The chemistry of pyrrolic compounds. XL. A new synthesis of protoporphyrins III and XIII and a 1H N.M.R. study of the preferred pathway of electron delocalization in the porphyrin macrocycle

1978 ◽  
Vol 31 (3) ◽  
pp. 639 ◽  
Author(s):  
PS Clezy ◽  
CJR Fookes ◽  
S Sternhell
Keyword(s):  
Double Bond ◽  
Bond Order ◽  
Oxidative Cyclization ◽  
Electron Delocalization ◽  
Coupling Constant ◽  
Proton Coupling ◽  
Porphyrin Macrocycle ◽  
New Synthesis

The synthesis of protoporphyrins III and XIII as the dimethyl esters has been completed by an oxidative cyclization of biladiene-ac intermediates. Protoporphyrin III has been converted into deuteroporphyrin III and measurements of the proton coupling constant in the allylic unit, CH3-C=C-H, of this latter porphyrin point to the double bond of this system having a significantly diminished bond order. This finding is in accord with the view that the π-electron delocalization pathway in the porphyrin macrocycle involves the periphery of the molecule.

The chemistry of pyrrolic compounds. LII. The preferred pathway of electron delocalization in metalloporphyrins

1982 ◽  
Vol 35 (11) ◽  
pp. 2315 ◽  
Author(s):  
S Chakraborty ◽  
PS Clezy ◽  
S Sternhell ◽  
Thuc L van
Keyword(s):  
Double Bond ◽  
Bond Order ◽  
Electron Delocalization ◽  
Similar Data ◽  
Coupling Constant ◽  
Metal Free ◽  
Proton Coupling ◽  
Synthetic Approaches

Measurement of the proton coupling constant in the allylic unit, CH3-C=C-H, of the zinc(II), nickel(II) and magnesium(II) chelates of the deuteroporphyrin isomer (3a) points in each case to the double bond of this system having a significantly diminished bond order. Similar data have been obtained for the dication derivative of (3a). These findings are in accord with the view that the π-electron delocalization pathway in porphyrin dications and metalloporphyrins involves the periphery of the molecule as was previously shown for the metal-free porphyrin. New synthetic approaches to the porphyrin (3a) have been studied.

Neutral hyperconjugation and one-bond couplings between heavy atoms

2000 ◽  
Vol 78 (11) ◽  
pp. 1441-1444 ◽  
Author(s):  
Joseph B Lambert ◽  
Catherine E Shawl ◽  
Ernani Basso
Keyword(s):  
Double Bond ◽  
Aromatic Ring ◽  
Bond Order ◽  
Coupling Constant ◽  
Heavy Atoms ◽  
Two Systems ◽  
The Relationship

The relationship has been examined between bond order and one-bond couplings involving heavy atoms, as modulated by neutral hyperconjugation. Two systems have been studied in which either an aromatic ring or a double bond can influence, through hyperconjugation, the α and β bonds (respectively, Ci—C and Ci—M in =C-C-M). Hyperconjugation may be modulated by substituents on the aromatic ring or double bond or by placement of different atoms (M = C, Si, Ge, or Sn) at the β position. The α bond exhibits no relationship between coupling constant and neutral hyperconjugation, but the β bond shows a strong relationship.Key words: hyperconjugation, germanium, σ-π conjugation, silicon, tin.

Das ν1/ν3-Frequenzen-Verhältnis bei tetraedrischen Oxoanionen der Hauptgruppen- elemente und die Schwingungseigenschaften von Xenon-Tetroxid / The ν1/ν3 Frequency Ratio in Tetrahedral Oxoanions of The Main Group Elements and the Vibrational Properties of Xenon-Tetroxid

1972 ◽  
Vol 27 (6) ◽  
pp. 1000-1004 ◽  
Author(s):  
Enrique J. Baran
Keyword(s):  
Periodic System ◽  
Related Species ◽  
Frequency Ratio ◽  
Bond Order ◽  
Main Group ◽  
Vibrational Properties ◽  
Coriolis Coupling ◽  
Coupling Constant ◽  
Main Group Elements ◽  
Mean Amplitudes Of Vibration

AbstractIn an earlier work we have theoretically derived and explained certain rules relating the ν1/v3 frequency ratio of tetrahedral oxoanions of the transition metals with some basic properties of the anions. It is now demonstrated that these rules are also valid for oxoanions of the main group elements of the periodic system. Applying these and other relations it was possible to predict the value of the symmetric stretching frequency ν1(A1) of xenon tetroxide. Some vibrational properties of XeO4 (force constants, mean amplitudes of vibration, the Coriolis coupling constant and the bond order) are also calculated and compared with those of related species.

