So we have a deadline next year to stop using DCM as a solvent. Any suggestions?

Has anyone done solvent suppression on 19F nmr? What pulse sequence did you use?

Hello Chempros, I recently discovered I have ~700€ left to spend from my PhD scholarship, since it will be a couple of months before defending and moving into a postdoc position (postdoc is biochemistry related and I come from an ochem background) I was thinking about spending in knowledge. However, I have no idea what course, possibly leading to a recognized certification, might be worth it, what would you suggest? Main topics I would like to study would be biochemistry, bioconjugation, proteomics, cell biology or related analytics. If possible stuff that industry would like to see on a CV.

Hi, long time lurker, first time poster.

From what I gathered online, quartz cuvettes are the superior investment due to their transparency in the UV region. However, my PI needs a circular dichroism measurement in a jiffy for publication and the order may not come in on time. We have access to UV-grade disposable plastic cuvettes - would those work?

For reference, the sample absorbs in the UV-region, which is my concern with using a plastic cuvette, even though it is UV-grade.

Thanks in advance!

I am on a second postdoc at a top 10 Pharma company with a solid publication record and good network. Unfortunately, the job market for pharma is the worst its been in 20 yrs. Despite peers reaching out on my behalf, I've not even landed a phone interview (75 applications and still applying). Through other contacts I've found out its not me, any other time I would be a top applicant but right now even entry level jobs are being swamped with dozens of applicants with 5-10 yrs industry experience. So it seems that I'm just not going to be able to remain in the pharmaceutical industry.

Has anyone else had to move away from their preferred field? How did you cope and what did you find?

Hey all, I'm a new PhD student and have recently been having trouble with what should be a straightforward chloro -> azido substitution. I've asked my lab/PI for help but we're not really sure what could be going on; I"m sure it's a me problem but I can't figure it out.

I've been running this reaction according to the first protocol (1 eq chloropropylamine, 2 eq sodium azide in water at 0.4M, 0.8M respectively). Heated to 80C in an oil bath with a greased condenser. Work up: Let cool, basify to pH 11-12 with 6M NaOH, extract with diethyl ether 5x (1x equal volume as reaction water, 4x with half vol). Organic phases dried with MgSO4, filtered, and concentrated with rotavap. I wasn't sure why the protocols I have here acidify with HCl or wash again with neutral water.

When I rotavap it down, I get almost no product when yields should be high. I got a clean NMR of product , so I think the reaction is working and the issue is with my workup. I considered that the product could be evaporating off, but I've tried cooling the rotavap bath with ice and the lit BP is 50C at 150mmHg, so I don't think that's it. My labmates have suggested increasing the pH even further and using higher volumes of ether to extract, but my PI didn't think that would help.

Reagents: I don't know when the chloropropylamine was purchased, but it was unopened before I used it. The sodium azide has been properly stored under the fume hood, but it was opened in 2017 so I ordered some more to see if that could be the issue?

I would appreciate any insight! I feel so silly for not being able to get this to work! Thanks in advance.

https://preview.redd.it/6f22t76487qd1.png?width=841&format=png&auto=webp&s=1ca9f99b7f55974583eaa91048c095408c63ef43

https://preview.redd.it/qc7wca6487qd1.png?width=742&format=png&auto=webp&s=e2445485f952887695b43433fe3dec10e118bda3

After my reaction, I saw that my septum was black even though it never came in contact with the solvent. It is my first time seeing this. Is there a gas that can react with these types of septa?

I've been on the search for a pump to deliver a 90 °C aqueous solution of 2M NaOH at 1 to 50 mL/min flow rates. It's expected the system will reach a back pressure of just under 300 psi and I've been having a lot of trouble finding something that meets all these criteria. Does anyone have any insight into where I can get a pump like this? I got a recommendation over at the pumps subreddit that is close, but it starts at 20 mL/min.

I'm sure I'm asking for too much of a pump, but I'm asking here on the off-chance anyone has a better recommendation here.

Thanks!

I have heard many rumors that certain equipment will not work inside an argon filled glove box because of dielectric breakdown. I have never been shown conclusive proof of this but have always erred on the side of caution to avoid ruining things.

For instance, as a postdoc, I put an X-ray diffractometer in a glove box and purposely chose nitrogen instead of argon despite the increased static because of the chance argon induced dielectric breakdown in the 30kV system would ruin the instrument.

Brushed motors I totally believe could fail. I am not sure about brushless.

Balances obviously work.

Anyone know of a resource that discusses this issue?

