Acidic Proton Chemical Shift in Periodic Acid (HIO_4)

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In summary, the greater the deshielding on a proton, the greater the chemical shift (as measured I believe from Si\left( {CH_3 } \right)_4 ), with smaller electron density to reduce the effect of the external magnetic field on THAT proton. This should see a strong correlation (I would think) with factors that increase the acidic nature of that proton.
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bomba923
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Acidic chemical shift--(NMR Question)

*Well, the greater the deshielding on a proton, the greater the chemical shift (as measured I believe from [itex] Si\left( {CH_3 } \right)_4 [/itex]), with smaller electron density to reduce the effect of the external magnetic field on THAT proton

Aside from organic molecules, let's take the acidic proton on periodic acid [itex] HIO_4 [/itex]. Now, due to the massive deshielding from periodate, I would expect the proton to have very great chemical shift.

What quantitatively is the average (or just the range of normal values) chemical shift of the acidic proton in periodic acid ([itex] HIO_4 [/itex]) ??
 
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Please---any numbers will be greatly appreciated!
 
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bomba923 said:
Aside from organic molecules, let's take the acidic proton on periodic acid [itex] HIO_4 [/itex]. Now, due to the massive deshielding from periodate, I would expect the proton to have very great chemical shift.
I know virtually nothing about NMR, so if the following is too naive or just plain stupid, please consider this a disclaimer.

Now, from my tiny understanding of things, the chemical shift from deshielding comes from a sort of "diamagnetic effect" from the H-atom's electron (and possibly other electrons - in alkali metal hydrides, for instance, but I could be totally wrong - in comparable proximity to the proton). So, in general, factors that increase the (negative) charge density around the proton, increase the shielding. Factors that reduce the charge density cause deshielding, which leads to a related chemical shift. The latter should see a strong correlation (I would think) with factors that increase the acidic nature of that proton, since this is essentially the same thing. So, I would imagine that you would see large chemical shifts in strong acids.

What I'm leading up to, is boldly (or naively) drawing a correlation between the chemical shift and the Ka for the acid. Since the proton chemical shift for most carboxylic acids is itself of order 10 or more, I would imagine the chemical shifts for the strong inorganic acids (like HIO4) to be bigger still.

Of course, the whole thing probably gets complicated because we are now talking about aqueous solutions where a large fraction of the protons are actually free, and there is a dynamic equilibrium between the free protons and the bound protons.
 
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I think that a better approximation of aqueous acid is that there is very little free H+ and a lot of H3O+. To really have "free" protons you'd have to have more H+ than H2O. Water is more basic than things like Cl-.

At any rate, I asked my professor a question like this once and he said that, theoretically, the proton that would have the greatest chemical shift would be a free proton. It is, of course, impossible to get that data in solution phase because you never have a free proton in solution. You'd have to use gas phase NMR.
 

What is the acidic proton chemical shift in periodic acid?

The acidic proton chemical shift in periodic acid (HIO4) refers to the position of the peak in the proton nuclear magnetic resonance (NMR) spectrum, which is associated with the acidic hydrogen atom in the molecule. It is a measure of the chemical environment and electronic structure of the hydrogen atom in the molecule.

Why is the acidic proton chemical shift in periodic acid important?

The acidic proton chemical shift in periodic acid is important because it provides valuable information about the molecular structure and composition of the compound. It can be used to determine the functional groups present in the molecule and to identify the position of the hydrogen atom within the molecule.

How is the acidic proton chemical shift in periodic acid measured?

The acidic proton chemical shift in periodic acid is measured using proton NMR spectroscopy. This technique involves exposing the compound to a strong magnetic field, which causes the hydrogen atoms to align either in the same direction or in the opposite direction to the field. The resulting energy difference between these two alignments is then measured and displayed as a peak in the NMR spectrum.

What factors can affect the acidic proton chemical shift in periodic acid?

The acidic proton chemical shift in periodic acid can be influenced by a number of factors, including the electronegativity of nearby atoms, the presence of neighboring functional groups, and the overall molecular structure. Additionally, changes in temperature, solvent, and pH can also affect the chemical shift of the acidic proton.

What is the typical range of the acidic proton chemical shift in periodic acid?

The acidic proton chemical shift in periodic acid typically falls within the range of 2-12 parts per million (ppm) in the NMR spectrum. However, this range can vary depending on the specific molecular structure and environmental factors mentioned above.

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