scholarly journals Thermolysis of 2,2-dimethoxy-5,5-dimethyl- Δ3- 1,3,4- oxadiazoline studied with photoelectron spectroscopy. He(I) photoelectron spectrum of dimethoxycarbene

1998 ◽  
Vol 76 (2) ◽  
pp. 238-240
Author(s):  
H M Muchall ◽  
N H Werstiuk ◽  
B Choudhury ◽  
J Ma ◽  
J Warkentin ◽  
...  
Keyword(s):  
Heat Source ◽  
Gas Phase ◽  
Photoelectron Spectroscopy ◽  
Photoelectron Spectrum ◽  
Ionization Potentials ◽  
Perfect Agreement ◽  
Dimethyl Oxalate ◽  
Orbital Energies ◽  
Vertical Ionization Potentials ◽  
Experimental Values

Gas phase thermolysis of 2,2-dimethoxy-5,5-dimethyl- Δ3-1,3,4-oxadiazoline (1) in an ultraviolet photoelectron spectrometer by means of a CW CO2 laser as directed heat source at 26 W gave a complex PE spectrum that included ionization bands belonging to acetone, tetramethoxyethylene (3), and dimethyl oxalate (4). Subtraction of the spectra of acetone, 3, and 4 from the pyrolysis spectrum of 1 left a simple PE spectrum that is attributed to dimethoxycarbene (2) along with some ethane. ecke3LYP/6-31+G* calculations gave first adiabatic and vertical ionization potentials of 2 as well as orbital energies that are in perfect agreement with experimental values. From the available experimental and calculational data, 2 is assumed to adopt a w conformation.Key words: dimethoxycarbene, 2,2-dimethoxy- Δ3-1,3,4-oxadiazoline, tetramethoxyethylene, He(I) photoelectron spectroscopy, thermolysis.

Pyrolysis of 2-methoxy-5,5-dimethyl-2-methylthio- 2,5-dihydro[1,3,4]oxadiazole studied with photoelectron spectroscopy and DFT calculations — He(I) photoelectron spectrum of methoxy(methylthio)carbene

2006 ◽  
Vol 84 (4) ◽  
pp. 546-554 ◽  
Author(s):  
N H Werstiuk ◽  
A Klys ◽  
J Warkentin
Keyword(s):  
Heat Source ◽  
Dft Calculations ◽  
Key Words ◽  
Gas Phase ◽  
Photoelectron Spectroscopy ◽  
Photoelectron Spectrum ◽  
Calculated Data ◽  
Experimental Results ◽  
Photoelectron Spectra ◽  
Key Words 2

Gas-phase pyrolysis of 2-methoxy-2-methylsulfanyl-5,5-dimethyl-2,5-dihydro[1,3,4]oxadiazole (1) (also known as 2-methoxy-5,5-dimethyl-2-methylthio-2,5-dihydro[1,3,4]oxadiazole and 2-methoxy-2-methylthio-5,5-dimethyl-Δ3-l,3,4-oxadiazoline) in the source of an UV photoelectron spectrometer, by means of a CW CO2 laser as directed heat source, gave a photoelectron (PE) spectrum that included ionization bands belonging to acetone and methoxy(methylthio)carbene (3). Photoelectron spectra of authentic samples of (E)-1,2-dimethoxy-1,2-dimethyl thioethene (4), (Z)-1,2-dimethoxy-1,2-dimethylthioethene (5), S-methyl thioethanoate (6), and O-methyl ethanethioate (7), which can be derived by dimerization and rearrangement of the carbene, established that these compounds are not present in the pyrolysate. DFT calculations at the B3PW91/6-31+G(d,p) level and simulation of PE spectra at the B3LYP/6-31+G(d,p) level were instrumental in the interpretation of the experimental results. From the available experimental and calculated data, 3 is formed in a Sickle conformation upon pyrolysis of 1. Transition states for the rearrangement of 3 were examined with QTAIM. Key words: 2-methoxy-5,5-dimethyl-2-methylthio-2,5-dihydro[1,3,4]oxadiazole, pyrolysis, He(I) photoelectron spectroscopy, methoxy(methylthio)carbene, DFT calculations, QTAIM.

