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Henry Rzepa's Blog

Henry Rzepa's Blog
Chemistry with a twist
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At the ACS conference, I have attended many talks these last four days, but one made some “connections” which intrigued me. I tell its story (or a part of it) here. But to start, try the following experiment. Find a Word document of .docx type on your hard drive Remove the .docx suffix and replace it with a .zip suffix. Expand as if it is an archive (it is!). A folder is created and this itself contains four further folders.

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The upcoming ACS national meeting in San Diego has a CINF (chemical information division) session entitled "Global initiatives in research data management and discovery". I have highlighted here just one slide from my contribution to this session, which addresses the discovery aspect of the session. Data, if you think about it, is rarely discoverable other than by intimate association with a narrative or journal article.

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I attended the first (of a proposed five) workshops organised by LEARN (an EU-funded project that aims to .. .Raise awareness in research data management (RDM) issues & research policy ) on Friday. Here I give some quick bullet points relating to things that caught my attention and or interest. The program (and Twitter feed) can be found at https://learnrdm.wordpress.com where other's comments can also be seen.

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In May 2015, the EPSRC funding council in the UK required researchers to publish the outcomes of the funded work to include an OA (open access) version of the narrative and to cite the managed research data used to support the research with a DOI (digital object identifier). I was discussing these aspects with a senior manager (research outcomes) at the EPSRC and he asked me to provide some examples from my area of chemistry;

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This question was posted on the CCL (computational chemistry list) by John McKelvey. Here, I give an answer in the form of a search of the CSD (crystal structure database). I was not sure if the question related purely to the geometries obtained using computational methods or to comparisons with experimentally determined structures. Or indeed whether it related to azobenzene specifically or to azobenzenes in general.

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Previously, I explored deviation from ideal tetrahedral arrangements of four carbon ligands around a central (sp 3 ) carbon using crystal structures. Now it is the turn of digonal (sp 1 ) and trigonal (sp 2 ) carbons.  Firstly, the digonal C≡C case. Attached to each carbon of the C≡C unit are two saturated carbon ligands; this to prevent conjugation from influencing our result.

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An article entitled " Four Decades of the Chemistry of Planar Hypercoordinate Compounds "[cite]10.1002/anie.201410407[/cite] was recently reviewed by Steve Bacharach on his blog, where you can also see comments. Given the recent crystallographic themes here, I thought I might try a search of the CSD (Cambridge structure database) to see whether anything interesting might emerge for tetracoordinate carbon.

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The previous post explored the structural features of amides. Here I compare the analysis with that for the closely related thioamides. Here is the torsional analysis around the C-N bond. The “diff” (difference) is that almost all the hits are concentrated into angles of 0° or 180°; the twist about the C-N bond from co-planarity is much less if S is present.

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The π-resonance in amides famously helped Pauling to his proposal of a helical structure for proteins. Here I explore some geometric properties of amides related to the C-N bond and the torsions about it. The key aspect of amides is that a lone pair of electrons on the nitrogen can conjugate with the C=O carbonyl only if the lone pair orbital is parallel to the C-O π-system.

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The first conference devoted to scientific uses of Wikipedia has just finished; there was lots of fascinating stuff but here I concentrate on one report that I thought was especially interesting. To introduce it, I need first to introduce WikiData. This is part of the WikiMedia ecosystem, and one of the newest. The basic concept is really simple. It is a repository for data objects; 14,757,419 of them as I write this to be precise.