Hydrogen with tritium

Two di-tritiated isocarbacyclin methyl esters 116 and 117 in the title have been synthesized95 from (Z)-olefinic precursors 118 and 119 at the >-side chain by catalytic hydrogenation with tritium gas (equations 44 and 45). The therapeutic candidates for cardiovascular deseases96, 116 and 117, were required for preclinical studies and for use in RIA analysis. 

The importance of conformation in selective attack of the 1 l/ -alkoxy radical on C18 and C19 was nicely illustrated by the photolysis of the nitrite 18 derived from the dienone 19. This afforded only C18 attack.7 Treatment of the derived oxime with nitrous acid gave 1-dehydro-aldosterone acetate 20. This is a convenient precursor for labelled aldosterone acetate since selective hydrogenation with tritium gives 1,2-ditritiated aldosterone acetate. 

Dictamnine labeled on the furan hydrogens with tritium or deuterium was prepared by cyclization of aldehyde 247 with tritiated or deuterated PPA (J). Treatment of [2,3-2H2]dictamnine with aqueous acid did not result in exchange of deuterium atoms. In the formation of [2,3-2H2]dictamnine, exchange of deuterium between the 2- and 3-positions of the furan ring may occur by a 1,2-shift, (251) (252) (Scheme 19), although an alternative mechanism for exchange of the aldehyde proton involves addition of D+ to the enol form of aldehyde 250 assisted by the... 

Retinol-11,12- H2 of low specific activity has been prepared (Isler et al., 1960) based on the work of Isler et al. (1947) on the synthesis of retinyl acetate. The same sequence of reactions as shown in Fig. 8, with several improvements in technique because of the small scale, was applied by Perry et al. (1982) to the preparation of retinoic acid tritiated at very high specific activity. Pure, recrystallized diol (XXVI) was partially hydrogenated with tritium over Lindlar catalyst in the presence of quinoline and the dihydro compound (XXVII), acety-lated in such a way as to afford mainly the monoacetate (XXVIII). Exposure of the acetate at low temperature for a very short time to very dilute hydrogen bromide in methylene chloride gave, after chromatography, pure retinyl-11,12- H2 acetate (XXIXa). Simultaneous hydrolysis and oxidation of the retinyl acetate by silver oxide in aqueous methanolic sodium hydroxide then yielded all-fran -reti-noic-11,12- H2 acid (Vllh). The specific activities obtained ranged from 25 to 40 Ci/mmol. 

A simple example occurs with hydrogen, which occurs naturally as three isotopes (hydrogen, deuterium, tritium), all of atomic number 1 but having atomic masses of 1, 2, and 3 respectively. 

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 ... 

Examples of isotopes are abundant. The major form of hydrogen is represented as H (or H-1), with one proton H, known as the isotope deuterium or heavy hydrogen, consists of one proton and one neutron (thus an amu of 2) and is the isotope of hydrogen called tritium with an amu of 3. Carbon-12 ( C or C-12) is the most abundant form of carbon, though carbon has several isotopes. One is the C isotope, a radioactive isotope of carbon that is used as a tracer and to determine dates of organic artifacts. Uranium-238 is the radioactive isotope (Note The atomic number is placed as a subscript prefix to the element s symbol—for example, —and the atomic mass number can be written either as a dash and number fol-... 

TRITIUM. The radioactive isotope of hydrogen, with a mass number 3, is termed tntnim. it is one form of heavy hydrogen, the other form being deuterium. See also Nuclear Power Technology. 

Tritium, Carbon-14, and Strontium-90. The other extreme of detectability might be thought to be low energy betas from hydrogen-3. Hydrogen-3 (tritium) emits an 18.6 k.e.v. 0-ray with a half-life of 12.26 years (no 7-rays). The sample sizes here must be small to permit detection of the 0-rays by the apparatus. Nevertheless, the detection sensitivities for these radioactivities are of the order of 10-3 pCi per gram. 

Hydrogen exchange reactions in liquid ammonia can be used to prepare many organic compounds labelled with tritium or deuterium. 

Timmons (12) showed that the water in a never dried freshcut tree, when exchanged with a series of organic solvents could be replaced with radioactively tritium labeled MMA (hydrogen-3). After polymerization and the use of autoradiography the MMA was located in the cell wall structure. If the same wood was dried normally, and then treated in the usual manner with tritium labeled IWIA, the polymer was located exclusively in the capillaries and none was found in the cell walls. 

Isolation of high yields of (201) from the analogous reaction of N-(2-chloroallyl)alkylamine argues against its involvement as a substitution intermediate. The sensitivity of the acetylene to nucleophilic addition rather than its mere isolation should be considered as part of the evidence concerning its role as an essential intermediate. Since neither (199) nor (200) exchange their CH2-hydrogens with the solvent, the isolation of labelled (200) from the reaction in tritiated liquid ammonia excluded (1) as the main substitution, while (2) and (4) are excluded since the exocyclic methylene was not labelled. The incorporation of tritium at... 

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