Mass spectrometric location of double bonds in unsaturated fatty acids including conjugated acids as their methoxybromo derivatives

Methoxybromo derivatives of unsaturated fatty acids including conjugated acids yield simple mass spectra and can be used to locate the position of double bonds in these acids. The derivatives are prepared under mild conditions by bromination of the unsaturated fatty acids in methanol. The method is illustrated with the methoxybromo derivatives from methyl esters of oleic, petroselenic, erucic, undecenoic, linoleic, linolenic, the conjugated diene acids from dehydrated castor oil, α-eleostearic, punicic and parinaric acids. Unlike other methods using methoxy derivatives, the methoxybromo derivatives yield fewer ions, the diagnostic peaks forming the most intense ions of the spectra. While unambiguous double bond location is possible with monoenoic acids and conjugated fatty acids, only the end carbon atoms of the unsaturation system in nonconjugated polyenoic acids is located. But the characteristic appearance of fragments corresponding to [CH₃(CH₂)_nCH(OMe)CH(Br)CH₂−2H]⁺ and fragments 24 mass units higher than those which locate the end carbons in such fatty acids indicate a methylene-interrupted system of double bonds.     

Stable isotope characterization of olive oils: II-deuterium distribution in fatty acids studied by nuclear magnetic resonance (SNIF-NMR)

Site-specific isotope fractionation of hydrogen was investigated, at natural abundance, by deuterium nuclear magnetic resonance (SNIF-NMR) on nearly two hundred olive oil samples. Owing to the complexity of the ²H-NMR spectra of the mixtures of fatty acids obtained after hydrolysis of the oils, the different signals were gathered into six clusters. Knowing the contribution to the clusters of each of the four fatty acids considered (C_16:0, C_18:0, C_18:1, and C_18:2) and the composition of the fatty acids in the mixture, it is possible to compute the site-specific isotope ratios of the clusters from the molar fractions obtained from the ²H-NMR-spectra and from the total isotope ratio of the mixture, determined by isotope ratio mass spectrometry (IRMS). The results are discussed in terms of geographical (country, region and elevation) and temporal (year) parameters and they are tentatively explained on a climatic basis.     

Multidimensional Proton Nuclear Magnetic Resonance Relaxation Morphological and Chemical Spectrum Graphics for Monitoring and Characterization of Polyunsaturated Fatty-Acid Oxidation

Polyunsaturated fatty acids (PUFA) are components of many commercial products such as edible oils, foods, cosmetics, medication, and in biological systems such as phospholipids of cellular membranes. Although PUFA aggregates are important functional components, they are also related to system degradation, because PUFA are susceptible to oxidation via their multiple double bonds and allylic carbons. Current technologies are not effective in characterizing the morphological and chemical structural domains of saturated, monounsaturated fatty acids (MUFA) and PUFA materials, or how the morphological structures of fatty acids, at the mesomolecular, nanomolecular, and molecular levels, affect their oxidation mechanisms. In this article, the ¹H low-field (LF) NMR energy relaxation time technology is proposed as a tool to analyze PUFA oils undergoing thermal oxidation. This technology generates two-dimensional (2D) chemical and morphological spectra using a primal-dual interior method for the convex objectives (PDCO) optimization solver for computational processing of the energy relaxation time signals T₁ (spin–lattice) and T₂ (spin–spin). The 2D graphical maps of T₁ vs. T₂ generated for butter, rapeseed oil, soybean oil, and linseed oil show that the different degrees of unsaturation of fatty-acid oils affect their chemical and morphological domains, which influences their oxidative propensity. The technology of the ¹H LF-NMR energy relaxation time proved to be an effective tool to characterize and monitor PUFA oxidation.     

On the structure of glasses in the Ge-S-Br and Ge-Se-Br systems

The structure of the vitreous GeSBr₂ and GeSeBr₂ compounds has been investigated using Raman scattering spectroscopy. The Raman spectra of the GeSBr₂ compound contain bands at 235 and 113 cm⁻¹, which are attributed to vibrations in the GeBr₄ molecule, and bands at 288, 254, 161, and 147 cm⁻¹, which are absent in the Raman spectra of binary compounds. The Raman spectrum of the GeSeBr₂ glass has common features with the spectra of the GeSe₂ and GeBr₄ compounds but also involves a number of new bands intermediate in position between the bands at 265 cm⁻¹ for the GeSe₂ compound and the bands at 325 cm⁻¹ for the GeBr₄ compound. The spectra obtained confirm the existence of equilibria between the formation and dissociation of ternary structural units in melts of the thiobromide and selenobromide systems.     

