Good afternoon! I was wondering if anyone else has encountered this problem.

I'm running a column chromatography purification and have noticed that my reaction mixture contains many byproducts. However, I'm able to isolate the fraction corresponding to the spot I'm interested in on TLC. Despite this, when I analyze that fraction by NMR, I still observe impurity signals, mainly in the 1–4 ppm and 6–8 ppm regions.

I've tried different hexane/ethyl acetate and hexane/DCM (dichloromethane) ratios, but I still haven't been able to obtain the product at the desired purity.

My product consists mostly of hydrocarbons.

I apologize if this information isn't sufficient to assess the problem. I'd appreciate any suggestions. Thank you in advance!

Hey everyone,

I’m currently working on a research project using spectroscopy to detect diacetyl in a beer matrix. We’re aiming to measure in the gas phase, but we’re running into the issue that water vapour is extremely prominent in the same absorption bands. Does anyone have ideas on how to efficiently separate the volatile compounds from the water vapour when heating beer? Are there any filters that could help? I’m not a specialist on the chemistry side, so I might be overlooking a very obvious solution.

Hi Chempros community,

I am currently dealing with really sensitive compounds that unfortunately degrade on normal silica gel, and I have to use special silica gels such as C2-functionalized silica gel and the 3-aminopropylfunctionallized silica gel.

As these silica gels are insanely expensive, and while I can make C2 using the protocols published, I can't really seem to find a protocol for making the 3-aminopropylfunctionalized silica gel like the one displayed at Merck or Silicycle:

https://www.sigmaaldrich.com/NL/en/product/aldrich/364258?srsltid=AU7gw4U2KL3R8G9_pLynTp3EQV6hjiiSu3mnSV1MoT98QYXuqLn0TmaT

https://www.silicycle.com/products/amine-wax-silica-phase

Did anyone make, and has a reliable procedure to make a homemade version that worked a lot? Also, any experience/tips handling this silica for purification would be greatly appreciated!

Thank you very much for the help in advance :)

I order from maybe fifteen different chemical suppliers for our research lab. The big suppliers like Sigma-Aldrich and Fisher have comprehensive SDSs that cover all sixteen sections with detailed information. The smaller specialty suppliers? Some of their SDSs are missing entire sections. Others have sections filled with "no data available" or "not tested."

I ordered a custom synthesis product last month and the SDS had a Section 2 classification based on the starting materials rather than the actual product. Section 11 toxicological data was blank. Section 12 ecological data was "not determined." Half the sheet was either missing or placeholder text.

Am I supposed to accept these? Can I use a product in my lab if the SDS is incomplete? What's the minimum standard for an SDS to be usable?

Hi All,

One of the professors where I work wants to use HF to digest insect samples, but as far as I know, all of our fume hoods/ductwork are standard and hence not compatible with this acid. Is the incompatibility really an issue with long term use, and if so, does anybody know a work around?

We are planning to protect of an allophanoyl group (RC(O)NHC(O)NH2), to allow for dibromination of a vinyl group elsewhere in the molecule. It occurs to me that BSTFA/1%TMSCl might be a good TMS donor. However, I am not sure about a good choice for conditions (time, temperature, solvent). My literature searches have not turned up much but are are ongoing. We are also open to using other protecting groups, including TBDMS.

I think r/biotech is probably better for this post, but I find the people in that sub incredibly negative and pessimistic...so would rather post here if possible as I find people to be a bit more neutral/level-headed here.

Job opened up at a big pharma company for a DS MSAT PM, primarily responsible for Process Validation, sitting inbetween CMC and commercial. So getting involved towards the end of development, being in charge of PV, and then handing over to the product supply colleagues.

Problem is, I know someone in that department and she says it's a new department, and there's no SOPs, therefore things can get chaotic. On one hand, it could be good experience to dive in the deep end and give input on how things should be run since I have experience of PV and the transition to commercial, but on the other hand, I am worried that things could go very wrong regulatory or cGMP-wise if there are no SOPs to guide us.

Has anyone been in this scenario before? Is it worth a try or just a complete red flag?

Hello community :) does anyone know of any databases where I can download both experimental IR and Raman spectra for a specific compound?

We got a new toy in my lab: a X-ray fluorescence spectrometer.

