Posts Tagged ‘Peter Murray-Rust’

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Data-round-tripping: moving chemical data around.

Saturday, November 20th, 2010

For those of us who were around in 1985, an important chemical IT innovation occurred. We could acquire a computer which could be used to draw chemical structures in one application, and via a mysterious and mostly invisible entity called the clipboard, paste it into a word processor (it was called a Macintosh). Perchance even print the result on a laserprinter. Most students of the present age have no idea what we used to do before this innovation! Perhaps not in 1985, but at some stage shortly thereafter, and in effect without most people noticing, the return journey also started working, the so-called round trip. It seemed natural that a chemical structure diagram subjected to this treatment could still be chemically edited, and that it could make the round trip repeatedly. Little did we realise how fragile this round trip might be. Years later, the computer and its clipboard, the chemistry software, and the word processor had all moved on many generations (it is important to flag that three different vendors were involved, all using proprietary formats to weave their magic). And (on a Mac at least) the round-tripping no longer worked. Upon its return to (Chemdraw in this instance), it had been rendered inert, un-editable, and devoid of semantic meaning unless a human intervened. By the way, this process of data-loss is easily demonstrated even on this blog. The chemical diagrams you see here are similarly devoid of data, being merely bit-mapped JPG images. Which is why, on many of these posts, I put in the caption Click for 3D, which gives you access to the chemical data proper (in CML or other formats). And I throw in a digital repository identifier for good measure should you want a full dataset.

It is only now that we (more specifically, this user) understand what had happened under-the-hood to break this round-tripping. In 1984, when Apple produced the Mac, they also produced a most interesting data format called PICT. A human saw the PICT as a PICTure, but the computer saw more. It (could) see additional data embedded in the PICT. The clipboard supported the PICT format, which meant that both picture and data could be transferred between programs. And ChemDraw and Word also understood this. Hence the ability to round-trip noted above (it has to be said between specifically these programs).

Times moved on and the limitations of PICT set in. Apple refocussed on the PDF format. Related, notice, to the Postscript format that Adobe had introduced in order to allow high quality laserprinting. PICT support was abandoned, and the various components no longer carried recognisable data (specifically the clipboard or the ability of Word to recognise the data). Round-tripping broke. Does this matter? Well, one colleague where I work had accumulated more than 1000 chemical diagrams, which he decided to store in Powerpoint (and yes, he threw the original Chemdraw files away). The day came when he wanted to round trip one of them. And of course he could not. He was rather upset I have to say!

PDF was not really a format designed to carry data (see DOI: 10.1021/ci9003688). But, bless their hearts, the three vendors involved in this story all agreed to support data embedded in the PDF hamburger (and Abobe to tolerate it) and now once again, a structure diagram can move into an Office program (on Mac) and out again and retain its chemical integrity. What lessons can be learnt?

  1. Firstly, out of side, out of mind. The clipboard is truly mostly out of sight, and it was not really designed from the outset to preserve data properly. Nowadays I wonder whether clipboards in general recognise XML (and hence CML) and preserve it. I truly do not know. But they should.
  2. Secondly, any system which relies on three or four commercial vendors, who at least in the past, devised proprietary formats which they could change without warning, is bound to be fragile.
  3. We have learnt that data is valuable. More so than the representation of it (i.e. a 2D or 3D structure diagram). But when its lost, the users should care! And tell the vendors.
  4. Peter Murray-Rust and his team have produced CML4Word (or as Microsoft call it, Chemistry add-in for Word). At its heart is data integrity. Fantastic! But I wonder if it survives on Microsoft’s clipboard (I know it does not on Apple’s, since CML4Word is not available on that OS. And is unlikely to ever become so).
  5. And I can see history about to repeat itself. The same seems about to happen on new devices such as the Apple iPad. It too has copy/paste via a clipboard. I bet this will not round trip chemistry (or much other) data! Want to bet that the lessons of this story have not yet been learnt?

Oh, for those who wish to round-trip chemistry on a Mac, you will have to acquire ChemDraw 12.0.2 and Word 2011 (version 14.01), as well as OS X 10.6 for it to work.

