Identification of O-Isobutyl S-(2-Diethylaminoethyl) Methylthiophosphonate Chemical Neutralization Products in Bitumen–Salt Matrices

Products of the chemical neutralization of O-isobutyl S-(2-diethylaminoethyl) methylthiophosphonate, a VX Group warfare agent, in bitumen–salt matrices were studied by gas chromatography–mass spectrometry. Forty-four compounds were characterized by their electron impact ionization mass spectra and gas chromatographic retention indices on standard nonpolar polydimethylsiloxane phases; seven of these compounds were determined as derivatives. The structures of 26 compounds were identified, including structures of 24 O-isobutyl S-(2-diethylaminoethyl) methylthiophosphonate neutralization products. To solve this problem, chromatographic retention indices of unknown compounds were evaluated using reference data for their structural analogues. Partition coefficients in the binary heterophase hexane–octanol system were determined for the major components.     

Chromatographic and chromatospectral characteristic of dicarboxylic acid monoesters

Monoalkyl esters of benzene-1,2-dicarboxylic (phthalic) acid have not been reliably characterized by analytical parameters for their chromatographic and chromatospectral identification. Mass spectra of a series of monoalkyl phthalates (R = C₁–C₈) are discussed; their gas chromatographic retention indices on the RTX-5 polydimethylsiloxane stationary phase (5% phenyl groups) are determined. A linear dependence of indices on the number of carbon atoms in n-alkyl fragments of molecules and a correlation between the indices of any monoalkyl phthalates and corresponding diesters were used for the control of the data obtained. Using the last correlation, we found that most part of index values of mono (2-ethylhexyl) phthalate given in literature is wrong and, therefore, the results of identification of this compound in various samples must be revised. It was found that simplest monoalkyl phthalates are unstable during gas chromatographic separation, which may result in distortions of their mass spectra. To compare with monoalkyl phthalates, a similar series of monoesters of (Z)-butenedioic (maleic) acid was characterized. Retention indices of monoalkyl phthalates in reversed phase HPLC were determined and discussed.     

GC/MS and ESI/MS identification of the new generation plasticizers - cis and trans isomers of some 1,2-cyclohexane dicarboxylic acid di(n- and isononyl) esters

1,2-Cyclohexane dicarboxylic acid diisononyl ester is also known as diisononyl cyclohexane-1,2-dicarboxylate (DINCH) is a complex mixture of the hydrogenation products of diisononyl benzene-1,2-dicarboxylate (DINP). They are the new generation plasticizers used instead of the dialkyl benzene-1,2-dicarboxylate in order to improve the flexibility of polymers (mainly PVC) and strongly reduce the toxic effects on human health during their release from polymers to the environment. The identification of these compounds was done by syntheses of some DINCH constituents, i.e. cis and trans isomers of three di(n- and isononyl) cyclohexane-1,2-dicarboxylates, such as di(3,5,5-trimethylhexyl) cyclohexane-1,2-dicarboxylates, di(2-methyloctyl) cyclohexane-1,2-dicarboxylates and dinonyl cyclohexane-1,2-dicarboxylates by catalytic hydrogenation of appropriate DINP and their analyses by gas chromatography – mass spectrometry (GC/MS) and electrospray - mass spectrometry (ESI/MS) methods. Both GC data (values of the retention times t_R and arithmetic retention indices I_A) and mass spectra obtained for these isomers allowed to determine their chemical structures. ESI/MS mode of analysis of these compounds gives the knowledge about their mass fragmentation without the differentiation between individual cis and trans isomers.     

Stability of diazocarbonyl compounds under the conditions of gas chromatography and chromatography-mass spectrometry analysis

The gas chromatographic analysis of alkyldiazoacetates N₂CHCO₂R (R = CH₃ ? C₄H₉), ??-aliphatic diazoketones RCOCHN₂ (R = C₃H₇, C₅H₁₁, and C₉H₁₉), and aryl-substituted diazoketones Ph (CH₂) _n COCHN₂ (n = 0?C2) is shown to be possible when their retention temperatures are below the boiling points of compounds of this series at atmospheric pressure without decomposition (about 140°C). At higher temperatures occurs partial or complete decomposition of ??-diazoketones in chromatographic columns to form ketenes. Among the impurities in the reaction mixtures at the diazotization of corresponding alkyl glycinates were identified for the first time the nitrate esters of glycolic acid O₂NOCH₂CO₂R, as well as the dimeric products. All diazocarbonyl compounds and the impurities were characterized by mass spectra. For the first time their gas chromatographic retention indices were determined.     

