Going through some old lab supplies and found an old visitrap with some filters. I'm wondering if this would be a suitable trap for my schlenk line so I can stop fussing with a huge LN2 dewar. I'm never pulling very large amounts of volatiles off in the line. Anyone have experience with these traps vs the clunky LN2 traps?

Does anyone else have this water filter system in their lab? I've been charged with getting this previously abandoned one up and running but it's been performing sanitization for days now (manual says 16 hours max). I've talked to the techs at Thermo and they said that it's likely an issue with the control board which has been discontinued. They recommend buying a new system.

I've tried resetting the CMOS chip using the jumper pins and using the red BIOS clear button on the board. The system refuses to move beyond "resume sanitization?" And both yes and no lead to never ending rinses.

Has anyone delt with this particular issue before?

Thanks!

I have basically no experience with UPS. Recently sent a sample to a collaborator and got the results using a HeI lamp source (21.22eV). My material should be a semiconductor, and literature data on similar materials gives an energy difference of ~1eV between the VBM and the Ef (so the tangent line of the on-set part has a kinetic energy of ~20 eV). However with my data the tangent line of the onset part intersects the x-axis at ~22 eV, which would mean that my VBM is higher in energy than the Ef. Can anyone suggest why this might be the case? Thanks!

Hello! I'm curious to hear from folks that have used the Signals ELN for awhile on how you've set it up and what works well for your group.

I am on a committee currently developing an implementation plan for switching about 40 chemists to a brand new blank slate installation of Signals ELN and we're currently trying to decide on some basic initial configuration policies.

Specifically: what kind of naming convention have you used for individual notebooks? Also, do you typically use one notebook per chemist or do you tend to organize new notebooks around specific projects?

Once something new is made in the lab, how to folks uniquely identify, inventory, and store those samples?

Hi all, I need some advices with preparing fresh LDA. Previously one of our senior graduate students has tried it but it never worked. I tried commercially bought LDA but my reaction yield was poor so I assumed that the LDA wasn't good at this point (it was bought few months ago). I thought I would freshly prepare it myself this time and the procedure I'm gonna follow is;

n-Butyllithium in n-hexane (2.55 mL, 6.38 mmol) was added slowly at 0 °C to diisopropylamine (700 mg, 0.98 mL, 6.94 mmol) in 28 mL of dry THF under nitrogen atmosphere.

I would appreciate it if you could give me some advices/tips that you would usually follow with this reaction to make it successful.

Trying to find the correct experiment/technique to do this. I am assuming ion chromatography, but I've only ever used it to determine ppm concentrations of ions in batches of compounds and never used to to determine molar equivalents. We want to determine %bromide, chloride, and iodide counterions to the ammonium cation. Anyone have experience in this realm? I am aware of techniques used to determine number of HCl adducts on an API. I figure this should be similar to that, no?

Hello, I am shopping for a sonicating bath for our lab. I bought a very cheap one off Amazon, but it is so loud that it is bothersome to every other lab and office in the hall and I can hardly stand being in the lab with it. Does anyone know of a relatively quiet option?

Thank you

In my various attempts at achieving decent yields for a miyaura borylation of a 5-bromo-4-methoxypyrimidin-2-amine, I often get a large volume of debrominated side products, some leftover starting material as well. Ballpark 30% yield of a 1:1 mixture of desired product and debrominated product.

The solution always turns pitch black/dark brown within minutes. Conditions are as follows:

1.5 eq (BPin)2, 3 eq KOAc, 0.1 eq (Dppf)PdCl2 dcm adduct, Dry 1,4-dioxanes (N2 Sparged 15 min), 120 C, 16h.

As much as I would love to delve into a series of trial and error ideas of how to optimize this, I want to seek advice first. My assumptions are its partucularly the catalyst. Am I overheating the reaction to the point where the catalyst is having alot more side reactions? Is DppfPdCl2 particularlt O2 sensative and I should perform a more rigorous degassing method? Is there a better catalyst choice I should try all togeather. Id appreciate any guidance.

Edit: I should specify that I mean as a whole, does the catalyst have greater or lesser tolerability for heat and O2. I get the precatalyst is shelf stable.

https://imgur.com/MqQ1qw9

How do I draw the mechanism of this reaction? I assume that the benzamide is deprotected quickly, but how does the resulting amine interact with the Sonogashira coupling reaction to form the ring? Does it insert itself in the middle of the catalysis cycle? Or does it wait until the coupling is done, then cyclize to form the product?

