We tend to think of simple hydrocarbons as relatively inert and un-interesting molecules. However, a recent article, which was in fact highlighted by Steve Bachrach on his blog , asks what “The Last Globally Stable Extended Alkane” might be. In other words, at what stage does a straight-chain hydrocarbon fold back upon itself, and no significant population of the linear form remain? The answer was suggested to be C17H36. I thought I might subject this conformation to an NCI (non-covalent-interaction) analysis.
The colour coding for the NCI surface is such that towards blue is attractive, with green being mildly attractive and yellow mildly repulsive. Both blue and yellow can be seen at the point where the molecule bends round, and attractive green dominates the region where the two chains are parallel. Much in the manner of a Gekko’s feet, the strangely attractive van der Waals terms in a hydrocarbon are surprisingly cumulative! You can generate an NCI surface for your favourite molecule here.
Addendum: To show that NCI interactions are pretty additive, here is C28H58:
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- N.O.B. Lüttschwager, T.N. Wassermann, R.A. Mata, and M.A. Suhm, "The Last Globally Stable Extended Alkane", Angew. Chem. Int. Ed., vol. 52, pp. 463-466, 2012. http://dx.doi.org/10.1002/anie.201202894
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