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Presence of one or more numbers of a particular functional group

apurvatr's picture

Say, If there are three -OH groups in 1 compound and eight -OH groups in another compound, would there be a difference in the adsorotion intensity? And if so can that be taken as a differentiating factor between those compounds? 

gabiruth's picture

Hi guys,

This is interesting question - well, in a theoretical case, there could be no difference between 3 OH and 8 OH - but this isn't a theoretical world - to have in a given molecule 8 OH instead of 3 OH - there must be other changes in the structure - and also - there will most likely be different interactions between the OH and their neighboring atoms, and there will be new interactions between the OH and themselves.

And - since the overall absorbance at a specific wavelength range that is typical of the O-H stretch, the intensity of absorption at this range will increase, and other absorption will probably decrease.

So without getting into too many details - there should and probably be a difference and it could be quite significance.

To the final question - if there is a difference - it can be used as a differentiating mean between them.

Gabi Levin