Archive for the ‘Interesting chemistry’ Category

Forming a stabilized m-benzyne.

Friday, January 20th, 2017
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The story so far. Inspired by the report of the most polar neutral compound yet made, I suggested some candidates based on the azulene ring system that if made might be even more polar. This then led to considering a smaller π-analogue of azulene, m-benzyne. Here I ponder how a derivative of this molecule might be made, using computational profiling as one reality check.

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Braiding a molecular knot with eight crossings.

Friday, January 20th, 2017
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This is one of those posts of a molecule whose very structure is interesting enough to merit a picture and a 3D model. The study[1] reports a molecular knot with the remarkable number of eight crossings.

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References

  1. J.J. Danon, A. Krüger, D.A. Leigh, J. Lemonnier, A.J. Stephens, I.J. Vitorica-Yrezabal, and S.L. Woltering, "Braiding a molecular knot with eight crossings", Science, vol. 355, pp. 159-162, 2017. http://dx.doi.org/10.1126/science.aal1619

Ritonavir: a look at a famous example of conformational polymorphism.

Monday, January 2nd, 2017
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Here is an inside peek at another one of Derek Lowe’s 250 milestones in chemistry, the polymorphism of Ritonavir.[1] The story in a nutshell concerns one of a pharma company’s worst nightmares; a drug which has been successfully brought to market unexpectedly “changes” after a few years on market to a less effective form (or to use the drug term, formulation). This can happen via a phenomenon known as polymorphism, where the crystalline structure of a molecule can have more than one form. In this case, form I was formulated into soluble tablets for oral intake. During later manufacturing, a new less-soluble form appeared and “within weeks this new polymorph began to appear throughout both the bulk drug and formulation areas[1]

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References

  1. J. Bauer, S. Spanton, R. Henry, J. Quick, W. Dziki, W. Porter, and J. Morris, "", Pharmaceutical Research, vol. 18, pp. 859-866, 2001. http://dx.doi.org/10.1023/A:1011052932607

The dipole moments of highly polar molecules: glycine zwitterion.

Saturday, December 24th, 2016
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The previous posts produced discussion about the dipole moments of highly polar molecules. Here to produce some reference points for further discussion I look at the dipole moment of glycine, the classic zwitterion (an internal ion-pair).

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Forking “The most polar neutral compound synthesized” into m-benzyne.

Wednesday, December 21st, 2016
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A project fork is defined (in computing) as creating a distinct and separate strand from an existing (coding) project. Here I apply the principle to the polar azulene 4 explored in an earlier post, taking m-benzyne as a lower homologue of azulene as my starting point.

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Molecules of the year? Pnictogen chains and 16 coordinate Cs.

Monday, December 19th, 2016
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I am completing my survey of the vote for molecule of the year candidates, which this year seems focused on chemical records of one type or another.

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Molecules of the year? The most polar neutral compound synthesized…

Sunday, December 18th, 2016
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This, the fourth candidate provided by C&EN for a vote for the molecule of the year as discussed here, lays claim to the World’s most polar neutral molecule (system 1 shown below).[1] Here I explore a strategy for extending that record.

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References

  1. J. Wudarczyk, G. Papamokos, V. Margaritis, D. Schollmeyer, F. Hinkel, M. Baumgarten, G. Floudas, and K. Müllen, "Hexasubstituted Benzenes with Ultrastrong Dipole Moments", Angewandte Chemie International Edition, vol. 55, pp. 3220-3223, 2016. http://dx.doi.org/10.1002/anie.201508249

Molecule of the year? “CrN123”, a molecule with three different types of Cr-N bond.

Friday, December 16th, 2016
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Here is a third candidate for the C&EN “molecule of the year” vote. This one was shortlisted because it is the first example of a metal-nitrogen complex exhibiting single, double and triple bonds from different nitrogens to the same metal[1] (XUZLUB has a 3D display available at DOI: 10.5517/CC1JYY6M). Since no calculation of its molecular properties was reported, I annotate some here.

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References

  1. E.P. Beaumier, B.S. Billow, A.K. Singh, S.M. Biros, and A.L. Odom, "A complex with nitrogen single, double, and triple bonds to the same chromium atom: synthesis, structure, and reactivity", Chem. Sci., vol. 7, pp. 2532-2536, 2016. http://dx.doi.org/10.1039/c5sc04608d

Molecule of the year (month/week)?

Monday, December 12th, 2016
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Chemical and engineering news (C&EN) is asking people to vote for their molecule of the year from six highlighted candidates. This reminded me of the history of internet-based “molecules of the moment“. It is thought that the concept originated in December 1995 here at Imperial and in January 1996 at Bristol University by Paul May and we were joined by Karl Harrison at Oxford shortly thereafter. Quite a few more such sites followed this concept, differentiated by their time intervals of weeks, months or years. The genre is well suited for internet display because of plugins or “helpers” such as Rasmol, Chime, Jmol and now JSmol which allow the three dimensions of molecular structures to be explored by the reader. Here I discuss a second candidate from the C&EN list; a ferrocene-based Ferris wheel[1],[2] (DOI for 3D model: 10.5517/CCDC.CSD.CC1JPKYQ) originating from research carried out at Imperial by Tim Albrecht, Nick Long and colleagues.

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References

  1. M.S. Inkpen, S. Scheerer, M. Linseis, A.J.P. White, R.F. Winter, T. Albrecht, and N.J. Long, "Oligomeric ferrocene rings", Nature Chemistry, vol. 8, pp. 825-830, 2016. http://dx.doi.org/10.1038/nchem.2553

Long C=C bonds.

Thursday, December 1st, 2016
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Following on from a search for long C-C bonds, here is the same repeated for C=C double bonds.

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