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Everything posted by hypervalent_iodine

  1. hypervalent_iodine

    Organic Research Project

    Not necessarily; with careful addition and control of equivalents I should think the esters would hydrolyse over the imide. A carbonate base may also do the trick.
  2. hypervalent_iodine

    Organic Research Project

    I didn’t say that. I said it can’t be done with an alkoxide. If you do the arrow pushing on the scheme you drew you should hopefully be able to see why it would never work. I also went on to say that in order to do the reaction you need hydroxide or some other aqueous base, but you can also use acid. I think hydroxide base would work fine, however.
  3. hypervalent_iodine

    Organic Research Project

    I’d say your main problem is that you can’t hydrolyse the ester with an alkoxide like that. You need a hydroxide, or you need to do it under acidic conditions.
  4. hypervalent_iodine

    Banned/Suspended Users

    Q-reuss has been permanently banned for spamming the forum with nonsense.
  5. hypervalent_iodine

    Global/Generalized Sagnac Effect Formula

    ! Moderator Note Since the OP appears impervious to reason and genuine scientific rebuttal, this thread is closed.
  6. hypervalent_iodine

    Exam question.

    Could you show your attempts at solving the question?
  7. hypervalent_iodine

    Ionic Charges

    They are all possible, depending on the circumstance. There are some elements that will only exist in one oxidation state other than 0, and from those you can normally garner the oxidation state and charge of other elements. In your case my suspicion is that you are only being asked to look at the more easily explained ions that result from the gain or loss of electrons to satisfy the octet. In the case of sulfur, that would make the ion 2-, since it only needs to gain 2 electrons in order to do this.
  8. hypervalent_iodine

    Genesis 1&2 The Beginning - Based on the Scripture

    ! Moderator Note Quit the preaching. Thread closed.
  9. hypervalent_iodine

    Extraction of caffeine from tea

    Probably, but it’s not needed. You can get away with just using water.
  10. hypervalent_iodine

    Extraction of caffeine from tea

    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.
  11. hypervalent_iodine

    Does anybody feel me here

    ! Moderator Note If you can repost this in a way that is coherent and scientific, please do so (but in Speculations, please.)
  12. 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.
  13. hypervalent_iodine

    TLC and polarity

    This is correct.
  14. 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.
  15. hypervalent_iodine

    TLC and polarity

    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?
  16. hypervalent_iodine

    Do you use atomic radius in your work?

    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.
  17. 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.
  18. 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 ).
  19. I would suggest adding the diacid to a dilute solution of diol.
  20. hypervalent_iodine

    Do you use atomic radius in your work?

    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.
  21. hypervalent_iodine

    Do you use atomic radius in your work?

    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.
  22. hypervalent_iodine

    A disappointing tale.

    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.
  23. hypervalent_iodine

    Problem with agarose gel with BrEt

    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.
  24. hypervalent_iodine

    A disappointing tale.

    ! 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.
  25. hypervalent_iodine

    Impure 9-bromofluorene from Sigma, but issues purifying

    Have you looked at literature NMR?