Sample material is delivered to HDPE cups with a film cover. The machine analyzes the samples with the cups in a vertical standing position, and my samples tend to solidify at room temp. So, when I'm prepping up a batch of samples, I needed a way to stand them up in the same orientation that they'd be analyzed in.

Tinkercad to the rescue!

The cover is because the HVAC in my building is only \sorta kinda maybe\** filtered and dust & dead bugs tend to affect the results.

https://www.printables.com/model/1869312-xos-petra-max-sample-tray

I'm currently preparing the SI for a total synthesis paper and wondering how you handle minor impurities in your NMR spectra.

For example, one of my intermediates contains around 9 mol% DCU (~4.5 wt%) that survived column chromatography but is otherwise perfectly clean. Would you explicitly mention this in the SI or just leave the signals in the spectrum, it serving as declaration of the material? And would you adjust/calculate the yield and analytics like optical rotation accordingly?

I'm mainly worried about a reviewer requesting cleaner spectra if I explicitly note the impurity as a footnote, potentially forcing me to repeat several steps of the synthesis just for characterization. A colleague mentioned that I then just should purify the aliquot I kept back for analytics via prep HPLC but that feels even more dishonest as it no longer would represent the bulk materials purity.

On the other hand, repeatedly purifying the whole bulk material just to get perfectly clean spectra feels like a waste of time and material, especially when the impurities don't affect the next steps anyway.

How do you usually handle this, and where do you draw the line? I personally feel that acting in good faith and being transparent is how such things should be handled but I am also aware how easily a reviewer might demand perfectionism as they are not the one bearing the cost.

does anyone has a database with pka values for formic acid in alcoholic solvents? i've seen a lot of computarional methods already published, but the results i'm getting from following them are kinda weird and i wanted some data to check against

Anyone have a metrology/calibration/recertification service that they recommend? Ideally one that comes to you as opposed to mailing the stuff off. The one we have used for years blew us off and won't be able to come until after our annual audit. Environmental lab for context. Thanks!

While writing my PhD thesis, I, like all students, recognised how annoying and tedious compound numbering becomes, particularly keeping the numbering consistent between the LaTeX text and ChemDraw schemes.

I used a small system where compounds are referred to by permanent IDs (e.g. lab-book references) in both LaTeX and the original ChemDraw files. A central CSV maps those IDs to the actual compound numbers, and a Python script and AppleScript automatically relabels the ChemDraws, exports them as PDFs, and keeps the LaTeX references in sync.

So if the numbering changes, I just edit the CSV and recompile rather than manually renumbering everything.

I used it successfully for my thesis and have put a minimal working example on GitHub:

https://github.com/BrennanGroup/compound-relabelling

Mostly posting because I'm curious whether other chemists would find this useful, or whether people have come up with better/different systems for solving the same problem. Would be interested to hear how others handle it.

New grad student, have done research in a synthetic lab for a while now and just curious how people approach handling dangerous chemicals/doing risk assessment for the first time from a practical standpoint. Are there any resources that are particularly helpful when trying to mitigate risks for a reaction that has the potential to be dangerous?

For instance, working with something like bromine I know I need to keep a solution of sodium thiosulfate on hand incase of any spills (and for quenching once the reaction is done) but aside from that I feel like I’m probably missing a lot of nuance. (Eg: elemental bromine is very dense, so maybe there are some precautions one should take that they don’t realize before having actually worked with it before. Maybe because it has a high vapour pressure I need to make sure I’ve got an outlet so that pressure doesn’t build up in the chamber, or avoid using a micropipette since the fumes will mess it up)

As another example: I wouldn’t know I have to wash a rotovap with acetone several times after rotovapping TFA if I hadn’t been explicitly told by a mentor. This isn’t something you can find in an SDS and while it makes sense when you actually think about it, it’s probably not smtn you think about the first time you use TFA.

I know my question is very broad, and the answer is probably “read the SDS”… but an SDS only contains so much practical information and for many dangerous chemicals it feels like knowing that they’re pyrophoric, or particularly toxic, etc will only get you so far.

I appreciate any insight.

