Pentafluorobenzyl bromide

Pentafluorobenzyl bromide [II] and a partially fluonnated alkyl iodide [12] react with potassium carboxylates An interesting replacement of iodine in a fluonnated alkyl iodide by an acetate group takes place with peroxyacetic acid [13] (equations 10-12)... 

Pentafluorobenzyl bromide has been used in the derivatization of mercaptans [55] and phenols [36], m the analysis of prostaglandins [37], and in quantitative GC-MS [5S] 1,3 Dichlorotetrafluoroacetone is used for the derivatization of amino acids to the corresponding cyclic oxazolidinones and allows the rapid analysis of all 20 protein ammo acids [d] Pentafluorophenyldialkylchlorosilane derivatives have facilitated the gas chromatographic analysis of a wide range of functionally substituted organic compounds, including steroids, alcohols, phenols, amines, carboxylic acids, and chlorohydrms [4]... 

The first bioanalytical application of LC-GC was presented by Grob et al. (119). These authors proposed this coupled system for the determination of diethylstilbe-strol in urine as a replacement for GC-MS. After hydrolysis, clean-up by solid-phase extraction and derivatization by pentafluorobenzyl bromide, the extract was separated with normal-phase LC by using cyclohexane/1 % tetrahydrofuran (THE) at a flow-rate of 260 p.l/min as the mobile phase. The result of LC-UV analysis of a urine sample and GC with electron-capture detection (ECD) of the LC fraction are shown in Ligures 11.8(a) and (b), respectively. The practical detection limits varied between about 0.1 and 0.3 ppb, depending on the urine being analysed. By use of... 

Sulfonylureas are not directly amenable to gas chromatography (GC) because of their extremely low volatility and thermal instability. GC has been used in conjunction with diazomethane derivatization, pentafluorobenzyl bromide derivatization, and hydrolysis followed by analysis of the aryl sulfonamides. These approaches have not become widely accepted, owing to poor performance for the entire family of sulfonylureas. Capillary electrophoresis (CE) has been evaluated for water analysis and soil analysis. The low injection volumes required in CE may not yield the required sensitivity for certain applications. Enzyme immunoassay has been reported for chlorsulfuron and triasulfuron, with a limit of detection (LOD) ranging from 20 to 100 ng kg (ppt) in soil and water. 

Pentafluorobenzyl bromide Carboxylic acids, phenols, mercaptens, sulfonuides section 8.10.4... 

Cyanide and thiocyanate anions in aqueous solution can be determined as cyanogen bromide after reaction with bromine [686]. The thiocyanate anion can be quantitatively determined in the presence of cyanide by adding an excess of formaldehyde solution to the sample, which converts the cyanide ion to the unreactive cyanohydrin. The detection limits for the cyanide and thiocyanate anions were less than 0.01 ppm with an electron-capture detector. Iodine in acid solution reacts with acetone to form monoiodoacetone, which can be detected at high sensitivity with an electron-capture detector [687]. The reaction is specific for iodine, iodide being determined after oxidation with iodate. The nitrate anion can be determined in aqueous solution after conversion to nitrobenzene by reaction with benzene in the presence of sulfuric acid [688,689]. The detection limit for the nitrate anion was less than 0.1 ppm. The nitrite anion can be determined after oxidation to nitrate with potassium permanganate. Nitrite can be determined directly by alkylation with an alkaline solution of pentafluorobenzyl bromide [690]. The yield of derivative was about 80t.with a detection limit of 0.46 ng in 0.1 ml of aqueous sample. Pentafluorobenzyl p-toluenesulfonate has been used to derivatize carboxylate and phenolate anions and to simultaneously derivatize bromide, iodide, cyanide, thiocyanate, nitrite, nitrate and sulfide in a two-phase system using tetrapentylammonium cWoride as a phase transfer catalyst [691]. Detection limits wer Hi the ppm range. 

Chau and Terry [146] reported the formation of penta-fluorobenzyl derivatives of ten herbicidal acids including 4-chloro-2-methyl-phenoxy acetic acid [145]. They found that 5h was an optimum reaction time at room temperature with pentafluorobenzyl bromide in the presence of potassium carbonate solution. Agemian and Chau [147] studied the residue analysis of 4-chloro-2-methyl phenoxy acetic acid and 4-chloro-2-methyl phenoxy butyric acid from water samples by making the pentafluorobenzyl derivatives. Bromination [148], nitrification [149] and esterification with halogenated alcohol [145] have also been used to study the residue analysis of 4-chloro-2-methyl phenoxy acetic acid and 4-chloro-2-methyl phenoxybutyric acid. Recently pentafluorobenzyl derivatives of phenols and carboxylic acids were prepared for detection by electron capture at very low levels [150, 151]. Pentafluorobenzyl bromide has also been used for the analytical determination of organophosphorus pesticides [152],... 

