Aldehydes iodination

If more concentrated solutions than those specified are employed for this method of analysis, an aldehyde-iodine compound is foimed which introduces an error in the results. ... 

Aminolhtazoles were synthetized from thiourea by three methods Method A, from a-haloketones or aldehydes designated as (Cl) or (Br) Method B, from ketones and iodine (fj) or bromine (Btj) Method C, from iodomercuriketones. Method D consists in condensing ketones with cyanamid and sulfur. 

Magnesium iodide is soluble in alcohols and many other organic solvents, and forms numerous addition compounds with alcohols, ethers, aldehydes, esters, and amines. One example is magnesium iodide dietherate [29964-67-8], Mgl2 prepared by gradual addition of iodine to a... 

Composition. Shellac is primarily a mixture of aUphatic polyhydroxy acids in the form of lactones and esters. It has an acid number of ca 70, a saponification number of ca 230, a hydroxyl number of ca 260, and an iodine number of ca 15. Its average molecular weight is ca 1000. Shellac is a complex mixture, but some of its constituents have been identified. Aleuritic acid, an optically inactive 9,10,16-trihydroxypalmitic acid, has been isolated by saponification. Related carboxyflc acids such as 16-hydroxy- and 9,10-dihydroxypalmitic acids, also have been identified after saponification. These acids may not be primary products of hydrolysis, but may have been produced by the treatment. Studies show that shellac contains carboxyflc acids with long methylene chains, unsaturated esters, probably an aliphatic aldehyde, a saturated aliphatic ester, a primary alcohol, and isolated or unconjugated double bonds. 

Ana.lytica.1 Methods. Various analytical methods involve titration with oxidants, eg, hexacyanoferrate (ferricyanide), which oxidize dithionites to sulfite. lodimetric titration to sulfate in the presence of formaldehyde enables dithionite to be distinguished from sulfite because aldehyde adducts of sulfite are not oxidized by iodine. Reductive bleaching of dyes can be used to determine dithionite, the extent of reduction being deterrnined photometrically. Methods for determining mixtures of dithionite, sulfite, and thiosulfates have been reviewed (365). Analysis of dithionite particularly for thiosulfate, a frequent and undesirable impurity, can be done easily by Hquid chromatography (366). 

The butanals form the conventional aldehyde hydra2one, semicarba2one, and dimedone-type derivatives. In the absence of other aldehydes and ketones, -butyraldehyde can be deterrnined by addition of sodium bisulfite and the excess bisulfite deterrnined with iodine or thiosulfate (34). 

Oxidative reactions frequently represent a convenient preparative route to synthetic intermediates and end products This chapter includes oxidations of alkanes and cycloalkanes, alkenes and cycloalkenes, dienes, aromatic fluorocarbons, alcohols, phenols, ethers, aldehydes and ketones, carboxylic acids, nitrogen compounds, and organophosphorus, -sulfur, -selenium, -iodine, and -boron compounds... 

As in the acid-catalyzed halogenation of aldehydes and ketones, the reaction rate is independent of the concentration of the halogen chlorination, bromination, and iodination all occur at the same rate. Fomnation of the enolate is rate-detemnining, and, once fomned, the enolate ion reacts rapidly with the halogen. 

The rate of iodine formation depends on the degree of A"-substitu-tion. Compounds which are unsubstituted on both the iV-atoms (35) and those wdth a single A -substituent (43) liberate instantly the calculated quantity of iodine in the cold. However, the 1,2-disubstituted diaziridines (44) need brief heating with the acid iodine solution they then give 95-100% of the calculated iodine. " This effect of substitution is so well defined that it can be used for a proof of constitution. The diaziridino-triazolidincs (37) prepared from aldehydes, ammonia, and chloramine give complete iodine liberation only on heating. Thus the structure 57 which is isomeric with 37 can be eliminated. ... 

The cyclic diazo compounds (diazirines 65) are very unreactive compounds. Specially noticeable is the absence of the reactivity toward electrophilic reagents which is characteristic of the linear isomers. Acids or aldehydes which react smoothly with the aliphatic diazo compounds are without action on the cyclic diazo compounds. Iodine does not attack the cyclic diazo compounds. 

Reaction of the potassium salt of salicylaldehyde with chlo-roacetone affords first the corresponding phenolic ether aldol cyclization of the aldehyde with the ketonic side chain affords the benzofuran (1). Reduction of the carbonyl group by means of the Wolf-Kischner reaction affords 2-ethyl-benzofuran. Friedel-Crafts acylation with anisoyl chloride proceeds on the remaining unsubstituted position on the furan ring (2). The methyl ether is then cleaved by means of pyridine hydrochloride (3). lodina-tion of the phenol is accomplished by means of an alkaline solution of iodine and potassium iodide. There is thus obtained benziodarone (4)... 

For the estimation of benzaldehyde, Eipper proposed a volumetric modification of the bisulphite process, the aldehyde being shaken with a measured volume of a standard solution of bisulphite, and the excess of bisulphite titrated back with iodine solution at a low tempe/atnrer Dodge found this give fairly accurate results, and recommends the iollowing method of carrying out the determination. About 0 15 gram... 

The adjacent iodine and lactone groupings in 16 constitute the structural prerequisite, or retron, for the iodolactonization transform.15 It was anticipated that the action of iodine on unsaturated carboxylic acid 17 would induce iodolactonization16 to give iodo-lactone 16. The cis C20-C21 double bond in 17 provides a convenient opportunity for molecular simplification. In the synthetic direction, a Wittig reaction17 between the nonstabilized phosphorous ylide derived from 19 and aldehyde 18 could result in the formation of cis alkene 17. Enantiomerically pure (/ )-citronellic acid (20) and (+)-/ -hydroxyisobutyric acid (11) are readily available sources of chirality that could be converted in a straightforward manner into optically active building blocks 18 and 19, respectively. 

A valuable feature of the Nin/Crn-mediated Nozaki-Takai-Hiyama-Kishi coupling of vinyl iodides and aldehydes is that the stereochemistry of the vinyl iodide partner is reflected in the allylic alcohol coupling product, at least when disubstituted or trans tri-substituted vinyl iodides are employed.68 It is, therefore, imperative that the trans vinyl iodide stereochemistry in 159 be rigorously defined. Of the various ways in which this objective could be achieved, a regioselective syn addition of the Zr-H bond of Schwartz s reagent (Cp2ZrHCl) to the alkyne function in 165, followed by exposure of the resulting vinylzirconium species to iodine, seemed to constitute a distinctly direct solution to this important problem. Alkyne 165 could conceivably be derived in short order from compound 166, the projected product of an asymmetric crotylboration of achiral aldehyde 168. 

It is not clear whether the silyl iodide causes activation of only one of the benzyloxy groups, or if a substitution by iodine takes place before reductive metalation. These reagents exhibit a high preference for aldehyde over ketone addition13. 

In the haloform reaction, methyl ketones (and the only methyl aldehyde, acetaldehyde) are cleaved with halogen and a base. The halogen can be bromine, chlorine, or iodine. What takes place is actually a combination of two reactions. The first is an example of 12-4, in which, under the basic conditions employed, the methyl group is trihalogenated. Then the resulting trihalo ketone is attacked by hydroxide ion ... 

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