Gas chromatography with mass spectrometry analysis of phosphoserine,phosphoethanolamine, phosphoglycerol,and phosphate

A new, rapid, sensitive, robust, and reliable method has been developed for the qualitative analysis of phosphoserine, phosphoethanolamine, phosphoglycerol, and phosphate using gas chromatography with mass spectrometry and two‐step trimethylsilylation. The method employs hexamethyldisilazane for silylation of the phosphate and hydroxyl groups in the first phase and bis(trimethylsilyl)trifluoroacetamide for silylation of the less‐reactive amino groups in the second phase. This order is of key importance for the method because of the different reactivities of the two reagents and the mechanism of derivatization of the active groups of the analytes. Trimethylsilylated derivatives of the analytes were identified on the basis of their retention times and mass spectra. The probable structures of the major fragments were identified in the spectra of the trimethylsilylated derivatives and characteristic m/z fragments were selected for each analyte. Fragments with m/z 73 and 299 occurred in the spectra of all the analytes. The characteristic retention data were employed to calculate the retention indices of the individual silylated phosphorylated substances in the hydrocarbon range C₁₂–C₁₉ for the DB‐5ms column. The method was employed to measure the polar fraction of the hydrolysate of the cytoplasmic membrane of Bacillus subtilis. The detection limits vary between 5 μg/mL (trimethylsilylated phosphate) and 72 μg/mL (trimethylsilylated phosphoethanolamine).     

New possibilities of dimethylformamide dimethylacetal as a derivatization agent for gas chromatography/mass spectrometry analysis

It is shown that the use of dimethylformamide dimethylacetal for the derivatization of analytes in gas chromatography/mass spectrometry cannot be restricted by the known conversion of carboxylic acids, phenols, and thiols into their methyl esters (ethers), as well as by the conversion of non-volatile amino acids (and C-amino compounds of other classes) into their dimethylaminomethylene derivatives. The application of this reagent to the derivatization of hydrazine derivatives and volatile carbonyl-containing analytes is considered. In the last case, the reaction proceeds selectively via CH₂ and/or CH₃ groups in the α-position to the carbonyl fragment. The principal predestination of the derivatization of such analytes is their characterization by differences of gas-chromatographic retention indices (ΔRI) of reaction products and initial substrates. The ranges of variation of such increments, ΔRI, appeared to be different for different subgroups of carbonyl compounds; this allowed us to determine their structures more precisely. The mass spectra of C-dimethylaminomethylene derivatives of some carbonyl compounds, preferably 2-substituted 1-methyl- and 1-aryl-3-(dimethylamino) prop-2-en-1-ones, revealed intense [M–17] peaks. The appearance of these signals can be explained by the migration of a hydrogen atom and the formation of [М–ОН]⁺ ions.     

Darstellung und reaktionen von 1,2-diaza-3-sila-5-Cyclopentenen

(Fluorosilyl)hydrazones are obtained from the reaction of lithiated hydrazones with fluorosilanes. On subsequent reaction with tert-butyllithium, cyclization takes place, to give 1,2-diaza-3-sila-5-cyclopentenes; this cyclization is favoured by the nitrogen-substituent of the hydrazone. The CH₂ group of the heterocyclic compounds is a nucleophilic centre, at which further substitutions are possible. The mass spec- trum and ¹H-, ¹⁹ F- and 2⁹Si-NMR spectra are reported.     

Transition metal complex stationary phases for the CGC analysis of ethers, thioethers and ketones

Summary The use of polysiloxanes with cyano or thiol groups as stationary phases for complexation gas chromatography is discussed. The polymers were obtained via polycondensation followed by polymerisation of the corresponding dichloro- or dimethoxy-silanes. Both the phases were modified by bonding transition metal chlorides with were modified by bonding transition metal chlorides with cyano (CuCl₂ or CoCl₂) and thiol groups (NiCl₂ or CoCl₂). The phases were examined in order to determine their application to the analysis of ethers, thioethers and ketones. Due to the presence of lone electron pairs on oxygen or sulphur atoms, the compounds should be capable of specific interacting with the electron-withdrawing centre of the liquid stationary phases. A number of retention parameters (retention indices, molecular retention indices and specific retention volume) were determined, which allowed characterisation of specific interactions between the bonded metal and the compound analysed. The results also enabled assessment of the influence of the structure of the compounds on their retention. The measurements were also carried out for the phases with free SH and CN groups as reference phases. The work demonstrates that the phases obtained may be useful for effective separations.     

