High Pressure Organic Chemistry
Organic Chemistry with Cold Seal and higher pressure Reactors - Working on this- see projects for more details - at least you can see what I am actually doing- while you do that I will work on this site.
INTRODUCTION and BACKGROUND: Whether studying the origins of life in deep sea hydrothermal vents or more recently interrogating intriguing organic solids formed under high pressures- At GL we continue to explore pressure as the "fourth variable" in X-t-T-P exploration. In my laboratory I focused first on studies of reaction products (largely simple organics) that were reacted at pressures up to 5 KB (500 MPa). Our first experiments were done using Hatten Yoder's Gas Pressure apparatus- an amazing thing to see- the pressure reactors were made from old naval cannons off of WW2 battle ships (I kid you not) PHOTO REQUIRED . Needless to say these were for our purpose over kill and now for such experiments we use much simpler Cold Seal "bombs" in a lab that was originally built by emeritus Staff member, John Franz, but has now been completely modernized by our colleague Dionysis Foustoukos. PHOTO REQUIRED.
More recently I have been involved in a wide range of collaborations with amazing chemists (mostly very young) who are exploring the role of really high P at ~ room T using a Paris-Edinburgh Press PHOTO REQUIRED. My first collaboration was with Tom Fitzgibbons (student of John Badding at PSU) who came to me with an intriguing white solid that he made by compressing benzene (at RT). We performed 13C solid state NMR on a TINY sample he made at ~ 20 GPa. What we observed was amazing (SEE FIGURE); benzene polymerized to a solid with ~ 80 % sp3 (methine carbon) and 20 % residual sp2 carbon. This was the beginning of the Diamond Nanothread story (Fitzgibbons et al. 2014 Nat. Materials). We also investigated the presence of benzene oligomers and oila! Interesting things- paper in the works.
The next cool subject I worked on (NMR again- that is a lot of what I do) was with a really great young hiP chemists Haiyan Zheng and Kuo Li (both at HPSTAR, Beijing) had cold compressed acetonitrile to ~ 25 GPa and produced a very surprising polymer- (SEE FIGURE). What we find is not at all what I would have expected- there is a pattern here (Zheng et al. Angewandte Chemie 2017). Again with the talented students of Haiyan Zheng and Kuo Li and their talented PD Jiangman Sun, we took a look at acetylene polymerization with SSNMR- again hiP ~ 20-25 GPa (Sun et al Angewandte Chemie, in press). A theme evolves... (SEE FIGURE) ... I continue to work with Haiyan and Kuo, we have some things I can't yet talk about as these are not yet in press.
I am also working with Tim Strobel and his group on some very cool HiP polymerization- stay tuned.
OUR HYDROTHERMAL ORGANIC EXPERIMENTS: We run these experiments at temperatures ranging from 50 up to 250 °C and at pressures from 2-3 MPa up to 400 MPa. Reactions that run at the vapor pressure of liquids are run in flame sealed silica or borosilicate tubes. Reactions at high pressure are run using a number of different high pressure devices. The simplest method utilizes cold seal pressure devices affording access to pressures up to 400 MPa. We have run experiments in a gas pressure reactor that provides pressures up to 1 GPa. Work with former post-doc Anurag Sharma using a hydrothermal diamond anvil cell allows for experiments at pressures exceeding 2 Gpa. We also have a high pressure flow reactor designed and assembled by former GL fellow Timothy Filley (now Professor at Purdue) that utilizes a pair of Quizix HP pumps and a titanium back pressure regulator. Dionysis Foustoukos has modified this apparatus to explore hydrogen oxidation kinetics in line with his interests in deep sea hydrothermal systems- he is currently using this device to culture micro-organisms that he and his colleagues capture while diving in Alvin down to the East Pacific Rise MOR hydrothermal systems. Dionysis Foustoukos has also set up a flexible gold bag apparatus, that provides very large volume but pressures are moderate < 100 MPa.
Picture (Right): NICE and SIMPLE! A snapshot of our hydrothermal reactors. We currently have 6 cold seal reactors and furnaces under individual pressure and temperature control. We can routinely run reactions up to 350 Mpa (hot!).
We like these because they are easy to operate. Pressure is achieved with water pressure. All are externally heated with clam type furnaces. Thermocouples feed into the region proximal to the sample region.