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Posted in Chemical IT | 5 Comments »

Semantically rich molecules

Sunday, May 2nd, 2010

Peter Murray-Rust in his blog asks for examples of the Scientific Semantic Web, a topic we have both been banging on about for ten years or more (DOI: 10.1021/ci000406v). What we are seeking of course is an example of how scientific connections have been made using inference logic from semantically rich statements to be found on the Web (ideally connections that might not have previously been spotted by humans, and lie overlooked and unloved in the scientific literature). Its a tough cookie, and I look forward to the examples that Peter identifies. Meanwhile, I thought I might share here a semantically rich molecule. OK, I identified this as such not by using the Web, but as someone who is in the process of delivering an undergraduate lecture course on the topic of conformational analysis. This course takes the form of presenting a set of rules or principles which relate to the conformations of molecules, and which themselves derive from quantum mechanics, and then illustrating them with selected annotated examples. To do this, a great many semantic connections have to be made, and in the current state of play, only a human can really hope to make most of these. We really look to the semantic web as it currently is to perhaps spot a few connections that might have been overlooked in this process. So, below is a molecule, and I have made a few semantic connections for it (but have not actually fully formalised them in this blog; that is a different topic I might return to at some time). I feel in my bones that more connections could be made, and offer the molecule here as the fuse!

Two chair conformations of the molecule DULSAE. Click here for 3D. Note the (attractive) short H...H contacts.

To list all the likely semantics that a chemist would perceive in the graphic above would take far too long (by the time one would have finished, a text book would have been written). So here is a very very short summary in the context of conformational analysis.

  1. The molecule has a six membered ring as its backbone
  2. which can adopt two possible chair conformations
  3. which can interconvert by exchanging the axial and equatorial group pair for each of the four carbon atoms in the ring.
  4. An organic chemist will immediately notice a very unusual group, Fe(CO)2Cp, which itself is a semantic goldmine,
  5. but for the purposes here we will regard merely as a C-Fe bond!

The (semantic) question to be posed is “which of the two conformations shown above is the most stable“? That too of course has an abundance of implicit semantics, but most human chemists will probably know that this refers to asking which of the two geometries represents the lowest thermodynamic free energy (and we leave aside the issue of what medium the molecule is in, i.e. solid, solution or gas). A far trickier question is “why”?

So to (some interim) answers. Well, a ωB97XD/6-311G(d) calculation (wow, think of what is implied in that concise notation) predicts conformation (a) to be more stable by 2.3 kcal/mol (2.1 in ΔG, see DOI: 10042/to-4911). Now to the why. What connections would someone well versed in conformation analysis spot?

  1. The molecule has two methyl groups on adjacent atoms. They may prefer to be di-axial rather than di-equatorial to avoid excessive steric repulsions (whatever we mean by that!). That might prefer (b).
  2. The molecule has one carbon with both a cyano and an ether linkage. Well, that is susceptible to an anomeric effect (although, as I pointed out in an earlier post here, this connection has in fact often NOT been made in the literature). Only in conformation (a) is one of the oxygen lone pairs aligned anti-periplanar to the axis of the C-CN bond. The reasons why this is important are outlined in my Lecture course.
  3. Having spotted the last, the human might ask whether there is any possibility of an anomeric effect between an oxygen lone pair and the axis of the C-Fe bond? Well, I rather think that not a single human ever has asked that question! (I cannot know that of course, and perhaps someone has speculated upon this in the literature; this is where a full semantic web would help. That question could be posed of it! The reason  I suspect the connection might not have been made is that the anomeric effect is the domain of the organic chemistry, and  C-Fe bonds are those of the organometallic chemist. They do tend to see the chemical world rather differently, these two groups of chemists). If there was such an effect, it would favour (a).
  4. Then we have an X-C-C-Y motif. Depending on the nature of X and Y, the molecule might actually prefer a gauche conformation, i.e the dihedral angle XCCY would be around 60°. There are several such motifs one can detect; X=Y=O (twice). It might be that other permutations such as X=CN, Y=Fe(CO)2Cp, favour anti-periplanar. There are other permutations whose orientational preference may not even be recorded (in text books). Suddenly its gotten complicated!
  5. There are a number of short (~2.4Å) H…H contacts
  6. We are starting to understand that to unravel the conformation of this molecule, one may have to identify quite a number of different “rules”, and then to quantify each, and add up the numbers to get the final result. That energy of 2.3 kcal/mol may be composed of the result of applying quite a number of different rules. Hence the title of this post, a semantically rich molecule!

