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Snippet chemistry fadtoids from my trips October 8, 2009

Posted by fetzthechemist in Uncategorized.
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It always seems funny that there are so many little facts in chemistry that can be important, yet are not common knowledge. I ran into a few on my trips to South Carolina and Nevada.

If you do sulfur speciation in petroleum samples, you will see a peak in many samples, m.w. of 256 and a sulfur detector shows it well. Other peaks dluster in a GC and have masses of192, 224, and 288. Answer to what they are? Elemental sulfur in its alleotropic rings form. Yes, the fluffy yellow powder is most S8, a nonpolar compounds (so it retains on most GC columns).

Water does not have a pH scale from zed to 14 except for one specific condition, standard temperature and pressure. Duh, you say? We are so programmed into 0 to 14 that we need to be reminded that water at any other temperature or under pressure has a smaller or larger scale. It’s in the equations for equilibrium.

NMR is not a structural answer all, nor is crystallography. Both require a fair amount of pure material, milligrams at least. One requires that you obtain nice crystals, which is not always easy. But the other requires a fair solubility in a deutero solvent. Also not always easy. Structure determination is an art within a science.

The non-retained peak in GC or LC is really very slightly retained and is only a close estimate for column volume. Even helium has interactions, small ones, but still there. A bigger, squishier diatomic like nitrogen has even more interactions with the column.

Carbon nanotubes are just fullerenes with more bands of encircled rings. Graphene is just a very, very large alternant polycyclic aromatic hydrocarbon. Being given the catchy name does not change the chemical structure. (and graphene has to be made from ultra-ultra high purity graphite or what behavior you see is from the dislocations of heteroatoms or nonplanarity from having rings other than six carbons).

More might follow in the comments if I think of them.

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Comments»

1. organikchemist - October 8, 2009

With modern NMRs, the need for deuterated solvent is dimishing. I used the “No-D” method on quite a few crude reactions and got great spectra. The key is a good set of starting shims. If you magnet drifts a little and you must have a lock, a sealed capillary of D6 Benzene (or whatever) placed in the NMR sample does a fine job of providing a lock signal .


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