This is one of those topics that seems to crop up every three years or so. Since then, new versions of operating systems, new versions of programs, mobile devices and perhaps some progress?  Right, I will briefly recapitulate. Chemical structure diagrams are special; they contain chemical semantics (what an atom is, what a bond is, stereochemistry, charges, etc). One needs special programs to represent this. Take two well-known ones.

Mercury (IV) tetrafluoride attracted much interest when it was reported in 2007[cite]10.1002%2Fanie.200703710[/cite] as the first instance of the metal being induced to act as a proper transition element (utilising d-electrons for bonding) rather than a post-transition main group metal (utilising just s-electrons) for which the HgF ₂ dihalide would be more normal (“Is mercury now a transition

Not long ago, I described a cyclic carbene in which elevating the carbene lone pair into a π-system transformed it from a formally 4n-antiaromatic π-cycle into a 4n+2 aromatic π-cycle. From an entirely different area of chemistry, another example of this behaviour emerges; Schreiner’s[cite]10.1039/C2SC21555A[/cite] trapping and reactions of t-butyl-hydroxycarbene, as described on Steve Bachrach’s blog.

In the previous post I mentioned in passing the Grignard reagent benzyl magnesium bromide as having tetrahedral coordination at Mg. But I have now noticed, largely through spotting Steve Bachrach’s post on “Acene dimers – open or closed?” another geometric effect perhaps worthy of note, certainly one not always noted in the past; that of dispersion forces.

The following is a short question in a problem sheet associated with introductory organic chemistry.

The concept of kinetic vs thermodynamic control of a reaction is often taught in the context of the enolisation of e.g. 1-methylcyclohexanone as induced by a base.

The element silicon best represents the digital era of the mid 20th century to the present;

The ¹ H NMR spectrum of an aromatic molecule such as benzene is iconic; one learns that the unusual chemical shift of the protons (~δ 7-8 ppm) is due to their deshielding by a diatropic ring current resulting from the circulation of six aromatic π-electrons following the Hückel 4n+2 rule.

Homoaromaticity is a special case of aromaticity in which π-conjugation is interrupted by a single sp ³ hybridized carbon atom (it is sometimes referred to as a suspended π-bond with no underlying σ-foundation). But consider the carbene shown below. This example comes from a recently published article[cite]10.1021/ja407116e[/cite] which was highlighted on Steve Bachrach’s blog.

I reminisced about the wonderfully naive but exciting Web-period of 1993-1994. This introduced the server-log analysis to us for the first time, and hits-on-a-web-pag e. One of our first attempts at crowd-sourcing and analysis was to run an electronic conference in heterocyclic chemistry and to look at how the attendees visited the individual posters and presentations by analysing the server logs.

In 1993-1994, when the Web (synonymous in most minds now with the Internet) was still young, the pace of progress was so rapid that some wag worked out that one “ web-year ” was like a dog-year, worth about 7 years of normal human time. So in this respect, 1994 is now some 133 web-years ago. Long enough for an archaeological excavation.