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Kaeroll

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Everything posted by Kaeroll

  1. Hi Lan®, Well, IR was around long before NMR (a comparatively young technique). NMR is more powerful, yes, but IR does have its niche (several of them). In my experience it does tend to be an 'afterthought' in characterisation - for a typical organic compound, my characterisation thought process tends to be along the lines of, "The proton NMR is good, and all the right peaks are there on my IR." So I do see your point. Though you can never have too much information to hand! DrDNA - good points, though I guess to an extent a proton NMR (for a simple hydrocarbon) does reveal the carbon skeleton. I'm yet to run a 2D NMR, though I'm sure the day will come... Kaeroll
  2. Hi peristar I know liquid oxygen is blue - but I suspect you want it to remain in the gas phase. I'm not aware of any others but it's not really my area. Kaeroll
  3. http://www.physorg.com/news153658987.html This recent news article seems relevant. For the tl;dr types like myself, apparently wurtzite boron nitride and lonsdaleite both have greater indentation strengths (whatever that means) than diamond. Apologies if this was already posted - didn't have time to read the whole thread! Kaeroll
  4. Hi there NMR is indeed much more useful, but does not negate IR. IR vibration frequencies can tell us about, inter alia, bond strengths. These can be used to 'fingerprint' the kinds of (for example) carbonyl compound you have - is it an aldehyde or ketone? Amide, anhydride? etc. If your spectrum is of good quality, you can also use the aptly-named 'fingerprint' region to identify many compounds. A very common application is to monitor growth or decay of peaks during a reaction. Recently my group carried out several LiAlH4 reductions. As the carbonyl peak is so strong, even minute amounts of remaining acid would show up on the FT-IR spectrum, which is much quicker and more convenient to run on-the-fly than an NMR spectrum. Like IR, UV-vis spectroscopy is often sidelined; yet all I've done for the past 6 hours is monitor an oxidation reaction using UV-vis (recording the decay in a peak at 350 nm arising from CrO3). I believe that IR also finds use in studies of stars and the like; by recording their IR spectra, organic molecules in clouds of gas in space can be found, for example. If you can find a way to run an NMR spectrum of a cloud of gas several lightyears away, I'll buy you a pint! Hope this helps. Kaeroll
  5. Kaeroll

    QM Cat!

    Hi there.. As I understand it, Schroedinger's cat is a thought experiment illustrating the concept of superposition - in which a system can be in several states simultaneously (e.g. both spin up and spin down at the same time). In the thought experiment, a cat is placed in a box with an explosive (or canister of cyanide, or some other deadly agent), to be triggered by the random decay of a radioactive nucleus. As we cannot see the cat, we cannot know whether it is dead or alive; quantum mechanics says it is in a superposition of both life and death. Upon observation, it is forced to take one state or the other, and this is what we observe. I believe it was originally proposed to highlight the apparently absurdity of quantum mechanics when applied to the macroscopic world - a cat clearly cannot be both alive and dead at the same time. It is often reinterpreted or misunderstood (as, for that matter, is the uncertainty principle) to reflect the observer effect, wherein the act of observation changes the experiment. In this variation, opening the box triggers the poison, killing the cat. Hope this helps. I'm not entirely sure how accurate my explanation of it is, though. Kaeroll
  6. Hello all... I'm taking a course covering, amongst other things, simple enzyme kinetics. I'm fine with the majority, but am not quite sure of the physical significance of the catalytic proficiency and catalytic efficiency, given by [math]proficiency = \frac{k(cat)/Km}{k(uncat)}[/math] and [math]efficiency = \frac{k(cat)}{Km}[/math] respectively. Can anyone shed some light on this for me? Cheers Kaeroll
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