So there’s a tertiary alkyl amine and an olefin in this molecule and I have to epoxidize the olefin. How would you do it?

Hi everyone!

I’m looking for recommendations on micro pipetters. I only need one that can do 100, 300, 500ul. It will probably only be used in one solution. (Zinc standard). I’m just wondering if there’s brands people prefer more. We buy most lab equipment from fisher scientific but it doesn’t have to be from there. There’s just so many options and I really don’t know much about them. User friendly is a plus! Price doesn’t matter too much since it’s for work. Thanks everyone!

• if you’re curious, my predecessor did this by hand using a 1ml glass pipet 😆. I want to be more accurate.

First off, I'll be up front and say that the Ph.D. program I'm currently in is the only one I got into, and only really had one choice of professor for organic synthesis. However, he's incredibly knowledgeable about organic chemistry, he has a modest but still respectable number of publications in good journals, and most importantly, we get along. So, given all the metrics of a good grad school gig, one might think I've hit the jackpot.

The most recent Ph.D. from his lab was awarded to my colleague who started a year before me. Her dissertation included a single project that was started before she arrived and was very closely related to past publications. She saw that project through to the end, got into JOC, and rode off into the sunset. Was very good work in my opinion, and she deserves the Ph.D. and the decent pub.

However, since then, everything my PI has proposed has failed horribly. I'm a 5th year grad student now, I've spent countless hours on 5-10 different projects now, and I'm no closer to the Ph.D. than when I started.

I think I'm progressing well as a grad student; getting better at organic synthesis, getting better with project/time management, becoming familiar with the literature, etc. I have faith in my abilities, but is it possible that I'm blinding both myself and my PI? Is it possible that, in other hands, these projects would have gone better? Should I be scrutinizing myself even more intensely due to all these failures?

Am I wrong to think that when people say "getting a Ph.D. is hard" they are talking about a situation completely different to mine? I imagine people say this because you have to spend many hours running experiments, analyzing them, compiling the results, and then having the results scrutinized by peer reviewers. Thing is, I haven't even gotten to that point. In my opinion, that will be the easy part. If I can just get one damn reaction to give me publishable results, I'll have a paper in a couple months. I feel like I'm trying to do an already very difficult thing on hard mode.

I know that research often "doesn't go well" but I feel like this is a bit ridiculous. Am I really doing a Ph.D. on "hard mode"? Has anyone else had to deal with bullshit like this?

I'm reading this article, and it states that a Pharma Lab "focuses on drug discovery and research," and a CRO, by definition is a "research organization." How are they different, and how are they the same?

I am looking for efficient procedures to demethylate methyl sulfides (thioethers), notably aryl derivatives, but maybe also alkyls. Are there straightforward, mild reactions for S-Me analogously to demethylation of ArOMe using BBr3? Can BBr3 be used with ArOSMe? Or iodotrimethylsilane? One option I have is using MeSNa or MeSeLi. Thanks!

Hi all,

I am requesting the help from people who actually know what they're doing (not me) when it comes to borylations/Palladium chemistry in general.

Substrate I'm trying to borylate is 2-bromopyridine. I know, borylating at the 2-position is unfortunate but I'm really just looking for anything that gets me above a 40% yield.

Conditions tried: (all using B2pin2, 1.2 to 1.5 equiv)

Bases: KOAc, K2CO3, Na2CO3 (3 or 5 equiv each)

Solvents: toluene, DMF, toluene/ethanol 5:1, DMSO, dioxane (0.2 to 0.4 M each)

Palladium catalysts: Pd(dppf)Cl2 DCM complex, Pd(PPh3)4, Pd(OAc)2 (5 mol% each), also tried Pd(OAc)2 + XPhos together (5 mol% and 20 mol%)

Running each at reflux or 100C in the DMF example. Basically any combination of the above reagents have been tried. All the usual troubleshooting that I know how to do has been done - solvents and reagents are extremely dry (sieves/sodium and stored in glovebox, respectively). System is perfectly sealed and my Schlenk technique is at least acceptable (other sensitive cross couplings I run work just fine, using N2 tank ran through Drierite first, etc.).

Initial monitoring by TLC circa 14 hours after setting them up usually gives two nice spots, one more polar spot that looks like product with varying amounts of starting material still present. NMR or column it though, and turns out my yields are in the single-digits. It's also not unstable/protodeborylating on silica via 2-D TLC (2-D definitively rules that out, right?).

