Molecules: You'd better learn to live with them.
Carbon, with its four valence electrons, is in a unique position; its valence shells are exactly half filled. Compounds of elements with three valence electrons (such as boron) and elements with five valence electrons (such as nitrogen) can act very much like their carbon analogues. Boron nitride, ("BN") for example, can exist in a very hard form, much like diamond. Similarly, many semiconductors are based on combinations of groups III and V. Gallium aluminum arsenide, indium nitride, and aluminum arsenide, for example.
In a few cases, alternating boron-nitrogen compounds can act much like carbon. "Borazine" is the boron-nitrogen analogue of benzene.
Comments
What does it do?
Posted by: Lab Lemming | April 20, 2007 3:52 AM
borazine only looks like benzene, it isn't aromatic as the bond lengths are too long and there are not that much in the way of ring currents. because of the charge difference between nitrogen and boron, the electron cloud doesn't spread its self out in a doughnut pattern like benzene does.
Posted by: mike | April 20, 2007 9:14 PM
Do we have a proton NMR of borazine? Do we see spectroscopic evidence of aromaticity as deshielding?
Posted by: Uncle Al | April 21, 2007 10:59 AM
Borazine is considered aromatic, but less so than benzene. There's less symmetry, surely, and the electronegativity difference between boron and nitrogen is significant, and electron localization is considerable. Nevertheless, it is interesting because it and other heteroaromatics can be used to determine an aromaticity scale. I had an inorganic prof in grad school who had a boron fetish...
I have heard that borazine and derivatives might be useful precursors for boron nitride and boron carbonitride ceramics, but I haven't paid any attention to that literature since, well, inorganic chemistry class with Dr. Boronski.
Posted by: Dave Eaton | April 23, 2007 11:08 AM