Question

preparation, properties, structure and uses of Borazine

Answer 1

Borazine is an inorganic compound with the chemical formula (BH)₃(NH)₃. It is a cyclic compound with alternating three BH units and three NH units.

Properties - The compound is isoelectronic and isostructural with benzene. It is a colorless liquid. It is a colorless liquid with an aromatic smell. In water, it hydrolyzes to boric acid, ammonia, and hydrogen. It is thermally very stable with a standard enthalpy change of formation ΔHf of −531 kJ/mol.

Structure - Borazine is isoelectronic with benzene and has similar connectivity, so it is sometimes referred to as "inorganic benzene". X-ray crystallographic structural determinations show that the bond lengths within the borazine ring are all equivalent at 1.429 Å, a property shared by benzene. However, the borazine ring does not form a perfect hexagon. The bond angle is 117.1° at the boron atoms and 122.9° at the nitrogens, giving the molecule distinct symmetry. The electronegativity of boron (2.04 on the Pauling scale) compared to that of nitrogen (3.04) and also the electron deficiency on the boron atom and the lone pair on nitrogen favor alternative mesomer structures for borazine.

Preparation - There are many methods to synthesize Borazine. One main method is that it is synthesized from diborane and ammonia in a 1:2 ratio at 250–300°C with a conversion of 50%.

3B₂H₆ + 6 NH₃ → 2B₃H₆N₃ + 12H₂

Uses - Borazines are also starting materials for other potential ceramics such as boron carbonitrides. Borazine can also be used as a precursor to growing boron nitride thin films on surfaces, such as the nanomesh structure which is formed on rhodium.