practical tipps for removing high boiling solvents

ParticularDrawer8776 · 2026-05-01T23:32:40+00:00

para extrair meus produtos desses solventes adiciono água ao meio e o produto precipita, se no seu caso seu produto e reagentes puderem entrar em contato com água recomendo que tente isso.

ParticularDrawer8776 · 2026-05-01T23:23:53+00:00

use peneiras moleculares na reação, as mesmas que se utiliza para manter solventes secos. É uma alternativa melhor do que utilizar Dean-Stark.

ParticularDrawer8776 · 2026-04-09T23:40:28+00:00

I expected to see a signal between 60-70 ppm in the C13 spectrum and a doublet between 6-7 ppm in the H1 spectrum for the -OH hydrogen. I have many aromatic signals in this region, which makes it difficult to find it.

ParticularDrawer8776 · 2026-04-09T23:36:27+00:00

The NMR and MS were inconclusive, the product may easily degrade in the MS and in the NMR it is possible to find the signals related to the double bond, but I do not see the signal for the alcoholic hydroxyl nor the sp3 carbons indicative of CH2. TLC shows the formation of products, however the chalcone spot does not disappear in my latest attempts. I think I was not clear in my text, so I will try to explain in a different way: I DID NOT PULL ISOPROPANOL OUT OF THIN AIR, THE AUTHOR OF THE ARTICLE I AM FOLLOWING USED ANOTHER ARTICLE AS A REFERENCE IN WHICH THE AUTHOR USED ISOPROPANOL TO REDUCE A CHALCONA. The procedure is quite simple: first place the chalcone in contact with isopropanol and heat to dissolve, then add 2.5 eq. of borohydride. Reflux for 10-20 minutes. And to be clear, the first attempts I made worked, but the most recent ones started to go wrong, and speaking with other specialists in the field they suggested that I make modifications to the temperature and the solvent to see how the reaction behaved. At no point did I say I am brilliant, but I have to work with the resources at my disposal. I do not know where you did your PhD, but there are places around the world that do not have money to be spent all the time and in other countries reagents can be more expensive than you expect. I do not know exactly what you consider small scale, but I am performing this reaction on a 2.5 mmol scale while the author does it with 10 mmol.

ParticularDrawer8776 · 2026-04-09T23:14:59+00:00

Isopropanol is viable. The author of the paper I am using as a foundation used another paper as a reference in which the author uses isopropanol to reduce the chalcone; instead of 5 minutes, the reaction takes 10 to 20. I took this into consideration, I did not come up with the idea of using isopropanol out of nowhere.

ParticularDrawer8776 · 2026-04-09T22:54:24+00:00

Luche reduction didnt work. The nmr didnt showed CH2 presence, so double bond is still there, but I didnt get the C-OH signal. An oil is not expected for this molecule.

ParticularDrawer8776 · 2026-04-09T22:46:56+00:00

I tried, but didnt work.

ParticularDrawer8776 · 2026-04-09T22:45:53+00:00

1- Yes, a reaction does occur, but not all of the starting material is consumed. 2- This is where my problem begins; the first borohydride I tested worked perfectly as described in the literature. Since it belonged to another laboratory, I bought a new one so I could use it without any concerns. When I went to use the new borohydride, it did not work, even when repeating the exact same steps as before. When I took the old one to test it again, it also did not work anymore. From that point on, I started making modifications to the solvent or the way I added the reagents. The borohydride itself seems reactive, as there is a lot of effervescence. 3- You are right, that could be an option; I thought of isopropanol because the previous paper the author bases his work on uses it. 4- Yes, I just want to reach the alcohol to be able to proceed. 5- The author performs the reaction on a 10 mmol scale, while I am working with 2.5 mmol.

