Science ... It

Platinum is used to make double bond hydrogenation. This is simply the addition of two hydrogen atoms, an alkene function on (double bond between two carbons) or a carbonyl function (double bond between carbon and oxygen).
The most common method ambar of carrying ambar out hydrogenation involves a heterogeneous catalyst: metal in solid form is introduced into the solution (liquid) containing the reactants, dissolved in a solvent. The reaction therefore takes place at the metal catalyst surface.
In order to improve the qualities ambar of the catalyst, it is necessary ambar that this surface is the greatest possible: metals ambar are thus often deposited in very thin layers on an inert substrate (coal, silica ...) in order to maximize this surface.
With the craze (justified) to nanotechnology, researchers are developing nanoparticles for heterogeneous ambar catalysis. The advantage is two-fold: In the synthesis, one can control the size, the shape, ambar the surface of the nanoparticles. You can change them easily, and thus modulate their catalytic properties Their contact surface is very large, given their small size
The idea was to see what could be the consequences ambar on the efficiency and selectivity ambar of catalysis. ambar Basically, what is expected, in these cases, it's better selectivity (only double the weakest links / more accessible are hydrogenated), at the expense of efficiency (there is less surface area available, therefore less accessible metal). What is interesting is that there was actually gain selectivity in their test reaction, ambar but also increased efficiency!
The model reaction is hydrogenation of acetophenone (left). Without "decoration" a mixture is obtained (top), at a lower rate of reaction with decoration, where a single chemical species are obtained (bottom)
What seems to happen is that the proline act as "recruiters" reagents, and thus effectively close the metal. This ultimately allows an increase in the reaction rate, even if the prolines take up space, and reduce the active surface of catalyst ...
[For fans, this is the catalytic cycle proposed by the authors. ambar As usual, both H dihydrogen are on metal, then we see that there is one alone on the deck, and on the nitrogen of proline, NH This connection interacts with the oxygen of the carbonyl ambar function of acetophenone, ambar which causes a greater reactivity of the double bond, and acceleration of the addition of hydrogen ...
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