Posts Tagged ‘first professor’

The mechanism of diazo coupling: more hidden mechanistic intermediates.

Saturday, March 8th, 2014
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The diazo-coupling reaction dates back to the 1850s (and a close association with Imperial College via the first professor of chemistry there, August von Hofmann) and its mechanism was much studied in the heyday of physical organic chemistry.[1] Nick Greeves, purveyor of the excellent ChemTube3D site, contacted me about the transition state (I have commented previously on this aspect of aromatic electrophilic substitution). ChemTube3D recruits undergraduates to add new entries; Blue Jenkins is one such adding a section on dyes.

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References

  1. S.B. Hanna, C. Jermini, H. Loewenschuss, and H. Zollinger, "Indices of transition state symmetry in proton-transfer reactions. Kinetic isotope effects and Bronested's .beta. in base-catalyzed diazo-coupling reactions", Journal of the American Chemical Society, vol. 96, pp. 7222-7228, 1974. http://dx.doi.org/10.1021/ja00830a009

Historical detective stories: colourful crystals.

Friday, October 21st, 2011
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Organic chemists have been making (more or less pure) molecules for the best part of 180 years. Occasionally, these ancient samples are unearthed in cupboards, and then the hunt for their origin starts. I have previously described tracking down the structure of a 120 year-old sample of a naphthalene derivative. But I visited a colleague's office today, and recollected having seen a well-made wooden display cabinet there on a previous visit. Today I took a photo of one of the samples:

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