Pentafluoropropionyl

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. 

Fluorination of caesium heptafluoropropoxide at —40°C with nitrogen-diluted fluorine exploded violently after 10 h. This may have been caused by ingress of moisture, formation of some pentafluoropropionyl derivative and conversion of this to pentafluoropropionyl hypofluorite, known to be explosive if suitably initiated. Other possible explosive intermediates are peroxides or peresters. 

Table 1 Gas chromatographic resolution factors of N-pentafluoropropionyl amino acid isopropyl esters on polysiloxanes carrying chiral L-valine t-butylamide groups (Val-NtBu)... 

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 acid enantiomers can be separated on a chiral stationary phase after derivatization with chloroformates (Abe et al., 1996). The derivatization procedure is quite simple and rapid, but the derivatizing reagent must be synthesized, which complicates the assay. Another method for the analysis of amino acid enantiomers uses N,0-pentafluoropropionyl isopropyl derivatives and a chiral column with NPD detection (Hashimoto et al., 1992). 

Acetyl hypobromite, 0725 Acetyl hypofluorite, 0748 Caesium fluoroxysulfate, 4250 Chlorodifluoroacetyl hypochlorite, 0600 Difluoroacetyl hypochlorite, 0649 Fluorine fluorosulfate, 4318 Heptafluorobutyryl hypochlorite, 1348 Heptafluorobutyryl hypofluorite, 1365 Hexafluoroglutaryl dihypochlorite, 1800 Pentafluoropropionyl hypochlorite, 1030 Pentafluoropropionyl hypofluorite, 1053 Propionyl hypobromite, 1150 Rubidium fluoroxysulfate, 4303 Trifluoroacetyl hypochlorite, 0591 Trifluoroacetyl hypofluorite, 0629 See Acetyl hypobromite, Propionyl hypobromite... 

Analytical Properties Baseline and near-baseline separations of racemic mixtures of /V-perfluoroacyl-2-aminoethyl benzenes, trifluoroacetyl (TFA), pentafluoropropionyl (PFP), heptafluorobutyl (HFB)... 

In contrast to other known fluorinated /3-sultones, reaction of compound 48 with triethylamine does not give the expected isomer 49, but only its decomposition products pentafluoropropionyl fluoride 50 and fhiorosulfonyldifluoro-acetyl fluoride 51 (Scheme 10) <2003JFC(121)147>. 

The L-(-)-proline was established by the checkers to be of >99.8% (estimated level of detection) enantiomeric purity by conversion to N-pentafluoropropionyl-L-(-)-proline isopropyl ester and GLC analysis on a 50-m glass capillary column containing the chiral phase, Chirasil-Val (Quadrex Inc.). Analyses were performed on a Hewlett-Packard HP 5710 A instrument operated isothermally at 140°C. Racemic proline was used as a control. 

Pentafluoropropionyl and heptafluorobutyryl derivatives have also been used for the GC analysis of amino acids in combination with esterification with various alcohols. In comparison with TFA derivatives, they are much more stable and resitant to hydrolysis, their retention times are shorter and all twenty protein amino acids can be separated on common phases (OV, SE, etc.). The price and restricted availability of the acylation reagents obviously hinder their wider application. 

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