Benzotriazole

Beige solid

Fixed

1.36 g · cm -3

100 ° C.

350 ° C.

5.3 Pa ( 20 ° C)

8.37

Poorly in water (20 g · l -1)

Attention

• 560 mg · kg -1 ( LD50, rat, oral)
• > 1000 mg · kg -1 ( LD50, rat, transdermal)

Template: Infobox chemical / molecular formula search available

1H- benzotriazole is an organic chemical, which is used as a complexing agent. A compound structurally communicates with the 1H- benzotriazole in tautomeric equilibrium, the 2H- benzotriazole.

Properties

1H - benzotriazole is a white crystalline powder which melts after purification by repeated sublimation in a high vacuum at 100.5 ° C. The compound crystallizes in a monoclinic crystal lattice. The relevant at a sublimation vapor pressure in the temperature range between 53.4 ° C and 71.7 ° C is between 0.000695 and 0.0048 torr torr and, by means of the equation log ( P / Pa) = 5159.5 ( T / K ) are described -1 14.77. The enthalpy of sublimation at 25 ° C ΔsubH = 98.15 kJ / mol, 63.4 ° C ΔsubH = 96.30 kJ / mol.

The compound decomposes strongly exothermic above the melting point. A distillation of the compound is therefore not advisable. A source from 1956 tells of an explosive decomposition of a 1 t approach during distillation at 160 ° C and 2.5 mbar. In a thermoanalytical investigation showed from 240 ° C, a decomposition reaction with a very high heat of reaction of -1590 kJ / kg. Despite the high heat of decomposition, the compound is not explosive within the meaning of the Explosives Act, as neither 50/60 steel tube test was still observed in the Koenen test with 2 mm hole diameter a positive result in the BAM. The Koenen test with 1 mm hole diameter is positive.

A tautomeric equilibrium can be formulated between 1H - benzotriazole and 2H- benzotriazole. Experimental measurements and quantum chemical calculations show, however, that this balance is practically in the solid state and in solution on the side of the 1H - benzotriazole. This is the energetically more favorable tautomer. In the photoexcited triplet state, however, the 2H- tautomer is energetically favored and stable.

Benzotriazole has amphiprotic properties, so it can be protonated in acidic medium and can be deprotonated in a basic medium. The Protolysekonstanten be pKa1 = 0.42 pKa2 = 8.27 and.

Production and representation

It is prepared by ring-closing diazotization of o- phenylenediamine with nitrite and ( acetic ) acid.

Use

Benzotriazole is used as a corrosion inhibitor in cooling liquids, antifreeze, de-icing, and in descaling. In dishwashing detergents, it serves as silver protection. In industry it is used in cooling lubricants metalworking. In photographic developers, there is used to reduce haze in the film.

Environmental relevance

Benzotriazole is relatively water soluble and readily degradable. It is therefore eliminated in sewage treatment plants only to a small extent and reaches high levels in rivers and lakes.