Protium and deuterium

Show that the zero point energies of H2 and D2 are 24.9 and 17.9kJ mol , respectively. 

When we compare H for reaction 10.4 with those for the formations of F and CP from F2 and CI2 (-249 and —228kJmor, respectively), we understand why, since H is about the same size as F , ionic hydrides are relatively unstable species with respect to dissociation into their constituent elements. Salt-like hydrides of metals in high oxidation states are most unlikely to exist. (There is more about binary hydrides in Section 10.7.) 

A deuterium label in heavy water is indicated by writing [ H2]water or water-r/2) and similarly for other labelled compounds. The formula for heavy water can be written as H20 or D2O. 

Many fully or partially deuterated compounds are available commercially, and the extent of deuterium labelling (see Section 3.9) can be determined by mass spectrometry, density measurements (after conversion into water) or IR spectroscopy. 

Compounds in which H atoms have been replaced by D are used for a variety of purposes, e.g. as solvents in H NMR spectroscopy (see Box 2.4). In a fully deuterated material, the D-for-H exchange can have significant effects on the properties of the compound as is shown in Table 

2 for H2O and D2O. The difference in boiling points indicates that intermolecular hydrogen bonding (see Sections 

2 and 9.6) is stronger in D2O than in H2O. The major industrial use of D2O is as a moderator in nuclear reactors D has a much lower cross-section for neutron capture than H, and D2O is a suitable material for reducing the energies of fast neutrons (see Section 2.4) produced in fission without appreciably diminishing the neutron flux. 

For a simple harmonic oscillator, the vibrational energies, Em, of a molecule are quantized and the vibrational energy levels are given by  

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Further substrate and solvent isotope effects were measured by Batts and Gold472 for the dedeuteration and detritiation of labelled 1,3,5-trimethoxy-benzene in aqueous protium- and deuterium-containing perchloric acid. Contrary to the observations above, they found the rate coefficients for dedeuteration to detritiation to be independent of the concentration of the catalysing acid (Table 125). Detritiation in the deuterium-containing aqueous perchloric acid media occurred 1.68 times faster than in the protium-containing media. 

From experimentally measured sensor signals as functions of distance X we estimated the coefficients of diffusion for protium and deuterium. At T = 345 K they are equal to 1.56-10 and I.OO-IO" m/s, respectively. 

Such a possibility has been pointed out for the first time in [13], where processes of diffusion and recombination of hydrogen atoms (protium and deuterium) have been studied in a water layer frozen on a semiconductor zinc oxide layer. 

By varying the temperature at which the experiments were conducted and the distance between the activator and the sensor, the data were obtained (Fig. 4.17) which allowed us to calculate the activation energy of migration of hydrogen adatoms (protium and deuterium) along the carrier surface and coefficients of lateral diffusion of hydrogen atoms appearing due to the spillover effect (see Table 4.2). 

If the atom fraction of deuterium in each separated coal product, given in Table I, is defined as Fy, the atom fraction of protium in the same coal product is therefore 1-Fy. The total amount of protium and deuterium in a given product fraction y is normalized to unity according to Equation 3,... 

Ramette, R.W. and Spencer, J.B. Electrolyte effects on silver bromate solubility in protium and deuterium oxide solutions at 25 °. Evidence for association of silver and nitrate ions, J. Am. Chem. Soc., 67(4) 944-946, 1963. 

Labeled compounds should prove valuable in studying liquid-phase oxidations, as they have in vapor-phase research, especially at low conversions where scrambling of protium and deuterium is avoided or held to a minimum. 

The comparison of the catalytic performances of metals and their alloys is sometimes hampered by the different degree of deactivation by carbonaceous residues (107, 67). Therefore, it seems appropriate to start with a discussion of the exchange reactions of the hydrogen isotopes protium and deuterium on platinum and Pt-Au films (31). A comparison of this reaction on platinum and its alloy shows that of the two reaction paths possible on platinum in the temperature region studied, one remains unchanged on the alloy but the other, which prevails on platinum except at very low temperatures, seems... 

To confirm reaction scheme (4) for the formation of naphthalene and biphenyl, phthalic anhydride was allowed to react with benzene-dx (Fields and Meyerson, 1966c). Barring an appreciable isotope effect, two-thirds of the naphthalene should contain a deuterium atom and one-third only protium. Biphenyl arises in two ways insertion of benzyne into a C—H bond of benzene and pyrolysis of benzene. Biphenyl from benzyne insertion should form with retention of the deuterium atom biphenyl from benzene pyrolysis should—again ignoring any isotope effect—be d0, dlt and dz on the statistical basis of losing two, one, or zero deuterium atoms from a total of twelve protiums and deuteriums in the over-all reaction of two benzene molecules. The amount of biphenyl-... 

