r/Chempros

Hello, I was reading an article ref(pubs.rsc.org/en/content/articlepdf/2016/nr/c6nr00735j), wherein I encountered a doubt.

The construction

Basic overview, creating a diode using organic molecules.

So the thing is, when the whole setup is in positive Bias(i.e energy of R > energy of L) the molecules are attracted together. Here is citation from text:

>As the energy of the sites is different at zero bias, the current is low. For positive bias, the sites are pulled towards each other and the current increases. At 0.55 V, a pronounced peak is visible. This is the point where the two sites have equal energy and resonant transport occurs.

So, my doubt here is, in the line, "The sites are pulled towards each other" why? I realize that 2 F on ortho reduce the electron density in the benzene ring, herewith reducing its energy(i hope i got it right), so providing it with more voltage, helps bring this energy difference down and now suddenly the gap that is present(the ethane bridge), that gap is lost and effectively the pi orbitals of the 2 benzene rings are close enough so that resonance can take place, hence a forward bias.

Please help me with this.

Whats your opinion on this company?

I plan to carry out the Buchwald-Hartwig coupling reaction using 2,6-diaminopyridine (DAP) and 2,6-dibromopyridine (DBP) in the presence of a palladium catalyst.

My experimental parameters are as follows:

1. **Reactants and Feed Ratio:**

   - 2,6-Diaminopyridine (DAP): 6 mmol

   - 2,6-Dibromopyridine (DBP): 3 mmol

   - Molar feed ratio: n(DAP) : n(DBP) = 2.0 : 1.0

2. **Reaction Conditions:**

   - Solvent: Toluene, 60 mL

   - Base: Potassium tert-butoxide (t-BuOK), 15 mmol

   - Catalyst: Pd₂(dba)₃, 0.06 mmol

   - Ligand: RuPhos, 0.12 mmol

   - Additive: 18-crown-6, 6 mmol

   - Reaction Temperature and Time: Stirred under reflux at 90 °C in an oil bath under an inert atmosphere (nitrogen) for 24 hours.

   - Workup: After the reaction, the mixture is quenched with saturated ammonium chloride solution, extracted with DCM, washed with saturated sodium chloride solution, dried over anhydrous sodium sulfate with stirring for 30 minutes, evaporated under reduced pressure to remove the solvent, and finally purified by column chromatography.

3. **Target Product:**

   - The target product is N²,N⁶-bis(6-aminopyridin-2-yl)pyridine-2,6-diamine.

   - Structural confirmation is planned via ¹H NMR.

4. **Actual Products:**

   - The actual products obtained are N²,N⁶-bis(6-bromopyridin-2-yl)pyridine-2,6-diamine and N²-(6-bromopyridin-2-yl)pyridine-2,6-diamine (mono-substituted byproduct).

These are my reaction conditions, which I followed based on literature references. Why am I not obtaining the desired product? Could any experts provide guidance?

Hi all. This question is for anyone that has personal experience with DPPA specifically. I have experience with all kinds of toxic and highly reactive chemicals, but I had always avoided using azides because I usually have to scale up to a kilo. But I'm told that this one is relatively safe to work with. Per a coworker "no thermal decomp below ~100C"?

Anyone have personal experience with it at the ~1kg scale? Concerns are runaway exotherm as well as hydrazoic acid generation. We have run a calorimetric and off-gassing test already, but this was a very small scale, and I'll be handling the stuff personally this time around.

Please don't tell me I should know how to research this if I'm going to be using it. I am going to spend all week on it, this is only in planning stages. I take most comments here with a grain of salt. I just figure this is a useful place to find someone that has personally handled it and may have some unique anecdotes that might not be found in the literature. Thanks!

I’m a 20-year-old from near Patna, Bihar, currently exploring an idea for a public-health tech project called Safe Sip Analyzer (SSA).

The concept is to create a portable device that could potentially detect methanol adulteration in sealed liquor bottles without opening them.

I started thinking about this after repeatedly seeing hooch tragedy news from Bihar and other states. Most current testing methods seem expensive, slow, or dependent on laboratory setups, which made me curious whether a faster and more accessible field-screening solution could be possible.

Right now this is still at the idea/research stage. I’ve been reading about spectroscopy, signal analysis, sensors, and portable detection systems to understand whether something like this could realistically work.

Some questions I’m trying to explore:

\- Can this type of detection work reliably through sealed bottles?

\- How difficult would real-world calibration be?

\- What challenges would appear in low-cost portable hardware?

\- Could a small device achieve useful screening accuracy?

I’d genuinely love feedback from people experienced in:

\- Hardware/embedded systems

\- ML or signal processing

\- Spectroscopy/chemistry

\- Startup building

\- Public-health technology

Not fundraising or selling anything — just learning, researching, and trying to understand whether this idea has real technical potential.

Would appreciate honest opinions, criticism, or guidance.

If anyone here has experience in spectroscopy, embedded systems, hardware prototyping, or ML/signal processing, I’d genuinely appreciate your feedback.

Even criticism or reasons why this idea may fail would help me learn faster.

Also open to connecting with students, researchers, or builders interested in public-health or deep-tech projects in India.

