1-122, rapid iodinations

Our production parameters for this generator are presented. The Xe-122/l-122 combination, a convenient source of a short-lived (3.6m) positron emitting iodine, is also discussed. Recent developments in rapid iodination procedures will broaden the potential applications of this generator. Finally, preliminary investigations of another generator derived radionuclide that may have promise is described. Tellurium-118 (6d) is the parent of the 3.5 minute positron emitter Sb-118 which may be useful for first pass angiography. 

The iodine solution is added dropwise at such a rate that the entire quantity of iodine is added over a period of 45-74 minutes. If the iodine is added too rapidly, iodination of acetone will take place. Caution. Iodoacetone species are extremely powerful lacrimators. During the addition of the iodine solution, a very slow flow of nitrogen should be maintained (1-5 bubbles per minute). The resultant product should consist of a dark brown solution and unreacted iron (150-mole % excess). This excess iron powder is necessary for the over-all reaction, for reducing the iodination of acetone, and for improving the yield of product. 

Radioiodination involves the substitution of radioactive iodine atoms for reactive hydrogen sites in target molecules. The process usually involves the action of a strong oxidizing agent to transform iodide ions into a highly reactive electrophilic iodine II compound (typically I2 or a mixed halogen species such as IC1). Formation of this electrophilic species leads to the potential for rapid iodination of aromatic compounds... 

Alkyl iodides have been widely used for selective alkylation of heteroaromatic bases. The method is based on rapid iodine abstraction by aryl radicals (obtained from benzoyl peroxide or diazonium salts) or by a methyl radical (obtained from MeCOOH, t-BuOH, t-BuOOH, (t-BuO)2, (MeCOO)2, MeS0Me/H202, or MeC0Me/H202) [2]. An example is depicted in Eq. (14) of Table 3. 

When cyclo-fMeAs), is treated with iodine in benzene, rapid iodine decolarization occurs. As—As ring bonds are cleaved and solid products form. End-group analysis has shown that molecular weights between 2700 and 4300 are obtained, depending more upon the initial concentration of cyclopentamer than upon the As I ratio. The solid products, however, were washed with ether prior to analysis, a procedure accompanied by the removal of from the polymers. The assignments of mol wts based upon their end-group analyses therefore appears questionable. 

The enol form is then rapidly iodinated or brominated ... 

Rapid iodine turnover Aggressive disease Adjuvant therapy in RAI remnant ablation [under investigation)... 

Mallik et al. [82] described a rapid iodine-catalyzed cyclocondensation of cinnam-aldehyde and thiophenol to synthesize trans-2-phenyl-4-thiophenoxy-3,4-dihydio-2//-1-benzothiopyran 57 in excellent yields with high diastereoselectivity (Scheme 10.39). 

Romain L, Mien V, Karine T, Rachida Z, Vincent S, Pierre K (2008) A facile and rapid iodine-catalyzed meso-tetraphenylporphyrin synthesis using microwave activation. Tetrahedron Lett 49 5537-5539... 

Pyrazole (7) undergoes rather more rapid iodination when it is complexed with nickel(n). The pH-dependence of iodination rates also differs for free pyrazole and its nickel complex. This difference arises from the additional pH-dependent equilibrium between aquo- and hydroxo-ligands on the nickel in the complex. The substituent effect of the —CH2—Co(dmgH)2Py moiety in... 

Trichloroethanoic acid, CCI3COOH. A crystalline solid which rapidly absorbs water vapour m.p. 58°C, b.p. 196-5" C. Manufactured by the action of chlorine on ethanoic acid at 160°C in the presence of red phosphorus, sulphur or iodine. It is decomposed into chloroform and carbon dioxide by boiling water. It is a much stronger acid than either the mono- or the dichloro-acids and has been used to extract alkaloids and ascorbic acid from plant and animal tissues. It is a precipitant for proteins and may be used to test for the presence of albumin in urine. The sodium salt is used as a selective weedkiller. 

The iodine produced in the Duslnnan process is rapidly reduced to iodide via the Roebuck reaction... 

