Deuterium to hydrogen ratio

Keeping in mind the entire set of components in the climate system as depicted in Figs 17-2,4-13, and 17-3, we can now re-examine Fig. 1-2 to emphasize that biogeochemical cycles are coupled with the climate system. The temperature (as inferred from the record of the deuterium to hydrogen ratio in Antarctic ice) covaries with CO2, CH4 and other species that derive from biological processes. Two simple, if extreme, possibilities can be drawn ... 

Strong H2 lines have been reported in 11 reddened stars (E (B - V) > 0.10). Considerably less or no H2 absorption was detected in unreddened stars. Large column densities have been reported in higher rotational levels (up to J = 6) which correspond to an excitation temperature between 150° and 200 °K. The ratio of ortho-hydrogen (J = odd) to para-hydrogen (J = even) correspond to about 80 °K. Absorption of two lines of the Lyman bands of HD were also reported in nine stars, indicating a ratio of HD/H2 10 6. However, in the star (3 Cen a deuterium to hydrogen ratio of N(D)/N(H) = 1.047 (0.125,... 

Although it is presently not possible to distinguish clearly between the different formation mechanisms, it is felt that more observational data will furnish the material necessary for that. There are two areas of immediate help which play a very important role in our understanding of interstellar chemistry Isotopic abundance determinations, notably deuterium to hydrogen ratios, and the identification of the unknown interstellar lines by astronomical, laboratory or theoretical means. 

The special position of the Earth among the terrestrial planets is also shown by the availability of free water. On Venus and Mars, it has not until now been possible to detect any free water there is, however, geological and atmospheric evidence that both planets were either partially or completely covered with water during their formation phase. This can be deduced from certain characteristics of their surfaces and from the composition of their atmospheres. The ratio of deuterium to hydrogen (D/H) is particularly important here both Mars and Venus have a higher D/H ratio than that of the Earth. For Mars, the enrichment factor is around 5, and in the case of Venus, 100 (deBergh, 1993). 

Catalytic conversion of l-Octanol-2-d to ketone A quantity (29.7 ml.) of l-octanol-2-d was charged (space velocity 0.2) to a 5-mm. reactor tube containing 18 ml. of 8- to 10-mesh chromium oxide catalyst maintained at 400°. The 27.7 ml. of liquid product was fractionated in a concentric-tube etjlumn. A 60.6% yield of di-n-heptyl ketone was obtained. Approximately 17% of the alcohol was recovered "unconverted. Mass spectrometric analysis of the gaseous product showed the atomic ratio of deuterium to hydrogen to be 0.106. The molal yields of deuterium, hydrogen, and carbon monoxide produced per mole of ketone were 0.216, 2.040, and 0.815 respectively. 

The experimental atomic ratio of deuterium to hydrogen of 0.106 corresponds closely to the ratio calculated for the aldol mechanism (0.091) on the supposition that deuterium and hydrogen atoms in the alpha position participate equally in the condensation. 

In view of the indicated absence of any marked hydrogen-deuterium exchange under ketone-synthesis conditions, the presence of substantially the theoretical atomic ratio of deuterium to hydrogen in the gaseous product provides additional support for the proposed aldol mechanism. 

One can show that the abundance ratio of deuterium to hydrogen in a quasi-equilibrium has an extremely small value, signifying that deuterium is destroyed in thermonuclear burning. The time dependence of deuterium... 

Water contains the three molecular species HjO, HDO, and DjO. In concentrating heavy water by distillation, the deuterium separation factor is defined as the ratio of the atomic ratio of deuterium to hydrogen in the liquid to the corresponding ratio in the vapor. In terms of the mole fractions of individual compounds in the liquid x and vapor y, the separation factor a is... 

In analogy to the values which are an index of carbon isotope composition in plants (see Chap. 3.3), the hydrogen isotope composition of plant material can be characterized by a term 3T> which expresses the ratio of deuterium to hydrogen as follows (see Ziegler et al., 1976)... 

Mass spectrometry has been used to determine the amount of H2 in complex gas mixtures (247), including those resulting from hydrocarbon pyrolysis (68). Mass spectrometry can also be used to measure hydrogen as water from hydrocarbon combustion (224,248). Moreover, this technique is also excellent for determining the deuterium hydrogen ratio in a sample (249,250). 

As in the case of hydrogen and tritium, deuterium exhibits nuclear spin isomerism (see Magnetic spin resonance) (14). However, the spin of the deuteron [12597-73-8] is 1 instead of S as in the case of hydrogen and tritium. As a consequence, and in contrast to hydrogen, the ortho form of deuterium is more stable than the para form at low temperatures, and at normal temperatures the ratio of ortho- to para-deuterium is 2 1 in contrast to the 3 1 ratio for hydrogen. 

An isotope that is used extensively is deuterium (heavy hydrogen), often in the form of a deuteromethyl (-CD3) group. The molecular weight of this compound is thus three Da higher than the unlabelled precursor and this is often sufficient to ensure that the ions in the molecular ion region of the unlabelled compound do not occur at the same m/z ratios as those from the labelled molecule. 

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