BF3/methanol

This product was characterized by its NMR spectrum and also by reaction with HC1 followed by BF3/methanol to yield methylcyanoacetate ester. The reaction occurs readily, and in the absence of detectable amounts of the oxidative addition product of acetonitrile with the iridium complex, [Hlr-(depe)2CH2CN]+. In contrast, neither Rh(depe)2Cl nor Rh(dmpe)2Cl (dmpe = Me2PCH2CH2PMe2) react with C02 in acetonitrile, though Rh(dmpe)2Cl does react with C02 in nitromethane to form the analogous nitro-acetate hydride complex, (57). 

Methanol can be used instead of diazomethane for esterification of herbicides. The reaction is catalyzed by BF3. To 1 mL of herbicide extract, add an equal amount of toluene or benzene. This is followed by 1 mL of BF3-methanol. The solution is heated in a water bath for a few minutes. Ether evaporates out. Addition of a few milliliters of water partitions unreacted methanol and BF3 into the aqueous phase, while the methyl esters of herbicides remain in the upper layer of benzene or toluene. The extraction steps discussed above are summarized in the following schematic diagram. 

Studies have also been carried out in systems containing excess BF3 (17,18). The results (18) show that when the base is dimethyl ether, anisole, tetrahydrofuran, or pyridine, the exchange of BF3 is rapid and probably proceeds through an electrophilic displacement reaction in which the excess BF3 attacks the complex. These reactions all have activation energies of less than 10 kcal/mole, eliminating the possibility of a dissociation process. The data available, however, do not allow a complete evaluation of the reaction mechanism. Studies carried out on BF3-methanol complexes by 19F NMR (17) indicate displacement reactions having an activation energy of 5.3 kcal/mole. 

Methyl urea +BF3-methanol GC of methyl esters Infra Red Flow injection analysis with microbial electrode Ghee Milk Milk Sharma and Bindal (1987) Buermeyer et al. (2001), Pedersen (2003) Ukeda et al. (1992)... 

Some methods which do not involve separation of the FFAs from the milk fat or the whole product have considerable appeal because of their simplicity. Sharma and Bindal (1987) exploited the property of methyl urea to complex triglycerides in producing methyl esters with BF3-methanol without first separating the FFAs from the fat, while Spangelo et al. (1986) were able to methylate FFAs in an acetonitrile extract of milk with methyl iodide in the presence of an anion exchange resin as catalyst. Miwa and Yamamoto (1990) derivatised the FFAs in milk and milk products for HPLC analysis by direct reaction with 2-nitrophenylhydrazine hydrochloride. 

Dinitrophenyl (DNP) derivatives of amino acids are used to identify terminal amino acids in proteins. They are determined by GC after the conversion of free carboxyl groups into methyl esters [283—285] with the aid of either diazomethane or BF3—methanol. 

Silylation reagents Acylation reagents BF3/Methanol reagents Reaction vials and accessories... 

Gas chromatography and gas chromatography/mass spectrometry were employed to identify and quantitate individual molecular components. Both 25 and 50 meter glass support coated open tubular (SCOT) and fused silica wall coated open tubular (WCOT) capillary columns (SE.30, BP.l and BP.5 phases) were used with H2 as a carrier gas and F.I.D. detection. Acidic components were derivitized (BF3/methanol) to their methyl esters and hydroxyl groups to their silyl ethers (N,0-bis-(trimethylsilyl)trifluoroacetamide) in order to improve chromatographic separation. Carbon Preference Indices (CPI) were calculated using the equation -... 

Capillary and packed (GC) columns are of value in the analysis of complex mixtures of lipids. The best capillary column length will depend on the complexity of the material injected, however, 30-m columns are often employed. In packed columns, many types of stationary phases are available for lipid separation, and these include silicone and alkylated or cyanogenated derivatives, polyesters, polyglycol, and carboranes. It is also common to derivatize the fatty-acid side chains to the corresponding methyl esters by reaction in BF3/ methanol prior to chromatographic analysis to achieve more distinct and uniform separations. 

R.F. Venn, B. Kaye, P.V. Macrae, K.C. Saunders, Clinical analysis of sampatrilat, a combined renal endopeptidase and angiotensin-converting enzyme inhibitor - I Assay in plasma of human volunteers by API-MS following derivatization with BF3-methanol, J. Pharm. Biomed. Anal., 16 (1998) 875. 

The phenoxyacetic acid is extracted into benzene, esterfied with BF3-methanol and the methyl phenoxyacetate reaction mixture chromatographed. A 6-foot... 

GC-MS Analysis and Identification. A portion of the acidic fractions were quantitatively converted to methyl esters using a BF3-methanol reagent. The procedure used was that of Metcalfe and Schmitz (8). The esterified acidic fractions were analyzed using a coupled gas chromatograph-mass spectrometer (GC-MS) system consisting of a Varian Moduline 2700 gas chromatograph equipped with a flame ionization detector interfaced by a jet separator to a Du Pont Instruments Model 21-490 mass spectrometer. A 10 ft x 1/8 in o d stainless steel column packed with 10% stabilized DEGS on 80/ 100 mesh Chromosorb W AW DWCS was used. The He flow rate was 30 ml/min. The column temperature was held 5 minutes at 30°C, then... 

Ishiwatari (1975a, unpublished) methylated a lake humic acid with BF3/ methanol, resulting in two fractions a benzene-soluble fraction from which (-hexane-soluble materials were removed (64% of the initial humic acid) and... 

