Archive for May, 2020

The first ever curly arrows. Revisited with some crystal structure mining.

Wednesday, May 27th, 2020

With the current global lockdown, and students along with everyone else staying at home, I have noticed some old posts of mine are getting more attention than normal. One of these is an analysis I did in 2012 of Robinson’s original curly arrow illustration.[1] That and the fact that I am about to give a lecture on what I call my autobiographical journey discovering them, to our own students here (remotely of course), has prompted me to revisit my original discussion.

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References

  1. "Forthcoming events", Journal of the Society of Chemical Industry, vol. 43, pp. 1295-1298, 1924. http://dx.doi.org/10.1002/jctb.5000435208

Posted in crystal_structure_mining, Curly arrows | 1 Comment »

The strongest bond in the universe: A crystallographic reality check?

Monday, May 25th, 2020

My previous two posts on the topic of strongest bonds have involved mono and diprotonating N2 and using quantum mechanics to predict the effect this has on the N-N bond via its length and vibrational stetching mode. Such species are very unlikely to be easily observed for verification. But how about a metal M+ instead of H+? It turns out that structures containing the fragment Ru-N≡N-Ru are a small but well studied class of organometallic. Here is a search of the CSD crystal database for this motif.

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The strongest bond in the universe: revisited ten years on.

Saturday, May 23rd, 2020

I occasionally notice that posts that first appeared here many years ago suddenly attract attention. Thus this post, entitled The strongest bond in the universe, from ten years back, has suddently become the most popular, going from an average of 0-2 hits per day to 92 in a single day on May 22nd (most views appear to originate from India). I can only presume that a university there has set some course work on this topic and Google has helped some of the students identify my post. Well, re-reading something you wrote ten years ago can be unsettling. Are the conclusions still sound? Would I establish my claim the same way now? After all, one picks up a little more experience in ten years. So here is my revisitation.

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Choreographing a chemical ballet: what happens if you change one of the actors?

Friday, May 8th, 2020

Earlier, I explored the choreography or “timing”, of what might be described as the curly arrows for a typical taught reaction mechanism, the 1,4-addition of a nucleophile to an unsaturated carbonyl compound (scheme 1). I am now going to explore the consequences of changing one of the actors by adding the nucleophile to an unsaturated imine rather than carbonyl compound (scheme 2). 

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Discussion of (the) Room-temperature chemical synthesis of dicarbon – open and transparent science.

Wednesday, May 6th, 2020

A little more than a year ago, a ChemRxiv pre-print appeared bearing the title referenced in this post,[1] which immediately piqued my curiosity. The report presented persuasive evidence, in the form of trapping experiments, that dicarbon or C2 had been formed by the following chemical synthesis. Here I describe some of what happened next, since it perhaps gives some insight into the processes of bringing a scientific result into the open.

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References

  1. K. Miyamoto, S. Narita, Y. Masumoto, T. Hashishin, M. Kimura, M. Ochiai, and M. Uchiyama, "Room-Temperature Chemical Synthesis of C2", 2019. http://dx.doi.org/10.26434/chemrxiv.8009633.v1

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