Following the discussion here of Kekulé’s suggestion of what we now call a vibrational mode (and which in fact now bears his name), I thought I might apply the concept to a recent molecule known as [2.2]paracyclophane. The idea was sparked by Steve Bachrach’s latest post, where the “zero-point” structure of the molecule has recently been clarified as having D2 symmetry.[cite]10.1002/chem.201304972[/cite]
Archive for the ‘Interesting chemistry’ Category
Kekulé’s vibration: A modern example of its use.
Friday, June 6th, 2014Ribulose-1,5-bisphosphate + carbon dioxide → carbon fixation!
Sunday, April 20th, 2014Ribulose-1,5-bisphosphate reacts with carbon dioxide to produce 3-keto-2-carboxyarabinitol 1,5-bisphosphate as the first step in the biochemical process of carbon fixation. It needs an enzyme to do this (Ribulose-1,5-bisphosphate carboxylase/oxygenase, or RuBisCO) and lots of ATP (adenosine triphosphate, produced by photosynthesis). Here I ask what the nature of the uncatalysed transition state is, and hence the task that might be facing the catalyst in reducing the activation barrier to that of a facile thermal reaction. I present my process in the order it was done‡.
More (blog) connections spotted. Something new about diphenyl magnesium?
Thursday, April 17th, 2014I have just noticed unexpected links between two old posts, one about benzene, one about diphenyl magnesium and a link to August Kekulé.†
Enantioselective epoxidation of alkenes using the Shi Fructose-based catalyst. An undergraduate experiment.
Tuesday, April 15th, 2014The journal of chemical education can be a fertile source of ideas for undergraduate student experiments. Take this procedure for asymmetric epoxidation of an alkene.[cite]10.1021/ed077p271[/cite] When I first spotted it, I thought not only would it be interesting to do in the lab, but could be extended by incorporating some modern computational aspects as well.
Artemisinin: are stereo-electronics at the core of its (re)activity?
Sunday, April 13th, 2014Around 100 tons of the potent antimalarial artemisinin is produced annually; a remarkable quantity given its very unusual and fragile looking molecular structure (below). When I looked at this, I was immediately struck by a thought: surely this is a classic molecule for analyzing stereoelectronic effects (anomeric and gauche). Here this aspect is explored.
A connected world (journals and blogs): The benzene dication.
Thursday, April 10th, 2014Science is rarely about a totally new observation or rationalisation, it is much more about making connections between known facts, and perhaps using these connections to extrapolate to new areas (building on the shoulders of giants, etc). So here I chart one example of such connectivity over a period of six years.
A congruence of concepts: conformations, configurations, amides and enzymes
Sunday, February 9th, 2014This is the time of year when I deliver two back-2-back lecture courses, and yes I do update and revise the content! I am always on the look-out for nice new examples that illustrate how concepts and patterns in chemistry can be joined up to tell a good story. My attention is currently on conformational analysis; and here is an interesting new story to tell about it.
Three-for-one: a pericyclic brain teaser.
Sunday, January 12th, 2014A game one can play with pericyclic reactions is to ask students to identify what type a given example is. So take for example the reaction below.
Does forming a Wheland intermediate disrupt all aromaticity?
Friday, December 6th, 2013Text books will announce that during aromatic electrophilic substitution, aromaticity is lost by the formation of a Wheland intermediate (and regained by eliminating a proton). Is that entirely true?