DEUTERIUM OXIDE

Description

Deuterium oxide (D2O), aka “heavy water”, is the form of water that contains two atoms of the 2H, or D, isotope. The term heavy water is also used for water in which 2H atoms replace only some of the 1H atoms. In this case, rapid exchange between the two isotopes forms twice as many “semiheavy” HDO molecules as D2O.
Harold Urey, the 1934 Nobel Prize laureate in chemistry, pioneered deuterium chemistry. In 1931, he and his colleagues at Columbia University (New York City) carefully distilled 5 L of liquid nitrogen to produce 1 mL of molecular deuterium. Shortly afterward, they produced D2O from ordinary water by using prolonged electrolysis.
For decades, D2O has been extremely useful in many chemical applications. The difference between a reaction rate in D2O solvent versus that in H2O often provides clues as to the reaction’s mechanism. This is especially important if water is one of the reactants.
In some nuclear reactors, D2O is used to slow down neutrons so that they react with fissionable 235U rather than nonfissioning 238U, thus eliminating the need for uranium enrichment. D2O is superior to H2O for this use because of its ≈6 times greater thermal neutron capture cross section.

Chemical properties

colourless liquid

The Uses of DEUTERIUM OXIDE

Deuterium Oxide is used to prepare specifically labelled isotopologs of organic compounds.

The Uses of DEUTERIUM OXIDE

To study chemical reaction rates and mechanisms. The cross section of deuterium for the capture of thermal neutrons is very low which makes it useful, in the form of heavy water, as a neutron moderator in nuclear reactors. Produces a considerable decrease in neutron energy per collision.

The Uses of DEUTERIUM OXIDE

Deuterium oxide is used in nuclear magnetic resonance spectroscopy (NMR). It is also useful in the identification of labile hydrogens. As a source of deuterium, it is utilized for preparing specifically labeled isotopologs of organic compounds. It is often used as a substitute for water in the analysis of proteins in solution by using fourier transform infrared spectroscopy (FTIR). It finds application in certain types of nuclear reactors and in tritium production.

Definition

deuterium oxide: Water in which hydrogen atoms, 1H,are replaced by the heavier isotopedeuterium, 2H (symbol D). It is acolourless liquid, which forms hexagonalcrystals on freezing. Its physicalproperties differ from those of ‘normal’water; r.d. 1.105; m.p. 3.8°C; b.p.101.4°C. Deuterium oxide, D₂O, occursto a small extent (about 0.003%by weight) in natural water, fromwhich it can be separated by fractionaldistillation or by electrolysis. Itis useful in the nuclear industry becauseof its ability to reduce the energiesof fast neutrons to thermalenergies and because its absorptioncross-section is lower than that of hydrogenand consequently it does notappreciably reduce the neutron flux.In the laboratory it is used for labellingother molecules for studies ofreaction mechanisms. Water alsocontains the compound HDO.

General Description

Deuterium oxide (D₂O) is a 100% isotopically enriched NMR (Nuclear Magnetic Resonance) solvent. It is widely employed in high resolution NMR studies. Various thermodynamic properties (such as intermolecular vibrational frequencies, energy of the hydrogen bond, free energy, enthalpy and entropy) of liquid deuterium oxide have been evaluated. Ionization constant for D₂O (in the range of 5-50°C), pK values (at 25°C) and enthalpy, entropy, heat capacity change (for the dissociation of D₂O) have been reported.

Purification Methods

Distil it from alkaline KMnO4 [de Giovanni & Zamenhof Biochem J 92 79 1963]. NOTE that D2O invariably contains tritiated water and will therefore be RADIOACTIVE; always check the radioactivity level of D2O in a scintillation counter before using.