Iodine thiocyanate

Preparation. Ethereal solutions of iodine thiocyanate are prepared essentially by the method of Raby. Bromine (0.025 mole) is added ail at once to a slurry of lead thiocyanate (0.025 mole, Eastman). The mixture is stirred at room temperature until the bromine fades (several minutes). A solution of iodine (0.025 mole) in dry ether is then added lo the solution of thioeyanogen, and the mixture is stirred for 15 min. at room temperature with protection from light. 

Episulfides. Hinshaw reasoned that addition of an alkene to such solutions should give jS-iodothiocyanates in analogy with the reaction of iodine isocyanate (1, 501 2, 223-224 . 3, 161 -16.3) with alkenes. indeed treatment of cyclohexene with iodine thiocyanate gives a /5-iodothiocyanate (2), which on treatment with methanolic... 

For reaction with A -cholestene, iodine thiocyanate was prepared in methylene chloride 2, 3 -cpithiocholestane was obtained in 46% yield. 

Unfortunately the reaction of iodine thiocyanate with acyclic olefins does not give useful yields of episulfides. 

EPISULFIDES Iodine thiocyanate. EPOXIDES Dimethyloxosulfonium meth-yilde. Hexamethylphosphorous triamide. EPOXYOLEFINS Hexamethylphospbor-ous triamide. 

Cycloalkenes may be converted into episulphides by reaction with an ethereal or dichloromethane solution of iodine and thiocyanogen, in equimolar proportions, followed by alkaline hydrolysis. Iodine thiocyanate (ISCN) appears to be present in the solution, and to add diaxially to the olefinic bond hydrolysis then closes the episulphide ring. 5a-Cholest-2-ene (156), for example, gave the 2/ff,3)5-epithio-derivative (157) in acceptable yield. 

The oxidation potential of the 2 SCN = (SCN)2 couple Mis between those of the corresponding couples for Br and 1 (Table II) (38-40). The SCN = OSCN couple is comparable to the corresponding 1 couple (41). The oxidation potential of SCN relative to the halides explains the oxidation of SCN by CI2 (42) and Br2 (43) and the oxidation of 1 by (SCN)2. The latter reaction is one that can be used to quantify (SCN)2 (44). The relative oxidation potentials also facilitate the definition of inter (pseudo)halogens like I -SCN (iodine thiocyanate) (45,46) versus Cl -SCN (thiocyanogen chloride) (47) and Br -SCN (thiocyanogen bromide), which react accordingly. 

R. Lagasse, P. Bourdoux, P. Courtois, P. Hennart, G. Putzeys, C. Thilly, M. Mafuta, Y. Yunga, A.M. Ermans and F. Delange, Influence of the dietary balance of iodine/thiocyanate and protein on thyroid function... 

The majority of reactions whose kinetics have been discussed in terms of dielectric constant effects have been examined in mixed aqueous solution, but a few studies in series of pure solvents have been described in the past year and a half. Ionization of iodine thiocyanate is slow, and incomplete, in solvents with low dielectric constants,... 

Selective hydrogenation of a -unsaturated carbonyl compounds can be carried out by reduction with iron pentacarbonyl and a small amount of base in moist solvents. The method is applicable to oc -unsaturated aldehydes, ketones, esters, and lactones with negligible over-reduction of the carbonyl group and is susceptible to the steric environment of the olefin. Spectroscopic evidence suggests that solutions of equimolecular amounts of iodine and thiocyanogen contain an appreciable concentration of iodine thiocyanate. Addition of alkenes results in tran.r-addition to yield jS-iodo-thiocyanates which in base suffer rapid hydrolysis of the thiocyanate followed by ring closure to the episulphide (516). As a synthetic procedure this does not appear to be applicable to acyclic olefins. ... 

Consequences of marginal iodine deficiencies on neurological and intellectual development and functions are not well documented in industrialized countries, particularly effects upon hearing capacity. The objective of the present study was to evaluate the possibility that a relative iodine deficiency in children, as assessed by urinary concentration of iodine used as an index of the dietary intake of iodine, could result in mild hearing impairment. As a combination of iodine deficiency and increase in thiocyanate intake may cocontribute to thyroid dysfunction, iodine thiocyanate ratio (I/SCN) in urine was also assessed. 

The halogen in the 5-position of 2-aminothiazoles is usually reactive and is used for further reaction (see Chapter V). The reaction may take place in the same medium as thiocyanation (437-440), rhodanation (441). or reaction with NaNO (435). Similarly, a mixture of 2-amino-4-methylthiazole and thiourea in H2O yields 5,5 -thiobis(2-amino-4-methyDthiazole (202) after addition of iodine (Scheme 128) (442). 

Thiocyanate ion, SCN , inhibits formation of thyroid hormones by inhibiting the iodination of tyrosine residues in thyroglobufin by thyroid peroxidase. This ion is also responsible for the goitrogenic effect of cassava (manioc, tapioca). Cyanide, CN , is liberated by hydrolysis from the cyanogenic glucoside finamarin it contains, which in turn is biodetoxified to SCN. 

Bromide ndIodide. The spectrophotometric determination of trace bromide concentration is based on the bromide catalysis of iodine oxidation to iodate by permanganate in acidic solution. Iodide can also be measured spectrophotometricaHy by selective oxidation to iodine by potassium peroxymonosulfate (KHSO ). The iodine reacts with colorless leucocrystal violet to produce the highly colored leucocrystal violet dye. Greater than 200 mg/L of chloride interferes with the color development. Trace concentrations of iodide are determined by its abiUty to cataly2e ceric ion reduction by arsenous acid. The reduction reaction is stopped at a specific time by the addition of ferrous ammonium sulfate. The ferrous ion is oxidi2ed to ferric ion, which then reacts with thiocyanate to produce a deep red complex. 

