Determination of the fragmentation mechanisms of organophosphorus ions by H2O and D2O atmospheric-pressure ionization tandem mass spectrometry

Dimethylmethyl phosphonate (DMMP), dimethyl phosphite (DMPI), trimethyl phosphite (TMPI) and trimethyl phosphate (TMP) were investigated using H₂O and D₂O atmospheric-pressure ionization (API) tandem mass Spectrometry. All daughter ions could be explained by losses of one or a successive number of stable molecules as opposed to losses of radicals such as the hydride, methyl and methoxy species. Losses of neutral methanol and dimethyl ether and of protonated methanol and formaldehyde ions from all four organophosphorus pseudo-molecular ions were observed. The DMMP and DMPI MH⁺ pseudomolecular ions produced the losses of neutral C₂H₆ and water, respectively. Formaldehyde loss was not observed for the MH⁺ ions, but it was well represented in the decomposition pathways of daughter ions. The D₂O reagent gas highlighted the role of the ionizing proton/ deuteron in the various daughter ions, including m/z 95, 79, 65, 49, 33, 31 and 47. The last ion was found to be isobaric in that m/z 47 and 48 both appeared with similar abundances in the D₂O-API daughter ion mass spectra of TMPI and TMP.     

The synthesis and chemistry of some bis-aziridinylketones and their spectral study

The synthesis and spectral characteristics of certain bis(1-alkyl-3-phenyl-2-aziridinyl)ketones are reported. The reactions of 1,2,4,5-tetrabromo-1,5-diphenyl-3-pentanone ( 2 ) with primary amines are assumed to have a mechanism similar to that of a simple dibromo-ketone. The so-called cis, cis- or trans, trans-configurations of the bis-aziridinylketones were determined by ¹H and ¹³C nmr spectra.     

Separation of Trp-Arg and Arg-Trp using G-quartet-forming DNA oligonucleotides in open-tubular capillary electrochromatography

DNA oligonucleotides that form intramolecular G-quartet structures were investigated as stationary phase reagents for separation of mixtures of the isomeric dipeptides Trp-Arg and Arg-Trp in open-tubular capillary electrochromatography (OTCEC). The oligonucleotides included a thrombin-binding aptamer that forms a biplanar G-quartet structure and an oligonucleotide that forms a 4-plane G-quartet structure. Fluorescence, circular dichroism and UV-visible absorbance spectroscopies were used in batch solution studies to indicate interactions between the dipeptides and the biplanar G-quartet structure. Results for OTCEC separations were compared with results obtained for capillary zone electrophoresis separations on a bare capillary. Temperature studies suggest that resolution is improved when the G-quartet structure is partially destabilized, but control experiments in which potassium chloride was not included in the mobile phase indicate that the G-quartet structure nevertheless plays a role in the separations.     

Surface characterization of Pt electrodes using underpotential deposition of H and Cu: Part I. Pt(100)

This paper is the first in a series describing the in situ surface characterization of platinum electrodes using H and Cu deposited at underpotentials. The surface of a Pt(100) electrode pretreated by simple flame annealing and quenching in aqueous sulfuric acid is shown to contain a high concentration of defects such as vacancies and self-adsorbed Pt atoms. Adsorbed hydrogen is more strongly bound at these defects than on a uniform Pt(100) surface. Potential cycling in 1 M HCl produces a higher concentration of defects, while oxide formation and reduction in 0.5 M H₂SO₄ has the opposite effect. The nature of (100)-like sites at a polycrystalline platinum electrode is also discussed.     

Solvent extraction and lanthanide complexation studies with new terdentate ligands containing two 1,3,5-triazine moieties

The extracting agent 2,6-bis(4,6-di-pivaloylamino-1,3,5-triazin-2-yl)-pyridine (L(5)) in n-octanol was found, in synergy with 2-bromodecanoic acid, to give D(Am)/D(Eu) separation factors (SFs) between 2.4 and 3.7 when used to extract the metal ions from 0.02-0.12 M HNO(3). Slightly higher SFs (4-6) were obtained in the absence of the synergist when the ligand was used to extract Am(III) and Eu(III) from 0.98 M HNO(3). In order to investigate the possible nature of the extracted species crystal structures of L(5) and the complex formed between Yb(III) with 2,6-bis(4,6-di-amino-1,3,5-triazin-2-yl)-pyridine (L(4)) were also determined. The structure of L(5) shows 3 methanol solvent molecules all of which form 2 or 3 hydrogen bonds with triazine nitrogen atoms, amide nitrogen or oxygen atoms, or pyridine nitrogen atoms. However, L(5) is relatively unstable in metal complexation reactions and loses amide groups to form the parent tetramine L(4). The crystal structure of Yb(L(4))(NO(3))(3) shows ytterbium in a 9-coordinate environment being bonded to three donor atoms of the ligand and three bidentate nitrate ions. The solvent extraction properties of L(4) and L(5) are far inferior to those found for the 2,6-bis-(1,2,4-triazin-3-yl)-pyridines (L(1)) which have SF values of ca. 140 and theoretical calculations have been made to compare the electronic properties of the ligands. The electronic charge distribution in L(4) and L(5) is similar to that found in other terdentate ligands such as terpyridine which have equally poor extraction properties and suggests that the unique properties of L(1) evolve from the presence of two adjacent nitrogen atoms in the triazine rings.     

