Benzotriazole
Encyclopedia
Benzotriazole is a heterocyclic compound
containing three nitrogen atoms, with the chemical formula C6H5N3. This aromatic compound is colorless and polar and can be used in various fields.
Various structural analyses with UV, IR and 1H-NMR spectra indicated that isomer A is predominantly present at room temperature. The bond between positions 1 and 2 and the one between positions 2 and 3 have proved to have the same bond properties. Hence, a more accurate representation of the BTA would involve its resonance structure:
As depicted in the figure above, the proton does not tightly bind to any of the nitrogen atoms, but rather migrates rapidly between positions 1 and 3. Therefore, the BTA can lose a proton to act as a weak acid (pKa = 8.2) or accept a proton using the lone pair electrons located on its nitrogen atoms as a very weak Bronsted base (pKa < 0). Not only it can act either as an acid or base, can it also bind to other species, utilizing the lone pair electrons. Applying this property, the BTA can form a stable coordination compound on a copper surface and behave as a corrosion inhibitor.
, sodium nitrite
and acetic acid
. The conversion proceeds via diazotization of one of the amine groups.
The synthesis can be improved when the reaction is carried out at low temperatures (5 - 10˚C) and briefly irradiated in an ultrasonic bath.
and a substantial fraction reaches surface water such as rivers and lakes.
Heterocyclic compound
A heterocyclic compound is a cyclic compound which has atoms of at least two different elements as members of its ring. The counterparts of heterocyclic compounds are homocyclic compounds, the rings of which are made of a single element....
containing three nitrogen atoms, with the chemical formula C6H5N3. This aromatic compound is colorless and polar and can be used in various fields.
Structure
Benzotriazole features two fused rings and its five-membered ring can exist in one of the following tautomers:Various structural analyses with UV, IR and 1H-NMR spectra indicated that isomer A is predominantly present at room temperature. The bond between positions 1 and 2 and the one between positions 2 and 3 have proved to have the same bond properties. Hence, a more accurate representation of the BTA would involve its resonance structure:
As depicted in the figure above, the proton does not tightly bind to any of the nitrogen atoms, but rather migrates rapidly between positions 1 and 3. Therefore, the BTA can lose a proton to act as a weak acid (pKa = 8.2) or accept a proton using the lone pair electrons located on its nitrogen atoms as a very weak Bronsted base (pKa < 0). Not only it can act either as an acid or base, can it also bind to other species, utilizing the lone pair electrons. Applying this property, the BTA can form a stable coordination compound on a copper surface and behave as a corrosion inhibitor.
Synthesis
A synthesis of the BTA invovles the reaction of o-phenylenediamineO-Phenylenediamine
o-Phenylenediamine is a organic compound with the formula C6H42. This aromatic diamine is an important precursor to many heterocyclic compounds...
, sodium nitrite
Sodium nitrite
Sodium nitrite is the inorganic compound with the chemical formula NaNO2. It is a white to slight yellowish crystalline powder that is very soluble in water and is hygroscopic...
and acetic acid
Acetic acid
Acetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...
. The conversion proceeds via diazotization of one of the amine groups.
The synthesis can be improved when the reaction is carried out at low temperatures (5 - 10˚C) and briefly irradiated in an ultrasonic bath.
Aplications
Benzotriazole has been known for its great versatility. It has already been used as a restrainer in photographic emulsions and as a reagent for the analytical determination of silver. More importantly, it has been extensively used as a corrosion inhibitor in the atmosphere and underwater. Also, its derivatives and their effectiveness as drug precursors have been drawing attention. Besides all the application mentioned above, the BTA can be used as antifreezes, heating and cooling systems, hydraulic fluids and vapor phase inhibitors as well.Corrosion Inhibitor
Benzotriazole is an effective corrosion inhibitor for copper and its alloys by preventing undesirable surface reactions. It is known that a passive layer, consisting of a complex between copper and benzotriazole, is formed when copper is immersed in a solution containing benzotriazole. The passive layer is insoluble in aqueous and many organic solutions. There is a positive correlation between the thickness of the passive layer and the efficiency of preventing corrosion. The exact structure of the copper-BTA complex is controversial and many proposals have been suggested.Drug precursor
Benzotriazole derivatives have chemical and biological properties that are versatile in the pharmaceutical industry. Benzotriazole derivatives act as agonists for many proteins. For instance, vorozole and alizapride have the inhibitory properties against different proteins and benzotriazole esters have been reported to work as mechanism-based inactivators for severe acute respiratory syndrome (SARS) 3CL protease. The methodology is not only limited to heterocyclization but was also successful for polynuclear hydrocarbons of small carbocyclic systems.Environmental relevance
Benzotriazole is fairly water-soluble, not readily degradable and has a limited sorption tendency. Hence, it is only partly removed in wastewater treatment plantsSewage treatment
Sewage treatment, or domestic wastewater treatment, is the process of removing contaminants from wastewater and household sewage, both runoff and domestic. It includes physical, chemical, and biological processes to remove physical, chemical and biological contaminants...
and a substantial fraction reaches surface water such as rivers and lakes.