Any thoughts/suggestions? Any "screw you just borylate" conditions that y'all go to? Or is this just a substrate that is probably just not going to borylate easily?

Hi all!

I have a problem with simply plotting my spectra in ggplot2. My spectra all look jagged for some reason, but original data in some other softwares look fine. I tried as.numeric() aproach after importing data into R, but it changes nothing.

Data is not that big, 351 points per spectra, or 1262 before deleting some points (OMNIC outputs whole 4000 to 400 region regardless of processing, unused region is just 0)

1. I use OMNIC to take .spa files and do some processing and output as .csv files. In OMNIC they look fine.

2. Next I just joined all spectra and cut off data at irrelevant wavenumbers in excel. When I try plotting it in ggplot2, spectra look messed up and jagged.

3. Same happens in Excel

4. If I try plotting original outputed .csvs (without their data cut and relevant data copied) Original uncut .csv outputs look fine in fityk

It looks fine in excel (when irrelevant data is cut in x-limiting in Format axis). As if the act of making headers and just deleting irrelevant data makes it break)

Do you have any idea what would be the cause of this?

Hi,
I am running a gradient from 85 percent 90/10 ACN/Water to 40 Percent 90/10 ACN/Water with 10 mM NH4ACo at pH 6.8 on a RRHD HILIC from agilent on a QTOF Ms with ESI source. The compound is polar and solved in 1 part PBS und 2 parts MeOH. I use this injection system, because my actual samples do have the same composition and I want to record a calibration curve under the same conditions.

The -TIC shows some uncommon negative slopes before the actual peaks arise (7 to 8 min and 10.0 to 10.3 min). My compound elutes at 10.5 min in tic and shows good peak shape in EIC and DAD at 254nm.
I am wondering: What could be the explanation for this kind of slope in ESI TIC? Have you ever saw something similar? Before my compound elutes, the TIC also drops. The signal at 8 to 9 min should be phosphate from PBS. The idea of this method is to only sent the compound to MS and the time before and after into waste to keep the ESI chamber clean after the appropriate diverter windows has been found. I am wondering if this effect is normal on HILIC or related to MS settings or else.

https://preview.redd.it/cx0qybofdxpd1.png?width=1255&format=png&auto=webp&s=f5577bc8a447c2145f1770a0eb70f32b1e35265c

I did the standard distillation with sodium wire and benzophenone. My advisor told me to wait just 10min until reflux before I could dispense and use the solvent ,and said that a purple colour indicates that the THF is water-free.

However, I decide to check the water content using KF titration, and it was 278 ppm. I have also seen a method online that says to distill for several hours (not minutes) until the solution turns blue (not purple)

In addition to that, I have some THF which has been standing over (partially) activated sieves (by that, I mean the sieves were kept in an oven at 150 C for several days-weeks, as our furnace is broken) and when I tested that on KF the water content was 138 ppm. This was strange, as we were under the impression that the distillation is the most effective method

Anyone have a tried and trusted method where they have used KF to confirm the THF is dry? (besides using properly activated sieves, as that is not possible at the moment sadly)

I am trying to make a Grignard reagent from an amide derived from a substituted bromoaniline (Ar-NH2) and a substituted benzoic acid (Ar'-COOH), so Ar-NH-CO-Ar'. Any attempts so far failed, although I am quite experienced in Grignard chemistry. I am aware that as a first step I need to deprotonate the amide NH, for that I used a simple alkyl Grignard like iPrMgBr. For the insertion of Mg into the aryl bromide, I have tried stirring the deprotonated amide over Magnesium metal, or just adding more alkyl Grignard to do a metal-halogen exchange. For reaction monitoring I use HPLC, looking for the deshalogenated species (which should arise from quenching the generated Grignard in the HPLC sample). As the easy ways described above did not work out, I read about adding metal salts like Fe(II) or Fe(III) to the reaction which should catalyze the Grignard formation or metal-halogen exchange, however this ended in what seems like reduction of the aryl bromide by the iron/Grignard system (which also gives the deshalogenated product -.-) or partial aryl alkyl cross coupling (not what I intended..). The reactivity of the assumably formed Grignard is tested by addition of an aldehyde, which should gladly react with the Grignard, but does not in any significant amount. Could the amide functionality itself interfere with the -MgBr group (if the latter is even formed), even if the amide is deprotonated? Another thought was to protect the amide in situ after deprotonation, with a Boc or silyl group, does anyone have experience with that and how compatible these protecting groups are with Grignards?

