hypervalent_iodine

Administrators
  • Content count

    4051
  • Joined

  • Last visited

  • Days Won

    3

Everything posted by hypervalent_iodine

  1. Nasal sprays

    They bind to the same type of receptors, but have varying affinities to the different subtypes. You might like to read this: https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1472-8206.2009.00805.x
  2. iodometric or iodimetric

    Thank you for the correction, I was unaware there was a difference.
  3. iodometric or iodimetric

    It’s called iodometry, so the second one (iodometric) would be appropriate.
  4. Writing a systematic review

    The format can depend on subject matter somewhat, but they generally start with an introduction that covers the history and importance / relevance of the subject to the modern chemist. This then segues into a more detailed coverage of the concepts behind what you are reviewing. These sections require a decent amount of research, and older reviews of similar topics are normally very good starting points. For example, if you were writing a review on a particular type of catalyst you would start with when it was discovered and who developed it, what it is used for and why it’s use is important. You would then want to cover the science of what makes a good catalyst, physicochemical properties and what they imply in terms of selectivity and reactivity, and synthesis. Once the stage is set, you then go into a breakdown of the literature on the topic. This part is the hardest in terms of research, but it’s not too difficult to write. I personally like to use Google scholar and SciFinder. Use simple search terms, and get to reading. It takes a long time if you do it properly. I would advise collecting all of the references you come across into a program like EndNote. This way you can read them and start to sort them out into categories as you go, and annotate them so you can keep track of important points for later inclusion. What you include and what you don’t comes down to the story you’re trying to tell. Going back to my example before, I would want to gather any reference in which the type of catalyst I am focusing on makes an appearance. Subheadings would be broken down into the type of reactions they are used in. I would highlight cases / reactions where they are superior, but I would still mention other examples where they are not, and include some sort of commentary as to why where appropriate. Often there are few enough examples that you can include all of them, but in cases where there are a lot you would draw the most attention to the ones that best illustrate what you are trying to argue, and make smaller mention of the others. The hardest part to write for me is the conclusion. A good conclusion summarises the main features the topic briefly, and then makes a summary of the future of where the topic is headed. Returning to my example, I would mainly discuss new catalyst systems that had been developed off the back of the ones featured in the review. There is also typically a lot of big picture talk, which ties up your story nice and succinctly. Again, I strongly recommend looking up papers you like the look of and contacting the authors for a copy. Their contact details will be available on the journal website.
  5. Writing a systematic review

    You are at least able to look through the abstracts. Find one you like and email the authors for a copy. Most are happy to oblige. Otherwise, was there a specific thing you wanted to know about? Are you curious about the format, or how one goes about finding and selecting literature to incorporate, or something else?
  6. Writing a systematic review

    Why don’t you look up a journal like Chemical Reviews and pick one from a recent issue you like?
  7. Banned/Suspended Users

    It seems that "ever" equals approximately 7 months. VictorMedvil has been banned as a sock puppet of VMedvil.
  8. Explanation of the killings in Exodus

    ! Moderator Note We do not allow proselytising on this forum. I am closing this pending further staff review. Do not attempt to reopen the topic.
  9. I am no expert in this, but is it possible that it is a coccobacilli?
  10. free 1 hour java lesson

    ! Moderator Note The rules you signed up to upon joining SFN very clearly prohibit using this site for advertising. I am closing this, and letting you know that if you attempt to use SFN again for blatant advertising, we will ban you from the site entirely.
  11. How to pure HCl

    ! Moderator Note Stop posting this. You have a topic with this question, you may respond there.
  12. How to pure HCl

    I think it's probably a waste of time to try given how easy and cheap it is to obtain.
  13. need help- esterification

    I have also made esters fairly easily by reaction with Cs2CO3, the carboxylic acid and iodoalkanes.
  14. Would you dare asking this question to your science professors?

    ! Moderator Note OP, you are expected to present your argument and discussion here without advertising or needlessly driving people off-site. Links and videos should only act as support for your case.
  15. Intramolecular Sn2 reactions

    For the last one, why are you ignoring the actual substrate in the reaction?
  16. D Block electron arrangements