Well, I will leave it here for this post, without giving answers to the six points listed above, or really answering my main question posed above. That would make the post too complex (but I will follow this up!). I do want to end by planting the idea that answering this question involves making a great many chemical connections about the properties of this molecule, and then identifying quantitative ways (algorithms) in which an answer can be formulated. The molecule above is presented as a challenge for the Semantic Web to address!

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Posted in Chemical IT, General, Interesting chemistry | 2 Comments »

(Hyper)activating the chemistry journal.

Monday, September 7th, 2009

The science journal is generally acknowledged as first appearing around 1665 with the Philosophical Transactions of the Royal Society in London and (simultaneously) the French Academy of Sciences in Paris. By the turn of the millennium, around 10,000 science and medical journals were estimated to exist. By then, the Web had been around for a decade, and most journals had responded to this new medium by re-inventing themselves for it. For most part, they adopted a format which emulated paper (Acrobat), with a few embellishments (such as making the text fully searchable) and then used the Web to deliver this new reformulation of the journal. Otherwise, Robert Hooke would have easily recognized the medium he helped found in the 17th century.

In 1994, a small group of us thought that one could, and indeed should go further than emulated paper. We argued [1] that journals should be activated by delivering not merely the logic of a scientific argument, but also the data on which it might have been based. Of course, we encountered the usual problem; doing this might cost publishers more in production resources, and in the absence of a market prepared to pay the extra, the business model did not make sense (to the publishers). Well, 15 years later, and most publishers are indeed now thinking about how their journals can be enhanced. A number of interesting projects (the RSC’s Project Prospect is one which strives to bring science alive) have emerged. Another is the topic of this blog; the activation of the journal with molecular coordinates and data using the Jmol applet.

Initially (~2005), this project met with resistance from publishers, and the issue really amounted to what the definitive version of a scientific article should be. Should that definitive version be printable? That model, after all had served the community well for more than 300 years! And journals from the very beginning are still as readable now as when first published. In other words, print lasts! But print is pretty limiting after all. For a start, it is limited to 2D static representations. Molecules, by and large, do their magic in a dynamic three dimensions (4D in an Einsteinian sense). But print is also expensive; not merely to produce, but to transport paper around the world.

From the turn of the millennium, a number of publishers, amongst them the American Chemical Society, started to evolve the scientific article such that the pre-eminent version would now be considered to be the HTML form (perhaps as a prelude to phasing out print entirely? See an interesting commentary by a journal editor) and perhaps a digital Acrobat form which would be deemed to loose some of its functionality once printed (again see here for how Acrobat can be used to enhance things). Again however, a chicken-and-egg scenario resulted. To enhance the articles with extra functionality (such as data), they would need to find authors prepared to put the extra work into preparing the material. In fact, most authors already do that, but they call it supporting information. This is often highly data rich, covering materials such as spectra, coordinates and other information nowadays provided to researchers for analysis. Unfortunately, what has been missing is the education of authors to provide this information in a proper digital form which can be easily re-used by others, and on a Web page, converted automatically to nice interactive models. Most spectra which form part of the supporting information are in fact still scanned versions of printed spectra!

Enter computational chemists. Nowadays, they live in a world that truly does not need printing! Almost all of their data is already suitably digital. So perhaps it is no surprise to find that when enhanced journal articles started appearing around 2005, many were produced by this group of chemists. By now perhaps you are wondering what such an article might look like. Well, the remainder of this blog will be devoted to listing some examples. You will also notice that they come exclusively from our own publications. Perhaps someone will find the time to collect a far more representative set to better illustrate the diversity of this form, and how it is evolving. Meanwhile, you might wish to take a look at the following.

Part 1: The early days: 1994 onwards

These examples all relied on a browser plugin called Chime, which is no longer with us! Hence the pages designed to invoke it no longer display properly. But the data associated with the articles is still there!

