Visible light mediated deoxygenations
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| Number of Parts | 163 | |
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| License | CC Attribution - NoDerivatives 4.0 International: You are free to use, copy, distribute and transmit the work or content in unchanged form for any legal purpose as long as the work is attributed to the author in the manner specified by the author or licensor. | |
| Identifiers | 10.5446/50367 (DOI) | |
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00:00
Organische ChemieMeeting/Interview
00:12
Organische ChemieTransformation <Genetik>Renewable resourceChemistLecture/ConferenceMeeting/Interview
00:35
GlucoseRenewable resourceMoleculeLactitolChemistryHydrateChemical compoundPharmaceuticsÖlHexaneLecture/Conference
00:54
ÖlLactitolCyclohexanChemical compoundPharmaceuticsChemistryLecture/Conference
01:11
Renewable resourceHydroxylÖlGlucoseMoleculeStockfishZunderbeständigkeitChemical compoundCobaltoxideLecture/Conference
01:40
StoichiometryTiermodellZinnorganische VerbindungenToxicityTransformation <Genetik>PhotocatalysisZunderbeständigkeitChemical compoundLecture/Conference
02:21
PhotochemistryReducing agentRiverDerivative (chemistry)Lecture/Conference
02:32
Systemic therapyElectronWalkingEsterLecture/Conference
02:44
Systemic therapyElectronLecture/Conference
02:58
ChemistryCobaltoxideLecture/Conference
03:18
Setzen <Verfahrenstechnik>CobaltoxideDerivative (chemistry)Lecture/Conference
03:36
Electrical breakdownHydrocarbonChemical reactionFunctional groupLecture/Conference
03:53
Functional groupPhotochemistryChemical reactionChemical experimentMeeting/Interview
04:07
StereoselectivityHuman body temperatureChemical reactionReactivity (chemistry)Chemical experiment
04:31
ReflexionsspektrumChemical reactionChemical reactorChemical experiment
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Chemical reactionPotenz <Homöopathie>Block (periodic table)SolutionHuman body temperatureWursthülleChemical experiment
04:56
GlassesChemical reactionSolutionPotenz <Homöopathie>Chemical experiment
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Chemical reactionGesundheitsstörungWursthülleGas chromatographyElectronChemistBreed standardMixtureElectron donorAlcoholAcetonitrileWaterChemical experiment
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Chemical experiment
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Chemical reactorPhotocatalysisChemical experiment
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Chemical experimentMeeting/Interview
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Chemical experiment
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Chemical reactionCobaltoxideSystemic therapySolutionStickstoffatomChemical experimentMeeting/Interview
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Base (chemistry)Chemical experiment
07:36
Breed standardChemical experiment
08:03
SolutionChemical compoundChemical reactionChemical experiment
08:17
WaterChemical reactionChemical compoundChemical experiment
08:33
SolutionPeriodateCobaltoxideRadioactive decayFreezingSystemic therapySample (material)Flüssiger StickstoffWaterVakuumverpackungChemical experiment
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SolutionSystemic therapyChemical experiment
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SolutionPolytetrafluoroethyleneCobaltoxideChemical reactionChemical experiment
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Chemical reactionMetalGas chromatographyGolgi apparatusWine tasting descriptorsMixtureChemical experiment
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Chemical reactionPhotocatalysisMetalIridiumSilicon dioxideGas chromatographyFiltrationSample (material)Chemical experiment
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AcetateSilicon dioxidePressureProcess (computing)FiltrationChemical experiment
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ChromatographyChemical reactionPhotocatalysisChemical experiment
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ChromatographyAzo couplingGas chromatographyChemical reactionComputer animationChemical experiment
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Chemical reactionGas chromatographyAzo couplingDiagram
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Gas chromatographyChemical reactionSolventComputer animation
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Chemical reactionChromatographyAreaSample (material)CobaltoxideInjection (medicine)Atom probeComputer animation
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PhotocatalysisArea
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HydrocarbonRenewable resourceCombine harvesterAreaÖlHope, ArkansasPhotocatalysisComputer animationDiagramMeeting/Interview
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Meeting/Interview
Transcript: English(auto-generated)
00:06
Welcome everyone. I'm very happy that I'm able to tell you something about our research today. My name is Oliver Reiser. I'm teaching organic chemistry at the University of Regensburg, and we are going to introduce to you a project which makes use of two
00:23
aspects which I believe will be very important for our future. The one is to make use of renewable resources and the other one is to make use of solar light for chemical transformations. The project which I will show you comes from the idea that if you want to use renewable resources and especially
00:46
carbohydrates, take glucose here as a simple molecule from renewable resources, what we would like to achieve is to be able to transfer this into compounds which we know very well from the chemistry of oil and where we have learned over
01:04
generations how to make very important intermediates, pharmaceuticals and other compounds out of this. So cyclohexane here would be a typical oil molecule, glucose a typical molecule you have from renewable feedstock and the question now is can we convert such a
01:23
molecule into such a molecule here. In order to do this we would have to remove these hydroxyl groups out of the glucose molecule. That is something which is very difficult to achieve. There have been a number of methods developed, the Barton-Mccombie deoxygenation for example,
01:41
but this one makes use of stoichiometric amounts of toxic organotin compounds and therefore that is not a very useful practical and especially on large scale practical method. What we would like to do is to use solar light for this and in order to do this we need a