Preparation,IR, UV,NMR, and Mass Spectral Fragmentations of New Substituted Phenoxaphosphinic Acids

The synthesis and IR, UV, NMR; and mass spectral fragmentations of substituted phenoxaphosphinic acids I – XIV are reported. A diazo method gave I, and the Friedel-Crafts method II – XIV. Infrared assignments: POH, broad bands, 2600, 2250, and 1650; C-P, 1490 - 1440; C-O, 1280 - 1260; P=0, 1190 - 1140; and P-O, 978 - 974 cm^?1. Characteristic bands also occur at 1330 - 1320 and 1230 - 1210 cm^?1. The UV spectra possess maxima at 210 - 220 mμ (log ∈ 4.50 - 4.60), 240 - 250 (4.20 - 4.30), and 298 – 304 (3.65 – 3.75). The NMR spectra give τ 7.56 ppm for a 2-methyl substituent, 7.48 for a 4-methyl and a quartet at 7.26 and a triplet at 8.71 (J = 7.7 Hz) for a 2-ethyl. The chemical shifts were virtually unaffected by alkyl or halogen substituents on the other aromatic ring but were shifted upfield by ortho or meta methyl substituents on the same ring. Singlets at τ 7.44 and 7.60 ppm in the spectrum of VIII gave calculated base values of about 7.28 and 7.44 for a 1-methyl and 3-methyl, respectively. The mass spectra are greatly influenced by the substituents. All showed loss of PO₂H from the molecular ion or in the case of ethyl compounds after CH₃^· expulsion. CHO or CCIO was then eliminated. The molecular ions of methyl compounds eliminated H₂O.     

Analysis of saturated free fatty acids from pollen by HPLC with fluorescence detection

A sensitive method for the determination of free fatty acids using 2‐(2‐(anthracen‐10‐yl)‐1H‐naphtho[2,3‐d]imidazol‐1‐yl) ethyl‐p‐toluenesulfonate (ANITS) as tagging reagent with fluorescence detection has been developed. ANITS could easily and quickly label fatty acids in the presence of the K₂CO₃ catalyst at 90 °C for 40 min in N,N‐dimethylformamide solvent. From the extracts of rape bee pollen samples, 20 free fatty acids were sensitively determined. Fatty acid derivatives were separated on a reversed‐phase Eclipse XDB‐C₈ column by HPLC in conjunction with gradient elution. The corresponding derivatives were identified by post‐column APCI/MS in positive‐ion detection mode. ANITS‐fatty acid derivatives gave an intense molecular ion peak at m/z [M+H]⁺; with MS/MS analysis, the collision‐induced dissociation spectra of m/z [M+H]⁺ produced the specific fragment ions at m/z [M–345]⁺ and m/z 345.0 (here, m/z 345 is the core structural moiety of the ANITS molecule). The fluorescence excitation and emission wavelengths of the derivatives were λ_ex = 250 nm and λ_em = 512 nm, respectively. Linear correlation coefficients for all fatty acid derivatives are >0.9999. Detection limits, at a signal‐to‐noise ratio of 3 : 1, are 24.76–98.79 fmol for the labeled fatty acids.     

Mass spectrometry of triglycerides: I. Structural effects

Mass spectra of several triglycerides of specific structure or with specific deuterium labeling have been measured with a low resolution mass spectrometer. With saturated triglycerides the abundances of ions characteristic of the component acids, [M-RCO₂]⁺, increase with increasing chain length, and [M-RCO₂CH₂]⁺ decrease with increasing chain length. Unsaturation in the acyl moiety causes the abundant formation of [RCO-1]⁺. Structures have been suggested for a number of the main peaks obtained from saturated triglycerides, and high resolution spectra of one triglyceride agree with the postulated structures. The peaks, [RCO+74]⁺, [RCO+115]⁺ and [RCO+128+14n]⁺, represent structures which contain the glyceryl portion of the triglyceride, since in case of the replacement of its hydrogens with deuteriums, these peaks are shifted accordingly. Evidence which indicates the possibility of determining the location of unsaturation by the interruption of homology of the [RCO+128+14n]⁺ series, brought about by the addition of deuterium to the unsaturated linkages, is introduced. Further evidence is also presented, which indicates that the [M-RCO₂CH₂]⁺ ions arise from the positions 1 and 3 and, in agreement with earlier studies from other laboratories, it is thus possible to identify the acyl groups attached to the 1 and 2 positions of the glyceryl moiety. Presented in part at the AOCS Meeting, New Orleans, April 1970. Part V of a series on Mass Spectrometry of Lipids. For IV see Lipids 4:421–427 (1969).     