  1. An early 1994 example of (hyper)activating a journal article can be seen here as the preliminary communication and
  2. in 1995 here as the final full article. I am told that this was the article that actually inspired the developers of Chime to enhance (Netscape) with a chemical plugin.
  3. This one from 1998 illustrates how articles can decay in functionality when Chime is no longer available.
  4. An ab initio and MNDO-d SCF-MO Computational Study of Stereoelectronic Control in Extrusion Reactions of R2I-F Iodine (III) Intermediates, M. A. Carroll, S. Martin-Santamaria, V. W. Pike, H. S. Rzepa and D. A. Widdowson, Perkin Trans. 2, 1999, 2707-2714 with the supporting information here.
  5. Huckel and Mobius Aromaticity and Trimerous transition state behaviour in the Pericyclic Reactions of [10], [14], [16] and [18] Annulenes. Sonsoles Martên-Santamarêa, Balasundaram Lavan and H. S. Rzepa, J. Chem. Soc., Perkin Trans 2, 2000, 1415. with the supporting information here.
  6. Peter Murray-Rust, H. S. Rzepa and Michael Wright, “Development of Chemical Markup Language (CML) as a System for Handling Complex Chemical Content”, New J. Chem., 2001, 618-634. DOI: 10.1039/b008780g. This article broke new ground in that the supporting information was something of a misnomer. It was expressed entirely in XML, including all the chemistry data, and used XSLT transforms on the fly to regenerate the article. In that sense, it was actually a superset of the published article. It would be fair to say that this article was rather ahead of its time (although it does seem appropriate to publish it in a new journal!).
  7. M. Jakt, L. Johannissen, H. S. Rzepa, D. A. Widdowson and R. Wilhelm, “A Computational Study of the Mechanism of Palladium Insertion into Alkynyl and Aryl Carbon-Fluorine bonds”, Perkin Trans. 2, 2002, 576-581 and supporting information.
  8. P. Murray-Rust and H. S. Rzepa, chapter in “Handbook of Chemoinformatics. Part 2. Advanced Topics.”, ed. J. Gasteiger and T. Engel, 2003, Vol 1, was not enhanced per se, but did lay out the principles of how it might/should be done.
  9. K. P. Tellmann, M. J. Humphries, H. S. Rzepa and V. C. Gibson, “An experimental and computational study of β-H transfer between organocobalt complexes and 1-alkenes”, Organometallics, 2004, 23, 5503-5513. DOI: 10.1021/om049581h and supporting information.

Part 2: 2005.

These four examples all now invoke Jmol, which downloads upon request and hence does not rely on the presence of any browser plugin. The four articles were submited with supporting information in the form of HTML. These were associated with the main article, but were not formal part of that article. In that sense, they represent an incarnation of the traditional model, with all the data firmly resident in the supporting information.

  1. Gibson, Vernon C.; Marshall, Edward L.; Rzepa, H. S. ” A computational study on the ring-opening polymerization of lactide initiated by β-diketiminate metal alkoxides: The origin of heterotactic stereocontrol”, J. Am. Chem. Soc., 2005, 127, 6048-6051. DOI: 10.1021/ja043819b and supporting information.
  2. H. S. Rzepa, Mobius aromaticity and delocalization”, Chem. Rev., 2005, 105, 3697 – 3715. DOI: 10.1021/cr030092l and supporting information.
  3. H. S. Rzepa, “Double-twist Mšbius Aromaticity in a 4n+2 Electron Electrocyclic Reaction”, 2005, Chem Comm, 5220-5222. DOI: 10.1039/b510508k The supporting information is also available directly.
  4. H. S. Rzepa, “A Double-twist Mobius-aromatic conformation of [14]annulene”, Org. Lett., 2005, 7, 637 – 4639. DOI: 10.1021/ol0518333 and supporting information.

Part 3: 2006 onwards

The supporting information has now been assimilated into the main body of the article proper, and within these confines contribute components such as enhanced figures or tables (i.e. enhanced with data)

