Iodine complex preparation

Electrochemical methods are being used increasingly in the carotenoid field. Electroreduction of /3,/3-carotene (62) at a mercury cathode gave 7,7 -dihydro-8,7 -retra-/3, -carotene (81). Similarly axerophtene (82) gave the 7,14-dihydro-product (83). Reductive electrochemical dehydrohalogenation of a j8-caro-tene-iodine complex prepared from jS-carotene with iodine and trifluoroacetic... 

Preswelled Sephacryl S-1000 was prepared in a K26/100 column (88 X 2.6 cm). Equilibration with 0.005 M NaOH containing 0.002% NaN3 at a flow rate of 0.67 ml/min was achieved after 20 hr. Sample solutions were applied with a 5-ml injection loop. The mass and iodine-complexing potential of separated glucan components was determined off-line for each of the subsequently eluted 5-ml fractions. Based on the determined mass of carbohydrate for each of the fractions, elution profiles such as Fig. 16.1 were constructed. 

Iodine makes blue colored complexes with many substances such as starch [1, 2] nylon-6 [3], poly(vinyl pyrrolidone) [4], poly(vinyl alcohol) PVA [5, 6], From the application point of view, the blue PVA-Iodine complex is the most important among them, for it is widely used for film polarizers [7,8]. The polarizers are prepared by soaking PVA films in a solution of iodine and potassium iodide (KI) with boric acid, and subsequent drawing to cause the high... 

Complexes. The iodine complexes of 1,5-naphthyridine and other heterocycles have been used under anhydrous conditions to estimate the pK.t values for such heterocycles.885 The structures of 1 1 complexes of 1,5-naphthyridine with oxalic acid,1024 fumaric acid,1024 or meso- 1,2-diphenyl- 1,2-ethane-diol1021 have been studied. Complexes of 1,5-naphthyridine with Co(II), Ni(II), Cu(II), Zn(II), and Ag(I) salts have been prepared 705 the mono- and... 

Several assays (Fig. 1) are available to measure branching enzyme activity. The iodine assay is based on the decrease in absorbance of the glucan-iodine complex (Krisman, 1962) resulting from the branching of amylose or amylopectin by the enzyme, provided that a-amylases are absent from the enzyme preparation or their activity is greatly reduced by adjusting the assay conditions. 

A method of determining airborne iodine has also been reported.241 Here, iodine is absorbed into 5% aqueous KI and spectrophotometrically determined at 590 nm in the form of its complex with starch. This method is selective with respect to bromine and chlorine, and the sensitivity of this method is 0.25 mg of I2 per m3 of air. The concentration of the, 31I isotope in water can be determined by a method involving isotope exchange in the starch-iodine complex.242 Flow-injection determination of ascorbic acid (0.1-40 mg/mL) has been proposed.243 Iodine is generated in the flow system as I3- ions, which are in turn exposed to starch to produce a steady signal at 350 and 580 nm. Ascorbic acid provides inversed maxima which are measured. This method is recommended for analysis of ascorbic acid in fruit juice, jam, and vitamin-C preparations. Use of the blue complex has also been reported for determination of sodium dichloro-isocyanurate in air.244 Obviously the blue reaction is applicable in the determination of amylose, amylopectin, and starch,245-252 as well as modified starches.245,253-255... 

In 1992 Kobayashi et al. [47] reported the first catalytic and enantioselective cyclo-propanation using the Furukawa modification [48] of the Simmons-Smith reaction of allylic alcohols in the presence of a chiral bis(sulfonamide)-Zn complex, prepared in-situ from the bis(sulfonamide) 63 and diethylzinc. When cinnamyl alcohol 62 was treated with EtgZn (2 equiv.), CHgIg (3 equiv.), and the bis(sulfonamide) 63 (12 mol %) in dichloromethane at -23 °C, the corresponding cyclopropane 64 was obtained in 82 % yield with 76 % ee (Sch. 26). They proposed a transition state XXIII (Fig. 5) in which the chiral zinc complex interacts with the oxygen atom of the allylic alkoxide and the iodine atom of iodomethylzinc moiety. They also reported the use of the bis(sulfonamide)-alkylaluminum complex 65 as the Lewis acidic component catalyzing the Simmons-Smith reaction [49]. 

The yield of bisarene complex prepared under Fischer-Hafner conditions appears to decrease in the order Cr > Mo > W for a given arene, the yield in the case of (CeH8)2W being only 2% 152). The neutral bisarene complexes are readily oxidized back to their cations by iodine 152) and, in the case of Cr, by oxygen 192) or AICI3 208) ... 

Although the Tilden-Hudson test is very useful it has certain drawbacks in precise work, (a) The exact time at which needles appear is difficult to determine, (b) Enzyme activity is slowed but not stopped by the addition of iodine solution in fact, it is possible to add starch to a mixture of enzyme and iodine solution and observe the gradual formation of the crystalline dextrin-iodine complexes, (c) The apparent activity depends very much on the presence of such foreign materials as salts, n-glucose, maltose, etc., which may be present in the enzyme solution. In some enzyme preparations which seem to have fair activity, the needles are never observed. 

The most versatile method for quantitatively determining copovidone is probably the photometric measurement of the iodine complex described in Section 4.3.I.2. It has been successfully tested on samples that also contained a series of auxiliaries and active substances, to verify its suitability for preparations. 

One example of a bonafide bis(alkyne) complex has recently been prepared. Reaction of the in situ generated olefin complex prepared by alkylation of ( -CsHs ZrC 50 with the diaryl alkyne in Equation (7) yields 253.130 In this structure, C-C coupling has not occurred, presumably a result of the steric strain associated with the zirconacyclo-pentadienyl fragment (Equation (7)). The solid-state structure further establishes the compound as a bis(alkyne) complex. Computational studies suggest that a Zr(iv) resonance structure is the most suitable representation of the compound. However, reaction of 253 with iodine in THF yields ( -CsHs Zrle 254 and the dialkyne starting material, suggesting that the zirconium center can act as a source of Zr(n) (Equation (8)). 

Two methods were used one is the iodine method that was used to determine dextrinization or the ratio of hydrolysis of the starch, and the other is the phenolphifaalein method lhat was used to determine CD formation. Starch-dextrinizing activity was determined in accordance with Fuwa (19) and Pongasawasdi and Yagisawa (20) with slight modifications. The reaction mixture containing 100 (iL of diluted enzyme aliquot and 300 pL of 0.5% soluble starch prepared in 0.1 M acetate buffer, pH 5.5, was incubated at 55 °C for 10 min. The enzyme reaction was stopped by the addition of 4.0 mL of 0.2 M HCl solution. Then, 0.5 mL of iodine solution (0.3 g/L I2 and 3.0 g/L KI) was added to form an amylose-iodine complex with residual amylose. The final volume was adjusted to 10 mL with distilled water. The absorbance of the blue color of the amylose-iodine complex was measured by spectrophotometer at 700 nm, and a decrease in absorbance was verified, when compared to a control tube with heat-inactivated enzyme. One unit of enzyme activity was defined as the quantity of enzyme that reduces the blue color of the starch-iodine complex by 10% per minute. 

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