Iodine monochloride method

In official methods of analysis i.e., the iodine monochloride method, the reduction of KI03 can be expressed as follows ... 

Theory The iodine monochloride method described earlier employing standard potassium iodate is the basis for the official assay of potassium iodide. Vigorous shaking is a prime requirement, as the end-point is approached in this assay, because of the fact that both iodine and iodate in different phases attribute a heterogeneous medium. However, the reaction involving the oxidation of KI by iodate may be designated as shown below ... 

For both polymerization and rubber processing it is important to know the type and amount of unsaturation. In this connection IR spectroscopy is perhaps the most useful technique, although it requires a preliminary evaluation of band absorptivities by means of suitable standards, analyzed by an independent technique. A number of methods are available to analyze these standards NMR spectroscopy, the iodine-monochloride method, gas-chromatographic analysis of pyrolysis products, materials balance determination, etc.12 Provided the termo-nomer content of the standard is not too low, the most useful technique is NMR, based on the ratio between the signal from all saturated protons (generally with chemical shifts of 2S from TMS) and the signal from olefinic protons, observed at lower fields (45-5.5 5). 

Table 3.6 shows that the data obtained by the NMR method agree more closely with the Lee [42] iodine monochloride method than with the iodine monochloride method of Kemp and Peters [43]. The difference between the latter two methods is best explained on the basis of side reactions occurring between the iodine monochloride and the polymer because of branching near the double bond [42]. The reason for the difference between the NMR method and the method of Lee and co-workers [42] is not clear. The reproducibility of the NMR method was 10-15%. 

The iodine monochloride method has been used for various polymers. These polymers include those which are highly unsaturated, such as polybutadiene and polyisoprene [91-94] and polymers having low unsaturation such as butyl rubber [95], and ethylene-propylene-diene terpolymers. Considerable work has been done investigating the side reactions of iodine monochloride with different polymers. [95]. These side reactions are substitution and splitting out rather than the desired addition reaction. 

Albert [10] compared determinations of butadiene in high-impact polystyrene by an IR method and by the iodine monochloride method described by Crompton and Reid [11]. The IR method is based on a characteristic absorbance in the IR spectrum associated with the transconfiguration in polybutadiene ... 

Sample Polybutadiene by the iodine monochloride method (wt%) Polybutadiene by an IR method (wt%)... 

Both the gel and toluene soluble fractions are reserved for determination of unsaturation by the iodine monochloride method. To determine unsaturation in styrene-butadiene rubbers with good accuracy using the iodine monochloride procedure, it was found necessary to contact the sample with chloroform for 15 hours before reaction with iodine monochloride. Even with a 30 hour reaction period, a constant iodine-value is obtained only when a five-fold excess of iodine monochloride reagent is used. 

That the figure for the iodine value depends on the method of determination employed, and that exact conditions of experiment are necessary in the case of this material, has been conclusively proved. Abraham and Cockton showed the necessity for specifying the exact quantity to be taken in the official iodine monochloride method using 1 0 g and 25 ml of approximately 0-2N Wijs solution, the iodine value increased from 27-3 in one hour to 29 9 in five hours, whereas using 0 2 g and the same quantity of iodine solution the results were of the order of 49. The jB.P. method uses 1 g with an iodine value range of 18 to 32, whilst the f/.5.F. limits are 18 to 36 with 0-78 to 0-82 g of wool fat. The length of time of exposure to the iodine does not appear to affect the result appreciably. 

Anonymous, Standard Test Method for Lead in Gasoline —Iodine Monochloride Method, ANSI/ASTM D 3341-79, Ann. Book ASTM Stand., Vol. 25, Am. Soc. Test. Mater., Philadelphia 1979, pp. 236/9. 

Sample Polybutadiene, %w (iodine monochloride method) Polybutadiene, %w (IR method)... 

The oxidation-reduction methods with potassium iodate invariably based on the formation of iodine monochloride (ICl) in a medium of strong hydrochloric acid solution. 

Iodine trichloride.—This compound was discovered by J. L. Gay Lussac as the result of treating warm iodine or iodine monochloride with an excess of chlorine. The trichloride collects as a citron-yellow crystalline sublimate on the cooler parts of the vessel. It is also formed by the action of liquid chlorine on iodine, or an iodide—say lead iodide.18 The iodine trichloride is almost insoluble in liquid chlorine, and hence, say Y. Thomas and P. Dupuis, this method of preparation is very convenient. It is also formed by the action of dry chlorine on hydrogen iodide (A. Christomanos) silver iodate (J. Krutwig) or methyl iodide (L. von... 

Kubina 6 recommends the following method for estimating arsine volumetrically. The absorbing medium is an acid solution of iodine monochloride, the iodine being liberated according to the equation... 

Iodoaniline has been prepared by the reduction of -nitro-iodobenzene 1 by the hydrolysis of -iodoacetanilide formed by the action of iodine monochloride on acetanilide 2 and by the direct iodination of aniline.3 The method described here is an adaptation of the procedure used by Wheeler/ and by Hann and Berliner 5 for the iodination of the toluidines. 

Iodine monochloride has been prepared by leading chlorine over solid iodine and distilling the crude product. Despite improvements to obtain a more nearly pure product, this method remains a tedious and time-consuming process. 

The usual method of preparing iodine trichloride by subliming iodine into a current of chlorine gas is tedious and gives a poor yield of a product contaminated with iodine and iodine monochloride. Furthermore, the product deposits on the sides of the flask in crusts which are difficult to remove. 

Diynes. A general method for preparation of 1,3-diynes, particularly terminal ones, involves palladium-catalyzed coupling of alkynylzinc derivatives with (E)-l-iodo-2-chloroethylene. This alkene is obtained in 83% yield by reaction of acetylene with iodine monochloride in 6 A HCI. Coupling results in a l -chloro-1,3-cnync (1), which is converted into a l-sodio-l,3-diyne (2), which in turn can be reduced or alkylated to give a 1,3-diyne. 

Fibrogen. Two methods were used to prepare I-labeled fibrinogen. In both methods, unincorporated iodide was removed immediately after the reaction by gel filtration on a G-25 Sephadex column preequilibrated in O.OIM HEPES, 0.147M NaCl, 0.02% azide, pH 7.4. The first method uses catalysis by lactoperoxidase and is based on studies by Marchalonis (23), and the second method uses iodine monochloride (ICI) and is based on work by Helmkamp et al. 24). 

Fibrinogen labeled with and Br B-H reagent more suitable than product labeled with I by iodine monochloride, CT, or LP methods for in vivo clearance studies... 

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