Analysis of the hydrothermal reaction products are performed in an number of different ways. Welded gold reactors are analyzed post reaction via GC-MS, LC-MS, and UV-vis spectroscopy. We have also successfully retrieved liquids from the hydrothermal Diamond Anvil Cells (DAC) and analyzed the reaction products using GC-MS. Of course the nicest aspects of the DAC is one can utilize Raman spectroscopy to follow reaction progress at T and P; this has been done recently by our former post Doc Anurag Sharma following our previous reactions involving citric acid in hot water (see for example Sharma et al. 2004, 2009).
A close up view of a cold-seal reactor. Note the water cooled end region. This allows us to do rapid heat up and quench in order to explore reaction kinetics at elevate pressures.
All reactions are performed in welded tube reactors: typically gold or platinum, but with our amazing PUK pulsed welder we can use Silver and titanium. The PUK makes this so much easier! I have welded frozen Xe into gold tubes while partially immersing the gold tubes in liquid N2 and it worked great! Hail the PUK!
Figure XXX: We (Dionysis Foustoukos) recently consolidated the furnaces from 14 to 6- Working with Joe Lai and Dionysis Foustoukos we now have a very advanced thermal control system. The silver box to the right controls all six furnaces. The blue cable is a network cable that allows one to access the controllers remotely from off site. The black box is a UPS.
We can't back up the furnace power remotely, but at least you can see what is going on and the data logger will let you know if something happened.
Beyond this, it is the same simple moderate pressure device that is very useful for those of use that consider crustal pressures as being most relevant.
Transition metal sulfide catalysts: With deepest thanks and respect to our former colleague:
Dr. Nabil Boctor- The grand master of Transition metal sulfide synthesis, RIP!
Natural metal sulfides are never compositionally pure, rather extensive cationic substitution is often encountered. Even a minor amount of substitution, e.g. Ni2+ for Fe2+ in FeS or Mn2+ for Zn2+ in ZnS, may affect significant changes in catalytic properties. Perhaps more critical it is now well known that natural sulfides are generally completely contaminated with organic compounds.
Warning to the experimenter: Transition metal sulfides are excellent organosynthetic catalysts, therefore, natural mineral sulfides are likely to be loaded with organic molecules. Only pure-laboratory synthesized minerals can be considered “clean”
In order to avoid the problems associated with natural contamination, therefore, we work with compositionally pure mineral sulfide phases to provide a better base line for the intrinsic catalytic qualities of simple metal sulfides. Our Co-I Nabil Boctor (recently deceased) synthesized all of our sulfides, utilizing dry methods that extend back to those first explored by the pioneers. In our case only puratronic grade metals (99.995-99.998 %) and S (99.9995 %) are used-futher purifying our catalysts. At the termination of the synthesis, a small portion of each charge is mounted in epoxy, polished with diamond abrasive paste, and examined optically in reflected light to ensure that the target phase is the only phase present. The chemical compositions of the synthetic sulfides are determined by electron microprobe analysis with a brand new JEOL Hyperprobe (LINK NEEDED). In some cases the crystal structure of the target phase is confirmed with X-ray diffraction (LINK NEEDED) (e.g. Cody et al., 2000).
Figure XXX: back in the day we used to use "The very dangerous arc welder" that I believe was invented at the Geophysical Laboratory. Welding was hard to do, in particular if you were welding mixtures of solids and liquids (which is pretty much all I do).
With this amazing pulsed welder - it is almost cheating- welding is so easy and anyone can do it! Plus we can weld while metal tubes are immersed in Liq N2.
Also, we can weld metals that would oxidize as the welder uses an Argon gas atmosphere. So we can use Titanium and silver- much cheaper.
The pulsed welder auto shades the eyes during weld protecting you from intense UV- nice!
If you don't have a PUK welder and you do what we do, you are at a disadvantage.
A Paris-Edinburgh Press: This is a PE press in the Strobel lab. This device can deliver very high pressures (up to 25 GPa) and relatively large sample (100's of micrograms to 1 milligram). This is surprisingly small relative to a piston cylinder press or multi-anvil press. High temperatures are not really the point of this press.
The relatively large volume means that you can make samples large enough to do solid state NMR (YES!). It is presses like this that enabled the synthesis of polybenzene, polyacetonitrile, and polyacetylene that we were able to do solid state NMR on (see Research Projects).
I have no idea how run this press- I just do the NMR. My understanding is that it works like a big diamond anvil cell but without diamonds- hence no windowing. The panoramic opening is likely for X-ray scattering-diffraction.