Jump to content


  • Posts

  • Joined

  • Last visited

  • Days Won


Everything posted by hypervalent_iodine

  1. Probably, but it’s not needed. You can get away with just using water.
  2. Possibly. I would suggest you first steep the tea in hot water, filter it, cool the water, and extract the caffeine from that solution by partitioning over DCM. You are more likely to avoid organic contaminants that way. If you like you can then recrystallise from ethanol.
  3. ! Moderator Note If you can repost this in a way that is coherent and scientific, please do so (but in Speculations, please.)
  4. Your reasoning for only being able to use the diacid still doesn’t make sense to me. There is no reason (based on what you have said) that you couldn’t start with a monoprotected diacid or something with a terminal alkene. These functional groups are converted after esterification with the diol to give you the terminal carboxylic acid groups. You will still get the product you need. The procedure I attached is actually quite straight forward so far as these things go. I certainly wouldn’t describe it as complicated, in any case. I don’t know what sort of purification is suitable for you, not knowing what you have available. You said you were familiar with synthetic chemistry so I have to assume you know the basic methods we would use for this sort of thing? A column could work, but you might have to pretreat the silica with acetic or formic acid. Depending on the diacid you use, there might be other methods such as recrystallisation or trituration that could work as well.
  5. Is there any reason you have to use the diacid? I have found some procedures, but they use a monoprotected version of the diacid (such as I mentioned in my previous post). For example, in this patent: Might not be very industry friendly (not sure), but you get the idea. I did also come across another paper that might be useful, but I don't have access to it.
  6. Without meaning to sound facetious, how do you think it might change it? Do you think that a polar solvent might be able to interact with the silica as well and if so, how might that change the ability for a polar substrate to move up the plate? Would it be more impeded or less?
  7. Great question, and not something I had thought of immediately, but something I am familiar with. In fact, it’s not so much the knot as it is the rubber of the balloon itself (as studiot mentioned). You have to buy balloons made of specific material for helium or it will rapidly deflate for this reason. You see the same with hydrogen, which is larger but still small enough that normal balloons are permeable to it. When I use hydrogen balloons in the lab, I use 2 helium quality rubber party balloons, one stuck inside the other, and seal the balloon around whatever tubing I’m using with rubber bands and film. You will still have a deflated balloon by the next day. The same balloon with argon or nitrogen gas will remain inflated. Probably an easy enough experiment to set up in class actually, if you have access to helium.
  8. Ah, I see. I was imaging a cyclic product for some reason. Huge excess of the acid might help, as JohnCuthber suggested, but you may also find you need to avoid the diacid entirely. You could use something that has a monoprotected end, or some other functional group that you can oxidise up after coupling to the diol. If you have access, you might wish to look through SciFinder. I should also ask if you have experience in synthetic chemistry at all? It’s not a trivial thing to do, not to mention all of the hazards involved.
  9. I had assumed from your post that you already had compounds in mind. What is this for? Minor side note: we would generally use the term method, procedure or protocol, not recipe (I realise that English may not be your first language, this is just a small point ).
  10. For example, in structural biochemistry you can infer what sort of binding interactions exist between an amino acid residue and some sort of ligand / substrate by looking at atomic distances. By knowing the radii of the atoms you are measuring, you can make predictions about the presence / absence of intermolecular attractive forces, such as short contacts. In terms of reactivity, just think about the difference in ionisation energy between, say, sodium and caesium. Thinking about atomic radii and what that means about the distance from valence electrons to the nucleus, why might caesium’s first ionisation energy be lower? These are all things that you might Google, so I would encourage you to do that and come back if you have questions.
  11. Studiot mentioned what we use it for. It’s primarily useful in chemistry for predicting or explaining bonding interactions. You use it in structural biochemistry, crystallography, etc. You might also it to infer reactivity of certain elements.
  12. We have no plans to close it. If you wish for it to end, stop participating in it and it will die its own death. Otherwise, please stop using this thread for comments that either don’t belong on the forum, or belong in a report.
  13. I was trying to think of what colours mine were under UV and realised that our imager only does black and white, and I use orange glasses and a Safe Imager when I am cutting gels. Google suggests that orange is reasonably normal though, so I’m not sure you have anything to worry about. @CharonY would know better.
  14. ! Moderator Note This is uncalled for, koti. I tolerated your comments before as I was participating in this thread, but you should know better than to think we will be tolerant of you insulting other members.