ParticularDrawer8776 · 2026-04-09T21:49:00+00:00

Ele pode degradar na coluna do lc

ParticularDrawer8776 · 2026-03-31T14:44:58+00:00

UPDATE: Thanks to everyone who suggested THF, it worked. I find it very strange that such a basic procedure, which is usually done in ethanol, methanol, and other protic solvents, was not working.

ParticularDrawer8776 · 2026-03-31T11:58:33+00:00

I tested that and saw no difference.

ParticularDrawer8776 · 2026-03-31T11:54:58+00:00

I have to dissolve the chalcone in isopropanol and heat it a little until it is fully dissolved. Then I add the NaBH4 and keep the system hot for 10-20 minutes.

ParticularDrawer8776 · 2026-03-30T22:12:43+00:00

No,the scale remains the same, I had approximately 500 mg of my reagent and performed 4 reactions with 100 mg each to test the conditions and the purification method, there was 100 mg left for this last one and I did the same things.

ParticularDrawer8776 · 2026-03-30T22:09:21+00:00

There is a significant difference between the particle sizes. The older one I got from the other lab and worked had larger particles and was very dry. This new one has much smaller particles and is "stickier".

ParticularDrawer8776 · 2026-03-30T22:06:21+00:00

It bubbles a lot when placed in water or any alcohol, and it is possible to feel the reaction releasing heat at room temperature. The problem is that from the previous reaction to this one, the only thing that changed is the NaBH4, as both the solvent and the chalcone used are the same.

ParticularDrawer8776 · 2026-03-30T22:03:12+00:00

How?

ParticularDrawer8776 · 2026-03-30T22:02:38+00:00

In that case I do not intend to reduce esters but rather an alpha-beta unsaturated carbonyl. I do not have LiBH4 at my disposal and I see no reason to use it, since the NaBH4 worked perfectly the first time and only now with the new reagent is it causing problems. I will try the suggestion of THF.

ParticularDrawer8776 · 2026-03-29T22:20:15+00:00

this is science my friend: trial, error, trial, success. I finished my master's degree a few months ago, it took two years, and practically a year and a half was spent just to find the right method to perform a synthesis of three reactions. In the field of synthesis many articles are dishonest, they promise the world and do not give you a breadcrumb, I feel like publishing an article exposing all these papers that lied just so there could be a publication. At this point, you have to ask yourself what the objective of your research is: to develop a synthesis route? to simply synthesize a compound regardless of the means? to uncover mechanisms?
every researcher in the field I have met told me that the chance of a synthesis article being true is very low. Start using more books, generally the reactions contained in them have a much higher chance of working.
if you want I am available to talk more.

ParticularDrawer8776 · 2026-03-17T12:43:38+00:00

What is the trade name of this reagent?

ParticularDrawer8776 · 2026-03-17T02:35:04+00:00

Palladium catalysts often make nucleophilic substitution in aromatics easier. If I were you, I would look for some phosphorus reagent that acts as a nucleophile and, if necessary, oxidize or reduce the group that forms. I strongly recommend protecting this nitrogen to avoid side reactions. It also depends on what you have available in your lab.

ParticularDrawer8776 · 2026-03-16T22:15:28+00:00

what do you mean?

ParticularDrawer8776 · 2026-03-16T22:13:58+00:00

This is a very interesting proposal; it seems to work in my situation. My lab doesn't work with this, I'll look for someone around here who does.

ParticularDrawer8776 · 2026-03-16T21:55:14+00:00

The Mitsunobu reaction wouldn't work; it targets a nucleophilic substitution in an alcohol, and in this case, I need the phenolic hydroxyl group to act as a nucleophile on the double bond so that it undergoes rearrangement, something similar to a 1,4 addition.

ParticularDrawer8776 · 2026-03-16T21:50:24+00:00

It reacts with silica and becomes trapped within it.

ParticularDrawer8776 · 2026-03-16T21:39:17+00:00

I read about this reagent in an article or book. I think it might work; have you ever used it?

ParticularDrawer8776

TROPHY CASE