Henry Rzepa's Blog Chemistry with a twist

November 2, 2011

Spotting the unexpected. Anomeric effects involving alkenes?

How one might go about answering the question: do alkenes promote anomeric effects? A search of chemical abstracts does not appear to cite any examples (I may have missed them of course, since it depends very much on the terminology you use, and new effects may not yet have any agreed terminology) and a recent excellent review of hyperconjugation does not mention it. Here I show how one might provide an answer.


July 6, 2011

Scalemic molecules: a cheminformatics challenge!

A scalemic molecule is the term used by Eliel to describe any non-racemic chiral compound. Synthetic chemists imply it when they describe a synthetic product with an observable enantiomeric excess or ee (which can range from close to 0% to almost 100%). There are two cheminformatics questions of interest to me: (more…)

May 31, 2011

Déjà vu all over again. Are H…H interactions attractive or repulsive?

Filed under: Interesting chemistry — Tags: , , , , — Henry Rzepa @ 6:51 am

The Pirkle reagent is a 9-anthranyl derivative (X=OH, Y=CF3). The previous post on the topic had highlighted DIST1, the separation of the two hydrogen atoms shown below. The next question to ask is how general this feature is. Here we take a look at the distribution of lengths found in the Cambridge data base, and focus on another interesting example.


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