Tautomerism of pyrazoline-5-thione and triazoline-5-thione studied by variable temperature photoelectron spectroscopy

1983 ◽  
Vol 61 (6) ◽  
pp. 1197-1203 ◽  
Author(s):  
Claude Guimon ◽  
Geneviève Pfister-Guillouzo ◽  
Mlkael Begtrup
Keyword(s):  
Gaseous Phase ◽  
Photoelectron Spectroscopy ◽  
Variable Temperature ◽  
Thermal Isomerization ◽  
Photoelectron Spectra ◽  
Planar Form ◽  
Mndo Calculations

Photoelectron spectra at variable temperatures demonstrate that the rate of thermal isomerization of pyrazoline-5-thione (1a) into methylthiopyrazole(s) in the gaseous phase is metal catalysed. Similar isomerizations of triazolethione (2a and 3a) are at best only slightly so.Furthermore, photoelectron spectra and MNDO calculations show that gaseous methylthiopyrazoles (1b and 1c) and methylthiotriazoles (2b and 2c) exist predominantly in planar form for the b isomer and in nonplanar form for the c isomer. The ΔH0 for the rotameric equilibria is 2.7–4.2 kJ•mol−1.

Variable-Temperature Ultraviolet Photoelectron-Spectroscopy of the Keto-Enol Tautomers of Pentane-2,4-Dione

1987 ◽  
Vol 40 (3) ◽  
pp. 599 ◽  
Author(s):  
NS Hush ◽  
MK Livett ◽  
JB Peel ◽  
GD Willett
Keyword(s):  
Photoelectron Spectroscopy ◽  
Energy Region ◽  
Variable Temperature ◽  
Photoelectron Spectra ◽  
Ultraviolet Photoelectron Spectroscopy ◽  
Molecular Orbital Calculations ◽  
Electronic Relaxation ◽  
Relaxation Effects ◽  
Enol Tautomer ◽  
Scf Calculations

The HeI photoelectron spectra of pentane-2,4-dione measured at various temperatures have been subjected to a spectrum-stripping technique to enable isolation of the complete HeI photoelectron spectra of the keto and enol tautomers. The resulting spectrum-stripping coefficients allow evaluation of the enolization equilibrium constant at each temperature and subsequently the enthalpy of enolization. Interpretation of the photoelectron spectra is achieved with the use of ab initio molecular orbital calculations. Photoionization of non-bonding oxygen, and π -type electrons, contribute to the low ionization energy region of the spectrum, with a πCC < no- <πCO ordering for the enol tautpmer , and no- < no+ < πCO+ for the keto tautomer . Because of different electronic relaxation effects, ∆SCF calculations are required to predict correctly the observed πCC/no- spacing for the enol tautomer.

Substitution effects in isomeric para and meta derivatives of benzonitrile revealed by UV photoelectron spectroscopy

1985 ◽  
Vol 50 (3) ◽  
pp. 650-657 ◽  
Author(s):  
Tomáš Juška
Keyword(s):  
Photoelectron Spectroscopy ◽  
Ionization Potentials ◽  
Photoelectron Spectra ◽  
Substitution Effects ◽  
Amino Group ◽  
Mndo Calculations ◽  
Derivatives Of ◽  
Uv Photoelectron Spectroscopy

The UV photoelectron spectra of isomeric para and meta derivatives of benzonitrile with substituents NO2, COCH3, Cl, Br, CH2I and NH2 were measured. Their assignment was carried out with the aid of MNDO calculations. The splitting of the highest π orbitals e1gS, e1gA is in all para derivatives greater than in their meta isomers, the greatest difference of splittings 0.25 eV being caused by the amino group. The level ordering e1gS, A exists in all molecules except meta NO2, and COCH3 derivatives where it is believed to be reverse. The π'CN - πCN splitting keeps nearly constant and it is close to that in benzonitrile. The ionization potentials of σ orbitals e1uS, e1uA, b2u and b1u in meta NO2 derivative are, in agreement with our expectation, higher than in benzonitrile. It is not true for para isomer where on the contrary, they are lower and they differ from meta isomer by 0.71-1.8 eV.