An alternative approach would be forming the Grignard from the aniline (after double deprotonation and protection), performing the reaction intended for the Grignard reagent, and afterwards installing the amide. Also here, does anyone have experience with making Grignards from anilines?

Any help is greatly appreciated!

I need jcpds card for comparison of my catalyst.can anyone help out with that ...how to access that?

Hello!

I've an interview for a synthetic chemistry position requiring at most a Master's degree for the higher position.

I have a PhD where I did some synthesis but didn't focus strictly on synthesis. I did well during my degree but feel rusty on retrosynthesis.

Can someone tell me the complexity of molecules I might expect in the retrosynthesis section of the interview?

Thank you!

I need a specific article from BULLETIN DE LA SOCIETÉ CHIMIQUE DE FRANCE vol 130 (1993), but it seems to be only available as physical print. Am I wrong? Is there someone with access to this journal who could help me?

Vol 130 (1993) page 475-478. It would be fantastic if someone could provide me a pdf!

Hi everyone, I truly hope than someone will be able to help me here. I have a polymer that is analyzed by GPC at two different labs to double check the results. The two labs observe quite similar Mn (+/- 10k) but the Mw is really different (>100k difference so one lab measured 210k and the other 350k)

Note that they use the same column, the same solvent system, flow rate, standard etc.. only not the same machine brand.

Do you see what would cause such a difference?

Hello everyone, gaussview 5 (GV05) refuses to open its viewing window even if I click or alt-tab into it ("G1:M1:V1", refer to screenshot), which means that I am unable to view the results of my calculations nor any of its input files as a result. As you might be able to guess, this issue is relatively recent for me and I have been able to use it normally before.

I've also thought about these possible issues;

1. file corruption - not possible, as the GV05 viewing window goes unresponsive upon launching.

2. license - should not be the issue, as my group has been using that license for forever

3. file size - again, not possible since it goes unresponsive before any sort of file opening.

Any help on this issue is very much appreciated.

P.S. Also on the topic, what are your views on ORCA as a replacement for gaussian? For context, I am an experimentalist that usually performs TD-DFT calculations, and I am afraid that switching to ORCA will make it difficult for me to integrate my results with those of my mentor/supervisor (who almost exclusively uses gaussian).

https://preview.redd.it/p7ai9bmv8qpd1.png?width=1910&format=png&auto=webp&s=5b1be0e768cb368bd0b4508ba0ea87ceba50e9ad

Hi all,

I've been given the exciting task of using up the last of a training budget before the end of the month, and have decided to spend a few hundred quid on microlitre syringes.

https://www.hamiltoncompany.com/laboratory-products/syringes/general-syringes/microliter-syringes/700-series?menu%5Bfilter_facet_19093%5D=100%20%C2%B5L&page=1&configure%5BhitsPerPage%5D=1000

Anyone have experience with these? I could do with some guidance on:

• Needle fittings (is cemented tip a waste of money over spending a little more for a removable needle?),
• Whether calibration is worth it (I do synthesis, but nothing massively sensitive or tiny scale - I just want something a bit more precise than a 1 mL syringe!
• Whether the heat limits of 10 - 115 °C are "our syringes will melt if you try to oven dry them" or "our syringes will slightly lose calibration"

TIA

Alright Schlenk Gang,

Im setting up a new schlenk line, mostly for slightly air/moisture sensitive reactions, nothing crazy, and all on pretty small scale. I found this teeny little gem, and my heart really wants to use it as a vacuum trap for the new schlenk line. What are the chances that this volume of dry ice could last longer than like an hour? I need someone else to destroy my dreams for me 😔.

EDIT:they make a glass stopcock version which I was looking at. mah bad

I think the purity of this reagent is messing up my reactions. Can anyone guide me to any papers that call for preparing the purification via recrystallization?

We ran out of phenylacetylene but found an old bottle in the back of a cabinet and it would be very helpful for me to be able to use it now and not have to wait for the new bottle to be delivered. The NMR indicates presence of styrene and some other impurities I can't identify. Can anyone advise on how I could purify it? Distillation is out since the bp's are too similar. Standard column maybe?

So recently I started doing XRPD measurements of organic compounds. But sample mounting on the Si plate is really annoying. Whenever I try to flatten the powder grain with e.g. a piece of weighing paper, the samples simply stick to the paper and it's really difficult to set the powder to some flat shape.

Another thing is static electricity, which simply makes the samples fly all over the plate when I try to apply them. Any advice on how could these two nuisances be avoided or solved?