Organic reactions tritium-labeled compounds

The production of tritium-labelled organic compounds was enormously facilitated by K. E. Wilz-bach s discovery in 1956 that tritium could be introduced merely by storing a compound under tritium gas for a few days or weeks the radiation induces exchange reactions between the hydrogen atoms in the compound and the tritium gas. The excess of gas is recovered for further use and the tritiated compound is purified chro-matographically. Another widely used method of... 

For mechanistic studies => to test some hypothesis about a reaction mechanism or about how a certain organism metabolizes a compound => often need to synthesize a particularly labeled compound (with deuterium, tritium, or C). 

Hot atom reactions can be used for synthesis of labeled compounds. So far this technique has been used primarily for and labeling. For example, an organic gaseous conqx)und is mixed with He and the sample is irradiated with neutrons. The reaction He(n,p) H produces tritium as hot atoms (indicated by the small arrow) with kinetic ergies of approximately 0.2 MeV. These hot atoms react with the organic molecules to produce labeled compounds. An example is the formation of labeled butanol... 

A 98% conversion efficiency has been achieved at 1.5 atmospheric pressure of CO2 and 10% excess of water, while the yield was 85% only when stoichiometric amounts of water and carbon dioxide were used. No isotopic fractionation has been noted when 5 to 10% excess of water has been used in the reaction in equation 5. Doubly labelled methane has been used in simultaneous analysis of and both in the atmosphere and in environmental carbon dioxide as well as in analysis of and H-labelled organic compounds. Proportional counters filled with methane possess very good counting properties and there is no need to add any inactive counting gas. and tritium-labelled methanes have also been produced" by pyrolysis of sodium acetate in molten sodium hydroxide (equation 6) ... 

Compounds labeled with isotopes such as carbon-14 or tritium have also contributed to numerous advances in studies of biochemistry, biosynthetic pathways, enzyme mechanisms, elucidation of organic reaction mechanisms and environmental sciences. 

Hot atom reactions have also been used to label organic compounds with T. Irradiation of helium-3 with neutrons according to the nuclear reaction produces very energetic tritium atoms that can displace ordinary hydrogen in organic compounds. This procedure is not very selective, and the labeling pattern must be determined to enable the tritiated product to be used effectively as a tracer (34). 

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

Wolf AP (1960) Labeling of organic compounds by recoil methods. Ann Rev Nud Sci 10 259 Wolf AP (1964) The reactions of energetic tritium and carbon atoms with organic compounds. Adv Phys Organ Chem 2 201... 

The Wilzbach procedure is a simple method of labelling organic compounds with tritium The substance is exposed to tritium gas in a sealed glass vessel for several days or weeks. During this period, some of the hydrogen atoms of the molecule to be labelled are substituted by H atoms. Chemical side reactions may take place however at the same time, e.g., unsaturated compounds may be partly or completely hydrogenated. Several firms carry out this type of labelhng on request [312]. 

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