Oxygen isotopic effects

An important criticism of the use of combustion trains is that combustion is not site specific, that is all atoms in the analyte end up in the gas transferred to the IRMS. For studies of carbon isotope effects this is invariably C02. The question is especially important for carbon isotope analysis because analyte molecules of interest usually contain several different kinds of carbon atoms and therefore combustion methods average or dilute the IE s of interest. Should site specific isotope ratios be required another method of sample preparation (usually much more tedious) is necessary. Combustion methods, however, are frequently used to study nitrogen and sulfur IE s because many organic molecules are singly substituted with these atoms. Obviously, oxygen isotope effects cannot be determined using combustion trains because external oxygen is employed. Rather some type of pyrolytic sample preparation is required. 

Johnson TM, Bullen TD (2004) Mass-dependent fractionation of selenium and chromim isotopes in low-temperature environments. Rev Mineral Geochem 55 289-317 Kim S-T, O Neil JR (1997) Equilibrium and nonequilibrium oxygen isotope effects in synthetic carbonates. Geochim Cosmochim Acta 61 3461-3475... 

Kyser TK, O Neil JR, Carmichael ISE (1986) Reply to Possible non-equilibrium oxygen isotope effects in mantle nodules, an alternative to the Kyser-O NeU-Carmichael geothermometer. 

Kondoh, S., Sera, M., Ando, Y. and Sato, M., Normal State Properties and Oxygen Isotope Effect of (Ba,K)BiOs. Physica C 157 469(1989). 

The computed 18 fCarbonyi oxygen isotope effects for the conversion of the carbonyl double bond of the reactant to the nearly single bond of a tetrahedral intermediate are about 1.025 for the very late transition state377-379. The computed Dk values have been estimated to be 0.89 (inverse, also for a very late TS of the formation of tetrahedral intermediate). In the concerted mechanism (equation 186) the carbonyl jr-bond may not be... 

Competitive oxygen isotope effects are measured using a custom apparatus that consists of two adjoined high-vacuum manifolds as shown in Figure 9.1.8,10,25... 

Calculations of 180 EIEs upon reactions of natural abundance O2 require the normal mode stretching frequencies for the 160—160 and 180—160 isotopologues (16 16j/ and 18 16, ). These values can often be obtained directly from the literature or estimated from known force constants. DFT calculations can be used to obtain full sets of vibrational frequencies for complex molecules. Such calculations are actually needed to satisfy the requirements of the Redlich-Teller product rule. In the event that the full set of frequencies is not employed, the oxygen isotope effects upon the partition functions change and are redistributed in a manner that does not produce a physically reasonable result. 

RothJ. P. Oxygen isotope effects as probes of electron transfer mechanisms and structures of activated 02. Acc. Chem. Res. 2009, 42, 399-408. 

Lanci M. P. Roth J. P. Oxygen isotope effects upon reversible 02-binding reactions characterizing mononuclear superoxide and peroxide structures. J. Am. Chem. Soc. 2006,... 

Smirnov, V. V. Lanci, M. P. Roth, J. P. Computational modeling of oxygen isotope effects on metal mediated 02 activation at varying temperatures. J. Phys. Chem. A 2009, 113, 1934-1945. 

Khasanov R., Eshchenko D.G., Luetkens H., Morenzoni E., Prokscha T., Suter A., Garifianov N., Mali M., Roos J., Conder K., and Keller H., (2003). The oxygen-isotope effect on the in-plane penetration depth in underdoped Y i Pr, BaoCuAW, as revealed by muon-spin rotation../. Phys. Condens. Matter 15 L17-L24. 

Zhao G.-M., Singh K.K., and Morris D.E., (1994). Oxygen isotope effect on Neel temperature in various antiferromagnetic cuprates. Phys. Rev. B 50 4112-4117. 

One of the first measures of how strongly hydrogen bonds can be reflected in isotope effects was the experimental determination of the oxygen isotope effect on binding of an inhibitor, oxamate, to lactate dehydrogenase.7 The inverse isotope effect... 

Farquhar G. D. and Lloyd J. (1993) Carbon and oxygen isotope effects in the exchange of carbon dioxide between terrestrial plants and the atmosphere. In Stable Isotopes and Plant Carbon—Water Relations (eds. J. R. Ehleringer, A. E. Hall, and G. D. Farquhar). Academic Press, pp. 47-70. 

There are many aspects of these materials which any suggested mechanism must be consistent with, including, but not limited to 1. The observed absence of an oxygen isotope effect upon... 

They also showed that the hydrolysis of methyl a-D-glucopyranoside is associated with an appreciable oxygen isotope-effect this evidence points to the mechanism given in equation 1. 

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