A study of the vacuum pyrolysis of 1,2,3-benzotriazines. The Hel ultraviolet photoelectron spectra of benzazete and o-benzyne

1995 ◽  
Vol 73 (1) ◽  
pp. 146-149 ◽  
Author(s):  
Nick Henry Werstiuk ◽  
Chandra Deo Roy ◽  
Jiangong Ma
Keyword(s):  
Heat Source ◽  
Ab Initio ◽  
Photoelectron Spectra ◽  
Equilibrium Geometry ◽  
Ionization Energies ◽  
Vacuum Pyrolysis ◽  
Ab Initio Hf

A CW CO2 laser is used as a directed heat source to carry out the vacuum pyrolysis of 1,2,3-benzo-triazine (1a) and 4-methyl-1,2,3-benzotriazine (1b). We report the first HeI photoelectron (pe) spectrum of benzazete (2a), which correlates with ionization energies calculated with HAM/3 using an equilibrium geometry obtained at the ab initio HF/6-31G** level of the theory. The pe spectrum of o-benzyne (3) obtained in this study correlates with the spectrum published by Zhang and Chen, but not with the spectra reported in two earlier publications. Keywords: 1,2,3-benzotriazines, vacuum pyrolysis, HeI ultraviolet photoelectron spectra, benzazete, benzyne.

A study of the vacuum pyrolysis of 11 -oxatricyclo[6.2.1.02,7]undeca-2,9-diene. The HeI ultraviolet photoelectron spectrum of 1,2-cyclohexadiene

1996 ◽  
Vol 74 (10) ◽  
pp. 1903-1905 ◽  
Author(s):  
Nick Henry Werstiuk ◽  
Chandra Deo Roy ◽  
Jiangong Ma
Keyword(s):  
Heat Source ◽  
Ab Initio ◽  
Key Words ◽  
Molecular Orbital ◽  
Photoelectron Spectrum ◽  
Equilibrium Structure ◽  
Ionization Energies ◽  
Vacuum Pyrolysis ◽  
Laser Apparatus ◽  
Ab Initio Hf

A newly developed ultraviolet photoelectron spectrometer – CO2, laser apparatus that utilizes a 50-watt CW CO2, laser as a directed heat source is used to study the vacuum pyrolysis of 11-oxatricyclo[6.2.1.02,7]undeca-2,9-diene (4). We report the HeI photoelectron spectrum of the strained cyclic allene 1,2-cyclohexadiene (1) that correlates with the HAM/3 ionization energies calculated with the optimized C2, equilibrium structure obtained with AM1 and the molecular orbital energies of the optimized C2, equilibrium structure calculated at the ab initio HF/6-31G** level of theory. Key words: 11-oxatricyclo[6.2.1.02,7]undeca-2,9-diene, vacuum pyrolysis, HeI ultraviolet photoelectron spectrum, 1,2-cyclohexadiene.

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.

A study of the vacuum pyrolysis of 4-diazoisothiochroman-3-one with Hel ultraviolet photoelectron spectroscopy

1996 ◽  
Vol 74 (12) ◽  
pp. 2536-2539 ◽  
Author(s):  
N.H. Werstiuk ◽  
J. Ma ◽  
C.D. Roy ◽  
A.J. Kresge ◽  
E.A. Jefferson
Keyword(s):  
Heat Source ◽  
Ab Initio ◽  
Photoelectron Spectroscopy ◽  
Laser Power ◽  
Activation Enthalpy ◽  
Power Level ◽  
Ultraviolet Photoelectron Spectroscopy ◽  
Wolff Rearrangement ◽  
Vacuum Pyrolysis ◽  
New Compounds

A newly developed ultraviolet photoelectron spectrometer apparatus that utilizes a tunable 50 W CW CO2 laser as a directed heat source is used to study the vacuum pyrolysis of 4-diazoisothiochroman-3-one (1a). Analysis of the pyrolysate with ultraviolet photoelectron spectroscopy shows that 1a undergoes a facile pyrolysis at a laser power level of less than 26 W, yielding two new compounds: thiaketene 3a, the product of a Wolff rearrangement, and benzocyclobutenthione (6a), which can be derived from thiacarbene 4a, the decarbonylation product of 3a. Activation enthalpies/energies calculated at the AM1 and ab initio levels of theory indicate that, unlike the case of 4-diazoisochroman-3-one (1b), the Wolff rearrangement of the incipient carbene may be concerted with loss of nitrogen from 1a. The activation enthalpy/energy calculated for the decarbonylation of 3a is significantly higher (AM1, 20.5 kcal/mol; RHF/6-31G(d), 11.7 kcal/mol; MP2(full)//RHF/6-31G(d), 14.3 kcal/mol) than the activation enthalpy/energy for the decarbonylation of 3b. This result is in keeping with the fact that we detect 3a, but 3b is not found in detectable amounts in the pyrolysate of 1b. Key words: vacuum pyrolysis, 4-diazoisothiochroman-3-one, HeI ultraviolet photoelectron spectroscopy, AM1 and ab initio calculations.