Fig. 9.72Structures of MCPA(4-chloro-2-methylphenoxyacetic acid (I)), its metabolites 4-chloro-o-cresol (II), 5-chloro-3-methyl catechol (III), 4-chloro-2-methyl muconic acid (IV), reagent pentafluorobenzyl bromide (V), and the derivatives VI-VIII from l-lll Source Reproduced with permission from the American Chemical Society [155]... 

Further steps may include derivatisation, necessary when using GC methods for the final detection [29]. Derivatisation has been performed with pentafluorobenzyl bromide [22,30], acetic anhydride [24], or N,0-bis(trimethylsilyl)trifluoroacetamide [25] (see also Chapter 2.1). A liquid-liquid separation with i-hexane and an alkaline aqueous solution proved to be unsuccessful as a clean-up step for alkylphenols, as the compounds ended up in both phases [23]. 

Thiocyanate Human urine, saliva Derivatization of basic pH sample with pentafluorobenzyl bromide in the presence of Kryptofix 222 B polymer and extraction into methylene chloride then back extraction into isooctane GC with ECD 0.0115 nmol (in 0.2 mL) 83-106 Chen et al. 1994... 

Chen S-H, Wu S-M, Kou H-S, et al. 1994. Electron-capture gas chromatographic determination of cyanide, iodide, nitrite, sulfide and thiocyanate anions by phase-transfer-catalyzed derivatization with pentafluorobenzyl bromide. J Anal Toxicol 18(2) 81-85. 

Liu X, Yun Z. 1993. High-performance liquid chromatographic determination of thiocyanate anions by derivatization with pentafluorobenzyl bromide. J Chromatogr A 653 348-353. 

Potable water and raw source water Sample acetylated in situ by addition of acetic anhydride, solvent extracted and concentrated alternatively, extracted acidic sample derivatized by pentafluorobenzyl bromide and cleaned up by column chromatography HRGC-ECD (for pentafluorobenzyl derivative) HRGC-MS (for acetyl derivative) <50 ng/L (pentafluorobenzyl) <50 ng/L (acetyl derivative) 10-64% (pentafluorobenzyl derivative) 70-132% (acetyl derivative) Sitholeetal. 1986... 

Neurosteroids (in this book) Exogenous Chemicals Amphetamine, methamphetamlne. Pentafluorobenzyl bromide Bis(trimethylsilyl) trifluoroacetamide El Purdy et al. (2006) Yonamine et al. 

A promising method involves derivatization by reaction with pentafluorobenzyl bromide (Chien et al., 1998). Carboxylic acids (RC(O)OH) react to form the esters, RC(0)0CH2C6F5, which can be measured by... 

Dilution of urine with acetonitrile, azeotropic distillation for water removal, evaporation of solvent, redissolution in acetone and derivatization using pentafluorobenzyl bromide. 

Table 5.4.4 Characteristic negative chemical ionisation mass fragments for pentafluorobenzyl bromide-trimethylsilylimidazole (TMSi)derivatives of known BAs (reprinted from [18])...

Fig. 5.4.6 Mass chromatograms of pentafluorobenzyl bromide-trimethylsilylimidazole derivatives of BA standards (reprinted from [18]). 1 3j5-hydroxychol-5-enic acid, 2 LCA, 3 DCA, 4 CDCA, 5 hyodeoxycholic acid (HDCA), 6 ursodeoxycholic acid (UDCA), 7 [ll,12-d2] CDCA,...

To a rapidly stirred solution of bcnzimidazole-2-thiol (7 1.00 g, 6.66 mmol) in THF (10 mL) was added 2 M NaOH (3.4 mL, 6.8 mmol). After 4 min, pentafluorobenzyl bromide (1.74 g, 6.67 mmol) was added within (.5 inin. After 10 min, the solution was poured into H20 (50 mL). A solid readily formed upon scratching. After 5 min, filtration gave a solid, which was washed with H20 (10 mL) and dried under full vacuum to give 2-(pentafluorobenzylsulfanyl)benzimidazolc (8) as a colorless solid [yield 1.91 g (87%) mp 188.5-191.5 C], which can be further purified by recrystallization (EtOH). 

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