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11.
Wyche KP Blake RS Willis KA Monks PS Ellis AM 《Rapid communications in mass spectrometry : RCM》2005,19(22):3356-3362
The technique of proton transfer reaction mass spectrometry (PTR-MS) couples a proton transfer reagent, usually H3O+, with a drift tube and mass spectrometer to determine concentrations of volatile organic compounds. Here we describe a first attempt to use chemical ionization (CI) reagents other than proton transfer species inside a PTR-MS instrument. The ability to switch to other types of CI reagents provides an extra dimension to the technique. This capability is demonstrated by focusing on the ability to distinguish several isobaric aldehydes and ketones, including the atmospherically important molecules methacrolein and methyl vinyl ketone. Two CI reagents were selected, H3O+ and NO+, both being cleanly generated in a low intensity radioactive source prior to injection into the drift tube. By recording spectra with both of these reagents, the contributions from different isobaric molecules can be separated by virtue of their unique spectrometric 'fingerprints'. The work demonstrates that this form of instrumentation is not restricted to proton transfer reagents and is the basis of a more general technique, chemical ionization reaction mass spectrometry (CIRMS). 相似文献
12.
Infrared (4000–200 cm?1) and Raman (3500–300 cm?1 ) spectra are reported for metal(II) halide and thiocyanate 4-methylpyridine complexes of the following stoichiometries: (MX2(4-Mepy)2) {M = Mn, Co, Cu or Zn, X = Cl or Br; M = Mn, Ni or Zn, X = NCS}; (MX2(4-Mepy)4) {M = Mn, Fe, Co or Ni, X = Cl or Br; M = Mn, Fe, Co, W or Cu, X = NCS}. For a given series of isomorphous complexes there is a correlation between the sum of the differences between the liquid and ligand values of the ν1, ν2, ν3, ν4, ν5, ν6, ν7, ν8, ν9, ν10, ν12, ν13 and ν14 modes of 4-methylpyridine and the strength of the metal-nitrogen bond. Comparison of the shift values of pyridine and 4-methylpyridine complexes supports the suggestion that, unlike the situation in the pyridine complexes, back-donation from the metal to the ligand is unimportant in the 4-methylpyridine complexes. 相似文献
13.
The title acetyl complex of the Cp(CO)2Fe system undergoes reaction with lithium hexamethyldisilazide to give the corresponding lithium enolate which reacts with a variety of electrophilic reagents. 相似文献
14.
Karukstis KK McDonough JR 《Langmuir : the ACS journal of surfaces and colloids》2005,21(13):5716-5721
We have characterized a new class of surfactant molecules using fluorescence spectroscopic and light-scattering techniques. Our results suggest that this homologous series of N-alkyl-N-methlypyrrolidinium bromide (CnMPB) surfactants with n = 10, 12, 14, 16, and 18 represents a bridge between the well-characterized alkyltrimethylammonium bromide (CnTAB) and dialkyldimethylammonium bromide (di-CnDAB) surfactant series. For the smaller members of the CnMPB series with n = 10, 12, and 14, our results are consistent with the formation of spherical micelles as the surfactant concentration is increased. With increasing alkyl chain length, we observe that the critical micelle concentration decreases and the aggregation number increases, typical of single-tail surfactants. For C16MPB, the formation of micelles at dilute concentrations (0.10 mM) is likely, followed by the coexistence of micelles and small unilamellar vesicles at higher concentrations up to 0.82 mM where only vesicles are present. For C18MPB, our data are consistent with the formation of vesicles only. We demonstrate in this study that the combination of spectroscopic and light-scattering methods is a powerful approach to reveal aspects of aggregate structure and morphology in aqueous CnMPB surfactant systems. In particular, the sensitivity of the fluorescence probe prodan to the polarity of its microenvironment enables the rich complexity of surfactant aggregates exhibited by this series of amphiphilic molecules to be detected. 相似文献
15.
Ann M. Tickner G. Kris Huang Kerry Gombatz Robert J. Mills Vance Novack Kevin S. Webb 《合成通讯》2013,43(16):2497-2505
Two efficient syntheses of methyl 4-mercaptobenzoate are described, one utilizing the dianion of 4-bromothiophenol, the other a SNAr reaction starting with 4-fluorobenzonitrile. 相似文献
16.
Copper Causes Regiospecific Formation of C4F8‐Containing Six‐Membered Rings and their Defluorination/Aromatization to C4F4‐Containing Rings in Triphenylene/1,4‐C4F8I2 Reactions 下载免费PDF全文
Kerry C. Rippy Dr. Eric V. Bukovsky Dr. Tyler T. Clikeman Dr. Yu‐Sheng Chen Dr. Gao‐Lei Hou Dr. Xue‐Bin Wang Dr. Alexey A. Popov Dr. Olga V. Boltalina Prof. Steven H. Strauss 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(3):874-877
The presence of Cu in reactions of triphenylene (TRPH) and 1,4‐C4F8I2 at 360 °C led to regiospecific substitution of TRPH ortho C(β) atoms to form C4F8‐containing rings, completely suppressing substitution on C(α) atoms. In addition, Cu caused selective reductive‐defluorination/aromatization (RD/A) to form C4F4‐containing aromatic rings. Without Cu, the reactions of TRPH and 1,4‐C4F8I2 were not regiospecific and no RD/A was observed. These results, supported by DFT calculations, are the first examples of Cu‐promoted 1) regiospecific perfluoroannulation, 2) preparative C?F activation, and 3) RD/A. HPLC‐purified products were characterized by X‐ray diffraction, low‐temperature PES, and 1H/19F NMR. 相似文献
17.