Comparative evaluation of retention of hydrocarbons present in the C5-petroleum fraction on methylsilicone and squalane phases

Summary The retention of hydrocarbons present in the C₅ pyrolysis fraction of gasolines on the stationary phases squalane and methylsilicone oil JXR at 30, 40 and 50°C was investigated by capillary gas chromatography. The unified retention indices of the hydrocarbons were also calculated on squalane. The retention indices obtained on these two phases were interrelated and the quantitative relationship with the structure of the solutes was studied. Equations based on the unified retention indices calculated on squalane and some selected structural elements of the solutes permit the calculation of their retention on methylsilicone with sufficient accuracy.     

Pesticidal and antifertility activities of triorganogermanium(IV) complexes synthesized using a green chemical approach

Microwave chemistry is a green chemical method that improves reaction conditions and product yields while reducing solvent amounts and reaction times. This paper deals with the synthesis, spectral and biological studies of germanium(IV) complexes with chelating hydrazones derived from 1‐(pyridine‐2‐yl)ethanone (F₁) and 1‐(furan‐2‐yl)ethanone (F₂) with isonicotinohydrazide (INH). The complexes have been synthesized under a microwave–green chemical approach and investigated using a combination of microanalytical analysis, melting point, IR spectra, ¹H NMR spectra and ¹³C NMR spectra. Trimethylgermanium(IV)chloride and triphenylgermanium(IV)chloride interact with the hydrazones in a 1:1 molar ratio (metal:ligand), resulting in the formation of coloured products. On the basis of conductance and spectral evidence, a pentacoordinated structure for germanium(IV) complexes has been assigned for these products. The ligand is coordinated to the germanium(IV) via the azomethine nitrogen atom and the enolic oxygen atom. The free ligands and their metal complexes have been tested in male rats in order to assess their antifertility properties. Ligands and their metal complexes have also been tested in vitro against a number of pathogenic microorganisms in order to assess their antimicrobial and pesticidal properties. Both the ligands and their complexes were found to possess appreciable antifertility activity and other activities, which have been discussed in brief. Copyright © 2013 John Wiley & Sons, Ltd.     

Studies on biologically active heterocycles. Part I. Synthesis and antifungal activity of some new aroyl hydrazones and 2,5-disubstituted-1,3,4-oxadiazoles

A series of new 1-(2,4-dichlorobenzoyl) hydrazones and 2-aryl/aralkyl-5-(2,4-dichlorophenyl)-1,3,4-oxadiazoles have been synthesized from 2,4-dichlorobenzoylhydrazine and different aldehydes. Subsequent ring closure of the substituted aroyl hydrazones yielded the 1,3,4-oxadiazoles. All the compounds were characterized by their sharp melting point, microanalysis, ir, ¹H nmr and mass spectra and screened for their fungitoxic properties against Alternaria tenuis and Curvularia verruciformis. A few of the compounds showed good activity.     

Gas chromatographic and mass spectrometric characterization of isomeric alkylthiophenes (C20) and their occurrence in deep sea sediments

Six isomeric C₂₀ alkylthiophenes were synthesized in order to prove the occurrence of such compounds in various deep sea sediments. As expected from the analogy with the corresponding saturated hydrocarbons, 2- and 3-heptadecylthiophene have considerably longer relative retention times than the isomeric isoprenoid compounds, i.e. 2- and 3-(4,8,12-trimethyltridecyl)thiophene and 3- and 4-methyl-2-(3,7,11-trimethyldodecyl)thiophene. Covats retention indices for all compounds were determined by isothermal analysis at 190°C on two different silicone-coated capillary columns. The mass spectra of the monoalkylated thiophenes show a base peak at m/z 98 corresponding to a Mcafferty rearrangement product in the case of the 3-substituted isomers, whereas a simple benzylic cleavage dominates in the mass spectra of 2-alkylthiophenes. 4-Methyl-2-(3,7,11-trimethylodecy)thiophene is an exception from this simple rule because also shows the McLafferty rearrangement as dominant fragmentation. Two of the isoprenoid thiophenes are prominent compounds in various deep sea sediments.     

