Mechanism of the Fujiwara Reaction: structural investigation of reaction products from benzotrichloride

1981 ◽  
Vol 46 (16) ◽  
pp. 3175-3178 ◽  
Author(s):  
Toyozo Uno ◽  
Kazuo Okumura ◽  
Yoshihiro Kuroda
Keyword(s):  
Structural Investigation ◽  
Reaction Products ◽  
Fujiwara Reaction

Structural investigation of perfluorocarboxylic acid derivatives formed in the reaction with N,N-dimethylformamide dialkylacetals

2019 ◽  
Vol 26 (2) ◽  
pp. 131-143 ◽  
Author(s):  
Monika Stróżyńska ◽  
Jürgen H. Gross ◽  
Katrin Schuhen
Keyword(s):  
Structural Investigation ◽  
Direct Analysis ◽  
Dimethyl Acetal ◽  
Negative Ion ◽  
Cluster Ions ◽  
Perfluorocarboxylic Acid ◽  
Reaction Products ◽  
Salt Structure ◽  
Negative Ion Mode ◽  
Positive Ion

A structural investigation of perfluorocarboxylic acid derivatives formed in the reaction with N,N-dimethylformamide dialkylacetals employing several techniques of mass spectrometry (MS) is described. Two derivatizing reagents, dimethylformamide dimethyl acetal (DMF-DMA) and dimethylformamide diethylacetal (DMF-DEA) were used. In contrast to carboxylic acids, perfluorocarboxylic acids are not able to form alkyl esters as the main product in this reaction. We found that perfluorooctanoic acid (PFOA) forms a salt with N,N-dimethylformamide dialkylacetals. This salt undergoes a further reaction inside the injection block of a gas chromatograph (GC) by loss of CO2 and then forms 1,1-perfluorooctane-(N,N,N,N-tetramethyl)-diamine. The GC-MS experiments using both electron ionization (EI) and positive-ion chemical ionization (PCI) revealed that the same reaction products are formed with either derivatizing reagent. Subjecting the perfluorocarboxylic acid derivative to electrospray ionization (ESI) and direct analysis in real time (DART), both positive- and negative-ion modes indicated that cluster ions are formed. In the positive-ion mode, this cluster ion consists of two iminium cations and one PFOA anion, while in the negative-ion mode, it comprises two PFOA anions and one cation. The salt structure was further confirmed by liquid injection field desorption/ionization (LIFDI) as well as infrared (IR) spectroscopy. We propose a simple mechanism of N,N,N′,N′-tetramethylformamidinium cation formation. The structure elucidation is supported by specific fragment ions as obtained by GC-EI-MS and GC-PCI-MS analyses.

Lead aspartate: a new en bloc stain for electron microscopy

1978 ◽  
Vol 36 (2) ◽  
pp. 34-35
Author(s):  
J.R. Walton
Keyword(s):  
Electron Microscopy ◽  
Calcium Ion ◽  
Enzyme Reaction ◽  
Lead Citrate ◽  
Reaction Products ◽  
En Bloc ◽  
Thin Sections ◽  
Lead Salts ◽  
Thin Sectioning ◽  
High Alkalinity

In electron microscopy, lead is the metal most widely used for enhancing specimen contrast. Lead citrate requires a pH of 12 to stain thin sections of epoxy-embedded material rapidly and intensively. However, this high alkalinity tends to leach out enzyme reaction products, making lead citrate unsuitable for many cytochemical studies. Substitution of the chelator aspartate for citrate allows staining to be carried out at pH 6 or 7 without apparent effect on cytochemical products. Moreover, due to the low, controlled level of free lead ions, contamination-free staining can be carried out en bloc, prior to dehydration and embedding. En bloc use of lead aspartate permits the grid-staining step to be bypassed, allowing samples to be examined immediately after thin-sectioning.Procedures. To prevent precipitation of lead salts, double- or glass-distilled H20 used in the stain and rinses should be boiled to drive off carbon dioxide and glassware should be carefully rinsed to remove any persisting traces of calcium ion.

Studies of Oxide Formation on Copper Thin Films by Electron Microscopy

1977 ◽  
Vol 35 ◽  
pp. 316-317
Author(s):  
G. G. Hembree ◽  
M. A. Otooni ◽  
J. M. Cowley
Keyword(s):  
Electron Microscopy ◽  
Electron Diffraction ◽  
Single Crystal ◽  
Crystal Surface ◽  
Crystal Defects ◽  
Diffraction Reflection ◽  
Reaction Products ◽  
Intermediate Energies ◽  
Crystal Films ◽  
Reflection Electron Microscopy

The formation of oxide structures on single crystal films of metals has been investigated using the REMEDIE system (for Reflection Electron Microscopy and Electron Diffraction at Intermediate Energies) (1). Using this instrument scanning images can be obtained with a 5 to 15keV incident electron beam by collecting either secondary or diffracted electrons from the crystal surface (2). It is particularly suited to studies of the present sort where the surface reactions are strongly related to surface morphology and crystal defects and the growth of reaction products is inhomogeneous and not adequately described in terms of a single parameter. Observation of the samples has also been made by reflection electron diffraction, reflection electron microscopy and replication techniques in a JEM-100B electron microscope.A thin single crystal film of copper, epitaxially grown on NaCl of (100) orientation, was repositioned on a large copper single crystal of (111) orientation.

Precipitation in silicon: Microanalysis

1988 ◽  
Vol 46 ◽  
pp. 474-475
Author(s):  
R.W. Carpenter
Keyword(s):  
Transition Metals ◽  
Spatial Resolution ◽  
Thin Foil ◽  
Precipitation Reaction ◽  
High Current ◽  
Reaction Products ◽  
Carbon And Nitrogen ◽  
Dielectric Layers ◽  
Precipitation Processes ◽  
Areas Of Interest

Interest in precipitation processes in silicon appears to be centered on transition metals (for intrinsic and extrinsic gettering), and oxygen and carbon in thermally aged materials, and on oxygen, carbon, and nitrogen in ion implanted materials to form buried dielectric layers. A steadily increasing number of applications of microanalysis to these problems are appearing. but still far less than the number of imaging/diffraction investigations. Microanalysis applications appear to be paced by instrumentation development. The precipitation reaction products are small and the presence of carbon is often an important consideration. Small high current probes are important and cryogenic specimen holders are required for consistent suppression of contamination buildup on specimen areas of interest. Focussed probes useful for microanalysis should be in the range of 0.1 to 1nA, and estimates of spatial resolution to be expected for thin foil specimens can be made from the curves shown in Fig. 1.

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