Borazine
| Names | |
|---|---|
| IUPAC name
1,3,5,2,4,6-Triazatriborinane
| |
| Other names
Borazole
Cyclotriborazaneborazol Inorganic benzene | |
| Properties | |
| B3H6N3 | |
| Molar mass | 80.50 g/mol |
| Appearance | Colorless liquid |
| Odor | Aromatic odor |
| Density | 0.81 g/cm3 |
| Melting point | −58 °C (−72 °F; 215 K) |
| Boiling point | 55 °C (131 °F; 328 K) (at 0.8 mmHg) |
| Reacts | |
| Solubility | Reacts with acids |
| Thermochemistry | |
| Std enthalpy of
formation (ΔfH |
−531 kJ/mol |
| Hazards | |
| Safety data sheet | Gelest |
| Flash point | <25 °C |
| Related compounds | |
| Related compounds
|
Benzene |
| Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
| Infobox references | |
Borazine or borazole, is a polar inorganic compound with the chemical formula B3H6N3. The compound is isoelectronic and isostructural with benzene (albeit the π structure of borazine is different from that of benzene), in that each C-H unit is replaced alternate B-H and N-H units, three each. For this reason borazine is sometimes referred to as “inorganic benzene”.
Although borazine may be described as a π aromatic compound, it is not a globally aromatic species, as the electronic system is not as delocalized as it is in benzene.
Contents
Properties
Chemical
Borazine will burn in an oxygen-rich atmosphere to form boric acid, boron nitride and nitrogen.[1]
Although often compared with benzene, borazine is far more reactive. Borazine will readily hydrolyze in water to form boric acid, ammonia and hydrogen.
- B3N3H6 + 9 H2O → 3 H3BO3 + 3 NH3 + 3 H2
With hydrogen chloride it forms an adduct, whereas benzene is unreactive toward HCl.
- B3N3H6 + 3 HCl → B3N3H9Cl3
Borazine can be further reduced with sodium borohydride:
- B3N3H9Cl3 + NaBH4 → (BH4N)3
Heating borazine at 70 °C expels hydrogen with formation of a borazinyl polymer or polyborazylene, in which the monomer units are coupled in a para fashion by new boron-nitrogen bonds.
Physical
Borazine is a colorless liquid with an aromatic smell. It reacts with water, but it's more soluble in other organic solvents, like dry ethers.
Availability
Borazine is hard to find as few chemical suppliers sell it. Since its precursors are somewhat pricey (except ammonia and its salts), the compound is hard get hold of.
Preparation
Borazine can be easily prepared from a reaction of diborane with ammonia, in a 1:2 molar ratio, at 250–300 °C. The yield of this reaction is 50%.[2]
- 3 B2H6 + 6 NH3 → 2 B3H6N3 + 12 H2
An alternative more efficient route that can be easily done in a lab involves reacting lithium borohydride and ammonium chloride:
- 3 LiBH4 + 3 NH4Cl → B3H6N3 + 3 LiCl + 9 H2
In a two-step process to borazine, boron trichloride is first converted to trichloroborazine:
- 3 BCl3 + 3 NH4Cl → Cl3B3H3N3 + 9 HCl
The B-Cl bonds are subsequently converted to B-H bonds by reducing the compound with sodium borohydride:
- 2 Cl3B3H3N3 + 6 NaBH4 → 2 B3H6N3 + 3 B2H6 + 6 NaCl
Projects
- Grow hexagonal boron nitride (h-BN) thin films and single layers
- Make boron carbonitride ceramics
- Compound collecting
Handling
Safety
Borazine rapidly hydrolyzes in contact with water. It is irritant to touch.
Storage
In air-tight containers.
Disposal
Can be safely neutralized by slowly adding it to cold water.
References
- ↑ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5287266/
- ↑ [Stock A, Pohland E (October 1926), "Borwasserstoffe, VIII, Zur Kenntnis des B2H6 und des B5H11" (Boric acid solution, VIII Regarding knowledge of B2H6 and B5H11), Berichte (in German), 59 (9): 2210–2215 https://chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/cber.19260590906]