Chemical Synthesis of Rare Natural Bile Acids: 11α‐Hydroxy Derivatives of Lithocholic and Chenodeoxycholic Acids

A method for the preparation of 11α‐hydroxy derivatives of lithocholic and chenodeoxycholic acids, recently discovered to be natural bile acids, is described. The principal reactions involved were (1) elimination of the 12α‐mesyloxy group of the methyl esters of 3α‐acetate‐12α‐mesylate and 3α,7α‐diacetate‐12α‐mesylate derivatives of deoxycholic acid and cholic acid with potassium acetate/hexamethylphosphoramide; (2) simultaneous reduction/hydrolysis of the resulting △¹¹‐3α‐acetoxy and △¹¹‐3α,7α‐diacetoxy methyl esters with lithium aluminum hydride; (3) stereoselective 11α‐hydroxylation of the △¹¹‐3α,24‐diol and △¹¹‐3α,7α,24‐triol intermediates with B₂H₆/tetrahydrofuran (THF); and (4) selective oxidation at C‐24 of the resulting 3α,11α,24‐triol and 3α,7α,11α,24‐tetrol to the corresponding C‐24 carboxylic acids with NaClO₂ catalyzed by 2,2,6,6‐tetramethylpiperidine 1‐oxyl free radical (TEMPO) and NaClO. In summary, 3α,11α‐dihydroxy‐5β‐cholan‐24‐oic acid and 3α,7α,11α‐trihydroxy‐5β‐cholan‐24‐oic acid have been synthesized and their nuclear magnetic resonance (NMR) spectra characterized. These compounds are now available as reference standards to be used in biliary bile acid analysis.     

Synthesis of 1-benzoylpyrene using silica-supported phosphotungstic heteropoly acid as an efficient and reusable catalyst

A novel one-pot catalytic synthesis of 1-benzoylpyrene through acylation of pyrene with benzoic anhydride catalyzed by several heteropoly acids (HPAs) was investigated. Pure 1-benzoylpyrene was obtained and its structure was identified by GC/MS, FT-IR and ¹H NMR spectra. Silica-supported phosphotungstic heteropoly acid (PW/SiO₂) was found to be the most active catalyst in the acylation. The yield and the selectivity of 1-benzoylpyrene were up to 62.5% and 100%, respectively. The effects of experimental parameters on the catalytic acylation reaction, and the possibility of reusability of PW/SiO₂ catalyst were studied. PW/SiO₂ catalyst is easily separable from the reaction mixture and reusable without loss of its activity.     

Determination of 1-alkene-1,3-sultones in alkylethoxy sulfates

1-Alkene-1,3-sultones, which have been found as skin sensitizers in certain batches of alkylethoxy sulfates, are measured by an isotope dilution method, using a¹³C-labeled sultone. The sultone is recovered by thin layer chromatography and gas chromatography, and its dilution with unlabeled sultone is measured by mass spectrometry. Chlorosultones, also implicated as sensitizers, are determined at the same time by a dehydrohalogenation treatment that converts them to unsaturated sultones.     

Preparation and conductivity of substituted germanic heteropoly acids polyethylene glycol hybrid materials

In this work, the polyethylene glycol (PEG) hybrid materials composited with substituted germanic heteropoly acids were prepared. Infrared (IR) spectra revealed that the Keggin structure characteristic of the GeM₁₁VO₄₀^5? anion were present in the hybrid materials. At room temperature (20°C), the conductivity of the products is 4.07 × 10^?3 S cm^?1 and 2.12 × 10^?3 S cm^?1, respectively. The results indicated that the conductivity of substituted germanic heteropoly acids PEG hybrid materials is higher than that of the corresponding pure substituted germanic heteropoly acids. According to the experimental results, we proposed a possible mechanism of the proton conduction of the hybrid materials. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

IR spectroscopy investigations of acidic character of carbonaceous films oxidized with HNO3 solution

Sorption of bases on carbonaceous films from liquid (NaHCO₃, Na₂CO₃ and NaOH solutions) and gaseous phases (NH₃) was studied using IR spectroscopy. Parallel to the IR spectroscopy the exchange of H⁺ ions for Na⁺ ions was determined by alkalimetry as well and NH₃ sorption isotherms were measured. The IR spectra indicate that chemisorption of NH₃ leads to the formation of amide structures and ammonium salts of carboxylic acids. The surface acidic centers on the films oxidized with HNO₃ solution are centres of Bronsted type.     

