Here is a little molecule that can be said to be pretty electron rich. There are lots of lone pairs present, and not a few electron-deficient σ-bonds. I thought it might be fun to look at the stereoelectronic interactions set up in this little system.
The previous post looked at anomeric effects set up on centres such as B, Si or P, and involving two oxygen groups attached to these atoms. Here I vary the attached groups to include either one or two nitrogen atoms.
- Henry Rzepa., "Anomeric effects at carbon, involving lone pairs originating from one or two nitrogens", 2016. http://dx.doi.org/10.14469/hpc/936
The anomeric effect occurs at 4-coordinate (sp3) carbon centres carrying two oxygen substituents and involves an alignment of a lone electron pair on one oxygen with the adjacent C-O σ*-bond of the other oxygen. Here I explore whether other centres can exhibit the phenomenon. I start with 4-coordinate boron, using the crystal structure search definition below (along with R < 0.1, no disorder, no errors).
- Henry Rzepa., "Anomeric effects at boron, silicon and phosphorus.", 2016. http://dx.doi.org/10.14469/hpc/696
I previously used data mining of crystal structures to explore the directing influence of substituents on aromatic and heteroaromatic rings. Here I explore, quite literally, a different angle to the hydrogen bonding interactions between a benzene ring and OH or NH groups.
Exploring the electrophilic directing influence of heteroaromatic rings using crystal structure data mining.June 21st, 2016
This is a follow-up to the post on exploring the directing influence of (electron donating) substituents on benzene with the focus on heteroaromatic rings such indoles, pyrroles and group 16 analogues (furans, thiophenes etc).
- H.S. Rzepa, "Discovering More Chemical Concepts from 3D Chemical Information Searches of Crystal Structure Databases", J. Chem. Educ., vol. 93, pp. 550-554, 2016. http://dx.doi.org/10.1021/acs.jchemed.5b00346
A while ago, I explored how the 3-coordinate halogen compound ClF3 is conventionally analyzed using VSEPR (valence shell electron pair repulsion theory). Here I (belatedly) look at other such tri-coordinate halogen compounds using known structures gleaned from the crystal structure database (CSD).
500 chemical twists: a (chalk and cheese) comparison of the impacts of blog posts and journal articles.June 3rd, 2016
The title might give it away; this is my 500th blog post, the first having come some eight years ago. Very little online activity nowadays is excluded from measurement and so it is no surprise that this blog and another of my "other" scholarly endeavours, viz publishing in traditional journals, attract such "metrics" or statistics. The h-index is a well-known but somewhat controversial measure of the impact of journal articles; here I thought I might instead take a look at three less familiar ones – one relating to blogging, one specific to journal publishing and one to research data.