02:03
photocatalyst and what Daniel will show you a little later in practice is how we try to achieve such transformations. We are still far away to take such molecules like glucose, but we are starting to use model compounds and the model compounds we are currently using are benzylic alcohols. What we have to do in
02:26
order to come to a suitable derivative which we can then try the photochemical reductions on is to make such esters here and
02:42
now the decisive step comes. We are injecting by visible light an electron into the system to generate such an intermediate here. And here you might already see the resemblance to the
03:12
intermediate from the Barton-Mccombie deoxygenation chemistry. We create a very analogous
03:24
radical intermediate and then the Barton-Mccombie deoxygenation. This one is fragmenting and what we are able to do here is to achieve the same type of fragmentation. And so this derivative breaks down to this benzylic radical which can be further reduced to the
03:45
hydrocarbon which we desire as our product in the reaction. Hello, my name is Daniel Rachle and I'm working in a group of Professor Dr. Oliver Reiser. In our group we also do photochemical reactions. Today
04:01
I want to present you our new reaction setup and I want to perform a test reaction in it. What one typical does is one runs photoreactions at normal room temperature since this is the most easiest setup. But to increase selectivity we can decrease the temperature or to increase reactivity we can also increase the reaction temperature. And
04:22
what one does is one sets up a Schlenk flask with the photoreaction in it and one can steer from below and heat from below while irradiated is from the side. But this setup has some severe disadvantages. As you can see here we have some light scattering effects, light reflection effects and the distance between the light source and the reaction vessel is quite large
04:44
altogether limiting the amount of light that gets into the reaction vessel. These disadvantages can be minimized with our new reaction setup. Temperature manipulation is carried out from below either by heating or a cooling bath or in this case by a metal block.
05:00
While light is generated above here in the high power LED and channeled into the reaction solution by this glass rod here while still being able to perform the reaction under inert conditions. Now I'm going to show you one test reaction with our new setup. For this photochemical deoxygenation we need a substrate alcohol, a photocatalyst, unix base, a sacrificial electron donor and a solvent
05:22
which is in this case a mixture of acetonitrile and water. And for easier following of the reaction with gas chromatography we also add an internal standard. Now I'm going to weight the derivative alcohol.
06:00
Now we're going to add the photocatalyst. Now we are going to connect our reaction vessel and all the liquid
06:31
reagents to the Schlenk system. Now we're going to add acetonitrile solvent.
06:48
To make sure to get no oxygen into the solution we flush the syringe with nitrogen before usage.
07:26
Now we are going to add unix base.
07:57
Afterwards we add the internal standard.
08:16
To mix the solution we're going to shake it. The last compound we add to the reaction is degassed water.
08:42
To degassed the solution properly we use a procedure called freeze-pump-thaw. Therefore we take our sample and freeze it to minus 200 degree with liquid nitrogen.
09:12
After applying vacuum for a certain period of time we bring it back to room temperature. Therefore we use our water pass. Now we see the evolution of dissolved gas.
09:31
After the solution is liquid again we freeze the sample again and repeat the cycle five times to really get rid of all the oxygen dissolved in the solution. After we degassed the solution thoroughly we mount our irradiation system.
09:44
In theory we could mount the irradiation system at any point prior to the step. But for easier handling we add it at the very end. We use teflon sealing to make sure that no oxygen gets into the solution.
10:01
Now we bring the light source in position and switch on the light and thereby start the reaction. The reaction takes about one hour. The progress of the reaction can be followed by gas chromatography analysis. After one hour we can analyze our reaction mixture. To make sure that no metal salts as our iridium photocatalyst gets into the
10:25
gas chromatography graph, we have to filter one aliquot of the reaction mixture through a plug of silica. I'm now removing the aliquot of the sample and passing it through a
10:43
plug of silica gel. We wash with three times one milliliter of isole acetate and we accelerate the filtration process with small pressure of air. As one can see no more yellow photocatalyst is in the reaction and
11:01
therefore we can analyze it by the GC. After retention time of about 1.6 minutes
11:23
we see the solvent come off the gas chromatography graph. Now we have to wait a couple more minutes till we see the reaction standard, the reaction product and the reaction educt. This is what the gas chromatography graph looks like before we started the reaction. At 1.6 minutes we have the solvent. At 2.7 minutes we have the internal standard and at 8.2 minutes we see the
11:46
educt of the reaction. When we compare it to the gas chromatogram after the reaction we can see that all of the starting material is gone and instead a new peak formed at a retention time of four minutes
12:00
which was confirmed to be the deoxygenated product by injection of our SENT example. By calculating the areas of the two peaks and comparing them we can calculate the direction work completely. So the photochemical deoxygenation on the visible light photocatalysis was very successful. I hope we could convince you that the combination of
12:21
photocatalysis and renewable resources as an abundant feedstock is a very promising research area. We are still at the very beginning but I believe it will be our future to use renewable resources as an alternative to hydrocarbons derived from oil. I hope you enjoyed this video and if you should have any further questions
12:42
please visit our website or contact us by email. We will be happy to answer any questions you might have. Thank you very much.