Mini Project
Some suggestions
Fuels of the future
Hydrogen is going to be the fuel of the future, however ways of storing
hydrogen safely are still on the drawing board. Ideally you want to
store hydrogen in a solid matrix eliminating the need for high
pressures and improving safety. Ammonia borane (NH3BH3)
is being investigated because it has a high hydrogen content and is a
stable solid at room temperature. You can calculate the structure of
ammonia borane to explore this issue. Some questions you might want to
consider are:
- is ammonia borane staggered or eclipsed?
- what is the energy difference between these conformers?
- how does this energy difference compare to that of ethane?
- what can you say about the bonding in this compound relative to the organic analogue?
- what is the stability of ammonia-borane relative to the suggested reactants (NH4Cl and NaBH4), which form NH4BH4 and NaCl, then H2 is released. You should calculate E(reactants)-E(products)
- ammonia-borane
is isoelectronic with ethane. But whereas ethane has an extremely low
melting point, the former melts around 110°C. Can you find an
explanation? (Hint: is there a way of modelling the solid state of this
species? Are any of the techniques described in Module 3 relevant?)
- Reference:Borane leads the way to alternative fuels an article from Chemistry World (02 July 2008)
- Reference:Ammonia-borane: the hydrogen source par excellence? Dalton Trans., 2007, 2613 - 2626, DOI: 10.1039/b703053c