Chemists now use the term “curly arrows” as a language to describe the electronic rearrangements that occur when a (predominately organic) molecule transforms to another – the so called chemical reaction. It is also used to infer, via valence bond or resonance theory, what the mechanistic implications of that reaction are.
I can remember a time when journal articles carried selected data within their body as e.g. Tables, Figures or Experimental procedures, with the rest consigned to a box of paper deposited (for UK journals) at the British library. Then came ESI or electronic supporting information.
I have written a few times about the so-called “anomeric effect”, which relates to stereoelectronic interactions in molecules such as sugars bearing a tetrahedral carbon atom with at least two oxygen substituents. The effect can be detected when the two C-O bond lengths in such molecules are inspected, most obviously when one of these bonds has a very different length from the other.
First, a very brief history of scholarly publishing, starting in 1665[cite]10.1098/rstl.1665.0001[/cite] when scientific journals started to be published by learned societies.
In an earlier post on this topic,[cite]10.59350/f00wf-5tq46[/cite] ‡ I described how the curly-arrows describing the mechanism of a nucleophilic addition at a carbonyl group choreograph in two distinct ways, as seen in red or blue below.
Respiratory pigments are metalloproteins that transport O 2 , the best known being the bright red/crimson coloured hemoglobin in human blood. The colour derives from Fe 2+ at the core of a tetraporphyrin ring. But less well known is blue blood , and here the colour derives from an oxyhemocyanin unit based on Cu 1+ (the de-oxy form is colourless) rather than iron.
One of the important aspects of chemical reaction mechanisms is the order in which things happen. More specifically, the order in which bonds make or break when there are more than two involved in undertaking a reaction.
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.
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