Loss Of Alkyl Group Research Articles

Interactions of CyMe4 -BTBP ligand with lanthanides and actinides: Insights from ESI-MS and DFT calculations.

Electrospray Ionization Mass Spectrometry (ESI-MS) technique and density functional theory (DFT) calculations were combined to study the formation of the complexes of lanthanides (Ln = La, Ce, Nd, Sm, Eu, Yb) and actinides (UO2 2+ , Th4+ ) with CyMe4 -BTBP (6,6'-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-benzo-[1,2,4-]triazin-3-yl)-[2,2']bipyridine) to understand the mechanisms during the extraction process. Mass spectrometry titrations showed the formation of the complexation in acetonitrile. For lanthanides, only 1:2 complexes ([Ln(L)2 ]3+ , [Ln(L)2 (CH3 CN)]3+ ), [Ln(L)2 (NO3 )]2+ ) were found at low [Ln]/[L] concentration ratios, whereas the 1:1 complexes ([Ln(L)(NO3 )2 ]+ ) were observed when the [Ln]/[L] concentration ratio reached 1.0. For uranyl complexes, 1:1 complex ([UO2 L(NO3 )]+ ) was the only species within the measuring range. Th4+ complexes had two compositions: 1:1 and 1:2, in which 1:2 species was the dominant complex. Collision-induced dissociation (CID) was employed to characterize the fragmentation process. The fragmentation process was unfolded sequentially on both sides of CyMe4 -BTBP ligand with the loss of alkyl groups and cleavage of triazinyl rings. The CID results of CyMe4 -BTBP complexes revealed a slight difference depending on the metal center. The DFT calculations showed that the stable complexes formed in acetonitrile solution were consistent with the ESI-MS results.

Liquid chromatography-tandem mass spectrometry determination of the degradation products of V-type nerve agnents, N,N-dialkylaminoethanesulfonic acids

Degradation products of V-type nerve agents are important markers of these toxic chemical warfare agents, hence their detection and identification is of high importance from verification point of view of Chemical Weapons Convention (CWC). We focused on detailed investigation of fragmentation of N, N-dialkylaminoethanesulfonic acids, degradation products of V-type nerve agents using liquid chromatography-tandem mass spectrometry (LC−MS/MS), a LCQ Deca XP max ion trap mass spectrometer via an electrospray ionization in ESI mode. Capillary and tube lens voltages were optimized to give maximum response to m/z 210 [M + H]+ ion of N,N-diisopropylaminoethanesulfonic acid. The main fragmentation pathways are loss of alkyl groups attached to the nitrogen atoms. Within the aims of CWC, LC−ESI-MSn represents an important tool to control the production of prohibited compounds among others due to a possibility of easy monitoring of their content in environmental matrices. The knowledge of the fragmentation pathway will be useful for the unambiguous identification of degradation products of V-type nerve agents in human urine matrices as well as environmental matrices in the Organization for the Prohibition of Chemical Weapons proficiency test.

Iodine Mediated Addition of Trialkylamines to Dimethyl Acetylenedicarboxylate

Addition reaction of tertiary amines to dimethyl acetylenedicarboxylate mediated by molecular iodine is described. The trialkylamines afford dealkylative adducts in moderate to good yields. Amines containing an aryl group react sluggishly in low yields with a loss of alkyl group.

Study of the thermal decomposition of tetrapyrazino[2,3-b]indoloporphyrazine films

Copper and metal-free tetrapyrazino[2,3-b]indoloporphyrazine films are prepared by vacuum thermal evaporation (TE) and Langmuir–Blodgett (LB) techniques. The spectroscopic properties of the thermally evaporated and Langmuir–Blodgett tetra(5-n-amyl-8-tert-butyl-2,3-pyrazino[2,3-b]indolo)porphyrazinato copper(II) and tetra(5-n-amyl-8-tert-butyl-2,3-pyrazino[2,3-b]indolo)porphyrazine films have been investigated and compared using UV–vis, X-ray photoelectron spectroscopy (XPS), and matrix-assisted laser desorption ionization time of flight (MALDI-TOF) techniques. UV–vis spectroscopy confirms decomposition of the tetrapyrazino[2,3-b]indoloporphyrazine's main macrocyclic ring structure, as evidenced by the disappearance of the Q band. The C 1s XPS spectra show that the area ratios between the fitted peaks (C285.5eV/C287.2eV) are 2.03 and 1.47 for LB and thermally evaporated films, respectively. The difference may be due to the decomposition of pyrrole rings and loss of alkyl groups during thermal evaporation. MALDI-TOF measures lower masses with a broader distribution for the thermally evaporated films compared to the LB films, which is caused by thermal decomposition of the tetrapyrazino[2,3-b]indoloporphyrazine molecules.

