Antimony trifluoroacetates

Antimony trifluoride, 16 181 preparation of, 7 14-15 solubility of, 7 6-7 Antimony trifluoroacetates, 17 12, 13 Antiperspirants, 36 16 Anti-Stokes emission, 35 342-343 Antitumor agents DNA and RNA cleavers, 45 252 phosphazotrihalides as, 14 90, 91... 

Radical cations that are produced by electrochemical oxidation are not stable in solvents with appreciable base character. This results because such radicals are subject to attack by available nucleophiles, and solvents that contain donor electron pairs are good nucleophiles. Cation radicals are most stable in solvents that are good Lewis acids and show negligible basic properties. Some of the solvent systems that have been employed to stabilize electrochemically produced cation radicals include nitromethane and nitrobenzene,21 dichloro-methane,22 trifluoroacetic acid-dichloromethane (1 9),23 nitromethane-AlCl3,24 and AlCl3-NaCl (1 l).25 Organic chemists should be familiar with the stabilization of carbonium ions by superacid media.26 These media usually contain fluorosulfuric acid, or mixtures of fluorosulfuric acid with antimony pen-tachloride and sulfur dioxide, and are potent solvents for the production and stabilization of organic cations. 

Reaction of antimony pentafluoride with trifluoroacetic acid anhydride yields a binu-clear antimony complex323 ... 

Table IV summarizes the trifluoroacetato complexes of the Group V elements that have been characterized. The simple trifluoroacetates of arsenic, antimony, and bismuth(III) have been isolated only recently, following the reaction of the corresponding trichloride with Ag(02CCF3) in CH2CI2 (123) and, for the bismuth derivative, by the reaction of Bi203 with (CFaCO)aO (200). These are reasonably volatile compounds which are extremely moisture-sensitive.

All manipulations were carried out in Kel-F, Teflon FEP, or fused silica reaction vessels attached to a stainless steel or Monel fluorine-type vacuum system and/or in a Vacuum Atmospheres inert atmosphere Dri lab. Hexafluorobenzme, oclafluorotoluene, octafluoronaphthalene (PCR Inc., Gainesville, FL), sulfur dioxide, anhydrous hydrogen fluoride (Matheson, E. Rutherford, NJ), cesium fluoride (ROC/RIC, Sun Valley, CA), trifluoroacetic acid (Aldrich, Milwaukee, Wl), and tungsten hexafluoride, arsenic pentafluoride, and antimony pentafluoride (Ozark-Mahoning, Inc., Tulsa, OK) were used as received after their purity was checked by infrared spectroscopy. Dioxygenyl salts and rhenium and... 

Initial bioassay techniques were too time consuming to be employed on a routine basis and were superseded by physicochemical methods based on colorimetry, e.g., after reaction with antimony trichloride (Carr-Price reaction), or trifluoroacetic acid, or based on ultraviolet (UV) spectrophotometry or fluo-rimetry. However, these procedures cannot readily discriminate molecular species with different vitamin A activities (e.g., cis-trans isomers, retinyl esters, or oxidative degradation products). 

The Carr-Price reaction for the colorimetric determination of retinoids, which has long been in use, is based on colored cations formed via antimony (III) chloride (Hubbard et aL, 1971 Blatz and Estrada, 1972 Bridges and Alvarez, 1982). In the same way, the protonation of retinoids with trifluoroacetic acid has been used for colorimetric analysis (Dugan et aL, 1964). 

When retinol or its ester is mixed with a Lewis acid under anhydrous conditions, an intense transient blue color forms. Using antimony trichloride as the Lewis acid and anhydrous chloroform as the solvent, Carr and Price (1926) developed a quantitative assay for retinol. A large number of assay methods have subsequently been developed using a variety of Lewis acids, including tri-fluoroacetic acid (TFA) and trichloroacetic acid (TCA) (Dugan etaL, 1964). The stability of the color complex formed in various solvents has also been carefully studied (Subramanyam and Parrish, 1976). Some commonly used procedures based on this method are summarized in Table VI. The maximal intensity of the initial blue color complex formed is about threefold higher than the ultraviolet absorbancy of retinol. The maximal wavelengths and extinction coefficients of initial color complexes of various retinoids with trifluoroacetic acid are summarized in Table VII. 

---