I am newbie in electrochemistry. I saw some reduction using photoredox catalyst to reduce alkyl bromide to alkyl radical and bromide. I wanted to do something similar using electrochemistry, but I later found out that the reduction potential of radical to anion is less negative than the first reduction which means with large enough current, all radicals will be reduced to anion. All thing I want is to stop at radical.

I have 2 questions: 1/ Why the second reduction may not be observed when using photo-redox catalyst? 2/ What will happen if I run reaction at very low current (0.1 mA), can I mimic the performance of the photoredox catalyst?

Thank y'all

I've been trying to improve this synthesis where I methylate an m-bromopyridyl group, the alkylation is regioselective and known but has poor yield, I've been thinking of going all out and refluxing the reaction when it's typically only done at RT. My main concern is halogen exchange between my Grignard and starting material. Does anyone know if I should be concerned with this or I'm overreacting. Note: I do not care if the product is methylated more than once, I just need the bromine intact. Also of note is there is more to the molecule but it is all far far more unreactive than what is pictured and will not interfere with the reaction.

Top reaction is known, bottom is not

Hey, does anyone here have experience with birch reduction/alkylations? Specifically, those that reduce aryl rings. It can be a really clean, useful reaction, but it is not robust or servicable despite the available literature. Sometimes, with the same reagents and proc., the reaction fails. My PI and a previous grad student (who was the picture of perfectionism and meticulousness, to a fault) failed to uncover this mystery. I've also heard this otherwise very useful reaction is avoided in pharma process chem. Any thoughts? Has anyone experienced something like this with a different reaction?

I have multiple IR files that I need to write an interpretation for my thesis, How can I do that? Is there any free software I can use or an easy chart that can guide me through the process?

I'm a university student involved in a scientific research project under my professor's guidance. We're using Shimadzu's HPLC, and although I've dedicated myself to studying chromatography, I'm facing difficulties with the LC Solution software.

Despite gaining a good theoretical understanding through books, scientific articles, and YouTube videos, learning to use the software has proven much more challenging than the theoretical aspects. My professor wants me to learn to operate the software on my own and bring the results to her.

However, as soon as I begin to familiarize myself with the basics, she requests a calibration curve. It feels like I'm trying to learn to drive a car just by reading an instruction manual, and as soon as I learn how to start the engine, I'm asked to parallel park.

If anyone has been through a similar situation, I would greatly appreciate guidance. Despite loving chromatography and finding its theory incredible, the practical aspect, especially the use of the software, has been intimidating for me. I'm determined to learn but i don't have the money to invest in courses or training.

How to effectively crash out Polymers

I’m trying to crash out a poly arylene ether sulphone (PAES) polymer in things like water, ethyl alcohol, methanol, and isopropyl alcohol at cold and room temperature conditions. The polymer is supposed to crash out in a fibrous fashion so, how can I make sure I’m crashing out the polymer the right way to ensure it comes out fibrous? What’s the best way to crash out a polymer?

I have some lithium pellets that have turned black being kept in mineral oil under argon. Before I throw them out I'd like to figure out if I can clean them enough to make them usable again for organolithiums. Will strong stirring be enough to knock outside layer off during addition of an alkyl halide? Or is there a better method to get them clean?

Hi All, I'm going to do a Sonogashira coupling reaction. So my plan is to add the solvent inside the glove box to maintain an inert atmosphere inside the Schlenk flask and seal the tapered end with a rubber septum and parafilm. However, my reaction needs refluxing so I'm wondering how to connect a condenser to the Schlenk flask without opening the septum if I'm going to connect the inert air line to the end with the tap.

I would appreciate if you can share how you usually do this type of air-sensitive reactions? Or is the Schlenk flask supposed to work as a pressure tube so it doesn't need a condenser at refluxing temperatures but I doubt it's ability to held the pressure 'cause basically one end is a septum?

Hi folks,

My lab does dissolved inorganic carbon analysis by collecting filtered water samples in amber borosilicate vials with lids containing a rubber septa (similar to the attached image). Our analyzer opens a hole in the septa, meaning we go through a ton of septa as consumables. Its very annoying and expensive. If we can, reusing the septa would be useful. I am not super worried about contamination because we reuse the vials and clean them extremely well, along with the septa less caps. I am however worried that not sealing the cap completely could cause the same to be at equilibrium with the atmosphere, defeating the purpose. I suggested that we attempt to reseal the septa with a flame, but I am unsure if it would work -- or how I would really even know.

Does anyone do this? Any suggestions on how to proceed?

​

https://preview.redd.it/smfi23req0qc1.png?width=449&format=png&auto=webp&s=b04011a0a2294bc13bca12972443c473fcad3dd3

Hello all! I have been pondering some things as my lab has just purchased one of those fancy electrochemical stirplates and I was hoping to propose some interesting reactions with this new piece of equipment.