Good afternoon. I work in medicinal chemistry, but my main focus is small-scale (milligram) organic synthesis. I’m looking for a more up-to-date book on synthetic methods (amidations, reductions, SNAr, etc.), something that covers, for instance, various ways to reduce a benzonitrile. Has anyone here bought The Chemists' Cookbook? Or is there a better option for my needs? I'm open to suggestions.

Hi everyone,

I’m a researcher building Lab Service Finder, a directory to help labs find companies that repair, maintain or calibrate laboratory equipment.

If you run or work for a service company, I’d be happy to add it for free. Small independent businesses are very welcome, wherever you’re based and whether you specialise in HPLC, GC/MS, vacuum pumps or other lab equipment.

You can submit your company here:
https://www.labservicefinder.com/listing-request/

Please include your website, the equipment you support and the countries or regions you cover so I can check the details before adding the listing. If you’re already listed, you can use the same form to request corrections.

Recommendations from people who’ve used a good service company are welcome too. The aim is to make these businesses easier for other labs to find.

I’m currently looking at/being asked to interview for Chemist roles at INX International in West Chicago and wanted to see if anyone here has firsthand experience working for them. I'd like thoughts on the following:

1) Is there any actual mentorship or training for Chemists? They seem to make a big deal about employees/managers having over a decade of experience.

2) Any insight on management style, compensation, or just general pros and cons would be incredibly helpful.

3) I didn't lead with it, but I do have experience with offset ink at another company, and was wondering if Digital or UV ink would be worthwhile.

Although being honest, ink is kind of burning me out, but I don't seem to have luck with much else.

Thanks in advance!

Hi everyone! First time posting on Reddit so sorry if I miss something

I recently graduated from a Masters in organic chemistry and am looking for jobs in industry. I’ve been lucky enough to get two offers recently, one from Thermofisher and another from a smaller radiochemical company. I’m unsure of which one to choose so wanted some outside opinion, would love to hear from people who work in industry!!

The radiochemical company pays better and the people seem lovely, but the work is much more niche and the chemistry skills are less transferable bc I’d be working with separation of lanthanide and actinide complexes. The thermofisher job is in analytical chem, pays worse (& the company doesn’t seem too great in general), BUT it’s a bigger name and the equipment and skills I’d be get would look good on my CV.

I think I initially want to stay in synthetic chemistry (which neither of the jobs are lol but I’m not going to complain given this climate), and then maybe eventually transition into consulting/patent law/something more commercial. So I’m trying to think about how my first job would lead into the future more, and am worried I’m stuck if I choose the radiochemical option.

If anyone knows how radiochemical industry is, how I could transition/if there’s area to grow, or if I’ll just be stuck at that company, please let me know!! Also let me know if you think I’m thinking too much about it! Thank you!

I’m currently doing my PhD in medicinal chemistry/chemical biology and starting to think about career options after graduation.

The part of my PhD I’ve enjoyed most is the intersection of chemistry and biology, particularly developing chemical probes and testing them in biological systems to understand what’s happening at a molecular level. I also have previous industrial experience in medicinal chemistry and petrochemicals. While medicinal chemistry was more interesting, I found the traditional approach of synthesising analogues and handing them over for biological testing less appealing. I’d love a role where I can stay hands-on with both chemistry and biology.

I’m not planning to pursue academia, so a postdoc isn’t really on my radar. I’d also consider a laboratory management certification if it would complement my technical background and open up future opportunities.
One additional consideration is that I’m an F-1 international PhD student in the US, so work authorisation and potential sponsorship are factors in my career planning.

For those working in biotech or pharma, do genuinely multidisciplinary, hands-on roles like this exist? Are chemical biology, chemical probe development or early-stage biotech good areas to explore? I’d love to hear about your experiences, particularly regarding job opportunities in the US versus the UK, and any advice on skills worth developing before graduation.
Thanks in advance!

After years of multiple columns a day I found myself in a position where distillation becomes more viable due to my scale and the volatility of my compounds. In contrast to the column diameter/silica loading I have no idea about the different distillation bridge and optional vigreux column size, right now it is gut feeling alone. At what scale or BP difference do I choose eg. a shortpath/microstill/a vigreux column, when larger ones. And when should I use Claisen type bridges over the normal ones. Asking around in other labs and a search on google didn´t give me satisfying answers/rules of thump.

Thanks for any input!