Nitrogen lone pairs and the ionization potentials of azines and azoles

1970 ◽  
pp. 286 ◽  
Author(s):  
A. D. Baker ◽  
D. Betteridge ◽  
N. R. Kemp ◽  
R. E. Kirby
Keyword(s):  
Ionization Potentials ◽  
Lone Pairs

Tautomerism in Five-membered Nitrogen Heterocycles. A Test of the Reliability of Semiempirical (AMI, PM3, MNDO) Quantum Chemical Methods

1990 ◽  
Vol 45 (11-12) ◽  
pp. 1328-1334 ◽  
Author(s):  
Walter M. F. Fabian
Keyword(s):  
Quantum Chemical ◽  
Dipole Moments ◽  
Nitrogen Heterocycles ◽  
Ionization Potentials ◽  
Semiempirical Methods ◽  
Chemical Methods ◽  
Pm3 Method ◽  
Lone Pairs ◽  
Quantum Chemical Methods ◽  
The Stability

AbstractThe reliability of three popular semiempirical quantum chemical methods (AM1, PM3, MNDO) for the treatment of tautomeric equilibria is tested in a series of five-membered nitrogen heterocycles. The known flaw of MNDO to overestimate the stability of compounds with two or more adjacent pyridine-like lone pairs is also present in AM1 and to a somewhat lesser extent in PM3. Tautomeric species differing in the number of adjacent pyridine-like lone pairs, thus, cannot be adequately treated by these semiempirical methods. Both AM1 as well as PM3, however, represent major improvements over MNDO in the case of lactam-lactim tautomerism. The stability of N-oxides as compared to N-hydroxy tautomers seems to be overestimated by the PM3 method. All three semiempirical methods yield quite reliable ionization potentials and dipole moments.

Photoelectron spectra of compounds containing thionyl and sulphuryl groups

1972 ◽  
Vol 329 (1578) ◽  
pp. 275-282 ◽  
Keyword(s):  
The Other ◽  
Ionization Potentials ◽  
Photoelectron Spectra ◽  
Lone Pairs

Photoelectron spectra over the range 6─20 eV have been measured for some molecules con­taining thionyl and sulphuryl groups. For thionyl fluoride and sulphuryl fluoride, a number of the bands corresponding to different ionization potentials show a vibrational pattern. Specific assignments of these ionization potentials have been made to orbitals of different kinds, including those which are determined by oxygen or fluorine lone pairs, or by S—O π bonding. With the other molecules, SOCl 2 , SOBr 2 , (CH 3 ) 2 SO, SO 2 Cl 2 , SO 2 FCl, (CH 3 ) 2 SO 2 , CH 3 SO 2 F and CH 3 SO 2 Cl, broad bands are usually observed, and although many ionization potentials have been determined, specific assignments are less certain. Trends in the ionization potentials from particular levels have been considered in terms of inductive and conjugative effects.

Configurational Assignment and Conformational Study of Methylglyoxal Bisdimethylhydrazones Derived from the 2-Ethoxypropenal Precursor

2006 ◽  
Vol 59 (3) ◽  
pp. 211 ◽  
Author(s):  
Leonid B. Krivdin ◽  
Lyudmila I. Larina ◽  
Kirill A. Chernyshev ◽  
Natalia A. Keiko
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Experimental Measurements ◽  
Conformational Study ◽  
Lone Pairs ◽  
Configurational Assignment ◽  
Out Of Plane ◽  
High Level

A configurational assignment of the isomeric methylglyoxal bisdimethylhydrazones derived from the 2-ethoxypropenal precursor has been performed based on experimental measurements and high-level ab initio calculations of 1J(C,C) and 1J(C,H) couplings. The results reveal the marked stereochemical dependence upon the orientation of the lone pairs of both nitrogen atoms in different isomers. Methylglyoxal bisdimethylhydrazone is shown to exist in a mixture of the EE and ZE isomers (ca. 75:25), both of which adopt predominant s-trans conformations with minor (up to 8°) out-of-plane deviations.

Self-passivation leads to semiconducting edges of black phosphorene

2021 ◽  
Author(s):  
Li Ping Ding ◽  
Feng Ding
Keyword(s):  
Lone Pairs ◽  
Black Phosphorene

Freshly cleaved BPNR edges are reconstructed into highly stable ones dominated by three bond configurations: double PP bonds, P(2)–P(4) with two lone pairs on one P atom and that with all P atoms having three sp3 bonds.

Sign in / Sign up

Export Citation Format

Share Document