  1. A. P. Dove, V. C. Gibson, E. L. Marshall, H. S. Rzepa, A. J. P. White and D. J. Williams, “Synthetic, Structural, Mechanistic and Computational Studies on Single-Site β-Diketiminate Tin(II) Initiators for the Polymerization of rac-Lactide”, J. Am. Chem. Soc., 2006,128, 9834-9843. DOI: 10.1021/ja061400a The enhancement can be seen in Figure 11.
  2. O. Casher and H. S. Rzepa, “SemanticEye: A Semantic Web Application to Rationalise and Enhance Chemical Electronic Publishing”, J. Chem. Inf. Mod., 2006, 46, 2396-2411. DOI: 10.1021/ci060139e
  3. H S. Rzepa and M. E. Cass, “A Computational Study of the Nondissociative Mechanisms that Interchange Apical and Equatorial Atoms in Square Pyramidal Molecules”, Inorg. Chem., 2006, 45, 3958–3963. DOI 10.1021/ic0519988. Interactive table at 10.1021/ic0519988/ic0519988.html
  4. M. E. Cass and H. S. Rzepa, “In Search of The Bailar Twist and Ray-Dutt mechanisms that racemize chiral tris-chelates: A computational study of Sc(III), V(III), Co(III), Zn(II) and Ga(III) complexes of a ligand analog of acetylacetonate”, Inorg. Chem., 2007, 49, 8024-8031. DOI: 10.1021/ic062473y The enhancement can be seen in Figure 2
  5. H. S. Rzepa, “Lemniscular Hexaphyrins as examples of aromatic and antiaromatic Double-Twist Möbius Molecules”, Org. Lett., 2008, 10, 949-952.DOI:10.1021/ol703129z The enhancement can be seen in Web Table 1.
  6. D. C. Braddock and H. S. Rzepa, “Structural Reassignment of Obtusallenes V, VI and VII by GIAO-based Density functional prediction”, J. Nat. Prod., 2008, DOI: 10.1021/np0705918 and WEO1.
  7. S. M. Rappaport and H S. Rzepa, “Intrinsically Chiral Aromaticity. Rules Incorporating Linking Number, Twist, and Writhe for Higher-Twist Möbius Annulenes”, J. Am. Chem. Soc., 2008, 130,, 7613-7619. DOI: 10.1021/ja710438j and WEO1 to 4
  8. C. S. M. Allan and H. S. Rzepa, “AIM and ELF Critical point and NICS Magnetic analyses of Möbius-type Aromaticity and Homoaromaticity in Lemniscular Annulenes and Hexaphyrins”, J. Org. Chem., 2008, 73, 6615-6622. DOI: 10.1021/jo801022b and WEO1
  9. C. S. M. Allan and H. S. Rzepa, “Chiral aromaticities. Möbius Homoaromaticity”, J. Chem. Theory. Comp., 2008, 4, 1841-1848. DOI: 10.1021/ct8001915 and WEO1
  10. C. S. M Allan and H. S. Rzepa, “The structure of Polythiocyanogen: A Computational investigation”, Dalton Trans., 2008, 6925 – 6932. DOI: 10.1039/b810147g and enhanced Table
  11. H. S. Rzepa, “Wormholes in Chemical Space connecting Torus Knot and Torus Link π-electron density topologies”, Phys. Chem. Chem. Phys., 2009, 1340-1345. DOI: 10.1039/b810301a and enhanced Table.
  12. H. S. Rzepa, “The Chiro-optical properties of a Lemniscular Octaphyrin”, Org. Lett., 2009, 11, 3088-3091. DOI: 10.1021/ol901172g
  13. C. S. Wannere, H. S. Rzepa, B. C. Rinderspacher, A. Paul, H. F. Schaefer III, P. v. R. Schleyer and C. S. M. Allan, “The geometry and electronic topology of higher-order Möbius charged Annulenes”, J. Phys. Chem., 2009, DOI: 10.1021/jp902176a and enhanced table
  14. H. S. Rzepa, “The distortivity of π-electrons in conjugated Boron rings.”, Phys. Chem. Chem. Phys., 2009, DOI: 10.1039/B911817A and enhanced table.
  15. H. S. Rzepa, “The importance of being bonded”, Nature Chem., 2009, DOI: 10.1038/nchem.373 and the exploratorium.
  16. King Kuok Hii, J.L.Arbour, H.S.Rzepa, A.J.P.White, “Unusual Regiodivergence in Metal-Catalysed Intramolecular Cyclisation of γ-Allenols”, Chem. Commun, 2009, DOI: 10.1039/b913295c and enhanced table.
  17. L. F. V. Pinto, P. M. C. Glória, M. J. S. Gomes, H. S. Rzepa, S. Prabhakar, A. M. Lobo. “A Dramatic Effect of Double Bond Configuration in N-Oxy-3-aza Cope Rearrangements – A simple synthesis of functionalised allenes”, Tet. Lett., 2009, 50, 3446-3449. DOI: 10.1016/j.tetlet.2009.02.228 and interactive table.
  18. H. S. Rzepa and C. S. M. Allan, “Racemization of isobornyl chloride via carbocations: a non-classical look at a classic mechanism”, J. Chem. Educ., 2010, DOI: 10.1021/ed800058c and interactive table.
  19. K. Abersfelder, A. J. P. White, H. S. Rzepa, and D. Scheschkewitz “A Tricyclic Aromatic Isomer of Hexasilabenzene”, Science, 2010, DOI: 10.1126/science.1181771 and interactive table.
  20. A. C. Spivey, L. Laraia, A. R. Bayly, H. S. Rzepa and A. J. P. White “Stereoselective Synthesis of cis- and trans-2,3-Disubstituted Tetrahydrofurans via Oxonium−Prins Cyclization: Access to the Cordigol Ring System”, Org. Lett., 2010, DOI 10.1021/ol9024259 and interactive table.
  21. J. Kong, P. v. R. Schleyer and H. S. Rzepa, “Successful Computational Modeling of Iso-bornyl Chloride Ion-Pair Mechanisms”, J. Org. Chem., 2010, DOI: 10.1021/jo100920e and interactive table.