scholarly journals Modification of Wood with Monoethanolamino-borate by The Data of X-Ray Photoelectron Spectroscopy

2018 ◽  
Vol 196 ◽  
pp. 04005
Author(s):  
Irina Stepina ◽  
Irina Kotlyarova
Keyword(s):  
Particle Size ◽  
Photoelectron Spectroscopy ◽  
Model Compound ◽  
Hydrolytic Stability ◽  
Photoelectron Spectra ◽  
Wood Cellulose ◽  
Rapid Loss ◽  
X Ray ◽  
Wood Protection ◽  
Cellulose Materials

The difficulty of wood protection from biocorrosion and fire is due to the fact that modifiers in use are washed out from the surface of the substrate under the influence of environmental factors. This results in a rapid loss of the protective effect and other practically important wood characteristics caused by the modification. To solve this problem is the aim of our work. Here, monoethanolaminoborate is used as a modifier, where electron-donating nitrogen atom provides a coordination number equal to four to a boron atom, which determines the hydrolytic stability of the compounds formed. Alpha-cellulose ground mechanically to a particle size of 1 mm at most was used as a model compound for the modification. X-ray photoelectron spectra were recorded on the XSAM-800 spectrometer (Kratos, UK). Prolonged extraction of the modified samples preceded the registration of the photoelectron spectra to exclude the fixation of the modifier molecules unreacted with cellulose. As a result of the experiment, boron and nitrogen atoms were found in the modified substrate, which indicated the hydrolytic stability of the bonds formed between the modifier molecules and the substrate. Therefore monoethanolaminoborate can be considered as a non-extractable modifier for wood-cellulose materials.

scholarly journals Impact of high temperatures on aluminoceladonite studied by Mössbauer, Raman, X-ray diffraction and X-ray photoelectron spectroscopy

2021 ◽  
Author(s):  
Mariola Kądziołka-Gaweł ◽  
Maria Czaja ◽  
Mateusz Dulski ◽  
Tomasz Krzykawski ◽  
Magdalena Szubka
Keyword(s):  
Photoelectron Spectroscopy ◽  
Integral Intensity ◽  
Photoelectron Spectra ◽  
X Ray Diffraction ◽  
Structural Reorganization ◽  
Oh Groups ◽  
X Ray ◽  
Al Content ◽  
Integral Intensity Ratio ◽  
Higher Temperature

AbstractMössbauer, Raman, X-ray diffraction and X-ray photoelectron spectroscopies were used to examine the effects of temperature on the structure of two aluminoceladonite samples. The process of oxidation of Fe2+ to Fe3+ ions started at about 350 °C for the sample richer in Al and at 300 °C for the sample somewhat lower Al-content. Mössbauer results show that this process may be associated with dehydroxylation or even initiate it. The first stage of dehydroxylation takes place at a temperature > 350 °C when the adjacent OH groups are replaced with a single residual oxygen atom. Up to ~500 °C, Fe ions do not migrate from cis-octahedra to trans-octahedra sites, but the coordination number of polyhedra changes from six to five. This temperature can be treated as the second stage of dehydroxylation. The temperature dependence on the integral intensity ratio between bands centered at ~590 and 705 cm−1 (I590/I705) clearly reflects the temperature at which six-coordinated polyhedra are transformed into five-coordinated polyhedra. X-ray photoelectron spectra obtained in the region of the Si2p, Al2p, Fe2p, K2p and O1s core levels, highlighted a route to identify the position of Si, Al, K and Fe cations in a structure of layered silicates with temperature. All the measurements show that the sample with a higher aluminum content and a lower iron content in octahedral sites starts to undergo a structural reorganization at a relatively higher temperature than the less aluminum-rich sample does. This suggests that iron may perform an important role in the initiation of the dehydroxylation of aluminoceladonites.

scholarly journals Photoelectron spectroscopy of the protoporphyrin IX dianion

2021 ◽  
Author(s):  
Jemma Gibbard ◽  
Connor Jack Clarke ◽  
Jan RR Verlet
Keyword(s):  
Photoelectron Spectroscopy ◽  
Femtosecond Lasers ◽  
Protoporphyrin Ix ◽  
Photoelectron Spectra ◽  
Two Dimensional

Two-dimensional photoelectron spectroscopy using nanosecond and femtosecond lasers has been used to study the Protopophyrin IX dianion at photon energies between 1.8 - 4.1 eV. The photoelectron spectra indicated the...

