I need the exact diameter of ortho silicic acid, Si(OH)4. Kindly provide reference if possible.
Thanking in advance for help.
Si(OH)4 suffers from the fact that it does not exist. It has such a high tendency to condensate that nobody has ever "seen" it. Of course in infinite diluted solution it will probably be there. On the other hand the answer of Eduardo Maurina Morais is very helpful. Si(OH)4 would very probably have the dimensions that Eduardo has calculated - if one had the chance of seeing it.
Mr. Siddiqui,
There is a couple of ways by which one can measure a molecule, but it depends on what you consider to be its borders. One of the ways is to use the van der Waals surface of the molecule, but since molecules don't stay in their lowest energy state, their size changes, therefore, there is no such thing as their "exact diameter". We can only make a rough estimation of what the diameter of the molecule is (if we consider it to be roughly a sphere), and as you can see in the file I've attached below (ortovdw.jpg) the molecule is roughly 6 Å (in the gas phase, in solution its effective diameter would be bigger due to solvation effects). I've also attached a picture showing the bond lengths and a xyz file that can be used to generate a 3D model of the molecule using softwares like Avogadro, Gabedit and others. I've calculated the geometry using DFT B3LYP-D3/6-31G*, this method should give a good idea of the true geometry of the molecule.
Thanks a lot for your prompt replies and wonderful graphics, especially Dr Morais.
I also got this info from the internet:
Topological Polar Surface Area = 80.9 A^2 from which I calculated an approx diameter of ~ 5.07 A.
I needed this info to check if silicic acid can pass through transmembrane aquaporin protein channel. I find that the diameter of silicic acid (5-6 A) is bigger than the pore diameter.
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