Resorcinol

D10AX02

Large, colorless, sweet-tasting needles

Fixed

1.28 g · cm -3

110.7 ° C

277 ° C.

1 Pa ( 20 ° C)

• PKS1 = 9.48
• PKS1 = 12.08

• Very good in water ( 1400 g · l-1 at 20 ° C ), ethanol, diethyl ether and glycerol
• Poorly in chloroform and carbon disulfide

Attention

Not yet classified

• 301 mg · kg -1 ( LD50, rat, oral)
• 3360 mg · kg -1 ( LD50, Rabbit, transdermal)

Template: Infobox chemical / molecular formula search available

Resorcinol (1,3- dihydroxybenzene ) is derived formally from the benzene. The benzene ring carrying two hydroxyl groups in the meta position. It belongs to the group of phenols ( diphenols ) and is isomeric with catechol (1,2- dihydroxybenzene ) and hydroquinone (1,4- dihydroxybenzene ).

Production and representation

You can win resorcinol by the distillation of natural resins (Latin resina ).

Technically put it out by melting of m- benzene disulfonic acid with sodium hydroxide ( alkali fusion ) ago. This sodium is a by- product.

Properties

Physical Properties

Resorcinol dissolves easily in water, ethanol and ether. At 20 ° C, dissolve in 1 liter of water 1400 grams of resorcinol. The good solubility in water is caused mainly by hydrogen bonds between the two phenolic hydroxyl groups and the solvent molecules.

Chemical Properties

With iron ( III) chloride solution is a resorcinol a characteristic color reaction of the phenols; it forms a deep purple solution.

Like all acts resorcinol weakly acidic phenols, because the phenolic hydroxyl groups are easily deprotonated as an alcoholic; the acidity constant for the first pK a = 9.48 is protolysis.

In contrast to catechol and hydroquinone, resorcinol, is only weakly reducing and falls from ammoniacal silver nitrate solution, no elemental silver from. Only in the heat, black silver precipitates.

Also, an alkaline solution turns very slowly yellow in air. Alkaline solutions of catechol and hydroquinone discolor quickly brown the other hand, by the action of oxygen.

In addition, resorcinol can be called upon to distinguish between fructose and glucose. If you mix fructose, resorcinol and concentrated hydrochloric acid together, resulting in a striking red color ( Seliwanow sample). This evidence is extremely helpful, since fructose, formed as ketohexose a positive Fehling's test supplies, because of the easy conversion of fructose to glucose, or halbacetalische OH groups.

Reactions

Sodium amalgam reduces dihydroresorcinol to resorcinol (1,3- cyclohexanedione ), which merges with a concentrated solution of barium hydroxide while heating to 150-160 ° C in 4 - acetylbutyric acid (5- oxohexanoic acid, CAS 3128-06-1 ).

With bromine to 2,4,6- Tribromresorcin forms. If bromine is used in excess, the 2,4,6- Tribromresorcin reacts further to 2,4,4,6,6 - pentabromo -1 - cyclohexen- 3 ,5 -dione. By the addition of potassium iodide, this reaction can be reversed.

With acids and acid chlorides takes place in the presence of dehydrating agents acylation, as formed in the reaction with glacial acetic acid with zinc chloride as catalyst at 145 ° C resacetophenone.

With the anhydrides of dibasic acids are formed fluorescein, eg fluorescein from phthalic anhydride is produced:

Sodium nitrite is a water-soluble blue substance that turns red in acid addition forms. This substance is called Lacmoid or Resorcinblau and used as an indicator.

Resorcinol condenses with aldehydes, such forms with formaldehyde in the presence of hydrochloric acid as catalyst, the Methylendiresorcin. With chloral hydrate forms in the presence of potassium bisulfate as catalyst, the lactone of Tetraoxydiphenylmethancarbonsäure.

In alcoholic solution of resorcinol condenses with Natriumacetylacetat to methylumbelliferone.

Trinitroresorcine ( styphnic ) is formed on reaction with concentrated nitric acid and cold concentrated sulfuric acid. Styphnic and especially his lead salt are used as explosives.

By carboxylation with potassium 2,4-dihydroxybenzoic acid may be prepared in a Kolbe-Schmitt reaction.

With aldehydes can condense with resorcinol Brønsted acid catalysis to resorcinarenes.

Use

Resorcinol particularly triphenylmethane dyes ( fluorescein, eosin Y), and plastic is used for the preparation of dyes, ( phenolic resins ) was used. Main use of resorcinol and resorcinol is the adhesion between the fabric inserts or steel cord with the rubber compounds in the tire construction. Resorcinformaldehydharze (phenol - resorcinol -formaldehyde glue) are also widely used as adhesive for large wooden structures. Newer applications are flame retardants phosphoric ester base and fade-resistant, transparent polymers.

Pharmacological action

In higher concentrations of resorcinol is poisonous in dilute solutions it develops antiseptic effect and is therefore used in dermatology to cure eczema ointments or hair tonics, as well as a keratolytic agent with dermatoses of the scalp.