DEVELOPMENT OF A CONICAL ENERGY ANALYZER FOR ANGLE-RESOLVED PHOTOELECTRON SPECTROSCOPY

2002 ◽  
Vol 09 (01) ◽  
pp. 583-586
Author(s):  
KOTA IWASAKI ◽  
KOICHIRO MITSUKE
Keyword(s):  
Gas Phase ◽  
Energy Resolution ◽  
Photoelectron Spectroscopy ◽  
Angular Resolution ◽  
Photoelectron Spectra ◽  
Sensitive Detector ◽  
Energy Analyzer ◽  
Position Sensitive ◽  
Pass Energy ◽  
Helium Discharge

A new angle-resolving electron energy analyzer composed of a conical electrostatic prism and a position-sensitive detector was developed for gas phase photoelectron spectroscopy. The performance of the analyzer has been tested by measuring photoelectron spectra of Ar using a helium discharge lamp. The angular resolution of 3° was achieved at the pass energy E of 5.6 eV. The best energy resolution was ΔE/E = 0.043 at E = 1.4 eV .

Gas-Phase Tautomerism in the Triazoles and Tetrazoles: A Study by Photoelectron Spectroscopy and ab Initio Molecular Orbital Calculations

1981 ◽  
Vol 36 (11) ◽  
pp. 1246-1252 ◽  
Author(s):  
Michael H. Palmer ◽  
Isobel Simpson ◽  
J. Ross Wheeler
Keyword(s):  
Ab Initio ◽  
Gas Phase ◽  
Molecular Orbital ◽  
Photoelectron Spectroscopy ◽  
Relative Stability ◽  
Photoelectron Spectra ◽  
Equilibrium Geometry ◽  
Molecular Orbital Calculations ◽  
Methyl Derivatives

The photoelectron spectra of the tautomeric 1,2,3,- and 1,2,4-triazole and 1,2,3,4-tetrazole systems have been compared with the corresponding N-methyl derivatives. The dominant tautomers in the gas phase have been identified as 2 H-1,2,3-triazole, 1 H-1,2,4-triazole and 2H-tetrazole.Full optimisation of the equilibrium geometry by ab initio molecular orbital methods leads to the same conclusions, for relative stability of the tautomers in each of the triazoles, but the calculations wrongly predict the tetrazole tautomerism.

Mass Selected ZEKE-Spectra of FeC2-Anions: A Spectroscopic Access to Intermediates in Catalytic Reactions of Hydrocarbons on Metal Surfaces

1994 ◽  
Vol 49 (12) ◽  
pp. 1256-1258 ◽  
Author(s):  
G. Drechsler ◽  
C. Bäßmann ◽  
U. Boesl ◽  
E. W. Schlag
Keyword(s):  
Mass Spectrometry ◽  
Photoelectron Spectroscopy ◽  
Metal Surfaces ◽  
Catalytic Reactions ◽  
Photoelectron Spectra ◽  
Mass Analyzer ◽  
Flight Mass Spectrometry ◽  
New Information ◽  
Zero Kinetic Energy ◽  
Conventional Laser

Abstract Zero-kinetic-energy (ZEKE) photoelectron spectra of metalcarbide anions are presented, allowing a high resolu­tion spectroscopic access to intermediates in catalytic reac­tions of hydrocarbons on metal surfaces. As a first compound, FeC2 (an intermediate of the iron/acetylene system) has been chosen. Important for successful ZEKE spectroscopy was a special anion source and the selection by time-of-flight mass spectrometry. In addition, conventional laser induced photo­ detachment photoelectron spectroscopy in combination with our anion source and mass analyzer delivered valuable new information.

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