There is often a disconnect between how a text-book (schematically) represents a reaction and a more quantitive “reality” revealed by quantum mechanics. Is the bromination of ethene to give 1,2-dibromoethane one such example?
Posts Tagged ‘Tutorial material’
Text-books and the bromination of ethene.
Sunday, October 14th, 2012Ring-flipping in cyclohexane in a different light
Friday, October 12th, 2012The conformational analysis of cyclohexane is a mainstay of organic chemistry. Is there anything new that can be said about it? Let us start with the diagram below:
Oxime formation from hydroxylamine and ketone. Part 2: Elimination.
Tuesday, September 25th, 2012This is the follow-up to the previous post exploring a typical nucleophilic addition-elimination reaction. Here is the elimination step, which as before requires proton transfers. We again adopt a cyclic mechanism to try to avoid the build up of charge separation during those proton movements.
The Sn2 reaction: followed up.
Wednesday, September 12th, 2012An obvious issue to follow-up my last post on the (solvated) intrinisic reaction coordinate for the Sn2 reaction is how variation of the halogen (X) impacts upon the nature of the potential.
The stereochemical origins of the Wittig reaction.
Tuesday, August 7th, 2012This is another of those textbook reactions, involving reaction of a carbonyl compound with a phosphonium ylid to form an alkene and a phosphine oxide. The reaction continues to be frequently used, in part because it can be highly stereospecific.
The Curtius rearrangement. One step or two?
Monday, August 6th, 2012The Curtius reaction is represented in most chemistry texts and notes as following path (a) below. It is one of a general class of thermally induced rearrangement which might be described as elimination/migration (in a sense similar to this ring contraction migration/elimination), in this case implicating a nitrene intermediate if the two steps occur consecutively. Wikipedia is normally very much on the ball with this sort of thing, and a comment about the reaction mechanism there notes that current evidence prefers route (b), avoiding nitrene intermediacy (and hence formally removing this from examples of nitrene reactions).
Curly arrow pushing: another reality check.
Sunday, August 5th, 2012Two years ago, I discussed how curly arrow pushing is taught, presenting four different ways of showing the arrows. One of the comments posted to that blog suggested that all of the schemes shown below were deficient in one aspect.
QR codes and InChI strings.
Sunday, July 22nd, 2012A month or so ago at a workshop I was attending, a speaker included in his introductory slide a QR (Quick Response) Code. It is a feature of most digital eco-systems that there is probably already “an app for it”. So I thought I would jump on the band wagon by coding an InChI string. Here it is below: