Borazine

• Cyclotriborazan
• Borazole

Clear, colorless liquid with an aromatic odor

Liquid

0.83 g · cm -3

-58 ° C

55.0 ° C

Decomposition in water

-541.0 KJ / mol

Template: Infobox chemical / molecular formula search available

Borazine ( Cyclotriborazan ) is a cyclic compound of boron, nitrogen and hydrogen, with the empirical formula B3H6N3. The nitrogen contributes with its free electron pair to the fact that this compound has a formal similarity to benzene, although they do not meet the criteria of aromaticity. As suggested by Nils Wiberg the base of these compounds is also referred to as " inorganic benzene ". It also systematically invalid name borazole derived.

The term borazine / borazines has also awarded based on the structurally related alkynes group of substances iminoboranes.

History

Borazine was first prepared by Alfred Stock at the beginning of the 20th century. He won it by heating diborane and ammonia.

Production and representation

Borazine can be prepared by heating a mixture of diborane and ammonia in a molar ratio of 1:2 to produce 250 to 300 ° C. The yield of this reaction is 50%:

Alternatively, the starting materials and lithium chloride and ammonium chloride can be used, which leads to a higher yield:

May also be used instead of lithium borohydride, sodium borohydride:

Another Borazinsynthese is the following two-step:

The synthesized borazine is then concentrated by distillation.

Properties

In water, borazine decomposes to boric acid, ammonia and hydrogen. Borazine ( enthalpy of formation ΔHf = -531 kJ / mol ) is thermally very stable.

Structure

Borazine is isosteric to benzene. That is, the bindings and binding ratios are consistent with the benzene match or are very similar. The C- C bond in the benzene is 139.7 pm. The bond length between boron and nitrogen is 143.6 pm in borazine. He is expected to be between the value for a BN single bond (151 pm ), as found in boron nitride, and for B = N double bond (131 pm ).

Mesomerism

The electronegativity difference between boron (2.04 Pauling scale) and nitrogen (3.04 ) and the electron deficiency at the boron atom and the lone pair at the nitrogen favor the formation of borazine mesomeric structure. Boron in this case plays the role of a Lewis acid, the Lewis base nitrogen.

Reactions

Due to the difference in the atoms, and thus the polarity of the B -N bond borazine is chemically much more reactive than benzene. So borazine reacts readily with polar compounds such as hydrogen chloride, water, and methanol. Hydrogen chloride reacts in an addition reaction with borazine. Benzene, this reaction would not take place. The reaction with bromine does not require a catalyst.

Use

Borazine and its derivatives are of interest as potential precursors of products on the way to boron nitride ceramics. Mixed amino -nitro substituted borazines promise according to recent calculations significantly higher detonation velocity, detonation pressure and Gurney energy than conventional explosives such as CL 20th

Swell

• Boron compound
• Nitrogen compound