This requirement could best be satisfied by formation of a complex— perhaps of the donor-acceptor type—or an actual compound, a phenyl-cyclohexadiene (13), between two molecules of benzene or other aromatic compound, in which protium and deuterium atoms readily move and exchange. 

Although the reaction of phthalic anhydride with benzene-ci showed scrambling of protium and deuterium at 690°, especially at 21 sec contact time, the scrambling at much shorter contact times is sufficiently low to permit ignoring it to simplify interpretation of results of labeling experiments. A solution of 0-002 mole of phthalic anhydride in 0-04 mole of benzene-d6 was pyrolyzed at 690° with a contact time of 4-2 sec. Starting benzene was 96-4% dQ and 3-6% ds recovered benzene was 92-3% d6 and 7-7% dB. The isotopic composition of the products is shown in Table 6. 

Evidently a similar mobility exists for protium and deuterium in the 1,4- and 1,2-adducts of benzyne with benzene-d6 ... 

Thienyldihydrothiophene is the thiophene analogue of the phenyl-cyclohexadiene intermediate deduced by Fields and Meyerson (1966c) from scrambling of protium and deuterium in pyrolysis of deuteriated benzene. Both intermediates account for the formation of dimeric species unaccompanied by highly energetic free hydrogen atoms. 

In chemical reactions, protium and deuterium show quantitative difference due to isotope effects. For example, ionisation of water is five times the ionisation of heavy water. Rate of breaking of H H bonds is 18 times the rate of breaking of... 

The equilibrium adsorption isotherms of protium and deuterium were measured volumetrically at temperatures within 67-78 K in the pressure range from 10 Pa to 0.2 MPa. The adsorption cell was cooled in liquid nitrogen boiling under vacuum. The error of determination of adsorbent capacity is not above 2 cm3. 

It was established that the temperature of regeneration of NPC within the limits of 473-673 K does not influence on adsorption capacity of NPC with respect to protium and deuterium. Hydrogen and deuterium are completely desorbed from the sample of NPC at temperature 470-480 K. Adsorption capacity of NPC samples is 10-15 cm3 hydrogen on lg adsorbent at room temperature and under atmosphere pressure. 

Adsorption isotherms of protium and deuterium on the samples of nanoporous carbon adsorbent at temperature 67-78 K are shown on Figures 1 and 2. The capacity of nanoporous carbon adsorbent on deuterium exceeds capacity on protium in all the investigated pressure range. The difference between adsorption value of deuterium and hydrogen is increased with rising of pressure. 

Form of protium and deuterium adsorption isotherms on the sample of nanoporous carbon are similar to ones on activated carbon and zeolites. They comparison is shown in figure 3. You can see that adsorption capacity of the NPC samples is larger than one on common sorbents such as zeolites [10-11] and it is close to active carbon [12]. 

Figure 3. Adsorption isotherms of protium and deuterium on different sorbents at 78 K.

If all of the protium and deuterium remains in the reactive components, the conservation of protiun can be written... 

Isotope effects in the range 0-97-T26 have been observed (Table 3) but according to Shiner (1970) an a-deuterium isotope effect close to unity (range 0-97-1-06) indicates a classical SN 2 reaction. The isotope effect is theoretically related to the molecular vibrational frequencies of the initial and transition states for the protium and deuterium compounds. Thus, nucleophilic attack must reduce the change in vibrational frequencies. 

Cold Trapping. There is considerable uncertainty in the concentration to which tritium can be cold trapped from Li (Figure 14). The work of Natesan and Smith (Figures 8 and 9 of Reference 16) can be used to estimate concentrations of 1800 wppm protium and 2700 wppm tritium at a cold trap temperature of 195°C. Katsuta ( ) estimates a protium concentration of 200 wppm at a cold trap temperature of 203 C. Veleckis (18) estimates protium and deuterium concentrations of 75 and 135 wppm at a cold trap temperature of 195°C. The corresponding tritium concentration would be j 200 wppm. Thus, Veleckis (200 wppm tritium) and Natesan (2700 wppm) bracket the available estimates. In a 1630 mp Li blanket (such as HYLIFE), 200 wppm and 2700 wppm tritium concentrations result in 160 and 2200 kg blanket tritium inventories, respectively. (The actual tritium inventory may be reduced by about 25% due to the presence of deuterium, but this effect has been ignored here.)... 

Grant, K. L., and Klinman, J. P., 1989, Evidence that both protium and deuterium undergo significant tunneling in the reaction catalysed by bovine serum amine oxidase. Biochemistry 28 6597n6605. 

The KIE of 50nl00 far exceeds the classical limits derived from the zero point energy difference between protium and deuterium the maximum expected kjj/ko is 6n7 (Bell, 1973). Larger isotope effects can be accounted for by mechanisms that involve branched reaction pathways. 

Seiler, P., Martinoni, B., and Dunitz, J. D. Can X-ray diffraction distinguish between protium and deuterium atoms Nature (London) 309, 435-438 (1984). 

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