The Use of Free Radical Probes in the Study of Mechanisms of Enzyme Inactivation

Some inorganic radical-anions, which have very strong absorption spectra, have some oxidative reaction specificity with amino acids. Combined pulse radiolysis and inactivation studies on the reactions of these radicals with several enzymes lead to identification of amino acid residues essential to enzymic activity. Data are reviewed for the enzymes, lysozyme, ribonuclease, trypsin, α-chymotrypsin, papain and carboxypeptidase. The reducing radical, CO₂^?, is more selective than the hydrated electron in its reactions with enzymes and proteins. Results from pulse radiolysis studies in electron-transfer and other reactions involving CO₂^? are compared with results from inactivation studies with lysozyme and ribonuclease.     

NMR study on sulfonation of internal olefins

Terminal olefins can be converted into the corresponding sulfonates by sulfonation with SO₃ followed by hydrolysis, the products are used as detergent ingredients. Although internal olefins were also expected to be good feed stocks, it was difficult to convert them into the corresponding sulfonates with as good of a yield as that of terminal olefins under the same synthesis conditions. Our studies have been carried out in order to clarify the reason for poorer conversion of the internal olefins. It was found by a nuclear magnetic resonance spectroscopic study that the major components of the sulfonated intermediate of internal olefins wereβ-sultones, the amounts of which were usually very small in sulfonated terminal olefins. A portion of theseβ-sultones was desulfonated, depending on temperature, to the original olefins and the corresponding sulfate salts during alkaline hydrolysis. The prevention of desulfonation of theβ-sultones in the hydrolysis process was one of the most important aspects for the production of internal olefin sulfonates. Finally, by keeping the hydrolysis temperature below 35°C, the conversion of internal olefins into sulfonates was achieved with the same yield as that of conventional terminal olefins.     

One-step analysis of major bile components in human bile using 1H NMR spectroscopy

Human gallbladder bile dissolved in dimethyl-sulfoxide provides sharp and resolved signals for major bile components in ¹H NMR spectra. Characteristic well-resolved marker signals that invariably appear in ¹H NMR spectra of bile were identified for cholesterol (H18 methyl signal at 0.643 ppm), lipids (glycerol CH signal at 5.064 ppm), total bile acids (H18 signals in the range 0.520–0.626 ppm), total glycine conjugated bile acids (NH signal at 6.958 ppm), total taurine conjugated bile acids (NH signal at 7.646 ppm), and urea (NH₂ signal near 5.48 ppm), which enabled their rapid and accurate analysis. Excellent linearity and precision of quantitative analysis was observed for all the identified bile components (R ²>0.99 for all). The method was demonstrated on gallbladder bile from 19 patients with gallbladder diseases. Urea in bile was identified by NMR for the first time and its quantitative analysis, along with several other bile components, is presented. The majority of the bile components could be analyzed in a single step. Accurate and rapid quantification of several bile components noninvasively by using the method presented herein may have far-reaching implications in the study of bile acid metabolism and pathophysiology of various hepatobiliary and gastrointestinal diseases.     

Characterization of fluorine-, aluminum-, silicon-, and phosphorus-containing complexes in wet-process phosphoric acid using nuclear magnetic resonance spectroscopy

Wet-process phosphoric acid is one product of the reaction between phosphate rock and sulfuric acid. The limiting step in this process occurs when the acid is filtered from the reaction slurry, which also contains calcium sulfate (gypsum). The acid-soluble impurities present in the phosphate rock (e.g., fluorine, silicon, and aluminum) form complexes in wet-process acid which can alter the optimum size and habit of gypsum crystals, thereby reducing the filtration rates. Fluorine-containing complexes are strongly suspected of being potent modifiers of the crystal habit of gypsum. However, the identities of the complexes responsible for the habit modification have not been established. The identities of the complexes formed in phosphoric acid (28% P₂O₅) containing additions of fluorine (HF and H₂SiF₆) and aluminum [Al(NO₃)₃ · 9H₂O or AlF₃ · 9H₂O] were established in this study by using fluorine-19 (¹⁹F) and phosphorus-31 (³¹P) nuclear magnetic resonance (NMR) spectroscopies. Peaks due to aluminum fluoride, fluorosilicate, and fluoroaluminum phosphate complexes were observed in the NMR spectra recorded from these solutions. In addition, the¹⁹F and³¹P NMR spectra of wet-process acids were recorded. These spectra contained peaks assigned to the hexafluorosilicate ion (major species), along with aluminum fluoride and fluoroaluminum phosphate complexes (minor species).     