A NEW MUSTARD OIL GLUCOSIDE SYNTHESIS: THE SYNTHESIS OF GLUCOTROPAEOLIN

1963 ◽  
Vol 41 (11) ◽  
pp. 2836-2838 ◽  
Author(s):  
M. H. Benn
Keyword(s):  
Double Bond ◽  
Mustard Oil ◽  
Nitrile Oxides ◽  
New Synthesis ◽  
Nitrogen Double Bond

A new synthesis of mustard oil glucosides is described, illustrated by the synthesis of glucotropaeolin. This synthesis, based on the reaction of thiols with nitrile oxides, leads to a conclusion concerning the stereochemistry about the carbon–nitrogen double bond in the mustard oil glucosides.

Concerning a relationship between long-range ring proton – methyl proton coupling constants and mobile bond order

1968 ◽  
Vol 46 (4) ◽  
pp. 654-656 ◽  
Author(s):  
D. J. Blears ◽  
S. S. Danyluk ◽  
T. Schaefer
Keyword(s):  
Linear Relationship ◽  
Long Range ◽  
Bond Order ◽  
Coupling Constants ◽  
Methyl Proton ◽  
Methyl Group ◽  
Potential Barriers ◽  
Proton Coupling ◽  
Induced Changes ◽  
Excitation Parameters

Long-range proton – methyl proton coupling constants in propene, mesitylene, 9-methylphenanthrene, and acenaphthene appear to be linearly related to the square of the mobile bond order between the carbon atoms bonded to the methyl group and the proton. However, substituent-induced changes in the charge on and hybridization state of the carbon atoms, in excitation parameters and in potential barriers to rotation of the methyl group, may also affect the coupling. Such changes must be considered in the application of a possible linear relationship.

Visible-light promoted oxidative cyclization of cinnamic acid derivatives using xanthone as the photocatalyst

2021 ◽  
Author(s):  
Bin Zhao ◽  
Bo Xu
Keyword(s):  
Double Bond ◽  
Visible Light ◽  
Cinnamic Acid ◽  
Oxidative Cyclization ◽  
Coumarin Derivatives ◽  
Cinnamic Acids ◽  
Cinnamic Acid Derivatives ◽  
Double Bond Isomerization ◽  
Photocatalytic Synthesis

We have developed an efficient photocatalytic synthesis of coumarin derivatives via a tandem double bond isomerization/oxidative cyclization of cinnamic acids.

Quantifying individual (anti)bonding molecular orbitals’ contributions to chemical bonding

2019 ◽  
Vol 21 (37) ◽  
pp. 20988-20998 ◽  
Author(s):  
Jurgens H. de Lange ◽  
Daniël M. E. van Niekerk ◽  
Ignacy Cukrowski
Keyword(s):  
Chemical Bonding ◽  
Bond Order ◽  
Molecular Orbitals ◽  
Electron Delocalization ◽  
Bond Interaction

Quantifying contributions to any kind of bond/interaction and diatomic electron delocalization (bond order) made by individual (non)bonding molecular orbitals.

Nuclear magnetic resonance studies of the solution chemistry of metal complexes. XIV. The aqueous chemistry of trimethyllead(IV) and its carboxylic acid complexes

1977 ◽  
Vol 55 (18) ◽  
pp. 3255-3260 ◽  
Author(s):  
T. L. Sayer ◽  
S. Backs ◽  
C. A. Evans ◽  
E. K. Millar ◽  
D. L. Rabenstein
Keyword(s):  
Carboxylic Acid ◽  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Ph Dependence ◽  
Equilibrium Constants ◽  
Formation Constants ◽  
Solution Chemistry ◽  
Resonance Spectroscopy ◽  
Coupling Constant ◽  
Proton Coupling

The aqueous solution chemistry of the trimethyllead(IV) species and the trimethyllead(IV) complexes of six carboxylic acids of pKa values ranging from 2.75 to 4.95 has been investigated by proton magnetic resonance spectroscopy. Equilibrium constants for the reaction of (CH3)3Pb+ with hydroxide ion to form (CH3)3PbOH and ((CH3)3Pb)2OH+, and the formation constants of the carboxylic acid complexes were determined from the pH dependence of the chemical shift of the methyl protons of trimethyllead. The formation constants of the complexes increase as the pKa of the ligand increases. The lead-207-proton coupling constant was found to be insensitive to complexation.

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