# Raman spectrum of acid acetic with deuterium?

I have raman spectrums of 3 differents acetic acid in solution :

$$CH_3COOH \qquad \qquad CH_3COOD \qquad \qquad CD_3COOD$$

All the following are hypothesis from me and I would like to know if it's good : The change of one H to one D is only changing the reducted mass and not the force constant since it's not changing the electronic configuration, so the spectrum should be the same but all moved to the lower $$cm^{-1}$$. However this is not what is observed (specially for the spectrum with 4D) My guess is that the solution is not perfect and some molecules still contain some $$H$$ and so we are observing a lot of peak at the area of $$CD_3$$ that shouldn't be if the solution was perfect.

Also, you can see that there is large and low peak at $$2350 \; cm^{-1}$$ for the spectrum $$CH_3COOD$$ which is not appearing on other : I don't know how to explain it ; my intuition is that it's coming from the bounding $$O-D$$

Sorry for bad english I'm not native speaker.

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