A little while ago, I set out some interpretations of how to push curly arrows.

Many moons ago, when I was a young(ish) lecturer, and much closer in time to my laboratory roots of organic synthesis, I made some chemistry videos. One of these has resurfaced, somewhat  (to me at least) unexpectedly. Nowadays of course, such demonstrations are all carried out using virtual simulations (Flash animations etc) as the equipment itself becomes less common.

In a time of change, we often do not notice that Δ = ∫δ. Here I am thinking of network bandwidth, and my personal experience of it over a 46 year period. I first encountered bandwidth in 1967 (although it was not called that then). I was writing Algol code to compute the value of π, using paper tape to send the code to the computer. Unfortunately, the paper tape punch was about 10 km from that computer.

A few years ago, we published an article which drew a formal analogy between chemistry and iTunes (sic )[cite]10.1021/ci060139e[/cite]. iTunes was the first really large commercial digital music library, and a feature under-the-skin was the use of meta-data to aid discoverability of any of the 10 million (26M in 2013) or so individual items in the store. ^‡ The analogy to digital chemistry and discoverability of

This is a follow-up to comment posted by Ryan, who asked about isocyanide’s role (in the form of the anion of tosyl isocyanide, or TosMIC): “In Van Leusen, it (the isocyanide) acts as an electrophile”. The Wikipedia article (recently updated by myself) shows nucleophilic attack by an oxy-anion on the carbon of the C≡N group, with the isocyanide group acting as the acceptor of these electrons (in other words, the electrophile). In the form shown

The title of this post comes from a comment posted by Ryan, who asks about isocyanide’s role (in the form of the anion of tosyl isocyanide, or TosMIC) in two named reactions, Van Leusen and Ugi FCR.  “In Van Leusen, it (the isocyanide) acts as an electrophile: however, in Ugi, it acts as a nucleophile”. Here are some valence bond forms for this species;

Here is another example gleaned from that Woodward essay of 1967 ( Chem. Soc. Special Publications (Aromaticity), 1967 , 21 , 217-249), where all might not be what it seems. Woodward notes that the reaction between the (highly reactive) 1 does not occur.

Sometimes the originators of seminal theories in chemistry write a personal and anecdotal account of their work. Niels Bohr[cite]10.1007/BF01326955[/cite] was one such and four decades later Robert Woodward wrote “ The conservation of orbital symmetry ” (Chem. Soc. Special Publications (Aromaticity), 1967 , 21 , 217-249;

In the preceding post, I introduced Dewar’s π-complex theory for alkene-metal compounds, outlining the molecular orbital analysis he presented, in which the filled π-MO of the alkene donates into a Ag ⁺ empty metal orbital and back-donation occurs from a filled metal orbital into the alkene π* MO. Here I play a little “what if” game with this scenario to see what one can learn from doing so. Firstly, I will use

The period 1951–1954 was a golden one for structural chemistry; proteins, DNA, Ferrocene (1952) and the one I discuss here, a bonding model for Zeise’s salt ( 3 ). In “A review of π Complex Theory”, Bull. Soc. Chim. Fr. , 1951 , 1 8 , C79 (it is not online) M. J. S. Dewar sets out his theory of the role of π-complexes in (mostly) organic chemistry.

Lukas, who occasionally comments on this blog, sent me the following challenge. In a recent article[cite]10.1021/jo3021709[/cite] he had proposed that the stereochemical outcome ( Z ) of reaction between a butenal and thioacetic acid as shown below arose by an unusual concerted cycloaddtion involving an S-H bond.