  15. If your NMR matches literature besides those two peaks (that I am fairly sure are residual solvent / grease peaks), I would proceed with whatever you’re using it in. Go small scale first so you don’t blow all your compound (just in case). For future, try and source the compound from another company if Sigma is giving you bad stock. We’ve had to do this on several occasions, with the added bonus that it’s often cheaper. If you’re in the US, I’ve always been fond of Oakwood Chemicals. Edit: For the record, you will sometimes find that your NMR solvent has a grease contaminant in that pops up at about 1.25 ppm or so. Some years ago my lab had a problem where every bottle of CDCl3 we got from Sigma had this peak, and it didn’t go away until we switched back to Cambridge Isotopes. What you may like to try is to run an NMR of just your solvent, to see whether or not those peaks come from there or from your compound.
  16. A rot evap won’t get rid of trace water, not to mention you likely have some water in your NMR solvent. I would suspect water and hexane or grease are the culprits here, based on chemical shifts. You need high vac and very dry NMR solvent to completely eliminate the water peaks. Have you run anything else? GCMS? 13C NMR? (edited)
  17. ! Moderator Note We don’t discuss the synthesis of illicit substances. Thread closed.
  18. I have read the OP of the thread under discussion a number of times as well as the rest of the thread. For what it's worth (probably not a lot) this is my take on it. The OP clearly has major difficulties with English. This is unfortunate since it detracts sigificantly from their attempt to get across a clear message. More than that it can create the impression, consciously or unconsciously sensed, that the poster is not the sharpest knife in the draw. At one end of the possibilities I see a deluded person, probably not well versed in science, but knowing enough (poorly understood and often wrong) to think they have had a revolutionary idea. At the other end is an individual who has had a relevant insight to a plausible renewable energy resource. They have likely been seriously overoptimistic about its potential, but yet is may offer a genuine benefit. In either case they lack the resources to construct a protype and fear loss of control if they publish details. The quality of their English makes it impractical to distinguish between these possibilites, though past experience might suggest the first is the more likely. In neither case was there much point in continuing the thread, but I sympathise to a degree with the point made by Studiot that the poster could have been treated with a little more courtesy. Obviously, all of the foregoing is an opinion and can certainly be disregarded, though I've always found it productive to reflect on all opinions Again, these are opinions made lacking all of the facts of the matter. We are not going to post the contents of private messages, but I can say that we were willing to reopen the thread IF we believed that they were willing to discuss anything. They weren’t, and so the thread stayed closed. It wasn’t a langauge barrier issue, it was an issue of the OP not wanting to give any details whatsoever about their alleged discovery. What point is there in allowing a thread (on a science forum) wherein the OP has absolutely no intention of discussing the scientific aspect of their ideas?
  19. I can understand how it may have seemed hasty without the added perspective of what was happening behind the scenes. As mentioned a few times already, after closing it staff discussed the closure and the member was contacted. We considered reopening the thread if we believed the member was hoping to participate in genuine discussion. They weren’t (as per PM), so it stayed closed. It wasn’t a spur of the moment decision, nor was it irreversible. I’m not sure what else there is to say on the matter. We take these things case by case, and a lot of staff discussions and interactions with members are not made public. That isn’t going to change. SFN is not a conspiracy forum, nor is it a make up whatever BS you want and call it science forum. We give a lot of leeway to people to post and defend their ideas, but we have to draw a line somewhere. If we identify early on that a poster has absolutely no interest in participating in rational discussion, why should we let it continue? That runs completely counterintuitive to the spirit of the forum, and has no place here.
  20. You can definitely hear the difference if you listen to them side by side. Plastic doesn’t give the same smooth, clear tone IMO. It’s not entirely surprising. Some people also say that you can tell a tonal difference between different finishes on trumpets as well, though I don’t know how much of that is actually true.
  21. Plastic mouthpieces are very common, but not preferred for normal playing. I have only ever used brass mouthpieces, but my guess is that the plastic would change the tonal qualities of the instrument, which would be why they aren’t preferred. It wouldn’t be to do with stiffness so much as how much the plastic diffuses the sound. You can get metal sleeves to go around the mouthpiece, called brass tone modifiers, and this is meant to improve the sound quality quite a bit, though I have not tried them. Personally, I don’t see that plastic would be too much different to metal once you get going. They warm up fairly quickly.
  22. States don't really matter here, just the reaction itself and relevant stoichiometric coefficients.
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.