Commercially available products iodine

From these equations it can be seen that each mole of water requires one mole of I2. In a visual endpoint Karl Fischer titration, a sample is titrated with the Karl Fischer reagent until a permanent iodine color (indicating that all water has been reacted) is observed. Because of other reaction products, the color change is usually from a yellow to a brownish color, which may be difficult to detect visually. Highly colored samples may affect the visual end point as well. A much sharper end point, known as the dead stop end point, can be obtained if the titration is done electrometrically. Here, two small platinum electrodes dip into the titration cell, a small constant voltage is impressed across these electrodes, and any current that flows is measured with a galvanometer. At the end point of the titration the current either goes to a minimum or else increases suddenly from nearly zero. Commercially available Karl Fischer instruments incorporate semiautomatic microprocessors based on this principle. 

An efficient method of resolution of diastereomeric mixtures of 5-substituted 2-oxazolidinones, utilizing commercially available (S)-l-phenylethylamine as the optically active portion of the molecule, has been developed16. Thus, the Ar-benzyloxycarbonyl derivative of (S)-TV-(l-phen-ylethyl)-2-propen-1-amine (1), treated with iodine in chloroform, affords the diastereomeric products as a 50 50 mixture which is easily separated by chromatography on silica gel. 

A water-insoluble lactoperoxidase, linked to CNBr-activated Sepharose beads, capable of iodinating serum albumin, is commercially available (Worthington Biochemical Corp.), and may be useful where avoidance of contamination of the product by the enzyme is important. 

More commonly, titrations involving iodine are performed with a suspension of starch as an indicator. The deep blue color that develops in the presence of iodine is believed to arise from the absorption of iodine into the helical chain of j8-amylose (see Figure 20-2), a macromolecular component of most starches. The closely related a-amylose forms a red adduct with iodine. This reaction is not easily reversible and is thus undesirable. In commercially available soluble starch, the alpha fraction has been removed to leave principally j8-amylose indicator solutions are easily prepared from this product. 

Benzyne is one of a group of reactive intermediates widely applicable to organic synthesis.2"5 The title hypervalent iodine-benzyne precursor, (phenyl)[2-(trimethylsilyl)phenyl]iodonium triflate 2,6 is prepared by only two steps from commercially available reagents. Products 1 and 2 are stable and easily purified. The hypervalent iodine-benzyne precursor 2 is obtained as a stable solid and handled without any precautions. More importantly, benzyne is generated by using... 

Fascinatingly, a wide array of products fortified with iodine are now commercially available in the market. This reflects the advancements in being able to design a consumer-preferred product with an additional advantage of fortification. So, not only are traditional milk-based formulas for infants and milk-based beverage powders for growing children fortified, but also a range of soy-based products or cereal (rice or wheat) based products in the form of biscuits, bars and pastas. 

Practical applications of polyvalent iodine derivatives are restricted by the low stability of many of these compounds. Among inorganic derivatives of polyvalent iodine, only iodine pentafluoride, iodine pentoxide and iodic and periodic acids and their salts are commercially available, stable products. These stable inorganic compounds have found some industrial use, mainly as powerful oxidants. 

Yao et al. [65] developed a simple, inexpensive, and efficient one-pot synthesis of 1,4-DHP derivatives 44 and 45 at room temperature using catalytic amount of iodine with excellent product yields (Scheme 10.29). This method offers several advantages such as shorter reaction times, milder conditions, simplicity of the reaction, and excellent product yields. The easy procedure to carry out the reaction using inexpensive and commercially available iodine made it a powerfirl catalyst for the synthesis of 1,4-DHPs. 

For the synthesis of the desired product, 30 mol% of catalyst was sufficient, and a small amount of EtOH afforded the corresponding 1,4-DHPs in 88-95 % yield at room temperature. This methodology offers very attractive features such as shorter reaction times, milder conditions with simplicity of the reaction, good to excellent product yields, and commercially available iodine as a powerful catalyst for the synthesis of 1,4-DHPs. 

With the help of a bifiinctional thiourea catalyst 55, Mukherjee and coworkers contemporaneously developed a related catalytic asymmetric iodoetherification of oximes (Scheme 2.31). A variety of p.y-unsaturated ketoximes were cyclized using commercially available A-iodosuccinimide (NIS) as the iodine source and iodine as the cocatalyst to furnish A -isoxazolines containing a quaternary stereogenic center in high yields and good to excellent enantioselectivities [47]. Besides, the oxime iodoetherification products could be subjected to a number of synthetically useful transformations to produce other important organic compounds. 

Cyclization of a substituted 1 -aiylanthranilamide was the key step for the synthesis of citrusinine-I (76) described by Kato ei al. (312). The required 2-(2-hydroxyphenylamino)-3,4,6-trimethoxy-Af -dimethylbenzamide (235) was obtained by Ullmann reaction of 2-aminophenol with 2-iodo-3,4,6-trimethoxy-iV -dimethylbenzamide (236), prepared in ee steps from commercially available 2,4,S-trimethoxybenzoic acid (237) via o-lithiation of the corresponding amide and subsequent iodination. Benzylation of 235 to 238 was followed by phosphoryl diloride cyclization and hydrolysis of the intermechate with aqueous hydrochloric acid to give 5 benzyloxy-l,3,4-trimethoxyacridone (239) as the major product. Methylation to 5-be izylo3 -l,3,4-trimethoxy-10-methylacridone (240), followed by simultaneous hydrolysis of the benzyloxy group, and of the methoxy group at C-1, gave citrusinine-I I (64). 

By this method the weighed dry product is dissolved in methanol and titrated with the Karl Fischer solution until the color changes from brown to yellow. The visual observation can be replaced by an ammeter, which shows an steep increase in current, when the titration is terminated (dead-stop-titration). The samples can be two to four times smaller than for the gravimetric method. To avoid the visual observation completely, iodine can be produced by electrolyzation and the water content is calculated by Coulomb s law. Such an apparatus (e. g. Fig. 1.97.1 and 1.97.2) is available commercially. The smallest amount of water to be detected by such instruments is 10 pg. Wekx and De Kleijn [1.84) showed, how the Karl Fischer method can be used directly in the vial with the dried product. The Karl... 

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