I have previously looked at the pigments used to colour the Book of Kells, which dates from around 800 AD and which contained arsenic sulfide as the yellow colourant. The Bayeaux tapestry is a later embroidery dating probably from around 1077 and here the colours are based entirely on mordanted natural dyes.
In the previous post, I discussed how data associated with two of the candidates for molecules of the year – 2022 could be retrieved and then used to inspect their three dimensional structures.
The list of molecules of the year is out now at C&E News (but you have to have an account to view the list, unlike previous years). ♣ These three caught my eye: Electron in a cube: Synthesis and characterization of perfluorocubane as an electron acceptor ,[cite]10.1126/science.abq0516[/cite]. I have already written about this system and will not discuss it further, except to note this one topped the poll!
The topic of dicarbon, C 2 , has been discussed here for a few years now. It undoubtedly would be a gas!
What’s a Journal For? This debate has been raging ever since preprint servers were introduced as far back as 1991!
Sometimes you come across a reaction which is so simple in concept that you wonder why it took so long to be accomplished in practice.
The term bispericyclic reaction was famously coined by Caramella et a l in 2002[cite]10.1021/ja016622h[/cite] to describe the unusual features of the apparently innocuous dimerisation of cyclopentadiene. It shows features of two paths for different pericyclic reactions, comprising a 2+4 cycloaddition in the early stages, but evolving into a (degenerate) pair of [3,3] sigmatropic reactions in the latter stages.
In previously asking what the largest angle subtended at four-coordinate carbon might be, I noted that as the angle increases beyond 180°, the carbon becomes inverted, or hemispherical (all four ligands in one hemisphere). So what does a search for this situation reveal in the CSD?
Four-coordinate carbon normally adopts a tetrahedral shape, where the four angles at the carbon are all 109.47°. But how large can that angle get, and can it even get to be 180°? A search of the CSD (crystal structure database) reveals a spiropentane as having the largest such angle, VAJHAP with 164°[cite]10.1021/ja00186a058[/cite] Because crystal structures might have artefacts such as disorder etc, it is always good to check this with a
The recently reported synthesis[cite]10.1126/science.abq0516[/cite] of octafluorocubane established a sublimation point as 168.1–177.1°C (a melting point was not observed). In contrast, the heavier perfluoro-octane has an m.p. of -25°C. Why the difference?