Detection of Polyaromatic Sulfur Heterocycles in Crude Oil Using Postcolumn Addition of Tropylium and Tandem Mass Spectrometry

To complement the gas chromatography/mass spectrometric separation and detection of 3- and 4-ring organosulfur compounds, established methods for the separation of polyaromatic sulfur heterocycles (PASH) have been coupled to high-performance liquid chromatography/atmospheric pressure chemical ionization/tandem mass spectrometry (HPLC/APCI/MS/MS). The latter technique is capable of detecting both thermally unstable and nonvolatile PASH compounds in a crude oil. Our protocol utilizes distillation, alumina, and ligand exchange chromatography and HPLC to partially fractionate the crude oil. Postcolumn addition of tropylium cations prior to APCI/MS leads to an increase in the sensitivity of the detector toward 3- and 4-ring organosulfur compounds. Nonalkylated species primarily generate radical cations in the APCI source, whereas alkylated species exhibit both radical cation and product ions resulting from addition and/or loss of hydrogen and loss of alkyl groups. MS2 and MS3 fragmentation patterns confirm the presence of dibenzothiophene and benzonaphthothiophene derivatives in an Arabian crude oil.

Particle beam liquid chromatography-mass spectrometry of triphenylmethane dyes: application to confirmation of malachite green in incurred catfish tissue.

Eight triphenylmethane dyes (malachite green, leucomalachite green, gentian violet, leucogentian violet, brilliant green, pentamethyl gentian violet, N',N'-tetramethyl gentian violet and N',N"-tetramethyl gentian violet) have been characterized by particle beam liquid chromatography-mass spectrometry. The electron ionization spectra obtained of these dyes by this technique exhibit similar fragmentation, with the formation of phenyl and substituted phenyl radicals, and loss of alkyl groups from the amines. It was observed that the six cationic dyes are reduced in the mass spectrometer source to form the corresponding leuco compounds. This technique was evaluated for the confirmation of malachite green and leucomalachite green in incurred catfish (Ictalurus punctatus) muscle tissue.

CRAMPS determined proton aromaticities of Australian coals: a comparison with dipolar dephasing

The proton (H ar ) and carbon aromaticities (f a ) of a range of Australian coals and a few coals from other sources have been measured by high-resolution solid-state nuclear magnetic resonance spectroscopy. Combined rotation and multiple pulse spectroscopy (CRAMPS) was used to measure proton aromaticities while cross polarization with magic angle spinning (CPMAS) was used in carbon aromaticity measurement. Whereas reasonable correlations (correlation coefficient r=0.85) were found between f a and atomic hydrogen to carbon ratios (H/C), proton aromaticities exhibited a greatly smaller dependence upon H/C which predominantly grouped around H ar =0.3 (r=0.62). It is proposed that, for the coal suite studied here, dealkylation with subsequent protonation of the aromatic rings competes with aryl-aryl ring cross-linking involving loss of aromatic hydrogen without loss of alkyl groups

Mass spectra of some high molecular weight tetra(alkyl)silanes

AbstractThe mass spectra of tetra(alkyl)silanes having one short and three long alkyl groups were recorded (C20C32). These silanes did not give molecular ions, and the dominant course of fragmentation involved the loss of alkyl groups, followed by elimination of alkenes. The loss of alkyl groups, followed by elimination of alkenes. The loss of alkyl groups followed the sequence iso‐Pr>Et, Pr,… C14H29» Me. With alkyl groups longer than hexyl, a rearrangement was observed in which n‐alkanes were eliminated from the base ion. When the alkyl group was hexyl, the alkane eliminated was methane; when the alkyl group was heptyl, ethane was expelled; with octyl, it was propane; and with decyl, n‐pentane was expelled. Deuterium labeling showed that at least two modes of rearrangement were occurring.