This 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.
Archive for the ‘Interesting chemistry’ Category
A 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.
The following is a short question in a problem sheet associated with introductory organic chemistry.
The element silicon best represents the digital era of the mid 20th century to the present; without its crystalline form, there would be no computers (or this blog). Although it was first prepared in pure amorphous (powder) form around 1823 by Berzelius, it was not until 1854 that Henri Sainte-Claire Deville made it in crystalline form, using metallic aluminium to isolate it. He described it  as having a “metallic luster”.
- "The discovery of the elements. XII. Other elements isolated with the aid of potassium and sodium: Beryllium, boron, silicon, and aluminum", 1932. http://doi.org/10.1021/ed009p1386
Homoaromaticity is a special case of aromaticity in which π-conjugation is interrupted by a single sp3 hybridized carbon atom (it is sometimes referred to as a suspended π-bond with no underlying σ-foundation). But consider the carbene shown below. This example comes from a recently published article which was highlighted on Steve Bachrach’s blog. Here aromaticity has resulted from a slightly different phenomenon, whereby a 4π-electron planar (and hence nominally anti-aromatic) molecule is elevated to aromatic peerage by promoting the two carbene σ-electrons to have π-status.
- B. Chen, A.Y. Rogachev, D.A. Hrovat, R. Hoffmann, and W.T. Borden, " How to Make the σ 0 π 2 Singlet the Ground State of Carbenes ", Journal of the American Chemical Society, vol. 135, pp. 13954-13964, 2013. http://dx.doi.org/10.1021/ja407116e
This is a continuation of the discussion started on Steve Bachrach’s blog about a molecule with a very short H…H interaction involving two Si-H groups with enforced proximity. It had been inferred from the X-ray structure that the H…H distance was in the region of 1.50Å. It’s that cis-butene all over again! So is that H…H region a bond? Is it attractive or repulsive? Go read Steve’s blog first.
- J. Zong, J.T. Mague, and R.A. Pascal, "Array", Array, pp. 130827160143003, 2013. http://dx.doi.org/10.1021/ja407398w