  22. A. Smith, H. S. Rzepa, A. White, D. Billen, K. K. Hii, “Delineating Origins of Stereocontrol in Asymmetric Pd-Catalyzed α-Hydroxylation of 1,3-Ketoesters”, J. Org. Chem., 2010, 75, 3085-3096. DOI: 10.1021/jo1002906 and interactive table.
  23. H. S. Rzepa “The rational design of helium bonds”, Nature Chem., 2010, 2, 390-393. DOI: 10.1038/NCHEM.596 and web enhanced table.
  24. P. Rivera-Fuentes, J. Lorenzo Alonso-Gómez, A. G. Petrovic, P. Seiler, F. Santoro, N. Harada, N. Berova, H. S. Rzepa, and F. Diederich, “Enantiomerically Pure Alleno–Acetylenic Macrocycles: Synthesis, Solid-State Structures, Chiroptical Properties, and Electron Localization Function Analysis”, Chem. Eur. J., 2010, DOI: 10.1002/chem.201001087 and interactive figure
  25. H. S. Rzepa, “The Nature of the Carbon-Sulfur bond in the species H-CS-OH”, J. Chem. Theory. Comput., 2010, 49, DOI: 10.1021/ct100470g and interactive table.
  26. H. S. Rzepa, “Can 1,3-dimethylcyclobutadiene and carbon dioxide co-exist inside a supramolecular cavity?”, Chem. Commun., 2010, DOI: 10.1039/C0CC04023A and interactive table
  27. M. R. Crittall, H. S. Rzepa, and D. R. Carbery, “Design, Synthesis, and Evaluation of a Helicenoidal DMAP Lewis Base Catalyst”, Org. Lett., 2011, DOI: 10.1021/ol2001705 and interactive table
  28. H. S. Rzepa, “The past, present and future of Scientific discourse”, J. Cheminformatics, 2011, 3, 46. DOI: 10.1186/1758-2946-3-46 and interactive figure 3, figure 4 and figure 5.
  29. H. S. Rzepa, “A computational evaluation of the evidence for the synthesis of 1,3-dimethylcyclobutadiene in the solid state and aqueous solution”, Chem. Euro. J., 2012, in press.
  30. J. L. Arbour, H. S. Rzepa, L. A. Adrio, E. M. Barreiro, P. G. Pringle and K. K. (Mimi) Hii, “Silver-catalysed enantioselective additions of O-H and N-H to C=C bonds: Non-covalent interactions in stereoselective processes”, Chem. Euro. J., 2012, in press, Web table 1 and Web table 2.
  31. H. S. Rzepa, “Chemical datuments as scientific enablers”, J. Chemoinformatics, submitted.
  32. A. P. Buchard, F. Jutz, F. M. R. Kember, H. S. Rzepa, C. K. Williams, C.K., “Experimental and Computational Investigation of the Mechanism of Carbon Dioxide/Cyclohexene Oxide Copolymerization Using A Dizinc Catalyst”, in press. Interactivity box
  33. D. C. Braddock, D. Roy, D. Lenoir, E. Moore, H. S. Rzepa, J. I-Chia Wu and P. von R. Schleyer, “Verification of Stereospecific Dyotropic Racemisation of Enantiopure d and l-1,2-Dibromo-1,2-diphenylethane in Non-polar Media”, Chem. Comm., 2012, just published. DOI: 10.1039/C2CC33676F and interactivity box.
  34. K. Leszczyńska, K. Abersfelder, M. Majumdar, B. Neumann, H.-G. Stammler, H. S. Rzepa, P. Jutzi and D. Scheschkewitz, “The Cp*Si+ Cation as a Stoichiometric Source of Silicon, Chem. Comm., 2012, 48, 7820-7822. DOI: 10.1039/c2cc33911k. Cites links to 10042/to-13974, 10042/to-13982, 10042/to-13969, 10042/20028, 10042/to-13973, 10042/to-13985
  35. H. S. Rzepa, “A computational evaluation of the evidence for the synthesis of 1,3-dimethylcyclobutadiene in the solid state and aqueous solution”, Chem. Euro. J., 2013, 4932-4937. DOI: 10.1002/chem.201102942 and WebTable
  36. H. S. Rzepa, “Chemical datuments as scientific enablers”, J. Chemoinformatics, 2013, 4, DOI: 10.1186/1758-2946-5-6. The interactivity box is integrated into the body of the article.
  37. M. J. Cowley, V. Huch, H. S. Rzepa, D. Scheschkewitz, “A Silicon Version of the Vinylcarbene – Cyclopropene Equilibrium: Isolation of a Base-Stabilized Disilenyl Silylene”, 2013, Nature Chem., in press and Webtable.
  38. M. J. S. Gomes, L. F. V. Pinto, H. S. Rzepa, S. Prabhakar, A. M. Lobo, “N-Heteroatom Substitution Effects in 3-Aza-Cope Rearrangements”, Chemistry Central, 2013, 7:94. doi:10.1186/1752-153X-7-94 and Table.
  39. H. S. Rzepa and C. Wentrup, “Mechanistic Diversity in Thermal Fragmentation Reactions: a Computational Exploration of CO and CO2 Extrusions from Five-Membered Rings”, J. Org. Chem., DOI: 10.1021/jo401146k and Table.
  40. D. C. Braddock, J. Clarke and H. S. Rzepa “Epoxidation of Bromoallenes Connects Red Algae Metabolites by an Intersecting Bromoallene Oxide – Favorskii Manifold”, Chem. Comm., 2013, DOI: 10.1039/C3CC46720A and Table.
  41. M. J. Fuchter, Ya-Pei Lo and H. S. Rzepa, “Mechanistic and chiroptical studies on the desulfurization of epidithiodioxopiperazines reveal universal retention of configuration at the bridgehead carbon atoms”, J. Org. Chem., 2013, in press. doi: 10.1021/jo401316a and table.

