Fluorine radioactive, production

F]FDT, 117, has been prepared16221 as shown in equation 72. Non-radioactive product has also been prepared in 53% yield by the fluorination of 118 with Me4NF followed by deprotection with BBr3. The in vivo behaviour of 118 in tumour-bearing animals had a... 

Fluorine, which does not occur freely in nature except for trace amounts in radioactive materials, is widely found in combination with other elements, accounting for ca 0.065 wt % of the earth s cmst (4). The most important natural source of fluorine for industrial purposes is the mineral fluorspar [14542-23-5] CaF2, which contains about 49% fluorine. Detailed annual reports regarding the worldwide production and reserves of this mineral are available (5). A more complete discussion of the various sources of fluorine-containing minerals is given elsewhere (see Fluorine compounds, inorganic). 

When radon is heated to 400°C with fluorine, a nonvolatile fluoride is formed (Fields et al., 1962, 1963). It has been deduced from the chemical behavior that the product is radon difluoride, RnF2. (Products of the tracer experiments have not been analyzed because of their small mass and intense radioactivity.)... 

Aromatic fluorination can be carried out by a regiospecific destannylation process shown in reaction 69. This is an effective method for producing fluorinated m-tyrosine and other radiopharmaceuticals, as shown in reaction 70. The process can be applied for radiolabelling with 18F, denoted as F in these reactions, and the products used as radioactive tracers for clinical and fundamental investigations318-321. 

For the 0(p,n) F nuclear reaction, the oxygen-18 target material normally consists of highly enriched (>95%) liquid [ 0]water, but [ 0]dioxygen gas has been used as well [19,37]. Appropriate cyclotron targetry allows a batch production of several Curies of [ F]fluorine in a single irradiation of a few hours. While the theoretical specific radioactivity of carrier-free fluorine-18 is 1.7 x 10 ... 

Noteworthy is a recent multi-step method for the production of molecular [ F]F2 of considerable higher specific radioactivity (100-925 Ci/mmol or 3.7-34 TBq/ mmol) starting from aqueous [" Fjfluoride produced with the 0(p,n) F reaction [38], The dried and activated [ F]fluoride is reacted with methyl iodide to yield methyl [ F]fluoiide (CHsf FjF) which is isolated by gas chromatography. The latter is then subjected to an electrical discharge (20-30 kV, 280 pA, 10 s) in the presence of small amounts of carrier fluorine (150 nmol) resulting in about 30% conversion of the original [ F]fluoride into molecular [ F]F2. 

In this section the production of a number of radioactive electrophilic fluorination agents that have not already been dealt with in Section 2.6 will be discussed. 

The other major springboard for the fluorocarbon chemical industry was the "Manhattan Project to develop the atomic bomb. This required the large-scale production of highly corrosive elemental fluorine and uranium(VI) fluoride for the separation of the radioactive 235U isotope. Oils capable of resisting these materials were needed to lubricate pumps and compressors, and polymers were needed to provide seals. Peril uorinated alkanes and polymers such as PTFE and poly(chlorotrifluoroethylene) (PCTFE) proved to have the appropriate properties so practical processes had to be developed for production in the quantities required. In 1947 much of this work was declassified and was published in an extensive series of papers3 which described the fundamental chemistry on which the commercial development of various fluoro-organic products, especially fine chemicals, was subsequently based. 

Radioactivation analysis has been used to measure bromine in polymers (37—39) and recently a novel technique for trace oxygen has been reported (40). Any polymer or other material (e.g. metal alkyl) which is miscible with butyl lithium solutions may be analysed since the procedure involves the intermediate production of triton particles by the nuclear reaction 6Li (n, a) t. The tritons then act as nuclear projectiles for the activation of oxygen 0 (t, n) 18F and the radioactivity due to fluorine-18 is measured. A sensitivity of 1 x 10 g in a 0.5 g sample is claimed. 

Pinder etal. (1985) deduced NSA values in the range 20-41 m2d kg-1 from measurements of 238Pu in corn near the Savannah River Plant. Similar values also apply to non-radioactive trace elements. Allcroft et al. (1965) made a series of measurements of fluorine in herbage on a farm near Stoke-on-Trent and also recorded fallout of fluorine in a nearby deposit gauge. During the period of study (1956-61) the productivity of the pasture was improved, and the yearly average NSA declined from 59 to 27 m2d kg-1 (Chamberlain, 1970). When productivity is low, the time T0 before maturity is increased, and so is the NSA (Table 2.17). Also XG may be increased, since the rate of field loss seems to be related to growth rate. 

Tritium is also one of the products obtained by bombardment of fluorine, beryllium, antimony, copper, or silver with deuterons, or the bombardment of boron and nitrogen with neutrons. Tritium is the simplest known radioactive isotope. It decays by emission of beta particles to form an isotope of helium and has a half-life of about 12 years. 

In PET, radioactive substances that emit positrons are introduced into a patient s bloodstream. As the radioactive atoms decay, the positrons they emit collide with electrons, producing gamma rays that escape from the body and are detected by an array of instruments surrounding the patient. Computer analysis of the amount and direction of gamma ray production, and comparison of the data collected for people with and without certain brain disorders provides doctors with valuable information. For example, PET scans of the brain have been used to study the movement of the medication L-dopa in the brains of people suffering from Parkinson s disease. In these procedures, fluorine-18 atoms are attached to L-dopa molecules, which are then injected into a patient. Each flourine-18 decays and emits a positron that generates gamma rays when it meets an electron. 

The enzyme has an absolute requirement for a divalent cation, which could function in substrate binding, catalysis, or both. Radioactive Mn " did not bind appreciably in the absence of substrate. With substrate or product present, 2 moles of metal were bound per subunit. Metal ions (Mn or Mg ) also enhanced the binding of substrates several-fold. Simultaneous binding of two unreactive fluorine analogs, one allylic the other homoallylic, did not enhance the binding of the metal ion. These experiments demonstrated that the metal ion is essential for catalysis and may not play an important role in substrate binding [6]. 

In the Aquafluor process [G4] developed by the General Electric Company, most of the plutonium and fission products in irradiated light-water reactor (LWR) fuel are separated from uranium by aqueous solvent extraction and anion exchange. Final uranium separation and purification is by conversion of impure uranyl nitrate to UFg, followed by removal of small amounts of PuF , NpFg, and other volatile fluorides by adsorption on beds of NaF and Mgp2 and a final fractional distillation. A plant to process 1 MT/day of irradiated low-enriched uranium fuel was built at Morris, Illinois, but was never used for irradiated fuel because of inability to maintain on-stream, continuous operation even in runs on unirradiated fuel. The difficulties at the Morris plant are considered more the fault of design details than inherent in the process. They are attributed to the attempt to carry out aqueous primary decontamination, denitration, fluorination, and distillation of intensely radioactive materials in a close-coupled, continuous process, without adequate surge capacity between the different steps and without sufficient spare, readily maintainable equipment [G5, R8]. 

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