Komodo9's comments

I don't know the statistics overall, but in my case the comparison of the inguinal hernia repair is even more damning: I'm positive it was more costly, but to add insult to injury, it (my hernia repair) was done as an outpatient procedure.

Although I am not a doctor (just a patient), if anyone tries to pitch you this as a good idea, run. The effective recovery time was insane, and not to mention the pain/temporary disability (also insane). An inpatient stay wasn't even offered, but in hindsight it shouldn't have even been optional.

By contrast, an unrelated abdominal surgery a few years later, despite being a much more involved procedure, had a much faster recovery. (10 day inpatient stay + probably 5 days of that with some physical therapy.)

Health care costs are a secondary issue to me, right behind health care quality. Unfortunately, I don't think either can be fixed unless they are entirely divorced from each other.

True. Even having a decent grasp on the topic (or perhaps, because having a decent grasp), I find it difficult to try to peel apart bond energy, electron density, bond length, etc, from each other; They're all effectively functions of each other and the entire system.

>Rings with fewer than 6 members are uncommon in chemistry

In chemistry, or in nature? five membered rings show up all over the place, both aromatic and otherwise. Granted, cyclobutyl (4 member, square) and cyclopropyl (3 membered, triangle) suffer from ring strain and are uncommon, but 5, 6, 7, (or higher) rings show up all over the place.

Examples off the top of my head are the cyclopentadienyl ion pervasive in inorganic chemistry (see ferrocene, et al) and amino acids tryptophan, tyrosine, histidine, and phynylalanine all feature cyclic aromatics 5 and 6 membered, as well as proline with a non-aromatic 5 member ring.

The takeaway point is that although ring-strain (having non ideal angles (120 or 109.5 degrees)) increases the internal energy of the molecule (destabilizing it), other factors, such as aromaticity, which decrease internal energy (stabilizing it) may balance or exceed the ring-strain, still giving a stabilized, if non-ideal geometry.

(But yeah, 3, 4 membered rings, ugh. Look up platonic alkanes for some really crazy strain angles.)

To answer your question (flat vs. artifact) directly: It's flat. Sorta. Bear with me a moment. If this is confusing, please let me know, and i'll try to clarify. Molecular symmetry isn't my strong point, unfortunately.

The trouble with all of this is the "picture" is not an actual picture-made-with-photons picture, but a visualization via computer. That isn't to say it's a poor reflection on reality, but that the limitations of the techniques should be accounted for. In this case, the electron density of the overall molecule is being measured. The brighter signals correspond to an increase in local electron density.

In such chemical structures as these, the aromaticity [1] is the main force at play. Without getting too technical, the brighter regions are those with increased electron density. (See figure 4 at the IBM Zurich page on pentacene [2])

The hexagons (and square and pentagons) in fact do not have idealized geometry, but not due to any curling. The unique environment of each carbon is more at play. Symmetry plays a large role; imagine a symmetric vs. unsymmetrical tug-of-war between the carbons with the electrons as the rope. The left hand side and lower right have a dihedral mirror plane, simplifying the density somewhat, where the upper right has a more muddled situation.

Getting back to the flatness, the target molecule is 'mounted' on a suitably uniform surface, such that only one side is being scanned/read by the probe. In a vacuum, the tug of war in the Z direction (into the plane) will cancel out between the +Z and -Z vectors, giving a 'flat' molecule. (Depending on your point of view, either because of this or due to this, each of these molecules has a mirror plane in the plane of the molecule, bisecting each atom.)

Setting all that aside, the entire process is really #$%*& cool, particularly to a chemist. (Yes, those crazy textbook pictures are often reflected in reality. If only the different atoms were color coded, though!)

[1] http://en.wikipedia.org/wiki/Aromaticity [2] http://www.zurich.ibm.com/st/atomic_manipulation/pentacene.h...