I am interested in what factors control whether a substance is reduced or oxidized in solution. For example oxidize cobalt (II) to cobalt (III) (without producing Co (I)) or reduce cobalt (II) to cobalt (I) (without producing Co (III)). Do any of you know how to control this in an electrochemical sense? Or have any resources that might help with this very fundamental line of questioning?

I’m just looking to expand my library and knowledge on a couple of inorganic topics. Any recommendations for books covering topics such as XAS, dft methods, metal metal bonds, or epr would be great.

Hi,

I have a colleague who needs to get sodium hydride into our glovebox. It is currently unopened in a steel can. What is the proper way to bring this material in? Do I keep the can sealed and bring it in as-is or do I open the can directly before pumping it down?

Thanks

Hi wonderful people,

it's my first time posting here after lurking for quite a while.

I would like to ask you for feedback regarding my short CV for my PhD application to a European university. I'm currently in my last semester and finishing my degree in about two months.

The spot I'm applying for is in force field development in nucleic acids.

My software repertoire isn't that large yet, but I feel I'm above average in AMBER and the visualization programs. What other programs or suites would you recommend to get into?

I hope all info is complete and clear, I'd appreciate suggestions and constructive criticisms regarding the mentioned points and the layout.

I censored the obvious stuff, but I think it's easy to find out about me using my output.

Thanks in advance!

https://preview.redd.it/vsv58sh2aypc1.png?width=1414&format=png&auto=webp&s=e0de4f9e113c6f73b3c038393b94d9532647974c

Hello,

I'm a PhD student working on RAFT polymerization to synthesize block copolymers. Without getting too much into the specifics, I am using a roughly 25kDa macro TTC CTA onto which I am hoping to add roughly 50 units of various methacrylate monomers.

Some information on the conditions: My monomers are passed through aluminum oxide prior to the reaction. I bubble my solutions with argon for 30min prior to running the reaction. The solvent is anisole. The temperature is 70C. I NMR my reaction mixture before bubbling and only after 24h to assess conversion since I want to avoid contamination with oxygen as much as possible (see below, I am not sure this is a valid concern). I have been doing this since I observed during the start of my PhD that my reactions were not starting immediately, ie I would start it, NMR at 3h, 6h, 9h, 12h and see nothing, but when I went to sleep and came back in the morning for a 24-28h time point the reaction had occured to various conversion ratios, which did not further increase after 3 more hours of reaction time. (I purge my syringe with argon 3 times before inserting to withdraw 0.1 mL for NMR).

I want to focus on one reaction, for which the [M]:[CTA]:[I] is 125:1:0.3. I have done this reaction five times now, with the first three times leading to no polymerization at 24h, the fourth yielding 5 units, and the fifth yielding 20 units. I am not understanding why the reaction is so inconsistent and the conversion, if any, is so low. One thing that I have been concerned with is the very low mass of initiator used, and how it may be comparable to residual oxygen or other quencher in the RM.

Since my CTA is 25kDa, my reaction looks like the following: 100 mg CTA + 2 mL Anisole + 0.2 mg AIBN (0.3 eq) along with roughly 50 mg monomer in a 5 mL round bottom.

Any thoughts on what is going on?

​

UPDATE: I ran two reactions with [M]:[CTA]:[I] is 50:1:0.15 OR [M]:[CTA]:[I] is 50:1:0.50. The lower initiator concentration resulted in no polymerization whereas the reaction with 0.5 equivalents (up from 0.30) resulted in about 7 units polymerized by NMR. It seems the lower quantity of initiator did not fix the problem. I will be seeing if freeze pump thaw x3 cycles helps using 0.30 equivalents of initiator and also attempting with 1 eq AIBN.

Are there go to resources to find experts at scaling an inorganic polymer synthesis for biomedical purposes? Unfortunately our lab is very much in an academic bubble so hoping to find someone whose services we can hire to outline and highlight challenges with our current ROP UV casting method.

normal NMR spectrum, solvent CDCl3, without chirality inducing solvent, molar mass of around 649

Hey y'all

I've got an old Genesys 5 Spectrophotometer I found in the winery lab. Trying to get it up and running, but during the boot up it gives me a baseline gain error. I called Thermo Fisher, but they said (pretty obviously I might add) that they don't service those old units anymore.

I'm not too optimistic about getting the thing running, but figured I would check if anybody here might know how I would trouble shoot that baseline gain error before throwing the thing out.

I can include more information if needed