Oxidation tritium

Sharpless and Flood682 observed reactions characteristic of monooxygenases, such as stereospecific epoxidation of olefins and arene hydroxylation, with oxotransition metal (M=0) oxidants. For example, Cr02X2 (X=C1, OAc) oxidized tritium labeled naphthalene to naphthoquinone accompanied by tritium migration. Rearrangement is suggestive of arene oxide transients. 

The results of a variety of mercury concentrations in solution, pH 7.2, on the ability of Alcaligenes paradoxus to oxidize tritium are shown in Figure 1. It is evident that this organism is very sensitive to somewhere between 0.1 and 1.0 ppm mercury in an uncomplexed solution. In soil amended with mercury (Figure 2), 1.0 ppm was sufficient to completely inhibit the oxidation reaction, but only after approximately 20-percent conversion of the tritium to tritiated water had taken place. For the same concentration of mercury in solution, only about 5-percent conversion took place. It is noteworthy that 100.0 ppm mercury in the soil produced the same effect as 1.0 ppm in solution. This suggests that the clay loam soil offered some degree of protection not available in solution. 

Even isotopes qualify as different substituents at a chirality center The stereo chemistry of biological oxidation of a derivative of ethane that is chiral because of deu terium (D = H) and tritium (T = H) atoms at carbon has been studied and shown to... 

Lithium Oxide. Lithium oxide [12057-24-8], Li20, can be prepared by heating very pure lithium hydroxide to about 800°C under vacuum or by thermal decomposition of the peroxide (67). Lithium oxide is very reactive with carbon dioxide or water. It has been considered as a potential high temperature neutron target for tritium production (68). 

AH operating facilities shear the spent fuel elements into segments several centimeters long to expose the oxide pellets to nitric acid for dissolution. This operation is often referred to as chop-leach. The design and operation of the shear is of primary importance because (/) the shear can be the production botdeneck, and (2) the shear is the point at which tritium and fission gases are released. 

Tritium differs from the noble gases. Tritium is very reactive and readily combines to form water. The voloxidation process, which controls the point at which the oxidation occurs and recovers the resulting tritiated water, has been developed. As of this writing it has not yet been used. 

The radioactive isotopes available for use as precursors for radioactive tracer manufacturing include barium [ C]-carbonate [1882-53-7], tritium gas, p2p] phosphoric acid or pP]-phosphoric acid [15364-02-0], p S]-sulfuric acid [13770-01 -9], and sodium [ I]-iodide [24359-64-6]. It is from these chemical forms that the corresponding radioactive tracer chemicals are synthesized. [ C]-Carbon dioxide, [ C]-benzene, and [ C]-methyl iodide require vacuum-line handling in weU-ventilated fume hoods. Tritium gas, pH]-methyl iodide, sodium borotritide, and [ I]-iodine, which are the most difficult forms of these isotopes to contain, must be handled in specialized closed systems. Sodium p S]-sulfate and sodium [ I]-iodide must be handled similarly in closed systems to avoid the Uberation of volatile p S]-sulfur oxides and [ I]-iodine. Adequate shielding must be provided when handling P P]-phosphoric acid to minimize exposure to external radiation. 

Gas Chromatography. Gas chromatography is a well recognised method for the analysis of H—D—T mixtures. The substrate is alumina, AI2O2, coated with ferric oxide, Fe202. Neon is used as the carrier gas. Detectors are usually both thermal conductivity (caratherometer) and ion chamber detectors when tritium is involved (see Chromatography). 

Properties of T2O. Some important physical properties of T2O are Hsted in Table 2. Tritium oxide [14940-65-9] can be prepared by catalytic oxidation of T2 or by reduction of copper oxide using tritium gas. T2O, even of low (2—19% T) isotopic abundance, undergoes radiation decomposition to form HT and O2. Decomposition continues, even at 77 K, when the water is fro2en. Pure tritiated water irradiates itself at the rate of 10 MGy/d (10 rad/d). A stationary concentration of tritium peroxide, T2O2, is always present (9). AH of these factors must be taken into account in evaluating the physical constants of a particular sample of T2O. 

Personnel are protected in working with tritium primarily by containment of all active material. Containment devices such as process lines and storage media are normally placed in well-ventilated secondary enclosures (hoods or process rooms). The ventilating air is monitored and released through tall stacks environmental tritium is limited to safe levels by atmospheric dilution of the stack effluent. Tritium can be efficiently removed from air streams by catalytic oxidation followed by water adsorption on a microporous soHd absorbent (80) (see Absorption). 

A. E. Sherwood, Tritium Removalfrom Air S treams by Catalytic Oxidation and Water Adsorption, Eawrence Eivermore Eaboratoy Report UCRE-78173, 1976. 

The isotopic purity of the product is usually about 48-62%, the rest of the material being mainly undeuterated. (An alternate preparation of a-mono-deuterio ketones of high configurational and isotopic purity is the mild oxidation of cis- or tra 5-deuterated alcohols under Jones conditions, see sections V-D and VII-A.) Treatment with zinc in acetic acid-OD has also been applied to the deiodination of 2a-iodoandrost-4-ene-3,17-dione. In a slightly modified version the iodine in 19-iodocholesterol acetate has been replaced with tritium by using tritium oxide as the isotope source/... 