Thibault Dutronc Dr. Emmanuel Terazzi Dr. Laure Guénée Kerry‐Lee Buchwalder Aurore Spoerri Dr. Daniel Emery Dr. Jiri Mareda Dr. Sébastien Floquet Prof. Claude Piguet 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(26):8447-8456
This work illustrates how minor structural perturbations produced by methylation of 4′‐(dodecyloxy)‐4‐cyanobiphenyl leads to enthalpy–entropy compensation for their melting processes, a trend which can be analyzed within the frame of a simple intermolecular cohesive model. The transformation of the melting thermodynamic parameters collected at variable temperatures into cohesive free‐energy densities expressed at a common reference temperature results in a novel linear correlation, from which melting temperatures can be simply predicted from molecular volumes. 相似文献
18.
Margherita Modesti Colleen Szeto Renata Ristic WenWen Jiang Julie Culbert Keren Bindon Cesare Catelli Fabio Mencarelli Pietro Tonutti Kerry Wilkinson 《Molecules (Basel, Switzerland)》2021,26(6)
When bushfires occur near grape growing regions, vineyards can be exposed to smoke, and depending on the timing and duration of grapevine smoke exposure, fruit can become tainted. Smoke-derived volatile compounds, including volatile phenols, can impart unpleasant smoky, ashy characters to wines made from smoke-affected grapes, leading to substantial revenue losses where wines are perceivably tainted. This study investigated the potential for post-harvest ozone treatment of smoke-affected grapes to mitigate the intensity of smoke taint in wine. Merlot grapevines were exposed to smoke at ~7 days post-veraison and at harvest grapes were treated with 1 or 3 ppm of gaseous ozone (for 24 or 12 h, respectively), prior to winemaking. The concentrations of smoke taint marker compounds (i.e., free and glycosylated volatile phenols) were measured in grapes and wines to determine to what extent ozonation could mitigate the effects of grapevine exposure to smoke. The 24 h 1 ppm ozone treatment not only gave significantly lower volatile phenol and volatile phenol glycoside concentrations but also diminished the sensory perception of smoke taint in wine. Post-harvest smoke and ozone treatment of grapes suggests that ozone works more effectively when smoke-derived volatile phenols are in their free (aglycone) form, rather than glycosylated forms. Nevertheless, the collective results demonstrate the efficacy of post-harvest ozone treatment as a strategy for mitigation of smoke taint in wine. 相似文献
19.
A fluorescence correlation spectroscopy experiment that combines two-photon excitation and a standing-wave interference pattern is presented. The experimental correlation function can be analyzed using a simple expression involving (1) an exponential decay with time constant tau(f), which reflects diffusion across the interference fringes, and (2) a longer-lived decay with time constant tau(omega), which reflects diffusion in and out of the focal spot. The diffusion of Rhodamine 110 in water and ethylene glycol is measured using this method. The ability to simultaneously measure diffusion on two different time and lengthscales makes this experiment especially useful in environments where anomalous diffusion is suspected. 相似文献
20.
Joshua Buse Randy W. Purves Ronald E. Verrall Ildiko Badea Haixia Zhang Christopher C. Mulligan Kerry M. Peru Jonathan Bailey John V. Headley Anas El‐Aneed 《Journal of mass spectrometry : JMS》2014,49(11):1171-1180
The safe use of lipid‐based drug delivery agents requires fast and sensitive qualitative and quantitative assessment of their cellular interactions. Many mass spectrometry (MS) based analytical platforms can achieve such task with varying capabilities. Therefore, four novel high‐throughput MS‐based quantitative methods were evaluated for the analysis of a small organic gene delivery agent: N,N‐bis(dimethylhexadecyl)‐1,3‐propane‐diammonium dibromide (G16‐3). Analysis utilized MS instruments that detect analytes using low‐resolution tandem MS (MS/MS) analysis (i.e. QTRAP or linear ion trap in this work) or high‐resolution MS analysis (i.e. time of flight (ToF) or Orbitrap). Our results indicate that the validated fast chromatography (FC)‐QTRAP‐MS/MS, FC‐ LTQ‐Orbitrap‐MS, desorption electrospray ionization‐collision‐induced dissociation (CID)‐MS/MS and matrix assisted laser desorption ionization‐ToF/ToF‐MS MS methods were superior in the area of method development and sample analysis time to a previously developed liquid chromatography (LC)‐CID‐MS/MS. To our knowledge, this is the first evaluation of the abilities of five MS‐based quantitative methods that target a single pharmaceutical analyte. Our findings indicate that, in comparison to conventional LC‐CID‐MS/MS, the new MS‐based methods resulted in a (1) substantial reduction in the analysis time, (2) reduction in the time required for method development and (3) production of either superior or comparable quantitative data. The four new high‐throughput MS methods, therefore, were faster, more efficient and less expensive than a conventional LC‐CID‐MS/MS for the quantification of the G16‐3 analyte within tissue culture. When applied to cellular lysate, no significant change in the concentration of G16‐3 gemini surfactant within PAM212 cells was observed between 5 and 53 h, suggesting the absence of any metabolism/excretion from PAM212 cells. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献