Chemical Forums
Chemistry Forums for Students => Physical Chemistry Forum => Topic started by: CopperSmurf on November 22, 2009, 07:11:45 AM
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I don't see how one can deduce the structure of a compound from a UV/Vis spectrum when it's colored. For example, I could just pick out numbers from the peaks in the spectrum that has X cm-1 with an extinction coefficient. How is this even useful? How can I even use this to deduce the structure when applied to inorganic complexes? The only thing remotely possible I can think of is to find the energy gaps of deltaoctahedral or deltatetrahedral for high/low spins.
Ex. if I say that I had some sort of complex with a "broad peak" at 13000 cm-1 with an extinction coefficient of 5 L/(mol cm), what should I know?
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Only in relatively rare cases can UV/VIS be used to determine a structure.
Having said that, lets go a little further. Typically, when you are analyzing a solution by UV/VIS, you have a general idea of the ingredients. You have a solution that may contain phenols. Phenols typically absorb at 280 nm. You run the uv vis and find there is no peak in the 280 nm range. It's a good bet that no phenols are present.
Another example. I have an unknown, and it shows a peak in the UV/VIS at 280 nm. The first ingredients I'll investigate are phenols. It's not proof a phenol is present, but it gives a good hint.
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sounds like it can turn into a nasty puzzle... thanks for the reply