We are approaching 1 million recorded crystal structures (actually, around 716,000 in the CCDC and just over 300,00 in COD). One delight with having this wealth of information is the simple little explorations that can take just a minute or so to do. This one was sparked by my helping a colleague update a set of interactive lecture demos dealing with stereochemistry.

This second report highlights two “themes”, or common ideas that seem to emerge spontaneously from diversely different talks. Most conferences do have them. The first is “ embedding ”, which in this context means treating different parts of a probably complex molecular system at different levels of theory.

I am attending a conference. Plenaries at such events can sometimes provide interesting pointers on things to come (and sometimes they simply point to things past). At WATOC2014 in Santiago Chile, the first plenary was by Paul Ayers with the impressive title “ Concepts for organising chemical knowledge ” which certainly sounds as if it is pointing forward!

ELNs (electronic laboratory notebooks) have been around for a long time in chemistry, largely of course due to the needs of the pharmaceutical industries. We did our first extensive evaluation probably at least 15 years ago, and nowadays there are many on the commercial market, with a few more coming from opensource communities. Here I thought I would bring to your attention the potential of an interesting new entrant from the open community.

In the beginning (taken here as prior to ~1980) libraries held five-year printed consolidated indices of molecules, organised by formula or name (Chemical abstracts). This could occupy about 2m of shelf space for each five years. And an equivalent set of printed volumes from the Beilstein collection.

In the previous posts, I explored reactions which can be flipped between two potential (stereochemical) outcomes. This triggered a memory from Alex, who pointed out this article from 1999[cite]10.1070/MC1999v009n02ABEH000995[/cite] in which the nitrosonium cation as an electrophile can have two outcomes A or B when interacting with the electron-rich 2,3-dimethyl-2-butene.

This post, the fifth in the series, comes full circle. I started off by speculating how to invert the stereochemical outcome of an electrocyclic reaction by inverting a bond polarity. This led to finding transition states for BOTH outcomes with suitable substitution, and then seeking other examples.

One thing leads to another. Thus in the previous post, I described a thermal pericyclic reaction that appears to exhibit two transition states resulting in two different stereochemical outcomes.

In my first post on the topic, I discussed how inverting the polarity of the C-X bond from X=O to X=Be (scheme below) could flip the stereochemical course of the electrocyclic pericyclic reaction of a divinyl system.

In my earlier post on the topic, I discussed how inverting the polarity of the C-X bond from X=O to X=Be could flip the stereochemical course of the electrocyclic pericyclic reaction of a divinyl system. An obvious question would be: what happens at the half way stage, ie X=CH ₂ ? Well, here is the answer.

I do go on a lot about the importance of having modern access to data. And so the appearance of this article[cite]10.1038/sdata.2014.22[/cite] immediately struck me as important. It is appropriately enough in the new journal Scientific Data . The data contain computed properties at the B3LYP/6-31G(2df,p) level for 133,885 species with up to nine heavy atoms, and the entire data set has its own DOI[cite]10.6084/m9.figshare.978904[/cite].