Crystal violet
- Hexamethylene -p- rosanilinchlorid
- Hexamethyl -p- rosaniliniumchlorid
- Gentian violet
- Methyl violet 10B
- Methylrosanilium
- Methylrosaniliumchlorid
- Methylrosanilin
- Blue Pyoktanin
- C. I. Basic Violet 3
- C. I. 42555
- (4 - (4,4 '-bis ( dimethylaminophenyl) benzhydryliden ) cyclohexa -2 ,5- dien-1- ylidene ) dimethyl
Green, odorless solid
Fixed
1.19 g · cm -3
189-194 ° C
10 g · l-1 in water at 20 ° C
Risk
Template: Infobox chemical / molecular formula search available
Crystal violet (after the botanical name of gentian also called gentian violet ) is a triphenylmethane dye violet.
Representation
Crystal violet is (4,4 '- bisdimethylamino -benzophenone ) with N, N-dimethylaniline obtained by the condensation of Michler's ketone in the presence of phosphoryl chloride. This is an electrophilic substitution of N, N -dimethylaniline in the para- position instead of the carbon of the carbonyl group of Michler's ketone. The phosphoryl serves as electron pair of the oxygen of the carbonyl group of the ketone. The carbon atom is thus positively charged and thus able to attack the aromatic electrophilic. From the resulting carbinol water is then eliminated.
Properties
Crystal violet is usually in the form of fine, metallic -gold shiny needles. It dissolves in water and other polar solvents with intense violet color and natural fibers dyed bright purple. However, it is relatively easy to wash. With iodine, it forms a charge-transfer complex.
Is added to a very dilute solution of crystal violet sodium hydroxide solution, then the solution fades slowly. Here, a hydroxide ion superimposed on the resulting in a mesomeric form in the center of the molecule carbenium ion. This reaction can be studied reaction kinetics using a photometer (see photometry). At a large difference in concentration (concentration of crystal violet is much smaller than the concentration of sodium hydroxide solution), a reaction first order (see kinetics (chemistry) ) progress.
Use
Crystal violet is used as a colorant in ink ribbons, as crystal violet lactone in carbonless papers or printing pins, and especially in the microscopic staining technique. Here it forms the main part of the so-called Gram stain, let that help divide bacteria into two classes.
Crystal violet is used as the pH indicator in the water-free assay of weak bases. Acidified to a solution of crystal violet light at a color change from violet to green occurs because the auxochrome the third core loses its electron-donating ability and thus its color Relevance by addition of a proton. A stronger acidification leads to a yellow compound, in which a further auxochrome is deactivated by protonation.
Medically crystal violet has been a long time, until the discovery of other effective antifungal agents, for the treatment of fungal skin infections (mycoses ), especially Fußpilzen, and use of oral thrush. There is painted as so-called Pyoktaninlösung ( 0.5-2 %). Today it is almost exclusively used in natural medicine because of the annoying coloration of the skin in the Western world. In the pediatric dermatology, it still finds use in herds of atopic Ekzemes when it is triggered by Gram-positive bacteria or dermatophytes. According to the WHO crystal violet, however, to be classified as an essential drug.
Intravenously it is used for the treatment of secondary Lungenmykosen. The fungistatic effect of crystal violet is, depending on Mykosenart, by a factor of 10-100 more than the now heavily used clotrimazole. Exceeded, it is second only to amphotericin B, which in comparison, however, is highly toxic. Therefore, crystal violet is often used in immuno-compromised patients.
Crystal violet can not enter the eye, as it can cause serious eye damage. Furthermore, when applied externally, an overdose is to be avoided as crystal violet, as well as the related and similar to that used triphenylmethane dyes malachite green and brilliant green, cell- toxic to the skin.