The simultaneous saccharification and fermentation of pretreated woody crops to ethanol

Four promising woody crops (Populusmaximowiczii x nigra (NE388), P.trichocarpa x deltoides (Nll), P.tremuloides, and SweetgumLiquidambar styraciflua) were pretreated by dilute sulfuric acid and evaluated in the simultaneous saccharification and fermentation (SSF) process for ethanol production. The yeastSaccharomyces cerevisiae was used in the fermentations alone, and in mixed cultures with β -glucosidase producingBrettanomyces dausenii. Commercial Genencor 150L cellulase enyme was either employed alone or supplemented with β- glucosidase. All SSFs were run at 37 …C for 8 d and compared to saccharifications at 45…C under the same enzyme loadings.S. cerevisiae alone achieved the highest ethanol yields and rates of hydrolysis at the higher enzyme loadings, whereas the mixed culture performed better at the lower enzyme loadings without β -glucosidase supplementation. The best overall rates of fermentation (3 d) and final theoretical ethanol yields (86–90%) were achieved with P.maximowiczii x nigra (NE388) and SweetgumLiquidambar styraciflua, followed by P.tremuloides and P.trichocarpa xdeltoides (N1l) with slightly slower rates and lower yields. Although there were some differences in SSF performance, all these pretreated woody crops show promise as substrates for ethanol production.     

The synthesis and thermal curing parameters of a novel quinoxaline monomer with terminal ethynyl thermoset and phenylethynyl intramolecular cycloaddition postcure capability

The Synthesis of 3,3′-bis(4-[3-ethynylphenoxy]phenyl)-7,7′-bis(phenylethynyl)-2,2′-diphenyl-6,6′-biquinoxaline (I) was accomplished by the reaction of 2,2′-bis(phenylethynyl)-5,5′-diaminobenzidine (II) and 4-(3-ethynylphenoxy)benzil. Thermal analysis of I indicated a softening temperature of 107°C, followed by an exotherm above 150°C that corresponded to a independent crosslinking reaction of the terminal acetylene groups and an intramolecular cycloaddition (IMC) reaction of the 2,2′-bis(phenylethynyl)biphenyl moieties. In the synthetic work substantial improvements were made in the synthesis of II. The sample of I was cured at 200°C and the maximum partially cured transition temperature attained was 280°C. A sample of 3,3′-bis(4,[3-ethynylphenoxy]phenyl)-2,2′-diphenyl-6,6′-biquinoxaline (IV) was similarly tested as a model without IMC capability and its corresponding value was 250°C. The difference between these two values is discussed briefly.     

Abnormally mild synthesis of bis(dithiolo)pyrroles from 2,5-dimethylpyrroles

[chemical reaction: see text]. Treatment of N-substituted 2,5-dimethylpyrroles 2 with an equilibrated mixture of disulfur dichloride and DABCO in chloroform at 0 degrees C gives pentathiepinopyrroles 3 in moderate yields; further reaction of 3 with the same mixture at room temperature leads, in an extensive reaction cascade, to bis(dithiolo)pyrroles 4 in high yield; 2 can be converted into 4 in a one-pot operation under unusually mild conditions.     

Elucidation of the structure of quindolinone,a minor alkaloid of cryptolepis sanguinolenta: Submilligram 1H-13c and 1H-15N heteronuclear shift correlation experiments using micro inverse-detection

Elucidation of minor natural product structures has been significantly augmented by inverse-detection; further improvement has been afforded by the development of micro inverse-detection probes. We report here the elucidation of the structure of a new alkaloid, quindolinone (5H, 10H-indolo[3,2-b]quinolin-11-one), from the West African plant Cryptolepis sanguinolenta. All nmr data for this minor, preparative hplc-isolated alkaloid, including ¹H-¹⁵N one? bond heteronuclear shift correlation (HMQC) data, were recorded on an 800 μg sample of the alkaloid dissolved in 140 μl of 100% d₆-DMSO using a 400 MHz spectrometer.     

Grignard-Addition an Pyridin-N-oxid

Addition of phenyl-, alkyl-, alkenyl- and alkinyl-Grignard reagents to pyridine-N-oxide in THF leads to 5-substituted (2Z, 4E)-pentadien-aldoximes 6 having (E) (syn)-configuration of the C, N-double bond. The unsaturated oximes are shown to arise through an electrocyclic ring opening reaction from the primary Grignard adducts 5 . These can be trapped by protonation at low temperature.