Structure-type separation of diesel fuels by solid phase extraction and identification of the two- and three-ring aromatics by capillary GC-mass spectrometry

A simple and effective solid phase extraction (SPE) method using silica gel micro glass columns has been developed for the separation of diesel fuel into groups of aliphatic, and mono-, di- and polyaromatic hydrocarbons. It is based on a stepwise gradient of dichloromethane in n-pentane. The resulting fractions were analyzed by capillary gas chromatography with a flame ionization detector and coupled gas chromatography-mass spectrometry. Commercially available standards, and retention indices and mass spectra were used for identification of individual aromatic compounds. The principal polycyclic aromatic hydrocarbons (PAHs) in diesel fuel are naphthalene, biphenyl, fluorene, phen-anthrene and their alkylated derivatives. Sulfur-containing PAHs are mainly represented by methyl-substituted dibenzo-thiophenes.     

Capillary gas chromatography-mass spectrometry of all 93 acyclic octenes and their identification in fluid catalytic cracked gasoline

The Kováts retention indices of all 93 acyclic octenes on polydimethylsiloxane and squalane as stationary phases as well as their mass spectra were measured. The means of gas chromatography-mass spectrometry (GC-MS) were used for confirmation of GC identification as well as for mass spectrometric deconvolution of the majority of gas chromatographic unseparated isomeric octene peaks. The distinction between corresponding E and Z acyclic octenes, that is either difficult or even impossible by means of GC-MS, was obtained on the basis of larger temperature coefficients of retention indices for Z isomeric octenes than for corresponding E isomers. The retention data expressed as homomorphy factors were correlated with the degree of branching, position of double bond, and position of alkyl group with respect to the double bond of acyclic octenes, and the structure-retention relationships were formulated. The 81 acyclic octenes were identified in FCC gasoline.     

Microsynthesis and mass spectral study of Chemical Weapons Convention related 2‐alkyl‐1,3,6,2‐dioxathiaphosphocane‐2‐oxides

Chemical Weapons Convention (CWC)‐related compounds where the phosphorus atom is part of a ring have very limited representation in mass spectral libraries and the open literature. Here we report electron ionization (EI), chemical ionization (CI) and electrospray ionization tandem mass spectrometry (ESI‐MSⁿ) spectra and retention indices for 2‐alkyl‐1,3,6,2‐dioxathiaphosphocane‐2‐oxides (alkyl C₁ to C₃) which are new cyclic chemicals covered under the CWC. The EI mass spectra show a pattern of ion fragmentation that is similar to that of other cyclic phosphonates in that loss of the alkylphosphonic acid as a neutral loss is more important than the presence of the protonated alkylphosphonic acid. In contrast to other cyclic phosphonates, the 2‐alkyl‐1,3,6,2‐dioxathiaphosphocane‐2‐oxides show almost no protonated alkylphosphonic acid and as a result the spectra do not carry the same distinctive signature of the phosphorus–carbon bond that is required for the chemical to be covered under the CWC. Copyright © 2008 John Wiley & Sons, Ltd.     

Forcing Twisted 1,7-Dibromoperylene Diimides to Flatten in the Solid State: What a Difference an Atom Makes

Perylene diimides (PDI) are workhorses in the field of organic electronics, owing to their appealing n-semiconducting properties. Optimization of their performances is widely pursued by bay-atom substitution and diverse imide functionalization. Bulk solids and thin-films of these species crystallize in a variety of stacking configurations, depending on the geometry of the stable conformation of the polyaromatic core. We here demonstrate that 1,7-dibromo-substituted perylene diimides, PDI(H₂Br₂), possessing a heavily twisted conformation in the gas phase, in solution and in the solids, can be easily flattened in the solid state into centrosymmetric molecules if the polyaromatic cores form π–π stabilized chains. This is achieved by using axial residues with low stereochemical hindrance, as guaranteed by a single CH₂/NH spacer directly linked to the imide function. Structural powder diffraction and DFT calculations on four newly designed species of the PDI(H₂Br₂) class coherently show that, thanks to the flexibility of the N−X−Ar link (X=CH₂/NH), flat cores are indeed obtained by overcoming the interconversion barrier between twisted atropoisomers, of only 26.5 kJ mol⁻¹. This strategy may then be useful to induce “anomalously flat” polyaromatic cores of different kinds (substituted acenes/rylenes) in the solid state, towards suitable crystal packing and orbital interactions for improved electronic performances.     

