I started chemistry with a boxed set in 1962. In those days they contained serious amounts of chemicals, but I very soon ran out of most of them. Two discoveries turned what might have been a typical discarded christmas present into a lifelong career and hobby. The first was 60 Stoke Newington High Street in north London, the home of Albert N. Beck, Chemist (or his son;
I have written earlier about the Amsterdam Manifesto. That arose out of a conference on the theme of “ beyond the PDF “, with one simple question at its heart: what can be done to liberate data from containers it was not designed to be in ? The latest meeting on this topic will happen in January 2015 as FORCE2015. The format is suitably modern, starting with a Hackathon, and then two days of talks, posters and demos.
These posts contain the computed potential energy surfaces for a fair few “text-book” reactions. Here I chart the course of the cyclopropanation of alkenes using the Simmons-Smith reagent,[cite]10.1021/ja01552a080[/cite] as prepared from di-iodomethane using zinc metal insertion into a C-I bond. Two reactions it can be compared with are the epoxidation of ethene using a peracid and dichlorocyclopropanation.
Continuing my hunt, here is a candidate for a strong(est?) halogen bond, this time between Se and I.[cite]10.1021/ic50038a006[/cite]. The features of interest include: The six-membered ring is in the chair conformation.
Nitrogen tri-iodide, or more accurately the complex between it and ammonia ranks amongst the oldest known molecules (1812). I became familiar with it around the age of 12-13, in an era long gone when boys (and very possibly girls too) were allowed to make such substances in their parent’s back gardens ‡ and in fact in the school science laboratory, † an experiment which earned me a personal request to visit the head teacher.
Pursuing the topic of halogen bonds, the system DABCO (a tertiary dibase) and iodine form an intriguing complex. Here I explore some unusual features of the structure HEKZOO[cite]10.5517/CCYJN03[/cite] as published in 2012[cite]10.1021/cg300669t[/cite] and ask whether the bonding between the donor (N) and the acceptor (I-I) really is best described as a “non-covalent-interaction” (NCI) or not.
Halogen bonds are less familiar cousins to hydrogen bonds. They are defined as non-covalent interactions (NCI) between a halogen atom ( X , acting as a Lewis acid, in accepting electrons) and a Lewis base D donating electrons; D….X-A vs D…H-A . They are superficially surprising, since both D and X look like electron rich species.
In London, one has the pleasures of attending occasional one day meetings at the Burlington House, home of the Royal Society of Chemistry. On November 5th this year, there was an excellent meeting on the topic of Challenges in Catalysis , and you can see the speakers and (some of) their slides here.
Solvolytic mechanisms are amongst the oldest studied, but reproducing their characteristics using computational methods has been a challenging business.
Egon Willighagen recently gave a presentation at the RSC entitled “The Web – what is the issue” where he laments how little uptake of web technologies as a “ channel for communication of scientific knowledge and data” there is in chemistry after twenty years or more. It caused me to ponder what we were doing with the web twenty years ago.