The Carbon−Lithium Electron Pair Bond in (CH3Li)n(n= 1, 2, 4)

1996 ◽  
Vol 15 (13) ◽  
pp. 2923-2931 ◽  
Author(s):  
F. Matthias Bickelhaupt ◽  
Nicolaas J. R. van Eikema Hommes ◽  
Célia Fonseca Guerra ◽  
Evert Jan Baerends
Keyword(s):  
Electron Pair ◽  
Pair Bond

G. N. Lewis's Views on Bond Theory 1900–16

1975 ◽  
Vol 8 (3) ◽  
pp. 233-239 ◽  
Author(s):  
Robert E. Kohler
Keyword(s):  
Electron Pair ◽  
Inorganic Compounds ◽  
Structural Formula ◽  
Pair Bond ◽  
Bond Theory ◽  
Scientific Significance ◽  
Structural Formulae ◽  
Chemical Evidence

In a recent paper on the origin of G. N. Lewis's concept of the shared electron pair bond, I argued that the sources of Lewis's novel conception were certain ideas of J. J. Thomson and Alfred Parson. Yet the only influence that Lewis explicitly acknowledged was neither of these, but Alfred Werner's. The following statement appears in his book, Valence (1923):I still have poignant remembrance of the distress which I and many others suffered some thirty years ago in a class in elementary chemistry, where we were obliged to memorize structural formulae of a great number of inorganic compounds. Even such substances as the ferricyanides and ferryocyanides were forced into the system, and bonds were drawn between the several atoms to comply with certain artificial rules, regardless of all chemical evidence. Such formulae are now believed to be almost, if not entirely devoid of scientific significance. Such abuse of the structural formula inevitably led to a reaction which found its best expression in the publications of Werner. His Neuere Anschauungen … (1905) marked a new epoch in chemistry; and in attempting to clarify the fundamental ideas of valence, there is no work to which I feel so much personal indebtedness as to this of Werner's.

Quantum Theory and Electron Pair Bond

1931 ◽  
Vol 38 (2) ◽  
pp. 243-247 ◽  
Author(s):  
By W. Heitler
Keyword(s):  
Quantum Theory ◽  
Electron Pair ◽  
Pair Bond

Some wave functions for the four-electron threecentre bonding of four- and eight-π-electron systems

1974 ◽  
Vol 27 (4) ◽  
pp. 691 ◽  
Author(s):  
RD Harcourt ◽  
JF Sillitoe
Keyword(s):  
Molecular Orbital ◽  
Configuration Interaction ◽  
Electron Pair ◽  
Valence Bond ◽  
Pair Bond ◽  
Wave Functions ◽  
Electron Systems ◽  
Numerical Evidence ◽  
The One ◽  
Increased Valence

For symmetrical four-electron three-centre bonding units, the standard valence-bond (VB), delocalized molecular orbital (MO), increased-valence (IV) and non-paired spatial orbital (NPSO) representations of the electrons are Diagram O3, NO2- and CF2 with four π-electrons, and N3-, CO2 and NO2+ with eight π-electrons, have respectively one and two four-electron three-centre bonding units for these n-electrons. By means of Pople-Parr-Pariser type approximations, the MO, standard VB, IV and NPSO wave functions for these systems are compared with complete VB (or best configuration interaction) wave functions for the ground states. Similar studies are reported for the n-electrons of N2O. Further demonstration is given for the important result obtained elsewhere that the IV formulae must always have energies which are lower than those of the standard VB formulae, provided that the same technique is used to construct electron-pair bond wave functions. The extra stability arises because IV formulae summarize resonance between the standard VB formulae and long-bond formulae of the type Diagram As has been discussed elsewhere, the latter structure can make appreciable contributions to the complete VB resonance when its atomic formal charges are either zero or small in magnitude.If two-centre bond orbitals are used to construct the wave functions for the one-electron bond(s) and the two-electron bond(s) of IV formulae, then the IV and MO wave functions are almost identical for the symmetrical systems. Further numerical evidence is provided for this near-equivalence.

1H and 13C NMR spectra of 2,2’-disubstitutedtrans-azobenzenes suitable for preparation of metallized azo dyes

1991 ◽  
Vol 56 (10) ◽  
pp. 2160-2168 ◽  
Author(s):  
Josef Jirman
Keyword(s):  
Nmr Spectra ◽  
Electron Pair ◽  
Phenyl Group ◽  
Aprotic Solvents ◽  
1H And 13C Nmr ◽  
Predominant Form ◽  
Rapid Equilibrium ◽  
Dipolar Aprotic Solvents ◽  
Free Electron Pair ◽  
C Nmr

The 1H and 13C NMR spectra have been measured of six trans-azobenzenes substituted at 2 and 2’ positions with substituents favourable for complex formation with a metal (OH, NH2, NHCOCH3, COOH). From the standpoint of NMR such substituted trans-azobenzenes are present in solution in a rapid equilibrium following from rotation around the bond between C-1 of phenyl group and N atom of azo linkage. The predominant form has the substituent in the syn-position with respect to the free electron pair of the nearer azo nitrogen atom. The equilibrium is affected by dipolar aprotic solvents (such as hexadeuteriodimethyl sulfoxide) by decreasing the presence of the predominant form by 1 to 11%.

Structure and bonding in cyclic phosphoramidates as determined by carbon-13 magnetic resonance

1979 ◽  
Vol 57 (1) ◽  
pp. 21-26 ◽  
Author(s):  
Gerald W. Buchanan ◽  
Frederick G. Morin
Keyword(s):  
Magnetic Resonance ◽  
Nitrogen Atom ◽  
Electron Pair ◽  
Chemical Shifts ◽  
Lone Pair ◽  
Ring Conformation ◽  
Delocalized Electron ◽  
Nitrogen Lone Pair ◽  
Structure And Bonding

13C chemical shifts and 13C–31P couplings are reported for 11 cyclic phosphoramidates of ring sizes from four to nine. Vicinal couplings are compared with those of carbocyclic analogs and provide insight regarding the degree of nitrogen lone pair derealization into the N—P bond. For six-membered and larger rings, there appears to be nearly complete lone pair delocalization, i.e., a trigonal planar nitrogen atom. In azetidine derivatives the nitrogen lone pair remains localized, giving rise to a highly puckered ring conformation. Pyrrolidine derivatives are viewed as having a nitrogen with a partially delocalized electron pair.

Recoil Momentum Distribution in Electron Pair Production

1959 ◽  
Vol 115 (3) ◽  
pp. 672-677 ◽  
Author(s):  
K. S. Suh ◽  
H. A. Bethe
Keyword(s):  
Pair Production ◽  
Momentum Distribution ◽  
Electron Pair ◽  
Recoil Momentum
Sign in / Sign up

Export Citation Format

Share Document