References

  1. H.S. Rzepa, B.J. Whitaker, and M.J. Winter, "Chemical applications of the World-Wide-Web system", Journal of the Chemical Society, Chemical Communications, pp. 1907, 1994. https://doi.org/10.1039/c39940001907

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Posted in Chemical IT, Interesting chemistry | 6 Comments »

On the importance of Digital repositories in Chemistry

Friday, April 3rd, 2009

The preceeding blog entries contain stories about chemical behaviour. If you have clicked on the diagrams, you may even have gotten a Jmol view of the relevant molecules popping up. But if you are truly curious, you may even have the urge to acquire the relevant 3D information about the molecule, and play with it yourself. Even after 15 years of the  (chemical) Web, this can be distressingly difficult to achieve (or can it be that it is only myself who wishes to view molecules in their  native mode?).  Thus the standard mechanism is to seek out on journal pages that disarming little entry entitled  supporting information and to hope that you might find something useful embedded there.  Embedded is the correct description, since the information is often found within the confines of an Acrobat file, and has to be extracted from there.  Indeed, that is what  I had to resort to in order to write one of the blog entries below. I ground my teeth whilst doing so. 
blog11
So is there a better way? We think so! The  digital repository. If you click on this you should see the entry directly. What can you do there? Well, if you have suitable programs, you can download eg a Checkpoint file of the calculation that created the molecule model and re-activate it there. Or you can download just the CML file for viewing in any CML-compliant program (such as e.g. Jmol). Or you can check up on the InCHi string or the InChI Key of the molecule.

What about the specific entry above? Well, it corresponds to the calculation for the π4 + π2 cycloaddition described in the blog entry below. You can now verify for yourself the assertions made in that entry, ie that the rotation mode is disrotatory, or that the bond is forming antarafacially. You do not need to take my word for it! If the Digital repository is too much trouble for you, click on the graphic instead to get a similar result.

We now regularly put such links into journal articles, in the form of Web-enhanced tables and figures, so that it is literally just one click away from such an article to having a vibrant molecule dancing in front of you. All (chemistry) journals should do this. If they do not yet, then contact their editor in chief when you next submit an article and ask them why not!

See also the blog by Peter Murray-Rust.

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