Adaptation of the Gelius intensity model in semiempirical HAM/3 molecular orbital calculations of valence photoelectron spectra excited by X-ray radiation

1985 ◽  
Vol 63 (7) ◽  
pp. 2007-2011 ◽  
Author(s):  
Delano P. Chong
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Cross Sections ◽  
Present Method ◽  
Photoelectron Spectra ◽  
Molecular Orbital Calculations ◽  
Ionization Energies ◽  
X Ray ◽  
Hartree Fock ◽  
Intensity Model

The Gelius intensity model has been adapted in the semiempirical HAM/3 method to calculate the valence ionization energies and intensities in XPS. Both semiempirical and àb initio Hartree–Fock–Slater atomic photoionization cross-sections can be used. Results presented for C2H2, C2H4, N2, H2O, CH3OH, and CH2F2 demonstrate that the present method can facilitate the interpretation of experimental XPS.

Quantum chemical prediction of 2H-pyran vibration spectrum

1990 ◽  
Vol 55 (1) ◽  
pp. 10-20 ◽  
Author(s):  
Stanislav Böhm ◽  
Josef Kuthan
Keyword(s):  
Vibrational Spectrum ◽  
Ab Initio ◽  
Quantum Chemical ◽  
Vibration Spectrum ◽  
Equilibrium Geometry ◽  
Heterocyclic Molecule ◽  
Vibrational Transitions ◽  
Correlation Corrections

Ab initio MO optimalization of the 2H-pyran molecule leads to a defined equilibrium geometry of this so far not identified heterocyclic molecule and to a physical justification of its existence. More advanced nonempirical wavefunctions and temperature corrections indicate that heterocyclic molecule I is energetically less stable than non-cyclic isomers II and III. Wavenumbers of fundamental vibrational transitions of heterocycle I and also known (2E)-2,4-pentadienal (IIIb were calculated using 3-21 G wavefunctions. The vibrational spectrum of compound I is predicted on the basis of correlation corrections.

FT-IR, FT-Raman spectra and ab initio HF and DFT calculations of 4-N,N′-dimethylamino pyridine

2008 ◽  
Vol 71 (3) ◽  
pp. 898-906 ◽  
Author(s):  
N. Sundaraganesan ◽  
S. Kalaichelvan ◽  
C. Meganathan ◽  
B. Dominic Joshua ◽  
J. Cornard
Keyword(s):  
Dft Calculations ◽  
Ab Initio ◽  
Raman Spectra ◽  
Ft Ir ◽  
Hf And Dft Calculations ◽  
Ab Initio Hf ◽  
Ft Raman

VUV FRAGMENTATION OF SOME HYDROFLUOROCARBON CATIONS STUDIED USING COINCIDENCE TECHNIQUES

2002 ◽  
Vol 09 (01) ◽  
pp. 153-158 ◽  
Author(s):  
WEIDONG ZHOU ◽  
D. P. SECCOMBE ◽  
R. Y. L. CHIM ◽  
R. P. TUCKETT
Keyword(s):  
Kinetic Energy ◽  
Ab Initio ◽  
Ground State ◽  
Lower Energy ◽  
Lone Pair ◽  
Electronic States ◽  
Photoelectron Spectra ◽  
Highest Occupied Molecular Orbital ◽  
Impulsive Model ◽  
Lone Pair Electrons

Threshold photoelectron–photoion coincidence (TPEPICO) spectroscopy has been used to investigate the decay dynamics of the valence electronic states of the parent cation of several hydrofluorocarbons (HFC), based on fluorine-substituted ethane, in the energy range 11–25 eV. We present data for CF 3– CHF 2, CF 3– CH 2 F , CF 3– CH 3 and CHF 2– CH 3. The threshold photoelectron spectra (TPES) of these molecules show a common feature of a broad, relatively weak ground state, associated with electron removal from the highest-occupied molecular orbital (HOMO) having mainly C–C σ-bonding character. Adiabatic and vertical ionisation energies for the HOMO of the four HFCs are presented, together with corresponding values from ab initio calculations. For those lower-energy molecular orbitals associated with non-bonding fluorine 2pπ lone pair electrons, these electronic states of the HFC cation decay impulsively by C–F bond fission with considerable release of translational kinetic energy. Appearance energies are presented for formation of the daughter cation formed by such a process (e.g. CF 3– CHF +), together with ab initio energies of the corresponding dissociation channel (e.g. CF 3– CHF + + F ). Values for the translational kinetic energy released are compared with the predictions of a pure-impulsive model.

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