Posts Tagged ‘Chemical bond’

The di-anion of dilithium (not the Star Trek variety): Another “Hyper-bond”?

Saturday, September 16th, 2017
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Early in 2011, I wrote about how the diatomic molecule Be2 might be persuaded to improve upon its normal unbound state (bond order ~zero) by a double electronic excitation to a strongly bound species. I yesterday updated this post with further suggestions and one of these inspired this follow-up.

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Two new types in the chemical bonding zoo: exo-bonds and hyper-bonds?

Wednesday, September 6th, 2017
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The chemical bond zoo is relatively small (the bond being a somewhat fuzzy concept, I am not sure there is an actual count of occupants). So when two new candidates come along, it is worth taking notice. I have previously noted the Chemical Bonds at the 21st Century-2017: CB2017 Aachen conference, where both were discussed.

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The conformation of enols: revealed and explained.

Thursday, April 6th, 2017
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Enols are simple compounds with an OH group as a substituent on a C=C double bond and with a very distinct conformational preference for the OH group. Here I take a look at this preference as revealed by crystal structures, with the theoretical explanation.

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First, hexacoordinate carbon – now pentacoordinate oxygen?

Saturday, March 25th, 2017
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The previous post demonstrated the simple iso-electronic progression from six-coordinate carbon to five coordinate nitrogen. Here, a further progression to oxygen is investigated computationally.

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George Olah and the norbornyl cation.

Friday, March 10th, 2017
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George Olah passed away on March 8th. He was part of the generation of scientists in the post-war 1950s who had access to chemical instrumentation that truly revolutionised chemistry. In particular he showed how the then newly available NMR spectroscopy illuminated structures of cations in solvents such “Magic acid“. The obituaries will probably mention his famous “feud” with H. C. Brown over the structure of the norbornyl cation (X=CH2+), implicated in the mechanism of many a solvolysis reaction that characterised the golden period of physical organic chemistry just before and after WWII. 

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The “hydrogen bond”; its early history.

Saturday, December 31st, 2016
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My holiday reading has been Derek Lowe’s excellent Chemistry Book setting out 250 milestones in chemistry, organised by year. An entry for 1920 entitled hydrogen bonding seemed worth exploring in more detail here.

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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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Long C-C bonds.

Wednesday, November 30th, 2016
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In an earlier post, I searched for small C-C-C angles, finding one example that was also accompanied by an apparently exceptionally long C-C bond (2.18Å). But this arose from highly unusual bonding giving rise not to a single bond order but one closer to one half! How long can a “normal” (i.e single) C-C bond get, a question which has long fascinated chemists.

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A periodic table for anomeric centres, this time with quantified interactions.

Monday, August 8th, 2016
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The previous post contained an exploration of the anomeric effect as it occurs at an atom centre X for which the effect is manifest in crystal structures. Here I quantify the effect, by selecting the test molecule MeO-X-OMe, where X is of two types:

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A periodic table for anomeric centres.

Saturday, August 6th, 2016
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In the last few posts, I have explored the anomeric effect as it occurs at an atom centre X. Here I try to summarise the atoms for which the effect is manifest in crystal structures.

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