How many tritium atoms are incorporated into acetate if a molecule of palmitic acid is oxidized in 100% tritiated water ... 

When specifically labelled compounds are required, direct chemical synthesis may be necessary. The standard techniques of preparative chemistry are used, suitably modified for small-scale work with radioactive materials. The starting material is tritium gas which can be obtained at greater than 98% isotopic abundance. Tritiated water can be made either by catalytic oxidation over palladium or by reduction of a metal oxide ... 

Table IV presents the results of the determination of polyethylene radioactivity after the decomposition of the active bonds in one-component catalysts by methanol, labeled in different positions. In the case of TiCU (169) and the catalyst Cr -CjHsU/SiCU (8, 140) in the initial state the insertion of tritium of the alcohol hydroxyl group into the polymer corresponds to the expected polarization of the metal-carbon bond determined by the difference in electronegativity of these elements. The decomposition of active bonds in this case seems to follow the scheme (25) (see Section V). But in the case of the chromium oxide catalyst and the catalyst obtained by hydrogen reduction of the supported chromium ir-allyl complexes (ir-allyl ligands being removed from the active center) (140) C14 of the...

Epoxyfarnesol was first prepared by van Tamelen, Stomi, Hessler, and Schwartz 4 using essentially this procedure. It is based on the findings of van Tamelen and Curphey5 that N-bromosuccinimide in a polar solvent was a considerably more selective oxidant than others they tried. This method has been applied to produce terminally epoxidized mono-, sesqui-, di-, and triterpene systems for biosynthetic studies and bioorganic synthesis.6 It has also been applied successfully in a simple synthesis of tritium-labeled squalene [2,6,10,14,18,22-Tetracosahexaene, 2,6,10,15,19,23-hexamethyl-, (all-E)-] and squalene-2,3-oxide [Oxirane, 2,2-dimethyl-3-(3,7,12,16,20-pentamethyl-3,7,ll,-15,19-heneicosapentaenyl)-, (all-E)-],7 and in the synthesis of Cecropia juvenile hormone.8... 

The number of polymer chains attached to zirconium atoms can be measured by treating the reaction mixture with excess tritium oxide giving a radioactive polymer (XXIX). Radiochemical measurements can therefore be used to determine the number of polymer chains attached to metal atoms during the polymerization. 

This reaction also takes place with retention of configuration => the stereochemistry of the reaction is like that of the oxidation of organoboranes => it can be very useful in introducing deuterium or tritium in a specific way. 

Sea cucumbers (Holothuroidea, Echinodermata) appear to be unique in their mode of squalene oxide (37) cyclization. Tritium-labeled lanosterol (33), cycloartenol (32) and parkeol (38) were individually administered to the sea cucumber Holothuria arenicola. While the former two triterpenes were not metabolized [22], parkeol was efficiently transformed into 14x-methyl-5a-cho-lest-9(l l)-en-3/ -ol (39) (Scheme 3). Other A1 sterols present in H. arenicola were not found to be radioactive and were thus assumed to be of dietary origin. The intermediacy of parkeol was confirmed by the feeding of labeled mevalonate (23) and squalene (26) to the sea cucumber Stichopus californicus [15]. Both precursors were transformed into parkeol, but not lanosterol nor cycloartenol, aqd to 4,14a-dimethyl-5a-cholest-9(ll)-en-3/J-ol (40) and 14a-methyl-5a-cholest-9(ll)-en-3/ -ol. Thus, while all other eukaryotes produce either cycloartenol or lanosterol, parkeol is the intermediate between triterpenes and the 14-methyl sterols in sea cucumbers. 

Measurement of the amount of tritium in the quenched samples was made by reheating them in a normal hydrogen ambient and measuring the evolved radioactivity. Since the samples contained tritium not only dissolved in the bulk crystal but also attached to the surface, mainly in a thin oxide film, measurements were made with and without removal of the latter by etching with HF, a procedure verified to remove the surface radioactivity. Their final results for the solubility s fell nicely on the Arrhenius line, ... 

Another possibility, suggested by Ichimiya and Furuichi, is that there may have been significant blockage of the escape of tritium from the samples by the presence of a thin oxide film, i.e., that the d s of Fig. 9 were not... 

This photoaffinity labelling analogue of all-fraws-retinal, 95b, has been tritium labelled80 by reduction of unlabelled aldehyde 95a with [3H]-NaBH4 and subsequent oxidation of the obtained tritium-labelled retinol with activated manganese dioxide. The product 95b (specific activity 38.3 mCimmol-1) has been isolated by preparative TLC (equation 36). 

One of the first pieces of evidence for the mechanism of this reaction involved an attempt to develop a new assay for the activity of tyrosine synthase, which converts phenylalanine to tyrosine. A tritium was placed in the para position of phenylalanine, and it was assumed that oxidation of this position would lead to the loss of tritium and the rate of this loss would be a measure of the activity of the enzyme (Fig. 4.76). 

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