a) Can you use IR spectroscopy to distinguish between the D 2 O (heavy water use

Question

a) Can you use IR spectroscopy to distinguish between the D2O (heavy water used to moderate neutrons in nuclear reactors), H2O and HOD species in solution?

b) Can you use IR spectroscopy to distinguish between the D2O (heavy water used to moderate neutrons in nuclear reactors), H2O and HOD species in crystals?

(Colorless crystals of pure D2O, pure H2O and pure HOD are obtained after freezing the solution and oriented in space such that the molecules can be aligned along the cartesian coordinates)

Explanation / Answer

IR spectroscopy

a) H2O molecule which can form strong hydrgen bonds with each other show a frequency in IR due to stretching of O-H bonds. HOD which can form stronger hydrogen bonds due to O-D linkage bonds would show slightly lower stretching freequency in its the spectrum. Lastly D2O which which forms the strongest hydrogen bonds than H2O and HOD would show a much lower frequency in the IR spectrum.

b) In crystal H2O forms ice with hydrogen bonds between other H2O molecules. The strength of hydrogen bonds is weaker in crystal for D2O when compared to H2O or HOD, which gives the melting point of D2O highest followed by HOD which has slightly lower melting point and H2O being the lowest melting point of all. Thus, in crystals we would see lowest frequency for O-D in D2O and highest frequency for stronger O-H in H2O crystals.

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