Posts Tagged ‘Functional groups’
The story so far. Imines react with a peracid to form either a nitrone (σ-nucleophile) or an oxaziridine (π-nucleophile). The balance between the two is on an experimental knife-edge, being strongly influenced by substituents on the imine. Modelling these reactions using the “normal” mechanism for peracid oxidation did not reproduce this knife-edge, with ΔΔG (π-σ) 16.2 kcal/mol being rather too far from a fine balance.
- D.R. Boyd, P.B. Coulter, N.D. Sharma, W. Jennings, and V.E. Wilson, "Normal, abnormal and pseudo-abnormal reaction pathways for the imine-peroxyacid reaction", Tetrahedron Letters, vol. 26, pp. 1673-1676, 1985. http://dx.doi.org/10.1016/S0040-4039(00)98582-4
Compounds with O-O bonds often have weird properties. For example, artemisinin, which has some fascinating stereoelectronics. Here is another such, recently in the news and known as HMTD (hexamethylene triperoxide diamine). The crystal structure was reported some time ago and the article included an inspection of the computed wavefunction. However this did not look at the potential stereoelectronics in this species, which I now address here.
- A. Wierzbicki, E.A. Salter, E.A. Cioffi, and E.D. Stevens, "Density Functional Theory and X-ray Investigations of P- and M-Hexamethylene Triperoxide Diamine and Its Dialdehyde Derivative", The Journal of Physical Chemistry A, vol. 105, pp. 8763-8768, 2001. http://dx.doi.org/10.1021/jp0123841
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.
In the previous post I described how hydronium hydroxide or H3O+…HO–, an intermolecular tautomer of water, has recently been observed captured inside an organic cage and how the free-standing species in water can be captured computationally with the help of solvating water bridges. Here I explore azane oxide or H3N+-O–,‡ a tautomer of the better known hydroxylamine (H2N-OH).
- M. Stapf, W. Seichter, and M. Mazik, "Unique Hydrogen-Bonded Complex of Hydronium and Hydroxide Ions", Chemistry - A European Journal, vol. 21, pp. 6350-6354, 2015. http://dx.doi.org/10.1002/chem.201406383