I am starting a project where I will need to synthesize a few hundred peptides (around 10 amino acids each) and cyclize them in milligram quantities. Does anyone have suggestions on instruments to look into or stay away from?

Hello!

We have decided to resurrect our ELSD that had been in storage since my predecessor. It works, and I’ve used ELSD once before, but that was many moons ago and I’d like to learn the tricks to optimizing it.

I know the gas flow controls the size of the aerosol/droplets, nebulizer temp is set to get as much of the aerosol as possible into the drift tube, and the drift tube is where the main evaporation happens. If I understand correctly, lower gas and thus larger droplets are better for sensitivity but are difficult to reproduce. Lastly, that you want the drift tube to be warm enough to evaporate the solvent but not vaporize the sample.

I guess my questions are:

1. Is the key to method development really doing a lot of runs changing one variable at a time? I know that seems kind of obvious, but that feels like a lot of time for optimization.
2. Is some liquid coming out of the elbow/siphon normal? I know too much can mess with the baseline, but I have also seen people say it is needed to seal the drift tube.

Thanks to anyone who can provide insight!

I want to metallate a porphyrin with Ni(acac)₂ in toluene. How dry and oxygen-free should the reactants ideally be? My first attempt yielded only a 60% yield....

The manuscript involves:

virtual screening of natural alkaloids,

molecular docking,

100 ns MD simulation,

in vitro enzyme inhibition assays (α-amylase, α-glucosidase, pancreatic lipase, cholesterol esterase),

antidiabetic + antihyperlipidemic focus.

The paper was rejected from a ~2.7 IF journal, so I’m now looking for realistic journals with:

IF roughly 1–2,

non-mandatory open access,

preferably hybrid/subscription journals,

Scopus/WoS indexed.

I specifically want journals that regularly accept docking + MD + enzyme inhibition pharmacology papers.

Would appreciate practical suggestions from people who publish in this area.

Hello, I am a first year organic PhD student. There is a compound I want to synthesize for my research, but the only reported synthesis of it is at 450 °C for 3 days. The reaction vessel must be sealed to prevent the starting material and product from evaporating away. Boro-silicate is only recommended to operate at 450 °C for 12 hours so I need something other than a rbf or pressure tube. I have a heating mantle that should get up to 450 C and the temperature probe on my hot plate is rated for up to 500 C. I just need a reaction vessel.

The options I have seen are making your own pressure tube with an Inconel tube (Ni/Cr/Fe alloy that is corrosion and oxidation resistant even in harsh conditions) and swagelok fittings, or if you purchase an entire tubular furnace it comes with a metal reaction vessel. I was wondering if there were any stand alone reaction vessels that I could purchase and put on my heating mantle.

If anyone has any experience on how to run a reaction at this temperature without having to own a specialized furnace/autoclave I would love to hear how you did it and what reaction vessel you used.

My research partner really wants me to synthesize this compound so we are going to just try in an old boro-silicate schlenk flask that we won't care if it breaks. We are going to completely evacuate the flask before heating to reduce the pressure that will build while heated. I am also most definelty setting up a blast shield around this reaction.

Hi Everyone,

I usually see a lot of posts on here like "my amide coupling didn't work, what reagent should I try next?" A useful, but less known reagent is the combination of TCFH and NMI to generate highly reactive N-acyl imidazolium ions. A few days ago, a review was published focusing on the use of this system. Link is below if you want to check it out.

PS. I have no affiliation with the authors.

https://pubs.acs.org/doi/10.1021/acs.oprd.6c00060

Happy amide couplings!

Hey fellow chemists,

right know I'm facing a problem I can't solve and even the literature doesn't seem to have encountered this problems; hence I'm seeking some of your expertise now.

---

What have we done:

• Raman spectroscopy of soy protein isolate (10 % in water)

• Laser: 532 nm

• Duration: 10 s, 12 counts

• Standardisation of spectrum: via Phenylalanin

---

The problem: We encounter a unexpected raman shift (compared to literature on Raman spectroscopy performed on either solid or dissolved protein) and can't explain it.

In particular

• our disulfid SS conformation peaks are all shifted by roughly -50 cm^(-1) showing up at 450 - 500 cm^(-1)

• our Tyrosine and Tryptophane doublet are shifted by roughly -20 cm^(-1) with Trp around 1320cm^(-1) and Tyr around 820 cm^(-1)

We don't suspect any instrumental errors, as a) it was calibrated/ checked recently and b) the Amide peaks show up as expected.

---

Does anyone here have an idea what could cause the problem and/ or ideas about how to revolve it?

Thanks in advance!

Best,

7

Is this common? My previous academic lab also had this but my previous company did not. I was wondering how bad it is in terms of toxic solvent release. The vent is also not directed into the fume hood. I have not noticed any solvent smells but I am worried about when we concentrate off acids such as HCl which happens often.

How to get a job in HR after 6 years of experience in R&D chemistry

Hi everyone,

we would like to buy some standards of synthetic cannabinoids and NSOs, but Cayman is quite expensive for us (at least for now).

Do anyone have experience with LGC Chemicals distributor and brands like TRC or LoGiCal (sold by LGC)?

Any comments will be appreciated, thank you!

Have a nice day!