Fatty Acids and Other Organic Acids. Fatty acids were extracted from Lake Haruna sediment humic acid by refluxing with BF3/methanol (Ishiwa-tari, 1975a). The fatty acids consisted of a series of long-chain saturated (Cu-C34 maximum at Cie), unsaturated (C16, Cig, and C24), and branched (C15 and Civ) monocarboxylic acids. The fatty acids amounted to 0.2-0.3% of the humic acid. 

Monobasic acids are determined by gas chromatographic analysis of the free acids dibasic acids usually are derivatized by one of several methods prior to chromatographing (176,177). Methyl esters are prepared by treatment of the sample with BF3—methanol, H2S04—methanol, or tetramethylammonium hydroxide. Gas chromatographic analysis of silylation products also has been used extensively. Liquid chromatographic analysis of free acids or of derivatives also has been used (178). More sophisticated hplc methods have been developed recently to meet the needs for trace analyses in the environment, in biological fluids, and other sources (179,180). Mass spectral identification of both dibasic and monobasic acids usually is done on gas chromatographically resolved derivatives. 

BF3/methanol. The extracts are measured with GC/ECD (electron capture detector) which detects halogenated derivatives with a high sensitivity. 

Epoxidation of oleic and linoleic acid was readily achieved by treatment with the acetonitrile complex of hypofluorous acid (55). Phase-transfer-catalyzed biphasic epoxidation of unsaturated triglycerides was accomplished with ethylmethyldioxirane in 2-butanone (56). The enantioselective formation of an a,P-epoxy alcohol by reaction of methyl 13()S)-hydroperoxy-18 2(9Z,llfi) with titanium isopropoxide has been reported (57). An immobilized form of Candida antartica on acrylic resin (Novozyme 435) was used to catalyze the perhydrolysis and the interesterification of esters. Unsaturated alcohols were converted with an ester in the presence of hydrogen peroxide to esters of epoxidized alcohols (e.g., epoxystearylbutyrate) directly (58). Homoallyl ethers were obtained from olefinic fatty esters by the ethylaluminium-in-duced reactions with dimethyl acetals of formaldehyde, acetaldehyde, isobutyralde-hyde, and pivaldehyde (59). Reaction of 18 2(9Z, 12Z) with 50% BF3-methanol gave monomethoxy and dimethoxy derivatives (60). A bulky phosphite-modified rhodium catalyst was developed for the hydroformylation of methyl 18 1 (9Z)and 18 1(9 ), which furnished mixtures of formylstearate and diformylstearate (61). 

To the acid (1-20 mg) in a ground-glass stoppered test tube or screw-capped vial is added 1 ml of 14% BF3— methanol or 10% BCl3-methanol, and the solution is heated on a boiling water bath for 2 minutes. The esters are extracted into n-heptane [36-38]. 

Methyl esters can also be made very simply without the need for special reagents using methanolic HCI made with acetyl chloride (method 2.1.1. or 2.1.2), and only slightly less simply with BF3/methanol (method... 

The values in the two columns refer to chromatoplates developed 14 cm from the starting line. Mobilities are given relative to that of methyl cholate. Absolute mobility of this compound 2.5 cm. The values in the right column are those obtained after treatment of the compounds listed in the left column with BF3- methanol (see 131). 

Two derivatization procedures, pentafluorobenzylation and BF3/methanol esterification, were compared for their applications to GC analysis of phenoxy acid herbicides... 

The parameters considered were the reaction time, the amount of reagent (penta-fluorobenzylbromide, PFBBr) or catalyst (BF3), and the reaction temperature. On derivatiz-ing with pentafluorobenzylation, the most critical factors were foimd to be the concentration of PFBBr and the interaction "temperature-time," which improve the derivatization efficiency. Therefore, after optimization, BF3 /methanol esterification followed by GC—MS is as sensitive as pentafluorobenzylation used with GC-ECD, and more reproducible. 

Indole-2-carboxylate (70) on Claisen condensation with butyro-lactones (71, 72) gave the lactones (73, 74) which on subsequent hydrolysis and decarboxylation gave the alcohols (75, 76). On oxidation with pyridiniumchlorochromate (PCC) the alcohols gave the aldehydes (77, 78) which on cyclisation with BF3-methanol gave 1-methoxycarbazole (74) derivatives. With 4-methylbutyrolactone (72) murrayafoline A (12) has been synthesised. 

Fatty acid determination Transfer all remaining saponified solution to a separatory funnel, add 100 mL water and 5 mL HCl, and extract twice with 50-mL portions of ethyl ether. Dilute the combined ether extracts to volume in a 100-mL volumetric flask. Transfer an aliquot to a 10-mL test tube, evaporate to dryness at 40 C, and add BF3-methanol reagent. React at 65°C for 5 min, then transfer to a 50-mL separatory funnel, add 15 mL saturated NaCl solution, and extract with 10 mL ethyl ether. Add 1 mL of 250 ppm n-eicosane internal standard solution, dilute to 10 mL with ether, and analyze by gas chromatography, comparing to ethyl ether solutions of fatty acids (100-500 ppm) derivatized in the same way. GC Conditions 2% DEGS + 0.5% H3PO4 on Chromosorb W (AW-DMCS), 0.3 X 225 cm, 165 C, FID. 

The fatty acid components of the phosphatides in lecithin may be characterized by gas chromatographic analysis. Depending on the objective of the study, either the total sample or isolated individual phosphatides are analyzed. Sample preparation may consist of saponification followed by formation of the methyl esters for GC analysis. More often, decomposition and formation of methyl esters occurs simultaneously in a transesterifica-tion reaction with BF3/methanol, HCl/methanol, or sodium methoxide (109,110). 

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