Heptafluorobutyryl

A chiral vanadium complex, bis(3-(heptafluorobutyryl)camphorato)oxovana-dium(IV), can catalyze the cycloaddition reaction of, mainly, benzaldehyde with dienes of the Danishefsky type with moderate to good enantioselectivity [21]. A thorough investigation was performed with benzaldehyde and different activated dienes, and reactions involving double stereo differentiation using a chiral aldehyde. 

The enantiomeric purity of optically active sulphoxides can be determined by chiral lanthanide shift reagents such as tris(3-trifluoroacetyl-ti-camphorato)europium(III) and tris(heptafluorobutyryl-d-camphorato)europium(III)218-219-221, the latter shown in Scheme 23. 

The relative response of the electron-capture detector to some haloalkylacyl derivatives is sumi rized in Table 8.17 [451]. In general terms, the monochloroacetyl and chlorodifluoroacetyl derivatives provide a greater response than the trifluoroacetyl derivatives. Increasing the fluorocarbon chain length of the fluorocarbonacyl derivatives increases t ir electron-capture detector response without inconveniently increasing their retention times. The heptafluorobutyryl and pentafluoropropionyl derivatives are considered to be the best compromise between detector sensitivity and volatility for most applications. 

Figure 1-18. Gas chromatographic separation of a) synthetic racemic dihydromanicone rac- 44 b) natural 44, obtained by hydrogenation of material from the heads of M. rubida c) co-injected natural-44 and rac-44 d) synthetic (4 5,65 )-44 and e) co-injected synthetic (4RS,6S)-44 and rac-44. Chiral GC phase nickel(II)-bis[3-heptafluorobutyryl-(lR)-camphorate]. Signals 1 and 4 correspond to the pair of diastereomers (4 5,65)-44 signals 2 and 3 correspond to (4RS,6R)-44. Reprinted, with permission, by VCH, Ref. 63.

Heptafluorobutyryl chloride, chiral derivatizing agent, 6 96t Heptafluoroisobutenyl methyl ether,... 

Sodium salts of fluoroacids react with chlorine fluoride at —112 to —78°C to give explosively unstable fluoroacyl hypochlorites. Trifluoroacetyl hypochlorite and its pentafluoropropionyl, heptafluorobutyryl, difluoroacetyl and chlorodifluo-roacetyl analogues explode without fail if the partial pressure exceeds 27-67 mbar. Hexafluoroglutaiyl dihypochlorite explodes above — 10°C [1]. Of the 4 compounds prepared, acetyl, propionyl, isobutyryl and pivaloyl hypobromites, the 2 latter appeared stable indefinitely at —41°C in the dark, while the 2 former exploded unpredictably as isolated solids [2],... 

Acetyl hypobromite, 0729 Acetyl hypofluorite, 0751 Caesium fluoroxysulfate, 4256 Chlorodifluoroacetyl hypochlorite, 0603 Difluoroacetyl hypochlorite, 0653 Fluorine fluorosulfate, 4324 Heptafluorobutyryl hypochlorite, 1352 Heptafluorobutyryl hypofluorite, 1369 Hexafluoroglutaryl dihypochlorite, 1806 Pentafluoropropionyl hypochlorite, 1034 Pentafluoropropionyl hypofluorite, 1056 Propionyl hypobromite, 1154 Rubidium fluoroxysulfate, 4309 Trifluoroacetyl hypochlorite, 0594 Trifluoroacetyl hypofluorite, 0633... 

Amino acids (chiral analysis) Pentafluoracetic anhydride Heptafluorobutyryl anhydride Esterification with deuterium Nkoihara and... 

Because the choice of a particular derivative is a compromise between good mass spectrometric characteristics and good chromatographic characteristics such as volatility, stability, and absence of interference, heptafluorobutyryl derivatives have been preferred to trimethylsilyl ethers because of their higher mass gain, which made interference less likely to occur, and their favorable fragmentation... 

There are a number of gas chromatographic procedures for the determination of the catecholamines. Methods generally accepted are making the trimethylsilyl ether derivative of the alcoholic group after using diazomethane to prepare the methyl ester and the heptafluorobutyryl derivative. The ethyl esters have been used for the separation of HVA and isoHVA and mass spectrometry applied to study their characterization. 

The naturally occurring amino acids are very polar, and cannot be separated as the free compounds by GC at a temperature below decomposition. If the polar groups in the molecule are chemically modified to produce a more volatile derivative a suitable temperature is then possible. Weinstein (25) reviews all the various derivatives which may be formed from amino acids and the GC conditions necessary to separate them. In actual practice only three derivatives are in popular use. These include the N-heptafluorobutyryl n-propyl ester derivatives, the N-trimethyl-silyl ether derivatives, and the n-trifluoroacetyl n-butyl ester derivatives. 

Gas chromatography and capillary column GC represent by far the most developed and most used analytical techniques for the determination of multiple trichothecenes, especially in view of the possibility of employing MS for confirmation of the peaks. The available methods, such as the Scott and Ware methods (90,91), differ in sample extraction, sample cleanup, and the derivatization step. Heptafluorobutyryl (HFB), trimethylsilyl (TMS), and trifluoroacetyl derivatives are frequently used, coupled with electron capture detection. A GC method (92) has recently been collaboratively tested in barley and malt and accepted by the American Society of Brewing... 

BL Worobey. Simplified heptafluorobutyrylation of linuron and its metabolite 3,4-dichloroaniline. J Chromatogr 262 328-330,1983. 

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