QuímicaInglêsWordPress

Henry Rzepa's Blog

Henry Rzepa's Blog
Chemistry with a twist
Pagina inicialFeed Atom
language
HistoricalQuímicaInglês
Publicados

In Internet terms, 23 years ago is verging on pre-history. Much of what was happening around 1997 on the Web was still highly experimental and so its worth taking a look at some of this to see how it has survived or whether it can be “curated” into a form that would still be useful.

Curly ArrowsPericyclicQuímicaInglês
Publicados

I occasionally spot an old blog that emerges, if only briefly, as “trending”. In this instance, only the second blog I ever wrote here, way back in 2009 as a follow up to this article.[cite]10.1021/ed084p1535[/cite] With something of that age, its always worth revisiting to see if any aspect needs updating or expanding, given the uptick in interest.

HistoricalQuímicaInglês
Publicados

With universities around the world having to very rapidly transition to blended learning (a mixture of virtual and face-2-face experiences) with a very large component based on online materials, I thought it might be interesting to try to give one snapshot of when the online experience started to happen in chemistry. My start point will in fact be 1993, when the method of exposing online content currently in use (the “web”) really got going.

Reaction MechanismQuímicaInglês
Publicados

These four posts (the box set) set out to try to define the energetics for a reasonable reaction path for the Willgerodt-Kindler reaction. The rate of this reaction corresponds approximately to a free energy barrier of ~30 kcal/mol. Any pathway found to be >10 kcal/mol at its highest point above this barrier was deemed less probable. The first three efforts at defining such pathways all gave such a result.

Interesting ChemistryQuímicaInglês
Publicados

Here I investigate a recent report[cite]10.1126/sciadv.abc0495[/cite] of a new generation of polyesters with the intrinsic properties of high crystallinity and chemical recyclability. The latter point is key, since many current plastics cannot be easily recycled to a form which can be used to regenerate the original polymer with high yield. Here I show some aspects of this fascinating new type of polymer.

Chemical ITQuímicaInglês
Publicados

The folks at DataCite have announced a new research object discovery service which aims to give users a “*comprehensive overview of connections between entities in the research landscape”*. The portal https://commons.datacite.org acts as the entry point for three basic types of persistent identifiers (PIDs); Research works, using the DOI (digital object identifier) as a PID.

Reaction MechanismQuímicaInglês
Publicados

The two previous surveys of the potential energy surface for this, it has to be said, rather obscure reaction led to energy barriers that were rather to high to be entirely convincing. So here is a third possibility. The red section corresponds to the previous exploration, in which a 3-membered sulfur ring intermediate was mooted. Here we go back to a 3-ring with nitrogen instead.

Reaction MechanismQuímicaInglês
Publicados

Continuing an exploration of the mechanism of this reaction, an alternative new mechanism was suggested in 1989 (having been first submitted to the journal ten years earlier!).[cite]10.1002/jhet.5570260518[/cite] Here the key intermediate proposed is a thiirenium cation (labelled 8 in the article) and labelled Int3 below.

GeneralInteresting ChemistryQuímicaInglês
Publicados

Sometimes a (scientific) thought just pops into one’s mind. Most are probably best not shared with anyone, but since its the summer silly season, I thought I might with this one. Famously, according to Einstein, m  = E/c^^2, the equivalence of energy to mass. Consider a typical exoenergic chemical reaction:  A → B, ΔG -100 kJ/mol.