A Discussion on photoelectron spectroscopy - Orderings of π and σ ionization potentials in carbocyclic and heterocyclic aromatic compounds

1970 ◽  
Vol 268 (1184) ◽  
pp. 131-140 ◽  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Aromatic Compounds ◽  
Lone Pair ◽  
Ionization Potentials ◽  
Photoelectron Spectra ◽  
Light Sources ◽  
Orbital Energies ◽  
Substituted Pyridines ◽  
Nitrogen Lone Pair ◽  
Electron Correlation Effects

Data on calculated orbital energies and experimentally measured ionization potentials of carbocyclic and heterocyclic aromatic compounds are compared and contrasted. The ordering or orbital energies and ionization potentials do not always seem to parallel one another, probably owing to either electron correlation effects, or to deviations from Koopman’s theorem. The effects on photoelectron spectra of using different light sources and analysers are discussed in relation to their bearing on the orbital orderings of aromatic compounds. The high resolution He 584 A. photoelectron spectrum of pyridine is shown to be open to two interpretations regarding the ordering of the ionization potentials of the π orbitals and the ‘nitrogen lone pair’ (n). One of the interpretations involves the three lowest pyridine ionization potentials being π (9.2 eV), π L (9.5 eV) and n (10.5 eV) whilst the other has the first three ionization potentials being the order π , n, π . The photoelectron spectra of substituted pyridines and diazines are discussed in the light of the two possible explanations for the pyridine spectrum.

scholarly journals Photoelectron spectroscopy of reactive intermediates

1988 ◽  
Vol 324 (1578) ◽  
pp. 197-207 ◽  
Keyword(s):  
Transition Metal ◽  
Gas Phase ◽  
Photoelectron Spectroscopy ◽  
Photoelectron Spectrum ◽  
Reactive Intermediates ◽  
Vapour Phase ◽  
Photoelectron Spectra ◽  
Triatomic Molecule ◽  
Recent Developments ◽  
Vanadium Monoxide

Recent developments in the use of photoelectron spectroscopy to study reactive intermediates in the gas phase are reviewed. The information to be derived on low-lying cationic states from such studies is illustrated by considering two diatomic molecules, NCI and PF, and one triatomic molecule, HNO. Also, the use of a transition-metal photoelectron spectrum to interpret the photoelectron spectrum of the corresponding transition-metal oxide is discussed by using the spectra of vanadium and vanadium monoxide as examples. The value of super-heating in high-temperature photoelectron spectroscopy is demonstrated by considering the vapour-phase photoelectron spectra of the monomers and dimers of sodium hydroxide.

A Discussion on photoelectron spectroscopy - Photoelectron studies of boron compounds I. Diborane, borazine and B-trifluoroborazine

1970 ◽  
Vol 268 (1184) ◽  
pp. 97-109 ◽  
Keyword(s):  
Fine Structure ◽  
Photoelectron Spectroscopy ◽  
Molecular Orbitals ◽  
Ionization Potentials ◽  
Photoelectron Spectra ◽  
Energy Separation ◽  
Hydrogen Bridge ◽  
Boron Compounds ◽  
Vertical Ionization Potentials

The photoelectron spectra of diborane, hexadeuterodiborane, borazine and B -trifluoroborazine are presented, and adiabatic and vertical ionization potentials have been measured. The vibrational fine structure observed on some of the diborane bands is shown to be consistent with the forms of the molecular orbitals calculated by rigorous s.c.f. methods. The vertical i.p. of diborane are in better accord with a calculation which predicts a boron-boron bond in addition to the hydrogen bridge than with the calculations which indicate no direct boron-boron interaction. In borazine it is shown that the uppermost orbital is of π type rather than the σ type predicted by calculations, and that the extent of the π bonding, as measured by the energy separation of the π-type orbitals, is about 85 % of that in benzene. The effect of fluorination of borazine, as in benzene, is to stabilize the σ orbitals more than the π orbitals.