Lipase-catalyzed monoesterification of 1-O-hexadecylglycerol in organic solvents

A simple method is presented to esterify 1-O-hexadecyl-rac-glycerol using lipases in different organic solvents. The following fatty acids were used: C_14∶0, C_16∶0, C_18∶0, C_18∶1, and C_18∶2. Monoesterification was achieved by using a limiting amount of the fatty acid. Both the 1-O-hexadecyl-3-O-acylglycerol and the 2-O-acylglycerol were obtained in a total yield of 75% and a ratio of 7∶1 in dichloromethane after 3 d. Chromatographic data for the monoesters, useful for the identification of the natural products, are given (gas-liquid chromatography, thin-layer chromatography, reverse-phase thin-layer chromatography). The structure was confirmed by a chemical synthesis of 1-O-hexadecyl-2-O-hexadecanoylglycerol. The 3-O-glyceride was also formed by acyl migration, as the minor component. The monoesters were separated by column chromatography and characterized by ¹H and ¹³C nuclear magnetic resonance spectra.     

Raman spectroscopic investigation of the effect of H2O on the molybdenum surface species in MoO3Al2O3 catalysts

The Raman spectroscopic characterization of a set of $\text{MoO}{}_3\text{Al}{}_2\text{O}{}_3$ catalysts containing 3 to 25 wt% MoO₃ is presented. Controlled atmosphere measurements show that the Raman spectra of these catalysts are influenced drastically by the water content of the samples. Catalysts calcined in O₂ at 500 °C have spectra very different from previously reported spectra. The MoO stretching vibration is at about 1000 cm^?1 in calcined samples, whereas in H₂O-exposed samples the frequency is near 950 cm^?1. The position of the MoO stretching vibration is shown by repeated H₂O exposure, O₂ calcination cycles to be reversible between 950 and 1000 cm^?1. Models for the interaction of H₂O with the surface molybdate species are presented and discussed with respect to the Raman data.     

The characterization of coal tar pitches used in electrode binder manufacture by n.m.r. spectroscopy

Coal tar pitches dissolved in a mixed solvent system comprising S₂Cl₂ and SO₂Cl₂ were analysed by ¹H and ¹³C n.m.r. spectroscopy. The extensive chlorination of the pitch by this solvent unfortunately leads to serious underestimations in aromatic hydrogen concentrations when these solutions are examined by ¹H n.m.r. spectroscopy. However, quantitative data can be obtained using ¹³C n.m.r. spectroscopy where the carbon skeleton is unaffected by the extent of chlorination of the pitch. The ¹H n.m.r. spectra of individual aromatic compounds, similar to those found in coal tars have been recorded. The ¹H n.m.r. spectra confirmed that extensive chlorination of the aromatic nuclei had occurred which results in the non-quantitative estimation of hydrogen concentrations.     

Infrared absorption of branched-chain fatty acids and derivatives in the carbon-hydrogen stretching region

Summary An investigation of the lithium fluoride region makes it possible to characterize a number of structural isomers of branched-chain fatty acids. For example, 2-methyl, 3-methyl, and 5-methyl hexanoic acids may be distinguished. Similarly a number of isomers of octanoic acid may be identified ; 2-n-propyl and 2-isopropyl hexanoic acid may be differentiated. The isomers of 2-n-butyl hexanoic acid may also be identified. Absorption bands at 2960 cm⁻¹ and 2930 cm⁻¹ have been assigned, respectively, to asymmetrical methyl stretching modes and in-phase vibrations of the methylene group. Absorption at 2870 cm⁻¹ is associated with symmetrical stretching modes of the methyl group. The absorption at 2860 cm⁻¹ has been assigned to the out-of-phase vibrations of the methylene group. These assignments correspond to those of Fox and Martin and of Pozefsky and Coggeshall. The absorption bands at 2930 cm⁻¹ and 2860 cm⁻¹ are stronger than those at 2960 cm⁻¹ and 2870 cm⁻¹ when the ratio of methylene groups to methyl groups equals or exceeds three to one. The one exception to this rule is the case of 2-methyl hexanoic acid and the corresponding silver salt and di-soap. An interaction between the methyl group in the two-position and the acid group has been proposed as an explanation for this case. As the spectra of the fatty acids and their silver salt and aluminum di-soap derivatives are identical in the carbon-hydrogen region, it is obvious that other derivatives of these acids may be identified by reference to the spectra reported.