Silver carboxylates

Silver carboxylates 1 can be decarboxylated by treatment with bromine, to yield alkyl bromides 2 in the so-called Hunsdiecker reaction. ... 

The reaction is likely to proceed by a radical-chain mechanism, involving intermediate formation of carboxyl radicals, as in the related Kolbe electrolytic synthesis. Initially the bromine reacts with the silver carboxylate 1 to give an acyl hypobromite species 3 together with insoluble silver bromide, which precipitates from the reaction mixture. The unstable acyl hypobromite decomposes by homolytic cleavage of the O-Br bond, to give a bromo radical and the carboxyl radical 4. The latter decomposes further to carbon dioxide and the alkyl radical 5, which subsequently reacts with hypobromite 3 to yield the alkyl bromide 2 and the new carboxyl radical 4Z... 

Figure 4.6 The dimeric structure adopted by some silver carboxylates such as silver trifluoroacetate.

When Br2 reacts with aryl R, at low temperature in inert solvents, it is possible to isolate a complex containing both Br2 and the silver carboxylate see Bryce-Smith, D. Isaacs, N.S. Tumi, S.O. Chem. Lett., 1984, 1471. 

The present procedure offers a convenient alternative to the Prevost reaction and the Woodward modification of the Prevost reaction in which silver carboxylates are used instead of thal-lium(I) carboxylates. Thallium(I) salts have the advantages of being generally stable crystalline solids that can be readily prepared in high yield by neutralization of the appropriate carboxylic acid with thallium(I) ethoxide. Silver salts, on the other hand, are frequently unstable and difficult to dry. Thallium and its compounds are, however, extremely toxic, and great care must therefore be taken in the use and disposal of thallium salts. ... 

Involvement of radical pathways in thermal decarboxylation is possible where no solvent or a nonpolar solvent is used. The pyrolysis of silver carboxylates in the absence of solvent under nitrogen gives radicals but no organometallics (21). 

When colloidal selenium was heated with mercuric trifluoroacetate or silver trifluoroacetate, bis(trifluoromethyl)diselenide was formed (43). Later work with selenium/silver carboxylate, RC02Ag (R = CF3, C2F5, or C3F7), mixtures at 280° C in a vacuum produced a mixture of the bis(perfluoroalkyl)selenide and the bis(perfluoroalkyl)diselenide (44). Formation of a polyselenium trifluoroacetate, which decarboxylates to produce the trifluoromethylselenides, was the proposed mechanism for R = CF3 (44). However, silver trifluoroacetate is a source of trifluoromethyl radicals when heated above 260° C (21), hence the trifluoromethylselenides may be formed by reaction of trifluoromethyl radicals with selenium, as in the reaction of CF3I with selenium [Eq. (34)] (45). 

Surface area controlled reactivity, of silver carboxylate, 19 340—342 Surface area measurement, 19 379 Surface area/volume (SAV) ratio in microfluidics, 26 961—962 Surface cartridges, for cartridge filters, 11 369... 

The procedure described here allows for a convenient and efficient preparation in very high yields of large quantities of bromides from carboxylic acids containing an olefinic functionality. The Hunsdiecker reaction is traditionally accomplished by treating anhydrous silver carboxylates with bromine or iodine.2 Heavy metal salts such as mercury,3 lead,4 and thallium5 have also been used successfully as well as tert-butyl hypoiodite.6 The major disadvantages associated with the above methods, such as use of heavy metal salts and non-tolerance towards olefins, has led to the development of a more versatile method using O-acyl thiohydroxamates.7 8 The O-... 

Hundsdieke reaction org chem Production of an alkyl halide by boiling a silver carboxylate with an equivalent weight of bromine in carbon tetrachloride. honz.dek-o re,ak-sh3n ... 

Conversion of silver carboxylate to halide by treatment with halogen. 

Hunsdiecker, H. Hunsdiecker, C. Ber. Dtsch. Chem. Ges. 1942, 75, 291. Clare Hunsdiecker was the only woman to give a name reaction in this book. 1 hope there will be many more in future editions. Clare Hunsdiecker was born in 1903 and educated in Cologne. She developed the bromination of silver carboxylate alongside her husband, Heinz. 

In the reaction of sulfenyl chlorides with silver carboxylates mixed anhydrides are formed they are known as sulfenyl carboxylates 90, 130) ... 

The Hunsdiecker reaction is a free-radical reaction for the synthesis of an alkyl halide. The starting material comes from the reaction of a silver carboxylate with a solution of a halogen in a solvent such as carbon tetrachloride (see Figure 12-44). The overall free-radical mechanism is shown in Figure 12-45. 

Both the reactions are essentially the additions of iodine carboxylate (formed in situ) to an alkene, i.e., the reaction of an alkene with iodine and silver salt. The Prevost procedure employs iodine and silver carboxylate under dry conditions. The initially formed transiodocarboxylate (b) from a cyclic iodonium ion (a) undergoes internal displacement to a common intermediate acylium ion (c). The formation of the diester (d) with retention of configuration provides an example of neighbouring group participation. The diester on subsequent hydrolysis gives a trans-glycol. 

The asymmetric stretching frequency for 24 silver carboxylates [v COj)] was observed to correlate with the Taft substituent constant o. IR absorption data could be used to predict o values with a standard deviation of O.l.252... 

Complex ions of the type Ag(02CR)J and Ag2(02CR)+ have been proposed to exist in solution, based on measurements of solubility in water and in mixed solvents. Some thermodynamic data for silver carboxylates are given in Table 35.253,254... 

The products of the reactions between silver(I) carboxylates and triphenylphosphine were colourless, diamagnetic solids, stable at room temperature to oxygen and not significantly light sensitive. Reaction with triphenylphosphine was also found useful as a method of solubilizing silver carboxylates. 

Reaction of [PdCl2(diene)] with silver carboxylates yields complexes [Pd2(/u -... 

Iodine-copper(II) acetate, 267 Iodine-mercury(II) oxide, 267-268 Iodine monochloride, 268-269 Iodine-silver carboxylates, 268 Iodine-silver nitrate, 268 lodoamination, 265-266 Iodocarbamation, 264-265 Iodocarbonates, 263 2 Iodoestradiol, 267 2-Iodoestrone, 267 Iodoiactonization, 263-264 C,-Iodomethylcephalosporins, 273 Iodonium di-svm-collidine perchlorate, 269 19-Iodononadecanic acid, 488 Iodophenylbis(triphenylphosphine)palladium, 269... 

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