Gas phase flash pyrolysis of 3-azido-1,2,4-triazole: generation and ultraviolet photoelectron spectrum of N-cyanomethanimine

1988 ◽  
Vol 66 (9) ◽  
pp. 2123-2129 ◽  
Author(s):  
I. B'Shary ◽  
C. Guimon ◽  
M. Grimaud ◽  
G. Pfister-Guillouzo ◽  
D. Liotard
Keyword(s):  
Thermal Decomposition ◽  
Gas Phase ◽  
Photoelectron Spectroscopy ◽  
Photoelectron Spectrum ◽  
Reaction Path ◽  
Ultraviolet Photoelectron Spectroscopy ◽  
Pyrolysis Gas ◽  
Flash Pyrolysis ◽  
Ionic States ◽  
Configuration Interaction Calculations

A dimer of HCN, N-cyanomethanimine 6, was prepared by flash pyrolysis (gas phase, 10−2 mbar) from 3-azido-1,2,4-triazole 1a and detected by ultraviolet photoelectron spectroscopy (HeI). Its ionization potentials were measured and the ionic states sequence proposed, with the aid of ab initio – CI (configuration interaction) calculations. The study of the MNDO potential hypersurface enabled us to propose a mechanism of the thermal reorganization of the precursor 1a. It is shown that the reaction path passes through the formation of the protomer 1b before thermal decomposition and the generation of the nitrene 2b.

Molecular Complexes of p-Chloranil with Aniline, Phenol and their Derivatives

2015 ◽  
Vol 670 ◽  
pp. 89-94
Author(s):  
Boris S. Pryalkin ◽  
Yulia S. Bodagova
Keyword(s):  
Charge Transfer ◽  
Electron Acceptor ◽  
Photoelectron Spectroscopy ◽  
Spectral Properties ◽  
Molecular Complexes ◽  
Ionization Potentials ◽  
Wide Range ◽  
Vertical Ionization Potentials ◽  
Vertical Ionization Energies

Classification of simple supramolecular structures (for example molecular complexes), which has been introduced and described by Mulliken [1], is based on types of molecular orbitals of the components. In the paper [2], disadvantages of such classification are shown, which motivate us to return to the re-examination properties of molecular complexes. By this reason, there is a need to research the molecular complexes of one electron acceptor with a wide range of electron donor molecules. This paper have continued work (Part I [3]) on the chloranil complexes by studying the spectral properties complexes of N- and O-unsubstituting anilines and phenols. The present work aimed at analyzing linear relation the energies of charge-transfer bands of molecular complexes are related to ionization potentials of the donor components. All complexes conform to linear relations like involving both adiabatic and vertical ionization potentials of donor components. Mulliken [1] has been proposed to apply the vertical ionization potentials of donor components only. The development of photoelectron spectroscopy has led to the measurement of adiabatic and vertical ionization energies for thousands of molecules, which allow theirs to the present analysis of spectral properties molecular complexes.

A study of the vacuum pyrolysis of 6,6-dihalobicyclo[3.1.0]hexanes with Hel ultraviolet photoelectron spectroscopy

1994 ◽  
Vol 72 (12) ◽  
pp. 2537-2539 ◽  
Author(s):  
Nick Henry Werstiuk ◽  
Chandra Deo Roy ◽  
Jiangong Ma
Keyword(s):  
Heat Source ◽  
Gas Phase ◽  
High Power ◽  
Photoelectron Spectroscopy ◽  
Laser Power ◽  
Continuous Wave ◽  
Spectroscopic Studies ◽  
High Yield ◽  
Ultraviolet Photoelectron Spectroscopy ◽  
Vacuum Pyrolysis

To establish the utility of using a high-power CW (continuous wave) CO2 laser as a directed heat source for preparing organic transients targeted for gas-phase ultraviolet photoelectron spectroscopic studies, we studied the vacuum pyrolysis of 6,6-dibromobicyclo[3.1.0]hexane (1a), 6,6-dichlorobicyclo[3.1.0]hexane (1b), and exo-6-bromo-endo-6-chlorobicyclo[3.1.0]hexane (1c). While it has already been established that 1a and 1b rearrange to the 2,3-dihalocyclohexenes 3a and 3b, respectively, when heated in the condensed phase, upon vacuum pyrolysis 1a and 1b readily eliminate HX — not the dihalogens — and give the 2-halo-1,3-cyclohexadienes 2a and 2b in high yield. That 2,3-dibromocyclohexene (3a) does not eliminate HBr at the laser power used to pyrolyze 1a and 1b and that bromochloro compound 1c selectively loses HCl to form 2a suggests that the 1,3-elimination of HX occurs in a concerted fashion without isomerization of the cyclopropane.

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