Posts Tagged ‘spectroscopy’

Organocatalytic cyclopropanation of an enal: (computational) assignment of absolute configurations.

Saturday, September 1st, 2018
No Gravatar

I am exploring the fascinating diverse facets of a recently published laboratory experiment for undergraduate students.[1] Previously I looked at a possible mechanistic route for the reaction between an enal (a conjugated aldehyde-alkene) and benzyl chloride catalysed by base and a chiral amine, followed by the use of NMR coupling constants to assign relative stereochemistries. Here I take a look at some chiroptical techniques which can be used to assign absolute stereochemistries (configurations).

(more…)

References

  1. M. Meazza, A. Kowalczuk, S. Watkins, S. Holland, T.A. Logothetis, and R. Rios, "Organocatalytic Cyclopropanation of (E)-Dec-2-enal: Synthesis, Spectral Analysis and Mechanistic Understanding", Journal of Chemical Education, 2018. http://dx.doi.org/10.1021/acs.jchemed.7b00566

FAIR Data in Amsterdam – FAIR data points.

Wednesday, July 18th, 2018
No Gravatar

FAIR is one of those acronyms that spreads rapidly, acquires a life of its own and can mean many things to different groups. A two-day event has just been held in Amsterdam to bring some of those groups from the chemical sciences together to better understand FAIR. Here I note a few items that caught my attention.

(more…)

Why do flowers such as roses, peonies, dahlias, delphiniums (etc), exhibit so many shades of colours?

Monday, June 18th, 2018
No Gravatar

It was about a year ago that I came across a profusion of colour in my local Park. Although colour in fact was the topic that sparked my interest in chemistry many years ago (the fantastic reds produced by diazocoupling reactions), I had never really tracked down the origin of colours in many flowers. It is of course a vast field. Here I take a look at just one class of molecule responsible for many flower colours, anthocyanidin, this being the sugar-free counterpart of the anthocyanins found in nature.

(more…)

Multispectral Chiral Imaging with a Metalens.

Saturday, January 6th, 2018
No Gravatar

The title here is from an article on metalenses[1] which caught my eye.

(more…)

References

  1. M. Khorasaninejad, W.T. Chen, A.Y. Zhu, J. Oh, R.C. Devlin, D. Rousso, and F. Capasso, "Multispectral Chiral Imaging with a Metalens", Nano Letters, vol. 16, pp. 4595-4600, 2016. http://dx.doi.org/10.1021/acs.nanolett.6b01897

MOLinsight: A web portal for the processing of molecular structures by blind students.

Friday, March 31st, 2017
No Gravatar

Occasionally one comes across a web site that manages to combine being unusual, interesting and also useful. Thus www.molinsight.net is I think a unique chemistry resource for blind and visually impaired students.

(more…)

George Olah and the norbornyl cation.

Friday, March 10th, 2017
No Gravatar

George Olah passed away on March 8th. He was part of the generation of scientists in the post-war 1950s who had access to chemical instrumentation that truly revolutionised chemistry. In particular he showed how the then newly available NMR spectroscopy illuminated structures of cations in solvents such “Magic acid“. The obituaries will probably mention his famous “feud” with H. C. Brown over the structure of the norbornyl cation (X=CH2+), implicated in the mechanism of many a solvolysis reaction that characterised the golden period of physical organic chemistry just before and after WWII. 

(more…)

Braiding a molecular knot with eight crossings.

Friday, January 20th, 2017
No Gravatar

This is one of those posts of a molecule whose very structure is interesting enough to merit a picture and a 3D model. The study[1] reports a molecular knot with the remarkable number of eight crossings.

(more…)

References

  1. J.J. Danon, A. Krüger, D.A. Leigh, J. Lemonnier, A.J. Stephens, I.J. Vitorica-Yrezabal, and S.L. Woltering, "Braiding a molecular knot with eight crossings", Science, vol. 355, pp. 159-162, 2017. http://dx.doi.org/10.1126/science.aal1619

Hydrogen bonding to chloroform.

Monday, November 14th, 2016
No Gravatar

Chloroform, often in the deuterated form CDCl3, is a very common solvent for NMR and other types of spectroscopy. Quantum mechanics is increasingly used to calculate such spectra to aid assignment and the solvent is here normally simulated as a continuum rather than by explicit inclusion of one or more chloroform molecules. But what are the features of the hydrogen bonds that form from chloroform to other acceptors? Here I do a quick search for the common characteristics of such interactions.

(more…)

Managing (open) NMR data: a working example using Mpublish.

Monday, August 1st, 2016
No Gravatar

In March, I posted from the ACS meeting in San Diego on the topic of Research data: Managing spectroscopy-NMR, and noted a talk by MestreLab Research on how a tool called Mpublish in the forthcoming release of their NMR analysis software Mestrenova could help. With that release now out, the opportunity arose to test the system.

(more…)