Tritium butyl

Nach Tritioborierung von Hexin-(l) mit Tritio-bis-[3-methyl-butyl-(2)]-boran und Protonolyse erhalt man allerdings ein Gemisch von 2-Tritio-hexen-(I) und 1,2-Ditritio-hexen-(l), da das saure Wasserstoff-Atom des Alkins teilweise gegen Tritium ausge-tauscht wird4. 

Saunders and co-workers (Amin et al., 1990) determined the secondary tritium KIEs for the E2 reactions of [19] with sodium ethoxide in ethanol, [20] with potassium t-butoxide in t-butyl alcohol and [21] with potassium t-butoxide in t-butyl alcohol over a temperature range of 40°C. The Arrhenius parameters were found for each isotopic reactant and the AhIAt ratios were calculated (Table 41). The AH/AT ratios for the reactions of [19] and [21] are both less than unity, confirming that, in agreement with the model calculations, tunnelling is important in these reactions. The AHIAT ratio for the reaction of... 

The rate of dehydration of the cis diol was about fifty times slower than that of the trans diol and the product of the reaction consisted mainly of cyclohexenol. The 1,4-epoxycyclohexane formed in the reaction was formed after a prior epimerization of the cis to the trans diol this was demonstrated by means of tritium tracer technique. When irons-1,4-cyclohexanediol was dissolved in ieri-butyl alcohol-T having the hydroxyl hydrogen marked with tritium (C4H,OT) the 1,4-epoxycyclohexane produced in this reaction had a very low tritium content. A similar reaction carried out with cis-1,4-cyclohexanediol produced a highly tritiated 1,4-epoxycyclohexane. The insertion of tritium in the 1,4-epoxycyclohexane produced from the cis diol can be explained as follows ... 

The hydrazone (XI) is the predominant form, and in acid and neutral solution no indication of either the azo- (X) or the ene-hydrazine form (XII) has been found. In alkaline solution, however, studies with tritium [56] have shown exchange both of the aldehyde hydrogen and of hydrogen atoms at the a-carbon, indicating the presence of both the forms (X and XII). The equilibrium constant in 0.1 M ethanolic KOH for the equilibrium benzyl phenyldiazene — benzaldehyde phenylhydrazone is about 10, but for monoalkylhydrazones of aliphatic carbonyl compounds a higher proportion of the azo form is found. Acetaldehyde propylhydrazone is thus in r-butanol containing 0.02 M potassium -butylate at 100°C in equilibrium with 3.7% of the azo form [57]. 

Retinyl esters 102a-c (1 mCirnl ) stored under argon at —60°C in toluene containing 40 /ig of 2-t-butyl-4-methoxyphenol and 4 pL of pyridine are quite stable. After 1 year about 60% decomposition was noted, due to radiolysis in the case of 102c. Retinoic acid 103 under similar conditions is also radiochemically stable, but after 4 months the material has to be repurified. Specific activities of tritium-labelled retinoids in the 10-40 Cimmol range have been found necessary in view of the discovery and use of cellular retinoid binding proteins. ... 

Tritium Manganese-54 Strontium-90 Perchlorate Total aldicarbs Bromodichloroacetic acid Chlorodibromoacetic acid Tribromoacetic acid Alpha chlordane Ethyl-f-butyl ether Dichlorofluoromethane... 

A solution of 50-mCi portions of [ Hgj-lSO in 9 1 EtOH/H20 mixture have been stored at — 20 °C at a radioactive concentration of 4.5 mCi mP and the radiochemical purity of the sample was 95-96% after one year. No labile tritium was found after refluxing a portion of the sample for 1 h in a methanolic solution of NaOH. The intermediate 131, 5-(4-chlorobenzoyl)-4-methyl-l//-pyrrole-2-acetic acid, has been obtained in an eight-step synthesis starting with rerr-butyl acetoacetate (equation 52). 

Site-specific tritium-labeled arenes. Taylor reports that tritium-labeled aromatics can be obtained by wetting dried ether with tritiated water, adding an aryl halide, cooling to -70°, and then adding n-butyllithium. Trimethylsilyl derivatives of aromatics can be prepared using trimethylchlorosilane in the same way. When the organometaUic intermediate is formed first and then treated with tritiated water, only the unlabeled hydrocarbon is obtained in some cases. Apparently, the cross-metalation reaction is faster than the reaction of -butyl-lithium with either water or trimethylchlorosilane. 

In early studies of this chemistry we had examined the ability of such thiazolium salts to catalyse the benzoin condensation, a process which also formally involves an acyl anion but which is really of course the anion in which the thiazolium salt has been added to the carbonyl group (Figure 2.10). In this sense the thiazolium anion is very much like cyanide anion, the normal catalyst for simple benzoin condensations. Benzaldehyde would be expected to bind into a j8-cyclodextrin cavity, so we attached a thiazolium salt to a primary carbon of j8-cyclodextrin and examined it as a catalyst. We found that this was not a better catalyst for the benzoin condensation, apparently because there was no room in the j8-cyclodextrin cavity for the binding of two benzaldehyde molecules. However it was clear that at least the reaction intermediate was being formed we got very rapid tritium exchange from the aldehyde by formation of the thiazolium adduct, and as well a very rapid oxidation of para-f-butyl benzaldehyde by ferricyanide ion since it was able to oxidize the reaction intermediate formed when the bound t-butyl benzaldehyde underwent addition of the thiazolium ring. 

Whyman, 1970 Chapman et al, 1971). Other surfactants such as Triton X-114 have also been investigated. Anderson and McClure (1973) report a formulation of Triton X-114 in xylene which will accept up to 30% (v/v) aqueous sample and provides up to 47% efficiency for tritium. Another scintillation cocktail dubbed "Plasmasol" is a mixture of xylene, Triton X-100 and mono- and di-butyl phosphate (Wiegman et al, 1975). As the name Plasmasol suggests, it was designed for use with aqueous solutions containing soluble protein and is especially suited for radioimmunoassay. 

LiEtaB H at nearly 100% abundance tritium is readily produced from Li H (as prepared in Section 4.3.4) and EtaB (THF r.t., lmin) ° . Earlier methods using less reactive crystalline Li H at lower specific activities had to be more drastic (r.t., 2 days or reflux, 2h) and are therefore less appropriate for the preparation of a highly tritiated reagent. Despite its excellent synthetic potential only a few applications have been published so far, aside from test reactions on model substrates. Among the simpler but elegant were tritio-deoxygenation of (/ )- and (5)-[l- H]ethyl and [l- H]butyl tosylates to give (R)- and (S)-[l- H,l- H]ethane and (/ )- and (5)-[l- H,l- H]butane, respectively, for use in... 

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