Iodides, alkaline, reducing agents

Phosphonic acid and hydrogen phosphonates are used as strong but slow-acting reducing agents. They cause precipitation of heavy metals from solutions of their salts and reduce sulfur dioxide to sulfur, and iodine to iodide in neutral or alkaline solution. 

Ideally, a solution for injection should be an isotonic solution with a neutral (physiological) pH. However, the pH of a radiopharmaceutical is very important for its stability, and for labelled compounds, the pH for optimal stability is not always equivalent to physiological pH. For iodide solutions, the pH should be alkaline to prevent loss of radioiodine. Reducing agents, such as thiosulfate, are often added to radioiodide solutions to help this situation. A preservative can act as a stabilizer, an antioxidant, or a bactericidal agent. 

Iodine is a moderately strong oxidizing agent and can be used to titrate reducing agents. Titrations with I2 are called iodimetric methods. These titrations are usually performed in neutral or mildly alkaline (pH 8) to weakly acid solutions. If the pH is too alkaline. I2 will disproportionate to hypoiodate and iodide ... 

POTASSIUM lODATE (7758-05-6) KIO, Noncombustible solid but many chemical reactions can cause fire and explosions. A strong oxidizer. Reacts violently with many materials, including reducing agents, hydrides, nitrides, and sulfides combustible materials, organic substances, manganese dioxide, arsenic, finely divided metals or carbon materials, hydrides of alkali or alkaline earth metalss, metal cyanides, metal thiocyanates, phosphonium iodide, red phosphorus, sulfides, sulfur, xenon tetrafluoride. Forms explosive compounds with solid organic matter. Mixture of powdered aluminum forms heat-, friction-, and shock-sensitive explosive. Attacks chemically active metals (e.g, aluminum, copper, zinc, etc.). Thermal deconposition, at temperatures above 1040°F/560°C, releases toxic iodine fumes. 

Piperidin—CtH,, N —which is a product of the action of KHO on piperin (see below), and may also be obtained from pyridin by the action of reducing agents, such as Sn-i-HCl. It is a colorless liquid, having a strongly alkaline reaction and an ammoniacal odor. When heated with methyl iodid it is converted into methyl-piperidin. The composition of piperidin and its formation from pyridin by reduction, as well as the fact that, on treatment with silver oxid, it produces pyridin, prove it to be hexa hydro-pyridin, or pyridin whose bonds have been released and satisfied by hydrogen atoms (see below). 

Practically, all radionucfides of iodine produced from target materials are purified and dissolved in dilute alkaline solution, or solution containing reducing agent to ensure that iodine stays in the reduced form of iodide (I ). However, in many cases where iodine activity occurs at very high concentrations in solution, a small fraction of iodate () is formed, most likely due to radiation-induced oxidation (discussed in Radiation chemistry of iodine in aqueous solutions ). This may cause some inconvenience when iodide is used. However, it is of interest to know that when iodine activity is administered for goiter prevention, radioiodine in the form of iodate is taken up by the thyroid rapidly as effectively as iodide (Cronquist etal.y 1971). 

Iron(iii) salts are readily reduced to iron(ii) salts by a variety of reducing agents, for example iodide ions, copper metal and copper(i) ions. Iron(ii) salts are readily oxidized under alkaline conditions ... 

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