Hydrogenative Couplings

The ROESY spectrum affords homonuclear transverse nOe interactions as cross-peaks between the various dipolarly coupled hydrogens. This... 

The ROESY spectrum of podophyllotoxin exhibits a number of crosspeaks (A-D) representing interactions between dipolarly coupled (space coupling) hydrogens, which can be helpful to determine the stereochemistry at different asymmetric centers. For example, based on the assumption that the C-1 proton (8 4.53) is /3-oriented, we can trace out the stereochemistry of other asymmetric centers. Cross-peak B represents dipolar coupling between the C-1 proton (8 4.53) and the C-2 proton (8 2.8), thereby confirming that the C-2 proton is also... 

Maglia, G. and AUemann, R.K. (2003). Evidence for environmentally coupled hydrogen tunneling during dihydrofolate reductase catalysis. J. Am. Chem. Soc. 125, 13372-13373... 

Knapp, M.J. and Klinman, J.P. (2002). Environmentally coupled hydrogen tunneling. Linking catalysis to dynamics. Eur. J. Biochem. 269, 3113-3121... 

The introduction of an electropositive substituent on the same carbon atom as the geminally coupled hydrogens. 

Hermes JD, Cleland WW. Evidence from multiple isotope effect determinations for coupled hydrogen motion and tunneling in the reaction catalyzed by glucose-6-phosphate dehydrogenase. J. Am. Chem. Soc. 1984 106 7263-7264. 

In aqueous solutions at OCP in the absence of redox couples, hydrogen evolution is... 

Another question relates to the availability of large enough quantities of iodine in the world. First estimates of the Iodine hold-up in a 600 MW VHTR coupled hydrogen production plant, designed using a detailed flow-sheet of the cycle, are on the order of 3 0001 (corresponding to a 45M capital cost, and consequently 0.045 per kg H2). This amount seems realistic when compared to the world yearly production of 20,000 t and the estimated world reserves of 15.10 t [2]. 

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