Are pyridinium ylides radicals?

2020 ◽  
Vol 56 (76) ◽  
pp. 11287-11290
Author(s):  
Fan Liao ◽  
Wenhuan Huang ◽  
Biao Chen ◽  
Zijing Ding ◽  
Xingxing Li ◽  
...  
Keyword(s):  
Electron Pairs ◽  
Pyridinium Ylides

Pyridinium ylides are usually considered nucleophiles that can undergo various reactions involving electron pairs.

scholarly journals Destruction of localized electron pairs above the magnetic-field-driven superconductor-insulator transition in amorphous In-O films

JETP Letters ◽  
1998 ◽  
Vol 68 (4) ◽  
pp. 363-369 ◽  
Author(s):  
V. F. Gantmakher ◽  
M. V. Golubkov ◽  
V. T. Dolgopolov ◽  
G. E. Tsydynzhapov ◽  
A. A. Shashkin
Keyword(s):  
Magnetic Field ◽  
Insulator Transition ◽  
Electron Pairs ◽  
The Magnetic Field ◽  
Superconductor Insulator Transition

Structural, vibrational and electronic properties of α′-Ga2S3 under compression

2021 ◽  
Author(s):  
S. Gallego-Parra ◽  
R. Vilaplana ◽  
O. Gomis ◽  
E. Lora da Silva ◽  
A. Otero-de-la-Roza ◽  
...  
Keyword(s):  
Electronic Properties ◽  
Theoretical Study ◽  
Low Pressure ◽  
Electron Pairs ◽  
System P ◽  
Pressure Phase

We report a joint experimental and theoretical study of the low-pressure phase of α′-Ga2S3 under compression. The structural, vibrational, topological and electronic properties have been evaluated to reveal the relevance of the vacancy channels and the single and double lone electron pairs in the pressure behaviour of this system.

A Novel Approach for the Synthesis of 5-Pyridylindolizine Derivativesvia2-(2-Pyridyl)pyridinium Ylides

2013 ◽  
Vol 50 (1) ◽  
pp. 78-82 ◽  
Author(s):  
Emilian Georgescu ◽  
Florea Dumitrascu ◽  
Florentina Georgescu ◽  
Constantin Draghici ◽  
Loredana Barbu
Keyword(s):  
Novel Approach ◽  
Pyridinium Ylides

Comparison of the Effect of Boron and Phosphorus Impurities on Solid Phase Epitaxial Regrowth of Amorphous Silicon

1989 ◽  
Vol 157 ◽  
Author(s):  
Young-Jin Jeon ◽  
M.F. Becker ◽  
R.M. Walser
Keyword(s):  
Amorphous Silicon ◽  
Isothermal Annealing ◽  
Solid Phase ◽  
Laser Interferometry ◽  
Electron Pairs ◽  
Quadratic Equations ◽  
Low Concentrations ◽  
Fractional Ionization ◽  
Reported Data

ABSTRACTThis work was concerned with comparing the relative effects of boron and phosphorus impurities on the solid phase epitaxial (SPE) regrowth rate of self-ion amorphized layers in silicon wafers with (100) orientation. We used previously reported data measured by in situ, high precision, cw laser interferometry during isothermal annealing for temperatures from 450°C to 590°C, and concentrations in the range from 7.8×1018 cm-3 to 5×l020 cm-3 for boron (NB), and from 5×l017 cm-3 to 3×1020 cm-3 for phosphorus (Np) impurities. The basis for the comparison was a recently developed model that extends the Spaepen-Turnbull model for silicon recrystallization to include ionization enhanced processes.The experimental data for bom boron and phosphorus exhibited the linear variation in regrowth rate expected for low concentrations of implanted hydrogenic impurities having a concentration-independent fractional ionization in amorphous silicon. In the linear range the relative enhanced regrowth rate produced by these impurities can be expressed as a product of their, relative fractional ionizations, and the relative amount the rate constant for reconstruction is altered by localizing an electron, or a hole, at the reconstruction site. Assuming that a localized hole and electron equally softened the potential barrier for reconstruction, the experimental results indicated that boron had an ?40 meV lower barrier to ionization in amorphous silicon than phosphorus.The variations in the SPE regrowth rates with higher concentrations of both implanted boron and phosphorus were well fit by quadratic equations, but with different curvatures (+ and - for B and P respectively). This result was interpreted to indicate that SPE regrowth was further enhanced by localized hole pairs, but retarded by localized electron pairs.

The gauche Effect. A Theoretical Study of the Topomerization (Degenerate Racemization) and Tautomerization of Methoxide Ion Tautomer

1973 ◽  
Vol 51 (15) ◽  
pp. 2423-2432 ◽  
Author(s):  
Saul Wolfe ◽  
Luis M. Tel ◽  
I. G. Csizmadia
Keyword(s):  
Electronic State ◽  
Ground Electronic State ◽  
Conformational Transformation ◽  
Molecular Orbital Calculations ◽  
Rotational Angle ◽  
Electron Pairs ◽  
Hydroxyl Proton ◽  
Gauche Effect ◽  
Internuclear Distances ◽  
Relationship Of

Non-empirical double zeta quality molecular orbital calculations on −CH2OH as a function of the C—O bond length (r), the rotational angle about the C—O bond (θ), and the pyramidal angle at carbon [Formula: see text] are described. From the stretching potential curve, E(r), it is shown that dissociation of −CH2OH proceeds to give CH2 and OH−. The rotation–inversion surface, [Formula: see text], has two types of minima; in both cases the most favorable pyramidal angle at carbon is 105°. The lower minimum corresponds to a structure (the Y conformation) having the hydroxyl proton on the external bisector of the HCH angle. The higher minimum is 6.67 kcal/mol less stable and corresponds to a structure (the W conformation) having the hydroxyl proton on the internal bisector of the HCH angle. The relationship of these results to the gauche effect is discussed and it is noted that at certain internuclear distances the nuclear–nuclear repulsion term (Enucl) may overcome the tendency of adjacent electron pairs and polar bonds to exist preferentially in that conformation which has the maximum number of gauche interactions between these electron pairs or polar bonds.The topomerization of −CH2OH, i.e., the conformational transformation from one Y conformation into another, proceeds, via the W conformation as an intermediate, by two separate events, viz. rotation about the C—O bond, having a barrier of 10.58 kcal/mol, and pyramidal inversion at carbon, with a barrier of 20.52 kcal/mol. Some factors governing the relative importance of rotation and inversion in degenerate racemization are discussed.In its ground electronic state CH3O− is 22.18 kcal/mol more stable than −CH2OH. However, in the low-lying excited states all conformations of −CH2OH are stabilized relative to CH3O−. The most stable excited state structure of −CH2OH corresponds to the energy maximum for rotation–inversion of the ground electronic state.

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