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The laughter continues, nitrous oxide II

Welcome back, the post from yesterday made my mind start to work and it made me think about what is nitrous oxide. Being a chemist I did search the crystallography database to see if nitrous oxide had been examined in the solid state by diffraction. I was pleased to discover that someone had done neutron diffraction on the solid.[1] But due to something called disorder things are not as clear as they could be. The neutron crystallography suggests that the nitrous oxide molecule is an linear triatomic where the distance between the atoms is 1.175 Å. A crystal is made of a series of repeating bricks which are named unit cells, these unit cells are stacked up together to make the solid.

Disorder is when the atoms in different unit cells are either in different arrangements inside the cells or they might be a random mixture of different elements. For instance two metals can replace each other randomly in the unit cells of an alloy.

As I know that nitrous oxide is soluble in fats, I choose to look next in the Cambridge database where all crystal structures containing carbon are present. I was rewarded with a reference to a polymeric rhodium containing solid[2] which contains nitrous oxide. While one of the nitrous oxide molecules is disordered the other is not, so at last I get a good view of nitrous oxide in the solid state.

Now we have a N-N distance of 1.149 Å and a N-O distance of 1.175 Å which suggests that the molecule is not perfectly symmetric in terms of bond lengths. While many of my readers will have been educated using the SI system of meters, kilos and seconds in which the prefered units are mili, micro, nano and pico I will have to explain to you that my type of chemist does not like the picometer when it comes to the distance between atoms. We use the angstrom which is equal to 100 picometers. Also for energy when we are dealing with single molecules and atoms we like to use the electron volt. When expressing the energy of an atomic or nuclear event it is much more easy to use an electron volt. For instance the gamma photon energy of “cesium-137” is about 0.66 megaelectron volts.[3]

Before we take a close look at the nitrous oxide molecule we should think for a moment about the rhodium solid. This is a solid which has lots of very small holes in it. This can be thought of as an organic version of a zeolite or a microporous silica. The holes in the solid can be filled up with gas molecules. I have rendered pictures looking down the pores in the solid with and without the gas molecules to allow you to see the way the nitrous oxide is packed inside the solid.

Rhodium coordiantion polymer with nitrous oxide in the holes

Now without the nitrous oxide molecules.

Rhdium coordination polymer now without the nitrous oxide in the holes

Finally we will get to nitrous oxide, if you want to know why it is not bent like sulphur dioxide then I would suggest that you use VSEPR to consider the molecule. Now here is a picture of nitrous oxide.

I have not started eating the cream yet, so please wait. Good things will come to those who wait !

References

1. W.C. Hamilton and M. Petrie, Journal of Physical Chemistry, 1961, 65, 1453-1454.

2. S. Takamizawa, E. Nakata and T. Saito, Inorganic Chemical Communications, 2003, 6, 1415.

3. In real life cesium-137 does not emit gamma rays, the cesium-137 is a beta emitter which decays to an excited state of barium-137. The excited state of barium-137 will decay to the ground state with a half life of minutes with the emission of gamma photons.

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