    Are you asking why is it 3 and not 4? This is to do with quantum numbers assigned to electrons, and what those numbers represent. Are you familiar with principal (n), azimuthal / angular (ℓ), and magnetic quantum numbers (mℓ) at all? In this example, the 3 represents the principal quantum number. At this energy level, there can be 3 values for ℓ, with each value essentially representing a type of orbital. For example, s orbitals are where ℓ = 0, p orbitals are described by ℓ = 1, d by ℓ = 2, and f by ℓ = 3. Since the value for ℓ under a given value for n can equal anything from 0 - n-1 (eg. if n = 2, ℓ can equal 0 or 1), there must be 3 possible types of orbitals that can be described by n = 3. Those are the s (ℓ = 0), the p (ℓ = 1) and d (ℓ=2). This is not possible when n = 2, because the highest possible value for ℓ is 1, which represents the p orbitals. Thus, the first time the d orbitals can appear is at n = 3, which is why you first row of transition metals have electronic configurations of 3d rather than 4, despite where they show up on the table. I hope that wasn't too confusing. I'll try and explain this a bit better. Firstly, note that the 4s and 3d energies are quite close together in Cr and Cu. I am unsure of why this is exactly. Probably something to do with nuclear charge. Consider chromium first. Pairing electrons costs energy because of Coulombic repulsion. This is why when we fill orbitals, we don’t start pairing until all the degenerate orbitals have an unpaired electron in them first. Because we fill electrons in order of energy, because the 4s and 3d are so close together, and because it costs more energy to pair an electron in the 4s than it is to place another unpaired electron into the 3d orbital, chromium exists as 3d5 4s1. Another explanation comes from effective nuclear charge and nuclear screening caused by the existence of s electrons. The nature of s orbitals means that when you place electrons in them, you place them close to the nucleus. This effectively screens or creates a barrier between the nucleus and the electrons in the d orbitals, and reduces the effective charge felt by them. If you were to only place one electron into the s orbital, there would be less screening, and thus the 5 or 10 electrons left over in the Cr / Cu d orbitals feel more charge from the nucleus and are more tightly held by it compared to if there were 2 electrons in the 4s. Of course, this phenomenon would also be true for all the other d block elements so I guess it begs the question of why do they have 2 s electrons and not 1. The 4s orbital is still lower in energy than the 3d, so the reason is likely because in other elements that energy gap is too high to be worth it. I believe that as you fill up the d orbitals, the energy difference between placing all the electrons in the d orbitals and one in the s instead of 2 does decrease. In any case, this effect isn’t as strong or prominent in all atoms which is why chromium and copper are exceptions to the rule and not the rule. Unfortunately, that's probably the only area fit to fully give you a full answer as to 'why.' Well, yes. Consider sodium as a simple example of what I am getting at. It has a configuration of [Ne] 3s1. When it ionises, it becomes Na+ and adopts a [Ne] configuration. We don't see Na2+ because [Ne] is a very stable configuration, certainly more so than [He]2s22p5. It is similar for Fe(II) and Fe(III), even if it isn't as simplistic, in the sense that the things you get out the most can be surmised to be the things that are the more stable in some sense. I realise that still doesn't answer you, but it's as good as I've got. What is very important to note is that firstly, when talking of Fe(II) and Fe(III), we are no longer speaking about neutral elemental species with degenerate orbitals, and more importantly, d electron counting is only a formalism. Not all complexes are able to be described very well by using this system, which is why things like crystal field and ligand field theory exist. I think it is probably too much to get into, but if you are interested I did find a related question with some great answers here: https://www.researchgate.net/post/Why_CuII_is_more_stable_than_CuI
  17. D Block electron arrangements

    Do you want to know why electrons are placed and lost first the 4s orbital, or specifically why Cu and Cr only have 1 electron in the 4s orbital or their ground state configuration? I am not an expert in this area of chemistry, but the intuitive / simple explanation in the case of Cu and Cr comes from considering stability of having a 3d4 / 3d9 configuration compared to a 3d5 / 3d10. The latter represents the more stable option, which is why you see 4s13d5/10 for Cr and Cu, and not 4s23d4/9. I am curious to know why you say that stability is not the answer? It generally is with these things, but the exact cause of that stability can get fairly involved. For iron oxidation states, I believe that you can use the same sort of logic. The two most commonly encountered states are iron(II) and iron(III). You need only look at the orbital diagrams or electronic configurations and compare to the above to guess as to why that might be. The compound you mention is a mix of oxidation states. It's not overly complicated, it just means that two of the iron atoms have given up 3 electrons, and the other has only given up 2 to form a stable structure. There are several definitions for noble metals, some are fairly arbitrary. Could you be more specific?
  18. Confused about resonance structures

    You might like to read these: http://www.science.oregonstate.edu/~gablek/CH334/Chapter1/resonance_MO.htm https://chem.libretexts.org/LibreTexts/Mount_Royal_University/Chem_1201/Unit_4%3A_Chemical_Bonding_II_-_Advanced_Bonding_Theories/4.11%3A_Multiple_Bonds_in_MO_Theory#Molecular_Orbitals_and_Resonance_Structures https://www.masterorganicchemistry.com/2017/01/24/conjugation-and-resonance/ You do realise they said pi bonds and atomic orbitals, not just pi bonds? Granted, it's still not complete. Hybridised orbitals containing lone pairs or radicals may also contribute.
  19. Confused about resonance structures

    I am not sure I follow the point of your bond length statement. While true, I don’t see it’s relevance to mine or the OP’s post. They didn’t mention bond length? I should say that I found the OP difficult to decipher, so I may well be misunderstanding them myself. I agree the OP seems to be mashing several different models and getting a little lost (understandable, it gets confusing), but the thrust of what they’ve taken out of it (from their final paragraph) reads okay. I think some clarification from the OP would be nice. Perhaps they are just not very articulate. I would like to know exactly what is meant by hybrid resonance orbital, for instance.
  20. Confused about resonance structures

    Why do you think this is not correct? It reads mostly fine to me.
  21. Can someone help me cut the fat out of this?

    Being concise and discerning over what subject matter to include is a skill you need to develop yourself, and is presumably part of what you are being assessed on. You won't achieve those goals by getting other people to do the work for you. I am closing this.
  22. What is faith?

    ! Moderator Note It is probably time we returned to the topic. Endercreeper, if you have further questions please PM staff or report the post you take issue with. Responding to moderator notes within threads constitutes derailment, which is against the forum rules.
  23. What is faith?

    ! Moderator Note Endercreeper01, to add a more official note to Phi's comment above, the preaching stops. If you are not willing to participate in honest discussion, then you are not welcome to participate. That goes as much here as in any thread, on any topic.
  24. Banned/Suspended Users

    Andy Dora has been banned as yet another sockpuppet of conway.
  25. What have you come up with? What have you come up with?