Glass capillary gas chromatography of C1−C4 mononitroalkanes. Pre-calculation of the relative retention

Summary The separation of C₁–C₄ mononitroalkanes on four wall-coated glass open tubular (capillary) columns (liquid phases: OV-101, Ucon-LB-550X, NPGS and Carbowax 20M) was investigated. Retention indices were determined and the influence of the different factors (analysis temperature, method of determining the gas holdup time and the nature of the stationary phases) on their reproducibility were studied. Linear regression equations permit the pre-calculation of the retention indices of C₁–C₄ mononitroalkanes from their properties on all liquid phases studied.     

Characterization of five [C4H7O]+ Ion structures. Fragmentation of the 2-pentanone molecular ion

The [C₄H₇0]⁺ ions [CH₂?CH? C(?OH)CH₃]⁺ (1), [CH₃CH?CH? C(?OH)H]⁺ (2), [CH₂?C(CH₃)C(?OH)H]⁺ (3), [Ch₃CH₂CH₂C?O]⁺ (4) and [(CH₃)₂CHC?O]⁺ (5) have been characterized by their collision-induced dissociation (CID) mass spectra and charge stripping mass spectra. The ions 1–3 were prepared by gas phase protonation of the relevant carbonyl compounds while 4 and 5 were prepared by dissociative electron impact ionization of the appropriate carbonyl compounds. Only 2 and 3 give similar spectra and are difficult to distinguish from each other; the remaining ions can be readily characterized by either their CID mass spectra or their charge stripping mass spectra. The 2-pentanone molecular ion fragments by loss of the C(1) methyl and the C(5) methyl in the ratio 60:40 for metastable ions; at higher internal energies loss of the C(1) methyl becomes more favoured. Metastable ion characteristics, CID mass spectra and charge stripping mass spectra all show that loss of the C(1) methyl leads to formation of the acyl ion 4, while loss of the C(5) methyl leads to formation of protonated vinyl methyl ketone (1). These results are in agreement with the previously proposed potential energy diagram for the [C₅H₁₀O]⁺˙ system.     

Novel derivatisation technique for the determination of chlorophenoxy acid type herbicides by gas chromatography–mass spectrometry

The analytical detection of chlorophenoxycarboxylic-acid-type herbicides (2,4-D, dichloprop, MCPA, etc.) in environmental samples is often a problem in instrumental analysis, as these compounds containing free carboxylic groups require chemical derivatisation prior to gas chromatographic (GC) methods. Nine chlorophenoxy-acid-type herbicide active ingredients have been derivatised successfully with trimethylsilyl N,N-dimethyl carbamate and t-butyldimethylsilyl N,N-dimethyl carbamate by forming their trimethylsilyl (TMS) and t-butyldimethylsilyl (TBDMS) esters, respectively. The detection and determination of the derivatives were performed by capillary gas chromatography–mass spectrometry. The study included determination of retention indices, mass spectral properties and comparison of derivatives produced. The mass spectra of TBDMS derivatives are usually dominated by very characteristic ions [M-57]⁺ resulting from the cleavage of t-butyl moiety during electron impact (EI) ionisation in the mass spectrometer. Limits of detection were 5 to 100 pg applying GC with EI-MS detection in full scan mode. The method, using SPE sample preparation, was applied for the analysis of 115 ground water and surface water samples collected in Békés County, Hungary in 2009.     

Characterization of O-trimethylsilyl oximes of trisaccharides by gas chromatography–mass spectrometry

Gas chromatography (GC) data (linear retention indices and relative areas) and mass spectra (most representative m/z fragments) of 12 reducing trisaccharides as trimethylsilyl oximes (TMSO) and four non-reducing as trimethylsilyl (TMS) ethers have been described for the first time and related to their structural features. Some trends have been observed: earlier elution of non-reducing compounds and fructotrioses; aldotrioses bearing the reducing end with link in position 6 showing the highest retention. Abundance of several fragment ions and their ratios were useful for trisaccharide characterization; some of these features seem to be useful for the characterization of new trisaccharides.