Ribulose-1,5-bisphosphate reacts with carbon dioxide to produce 3-keto-2-carboxyarabinitol 1,5-bisphosphate as the first step in the biochemical process of carbon fixation. It needs an enzyme to do this (Ribulose-1,5-bisphosphate carboxylase/oxygenase, or RuBisCO) and lots of ATP (adenosine triphosphate, produced by photosynthesis). Here I ask what the nature of the uncatalysed transition state is, and hence the task that might be facing the catalyst in reducing the activation barrier to that of a facile thermal reaction. I present my process in the order it was done‡.
Posts Tagged ‘low energy’
Ribulose-1,5-bisphosphate + carbon dioxide → carbon fixation!
Sunday, April 20th, 2014Six vs ten aromatic electrons?
Sunday, October 20th, 2013Homoaromaticity 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[1] 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.
References
- B. Chen, A.Y. Rogachev, D.A. Hrovat, R. Hoffmann, and W.T. Borden, "How to Make the σ0π2 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
Scalemic molecules: a cheminformatics challenge!
Wednesday, July 6th, 2011A scalemic molecule is the term used by Eliel to describe any non-racemic chiral compound. Synthetic chemists imply it when they describe a synthetic product with an observable enantiomeric excess or ee (which can range from close to 0% to almost 100%). There are two cheminformatics questions of interest to me: (more…)