Thymol

THYMOL, Thymolum, methylisopropylphenol (1, 4, 3) (the incorrect name Acid, thymicum, should be avoided, as it denotes a product of nuclein decomposition, C₁₆H₂₅N₃P₂O₁₂), CH₃ O C₆H₃OH C₃H₇; molecular weight 150.11 (F VII); a phenol obtained from various essential oils, more rarely synthetically. Thymol consists of colorless, transparent, brittle crystals, specific gravity 1.028; melts at 50-51°, boils at 228-232° (molten thymol is lighter than water). Easily distills with steam; volatilizes at ordinary temperature. The odor of thymol is characteristic, pleasant; taste is spicy and burning. Sparingly soluble in water: in 100 g of water dissolves at 15° approx. 0.075, at 25° approx. 0.1; easily soluble in alcohol (1:1), ether (1:1.5), chloroform (1:0.7). Easily soluble in alkalis, forming corresponding thymolates, e.g., CH₃OC₆H₃ONa. Concentrated sulfuric acid gives thymol-sulfonic acids. With menthol, camphor, and many other substances, thymol forms eutectic mixtures, liquid at ordinary temperature. Iron chloride solution does not give coloring with thymol solution and causes cloudiness (dithymol, C₁₀H₁₄O₂ is obtained). When iodine acts on an alkaline solution of thymol, a precipitate of arietol is obtained (see). Thymol is obtained from various essential oils containing it, e.g., oil of thyme (20-50%), oil of ajowan (up to 60%), by converting it into water-soluble thymolate, separating from the hydrocarbon part, followed by precipitation with acid and recrystallization from alcohol. Store in dark, tightly closed vessels. Thymol has significance as an antiseptic and anthelmintic agent; at a concentration of 1:3,000 it inhibits the reproduction of staphylococci and streptococci, with prolonged exposure at a concentration of 1:1,500 it kills tubercle bacilli, and anthrax bacilli at a dilution of 1:4,000. The local action of thymol is weak. It has almost no effect on intact skin; on mucous membranes, with prolonged use, it causes exfoliation of the epithelium from the surface. When absorbed from the gastrointestinal tract, thymol produces poisoning phenomena, in general resembling other phenols; the paralyzing action of thymol on the central nervous system comes to the fore: it causes a feeling of depression, nausea, vomiting, dizziness, ringing in the ears, arrhythmia, fainting, and collapse. Sometimes kidney irritation is observed (albuminuria, hematuria). Death occurs with symptoms of paralysis of the heart in diastole. At autopsy, hyperemia of the intestines, lungs, and fatty degeneration of the liver are observed. Thymol is excreted from the body in the form of thymol-glucuronic acid and in the form of the sodium salt of thymol-sulfur ether. The urine is colored green. A considerable obstacle to the use of thymol as an antiseptic is its low solubility in water, irritating action on mucous membranes, and burning taste. As an anthelmintic, thymol is used mainly in the treatment of ankylostomiasis (see Ankylostoma), necatoriasis (see), and trichocephaliasis (see Trichocephalus); against other helminthiases, thymol is less effective. When prescribing thymol internally (in gelatin capsules or cachets), simultaneous prescription of substances that dissolve thymol (fats, alcoholic liquids, vinegar) and prescription on an empty stomach should be avoided. Dose 1.0-2.0 up to 4 times a day. The lethal dose of thymol varies; a case of death after taking 6.0 thymol is known. Thymol is used externally in aqueous solutions 1:1,000 in the treatment of wounds, antiseptic washings. In alcoholic solutions and ointments (1-5%) in the treatment of wounds and skin diseases. In a 2% alcoholic solution (50% alcohol) as a mosquito and midge repellent. Internally for increased fermentation processes in the gastrointestinal tract 0.05-0.1, preferably in emulsions. Against worms (see above) - according to some authors not more than 3.6 per day, according to others up to 10.0 (!) per day. Do not prescribe oil of castor! As a laxative during anthelmintic treatment, sodium sulfate or magnesium sulfate is best. Recently, it has been proposed for the treatment of angina (1% alcoholic solution) and for smearing (3%) hypertrophied tonsils. Thymol has special importance in dentistry as an antiseptic in conservative treatment and as a good preventive agent in pastes, tooth powders and mouthwashes (0.3-1%). Thymol is included in many patented foreign preparations for cleaning teeth (Euthymol). In forensic chemical analysis, thymol can be easily isolated by distillation with steam and recognized in the distillate by smell, and after isolation (shaking out with ether) by the following reactions: a) a solution of thymol in glacial acetic acid gives a blue-green coloration upon addition of 5 drops of concentrated sulfuric and 1 drop of nitric acid; in transmitted light the liquid has a red color; b) thymol triturated with KOH gives a violet coloration with chloroform; c) an aqueous solution of thymol, mixed with half its volume of sulfuric acid, takes on a red-violet coloration.