Sodium thiocyanate has also been recrystd from water, acetonitrile or from MeOH using Et20 for washing, then dried at 130°, or dried under vacuum at 60° for 2 days. [Strasser et al. J Am Chem Soc 107 789 1985 Szezygiel et al. J Am Chem Soc 91 1252 1987.] (The latter purification removes material reacting with iodine.) Sodium thiocyanate solns can be freed from traces of iron by repeated batch extractions with Et20. 

Replacement of iodine in (perfluoroalkyl)ethyl iodides predominates over the usual conversion to olefins when the reagent is very nucleophilic and weakly basic Soft nucleophiles like sodium thiocyanate and sodium thiolates react well in displacements [46, 47] (equation 42)... 

After the addition of the potassium iodide solution, run in standard 0.1M sodium thiosulphate until the brown colour of the iodine fades, then add 2 mL of starch solution, and continue the addition of the thiosulphate solution until the blue colour commences to fade. Then add about 1 g of potassium thiocyanate or ammonium thiocyanate, preferably as a 10 per cent aqueous solution the blue colour will instantly become more intense. Complete the titration as quickly as possible. The precipitate possesses a pale pink colour, and a distinct permanent end point is readily obtained. 

Dithiol is a less selective reagent than thiocyanate for molybdenum. Tungsten interferes most seriously but does not do so in the presence of tartaric acid or citric acid (see Section 17.34). Tin does not interfere if the absorbance is read at 680 nm. Strong oxidants oxidise the reagent iron(III) salts should be reduced with potassium iodide solution and the liberated iodine removed with thiosulphate. 

A number of methods have been proposed for the detection of rancidity. The determination of active oxygen consists of dissolving the fat in a suitable medium such as chloroform and acetic acid, adding potassium iodide, and titrating the liberated iodine with a standard thiosulfate solution (16, 20). This is perhaps the most widely used method at the present time. Another procedure which has been proposed for the detection of peroxides employs ferrous ammonium sulfate and ammonium thiocyanate in acetone. The resulting red color of ferric thiocyanate is measured spectrophotometrically, and is said by the authors to yield more reproducible results than do the usual titration methods (21). 

Iodine starch inclusion compounds 46 Iodine vapor reagent 46, 64, 78 2-Iodoestrone 66 Ipecacuanha alkaloids 46, 263 Ipecacuanhae radix extract 263 Iron cadons 144, 217, 311 Iron(IIl) chloride reagent 170,216,314 Iron(III) thiocyanate reagent 170 Isoascorbic acid 376 Isoleucine 246,247... 

These and similar results can be explained if the simultaneous reduction of hydrogen peroxide is due to an induced reaction. To show the characteristic features of this reaction some results are presented in Table 19 and Table 20. The procedure for these measurements was as follows. The solution of peroxy compounds given in columns 1 and 2 was made up to 20 ml and the pH was adjusted to the given value. Then potassium thiocyanate solution was added and, after the reaction time noted, the process was quenched by adding potassium iodide solution (0.3 g KI). After 5 sec the solution was acidified with 1 ml 2 iV sulphuric acid then using, molybdate catalyst solution, the iodine liberated was titrated with standard thiosulphate. 

Cyanide and thiocyanate anions in aqueous solution can be determined as cyanogen bromide after reaction with bromine [686]. The thiocyanate anion can be quantitatively determined in the presence of cyanide by adding an excess of formaldehyde solution to the sample, which converts the cyanide ion to the unreactive cyanohydrin. The detection limits for the cyanide and thiocyanate anions were less than 0.01 ppm with an electron-capture detector. Iodine in acid solution reacts with acetone to form monoiodoacetone, which can be detected at high sensitivity with an electron-capture detector [687]. The reaction is specific for iodine, iodide being determined after oxidation with iodate. The nitrate anion can be determined in aqueous solution after conversion to nitrobenzene by reaction with benzene in the presence of sulfuric acid [688,689]. The detection limit for the nitrate anion was less than 0.1 ppm. The nitrite anion can be determined after oxidation to nitrate with potassium permanganate. Nitrite can be determined directly by alkylation with an alkaline solution of pentafluorobenzyl bromide [690]. The yield of derivative was about 80t.with a detection limit of 0.46 ng in 0.1 ml of aqueous sample. Pentafluorobenzyl p-toluenesulfonate has been used to derivatize carboxylate and phenolate anions and to simultaneously derivatize bromide, iodide, cyanide, thiocyanate, nitrite, nitrate and sulfide in a two-phase system using tetrapentylammonium cWoride as a phase transfer catalyst [691]. Detection limits wer Hi the ppm range. 

Such iodine is easily replaced by several nucleophiles. Methoxide displaces it to give methoxyfuran, and thiocyanate to give furyl thiocyanate, but phenoxide ion fails.248... 

Oxidative stress Lipid oxidation Oxygen absorption Manometric, polarographic Diene conjugation HPLC, spectrophotometry (234 nm) Lipid hydroperoxides HPLC, GC-MS, chemiluminescence, spectrophotometry Iodine liberation Titration Thiocyanate Spectrophotometry (500 nm) Hydrocarbons GC Cytotoxic aldehydes LPO-586, HPLC, GC, GC-MS Hexanal and related end products Sensory, physicochemical, Cu(II) induction method, GC TBARS Spectrophotometry (532-535 nm), HPLC Rancimat Conductivity F2-iP GC/MS, HPLC/MS, immunoassays... 

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