Continuous flow α-aminoxylation monitored by in-situ IR spectroscopy
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| Anzahl der Teile | 163 | |
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| Lizenz | CC-Namensnennung - keine Bearbeitung 4.0 International: Sie dürfen das Werk in unveränderter Form zu jedem legalen Zweck nutzen, vervielfältigen, verbreiten und öffentlich zugänglich machen, sofern Sie den Namen des Autors/Rechteinhabers in der von ihm festgelegten Weise nennen. | |
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00:11
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Transkript: Englisch(automatisch erzeugt)
00:11
Welcome to the Institute of Chemical Research of Catalonia, what we call ICIQ. I am Michal Perikas, I'm in charge of one of the research groups of ICIQ.
00:23
We work in flow chemistry, but probably more importantly in polymer supported catalysts. What you will see today is a particular example of a reaction which we have now performed under flow conditions using an immobilized catalyst.
00:42
This reaction is the alpha aminoxylation of aldehydes. When this reaction is performed under batch conditions, you normally start with an aldehyde and your reagent is nitrobenzene.
01:03
You have a certain catalyst and this promotes the initial process, but this is complicated by the fact that a secondary reaction which is non-catalytic
01:23
uses another molecule of nitrobenzene which reacts with the primary product and this leads to the alpha hydroxy aldehyde plus a byproduct which is asoxybenzene.
01:53
This is negative because you are consuming a lot of nitrobenzene and you generate this impurity that you must separate
02:01
and moreover you are generating a mixture of two products. We support our catalyst on a polymer just to facilitate separation at the end of the process. We are using a chiral catalyst and we are creating this new bond
02:22
in a completely anti-selective manner. Moreover, since we are working under flow conditions, the contact time of this product with reagents and catalysts is very short, so we are minimizing this secondary reaction. Under flow conditions, this is highly minimized
02:41
and this helps in the isolation of beta-years of the enantiomerically pure product and avoids deformation of the byproduct.
03:05
Okay, so what we are going to do is an example of a continuous flow process in which we will do the amine oscillation of propanol with nitrous benzene. This is the catalyst, it's a polystyrene resin in which we have immobilized a proline.
03:34
So this is the structure of the catalyst we are using. This unit here is proline which is actually the active catalyst in the system
03:45
and we have immobilized it in polystyrene beads. Polystyrene is just a polymer, it's inactive. And we introduce in the middle a spacer which serves for keeping the proline apart from the polystyrene so they don't interfere.
04:03
So this is the catalyst we are going to use which is a proline immobilized on a polystyrene resin. And here we have weighted 300 milligrams of it which is what we are actually going to use for the reaction. So I will just introduce it in this column
04:21
which is the reactor where the reaction will take place. The reactor we are going to use is just a glass tube where we have put the resin. And it is jacketed so we can keep a constant temperature here.
04:41
So we are circulating a liquid in these tubes which comes from this unit that can warm up or cool down. Now we have set it at zero degrees. So the reaction will take place all the time at zero degrees. Now I'm going to close the reactor with this teflon piece.
05:03
It has a filter here in such a way that the resin will not come out through the tubing. So this is closed now but we have still left space for the resin to solve.
05:25
And now is the moment for starting circulating chloroform through the tubing. So just the solvent by now without any reagents. So we have the two pumps with these three wave valves
05:42
which allows us to connect to the pump. This goes to the pump. Chloroform only, or the solution with the reagent. In this case nitrous resin. And this one is connected to pro-panel. So now the position of the valves both are connected to chloroform
06:02
so we just have to start the pumps and the solvent will come to the reactor. So we are going to set the flow to one milliliter per minute in total at the beginning just for passing the solvent fastly and by equilibrating the system.
06:21
Because at this stage we don't really mind which is the flow. Now the system is just filling the syringes, they are syringe pumps. Just filling them with the solvent. And then once both syringes in both pumps are full it will start pumping.
06:47
So now the solvent has arrived to resin. The resin is actually floating in the solvent. And you can see as before the resin was like a small powder. And now you can actually see the beads because they are swollen.
07:15
So what I have done now is pressing the resin in such a way that it's in a packed bed at the bottom of the reactor.
07:24
This makes the solvent, and afterwards it will be the reagent solutions, forces them to go in close contact with the resin. So they have to pass through the pores of the resin. If I had just let it floating on the solvent,
07:43
the reagents could just go around the beads without really reaching a close contact with the catalyst. So we just have installed a needle in the outlet of the whole system that we can set in the collecting flask. And now for avoiding building up pressure in the collecting flask we will put a balloon with a bit of nitrogen.
08:14
So we have all the systems set up now and we can actually start the reaction.
08:20
We have here two bottles with the solutions of the reagents that we have already prepared. So we just have to adjust the flow of the pumps. We're going to use 100 microliters per minute in each pump. Now the flow is set and we just have to change this three-way valve.
08:40
This goes to chloroform, this goes to reagent. So we just close chloroform and open reagents. And the same here. So now the reagents are actually going through the pump to this mixing chamber.
09:04
Then they go already together through this short piece of tube and into the column. This machine is an IR spectrometer with a flow cell. So the product of the reaction is coming through this flow cell. And we can actually monitor in situ how the reaction is working.
09:20
With this program we can monitor the process of the reaction by IR spectroscopy. And depending on the concentration of the reagents the intensity of the bands changes.
09:41
So previously to the reaction we measured the single IR spectra of the components. That means chloroform as a solvent and then both reagents in the corresponding solvent. And here you can see that the red band corresponds to the IR spectrom of nitrozobenzene.
10:03
Which is the reagent we did not use in excess. And the change of the intensity of this band we can detect by the time which is shown in the graphic above. And here you can see that first of all we only pumped solvent through the system.
10:21
And at this point the reagent started to enter to the IR spectrometer and the band is detected. And then depending on the flow rate the time of the catalyst to react with the reagent changes.
10:41
So when we increase the flow rate the overall reaction time is shorter and the conversion is lowered. So by modifying the flow rate we can also change the conversion and optimize the reaction conditions. So this method with the NZ2IR spectrometer allows us to optimize the reaction much faster and much easier.
11:05
Because we can instantly see the influence of the flow rate on the conversion of the reaction. And in the end this allows us to optimize the reaction conditions much faster. So as you have seen it's easy to implement a continuous flow version of the catalytic anti-selective alpha-minoxidation of LDIs.
11:30
And by simply adding some element of control like in-situ online IR we can monitor the reaction. And we can follow up conversion, we can optimize conversion, we can optimize flow.
11:45
And in this way we save a lot of time, a lot of reagents for the optimization of chemical processes. And of course if someday we think in scaling up this kind of reaction for industrial use continuous flow version is clearly the solution.
12:04
Thanks for watching and I hope this video will help you. If you have to implement this chemistry in your lab.