These values indicate a rapid fall in thermal stability of the halide from fluorine to iodine, and hydrogen iodide is an endothermic compound. If we now examine the various enthalpy changes involved. we find the following values (in kJ) ... 

Reaction (11.4) is really a disproportionation reaction of the halate(I) anion 3XO 2X -E XO. ) Reaction (11.3) is favoured by the use of dilute alkali and low temperature, since the halate(I) anions, XO are thermally unstable and readily disproportionate (i.e. reaction (11.4)). The stability of the halate(I) anion, XO , decreases from chlorine to iodine and the iodate(I) ion disproportionates very rapidly even at room temperature. 

Hence hydrogen iodide cannot be produced by the reaction of sulphuric acid with an iodide. Hydriodic acid is slowly oxidised by air (more rapidly in light) liberating iodine ... 

If cold benzene is treated with bromine in the absence of sunlight, very little reaction occurs if, however, a halogen carrier, such as iron, iodine, pyridine, etc., is also present, a rapid reaction by substitution occurs, forming first... 

This should be free from sulphur, and obtained in small containers so that a specimen is rapidly used it should be in dark bottles and stored in the dark. When withdrawing a specimen, the acid should be exposed to the air for as short a time as possible, as both air and light promote its decomposition to iodine. 

Hydrazine hydrate may be titrated with standard acid using methyl orange as indicator or, alternatively, against standard iodine solution with starch as indicator. In the latter case about 0-1 g., accurately weighed, of the hydrazine hydrate solution is diluted with about 100 ml. of water, 2-3 drops of starch indicator added, and immediately before titration 6 g. of sodium bicarbonate are introduced. Rapid titration with iodine gives a satisfactory end point. 

A special apparatus (Fig. Ill, 40,1) renders the preparation of iodides from alcohols a very simple operation. The special features of the apparatus are —(i) a wide bored (3-4 mm.) stopcock A which considerably reduces the danger of crystallisation in the bore of the tap of the iodine from the hot alcoholic solution (ii) a reservoir B for the solid iodine and possessing a capacity sufficiently large to hold all the alkyl iodide produced (iii) a wide tube C which permits the alcohol vapour fix)m the flask D to pass rapidly into the reservoir B, thus ensuring that the iodine is dissolved by alcohol which is almost at the boiling point. An improved apparatus is shown in Fig. Ill, 40, 2, a and b here a... 

Rapid halogenation of the a carbon atom takes place when an enolate ion is generated m the presence of chlorine bromine or iodine... 

Unlike the situation regarding the crossing between the Vq and Fj potentials for Nal (see Figure 9.41), that for NaBr results in very efficient and rapid dissociation to give Na + Br when it is excited to Fj. Flow would you expect the fluorescence intensity from the neutral bromine atoms to vary with time compared with that for iodine atoms from Nal in Figure 9.42 ... 

Moist iodine vapor rapidly corrodes metals, including most stainless steels. The initial process is the formation of corrosion centers where small amounts of metal iodide are formed which deHquesce, and the corrosion then takes place electrochemically (41,42). Only titanium and molybdenum steels are unattacked by iodine (42,43). The corrosion of molten iodine has also been studied. 

Photography. Photography (qv) represents one of the oldest industrial uses of iodide. The sensitive silver salt in rapid negative emulsions contains up to 7% or mote silver iodide [7783-96-2], Agl. Erom 1969 to 1985 estimates on iodine consumption for this purpose varied from 150 to 270 t/yr (66). Ttiphenylphosphonium iodide is also among the iodine derivatives used in photography. This derivative permits faster development and higher contrast photography. 

Ha.logen Compounds. Fluorine is unreactive toward ozone at ordinary temperatures. Chlorine is oxidized to Cl20 and Cl20y, bromine to Br Og, and iodine to I2O2 and I4O2. Oxidation of haUde ions by ozone increases with the atomic number of haUde. Fluoride is unreactive chloride reacts slowly, ultimately forming chlorate and bromide is readily oxidized to hypobromite (38). Oxidation of iodide is extremely rapid, initially yielding hypoiodite the estimated rate constant is 2 x 10 (39). HypohaUte ions are oxidized to haUtes hypobromite reacts faster than hypochlorite (40). 

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