pyrocatechol and diresorcin. It condenses with acids or acid chlorides, in the presence of dehydrating agents, to oxyketones, e.g. with zinc chloride and glacial acetic acid at 145 °C it yields resacetophenone (HO)₂C₆H₃~CO.CH₃(M. Nencki and N. Sieber, Jour. prak. Chem., 1881, 23, p. 147). With the anhydrides of dibasic acids it yields fluoresceins. When heated with calcium chloride—ammonia to 200 °C it yields meta-dioxydiphenylamine (A. Seyewitz, Bull. Soc. Chins., 1890, 3, p. 811). With sodium nitrite it forms a water-soluble blue dye, which is turned red by acids, and is used as an indicator, under the name of lacmoid (M. C. Traub and C. Hock, Ber., 1884, 17, p. 2615). It condenses readily with aldehydes, yielding with formaldehyde, on the addition of catalytic hydrochloric acid, methylene diresorcin [(HO)C₆H₃(O)]₂•CH₂, whilst with chloral hydrate, in the presence of potassium bisulfate, it yields the lactone of tetra-oxydiphenyl methane carboxylic acid (J. T. Hewitt and F. G. Pope, Jour. C/tern. Soc., 1897, 75, p. 1084). In alcoholic solution it condenses with sodium acetoacetate to form 13-methylumbelliferone, C~OH₈O₃ (A. Michael, Jour. prak. Chem., 1888, 37, 470).

With concentrated nitric acid, in the presence of cold concentrated sulfuric acid, it yields trinitro-resorcin (styphnic acid), which forms yellow crystals, exploding violently on rapid heating.

Applications

Medical

Used externally it is an antiseptic and disinfectant, and is used 5 to 10% in ointments in the treatment of chronic skin diseases such as psoriasis and eczema of a sub-acute character.^{[citation needed]} It is present in over-the-counter topical acne treatments at 2% concentration, and in prescription treatments at higher concentrations.^{[citation needed]} Weak, watery solutions of resorcinol (25 to 35 g/kg) are useful in allaying the itching in erythematous eczema.^{[citation needed]} A 2% solution used as a spray has been used with marked effect in hay fever and in whooping cough.^{[citation needed]} In the latter disease 0.6 mL of the 2% solution has been given internally. It can be included as an anti-dandruff agent in shampoo or in sunscreen cosmetics.^{[citation needed]} It has also been employed in the treatment of gastric ulcers in doses of 125 to 250 mg in pills, and is said to be analgesic and haemostatic in its action.^{[citation needed]} In large doses it is a poison causing giddiness, deafness, salivation, sweating and convulsions. It is also worked up in certain medicated soaps.^{[citation needed]} Monoacetylresorcinol, C₆H₄(OH)(O-COCH₃), is used under the name of euresol.^{[citation needed]}

Chemical

Resorcinol is also used as a chemical intermediate for the synthesis of pharmaceuticals and other organic compounds. It is used in the production of diazo dyes and plasticizers and as a UV absorber in resins.

An emerging use of resorcinol is as a template molecule in supramolecular chemistry. The -OH groups on resorcinol form hydrogen bonds to target molecules holding them in the proper orientation for a reaction. Many such reactions are able to be carried out in the solid state thereby reducing or eliminating the use of solvents that may be harmful to the environment. (see Green chemistry)

Resorcinol is an analytical reagent for the qualitative determinaion of ketoses (Seliwanoff's test).

Resorcinol is the starting material for resorcinarene molecules.

Related compounds

Resazurin, C₁₂H₇NO₄, obtained by the action of nitrous acid on resorcinol ^[3], forms small dark red crystals possessing a greenish metallic glance. When dissolved in concentrated sulphuric acid and warmed to 210 °C, the solution on pouring into water yields a precipitate of resorufin, C₁₂H₇NO₃, an oxyphenoxazone, which is insoluble in water, but is readily soluble in hot concentrated hydrochloric acid, and in solutions of caustic alkalis. The alkaline solutions are of a rose-red color and show a cinnabar-red fluorescence. A tetrabromresorufin is used as a dye-stuff under the name of Fluorescent Resorcin Blue.

Thioresorcinol is obtained by the action of zinc and hydrochloric acid on the chloride of benzene meta-disulphonic acid. It melts at 27 °C and boils at 243 °C. Resorcinol disulfonic acid (HO)₂C₆H₂(HSO3)₂, is a deliquescent mass obtained by the action of sulphuric acid on resorcin ^[4]. It is easily soluble in water and decomposes when heated to 100 °C.

References

This article incorporates text from the Encyclopædia Britannica Eleventh Edition, a publication now in the public domain.