Here is another exploration of simple chemical concepts using crystal structures. Consider a simple diene: how does the central C-C bond length respond to the torsion angle between the two C=C bonds?
Posts Tagged ‘Chemical bond’
A visualisation of the effects of conjugation; dienes and biaryls.
Tuesday, August 25th, 2015Intermolecular atom-atom bonds in crystals? The O…O case.
Saturday, July 25th, 2015I recently followed this bloggers trail; link1 → link2 to arrive at this delightful short commentary on atom-atom bonds in crystals[1] by Jack Dunitz. Here he discusses that age-old question (to chemists), what is a bond? Even almost 100 years after Gilbert Lewis’ famous analysis,[2] we continue to ponder this question. Indeed, quite a debate on this topic broke out in a recent post here. My eye was caught by one example in Jack's article: "The close stacking of planar anions, as occurs in salts of croconic acid …far from producing a lowering of the crystal energy, this stacking interaction in itself leads to an increase by several thousand kJ mol−1 arising from Coulombic repulsion between the doubly negatively charged anions" I thought I might explore this point a bit further in this post.
References
- J.D. Dunitz, "Intermolecular atom–atom bonds in crystals?", IUCrJ, vol. 2, pp. 157-158, 2015. http://dx.doi.org/10.1107/S2052252515002006
- G.N. Lewis, "THE ATOM AND THE MOLECULE.", Journal of the American Chemical Society, vol. 38, pp. 762-785, 1916. http://dx.doi.org/10.1021/ja02261a002
The mechanism of borohydride reductions. Part 1: ethanal.
Sunday, April 12th, 2015Sodium borohydride is the tamer cousin of lithium aluminium hydride (LAH). It is used in aqueous solution to e.g. reduce aldehydes and ketones, but it leaves acids, amides and esters alone. Here I start an exploration of why it is such a different reducing agent.
