scholarly journals Tuning the electronic effects of aromatic phosphorus heterocycles: an unprecedented phosphinine with significant P(π)-donor properties

2014 ◽  
Vol 50 (64) ◽  
pp. 8842-8844 ◽  
Author(s):  
Antonia Loibl ◽  
Iris de Krom ◽  
Evgeny A. Pidko ◽  
Manuela Weber ◽  
Jelena Wiecko ◽  
...  
Keyword(s):  
Substituent Effects ◽  
Electronic Effects ◽  
Phosphorus Heterocycles ◽  
First Time

Substituent effects in phosphinine chemistry have been studied systematically and for the first time considerable π-donor properties of the aromatic phosphorus heterocycles have been revealed.

scholarly journals Substituent Effects on EI-MS Fragmentation Patterns of 5-Allyloxy-1-aryl-tetrazoles and 4-Allyl-1-aryl-tetrazole-5-ones; Correlation with UV-Induced Fragmentation Channels

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3282
Author(s):  
Alina Secrieru ◽  
Rabah Oumeddour ◽  
Maria L. S. Cristiano
Keyword(s):  
Theoretical Calculations ◽  
Substituent Effects ◽  
Radical Cations ◽  
Electronic Effects ◽  
Diverse Range ◽  
The Matrix ◽  
Electron Impact Mass ◽  
Fragmentation Patterns ◽  
Tetrazole Derivatives ◽  
Impact Mass

1,4- and 1,5-disubstituted tetrazoles possess enriched structures and versatile chemistry, representing a challenge for chemists. In the present work, we unravel the fragmentation patterns of a chemically diverse range of 5-allyloxy-1-aryl-tetrazoles and 4-allyl-1-aryl-tetrazolole-5-ones when subjected to electron impact mass spectrometry (EI-MS) and investigate the correlation with the UV-induced fragmentation channels of the matrix-isolated tetrazole derivatives. Our results indicate that the fragmentation pathways of the selected tetrazoles in EI-MS are highly influenced by the electronic effects induced by substitution. Multiple pathways can be envisaged to explain the mechanisms of fragmentation, frequently awarding common final species, namely arylisocyanate, arylazide, arylnitrene, isocyanic acid and hydrogen azide radical cations, as well as allyl/aryl cations. The identified fragments are consistent with those found in previous investigations concerning the photochemical stability of the same class of molecules. This parallelism showcases a similarity in the behaviour of tetrazoles under EI-MS and UV-irradiation in the inert environment of cryogenic matrices of noble gases, providing efficient tools for reactivity predictions, whether for analytical ends or more in-depth studies. Theoretical calculations provide complementary information to articulate predictions of resulting products.

scholarly journals Effects of substituents on the 1H-NMR chemical shifts of 3-methylene-2-substituted-1, 4-pentadienes

2003 ◽  
Vol 68 (7) ◽  
pp. 525-534 ◽  
Author(s):  
Natasa Valentic ◽  
Gordana Uscumlic
Keyword(s):  
Chemical Shifts ◽  
Substituent Effects ◽  
Electronic Effects ◽  
Resonance Effects ◽  
Charge Densities ◽  
Linear Free Energy ◽  
Energy Relationships ◽  
Consistent Picture ◽  
Vinyl Group ◽  
Proton Chemical Shifts

The principle of linear free energy relationships was applied to the 1H chemical shifts of the ?-vinyl proton atoms of 3-methylene-2-substituted-1,4-pentadienes. The correlations of the proton chemical shifts with Swain and Lupton substituent parameters provide a mutually consistent picture of the electronic effects in these compounds. The overall pattern of proton chemical shifts can be largely accounted for by a model of substituent effects based on field, resonance and ? polarization effects. Owing to the particular geometric arrangement of the vinyl group in 3-methylene-2-substituted-1,4-pentadienes, the ?-vinyl protons HB and HC have different sensitivities to polar and resonance effects. The different sensitivities of the 1H chemical shifts to resonance effects reveals some effects not predicted by the model outlined above. Evidence is presented that demonstrates that both the 1H and 13C chemical shifts for these compounds reflect their ground-state charge densities.

scholarly journals Substituenteneinflüsse auf die 13C–NMR-chemischen Verschiebungen cis- und trans-konfigurierter Trimethincyanine / Substituent Effects on the 13C NMR Chemical Shifts of Trimethincyanines with cis and trans Configuration

1976 ◽  
Vol 31 (12) ◽  
pp. 1641-1645 ◽  
Author(s):  
Walter Grahn
Keyword(s):  
13C Nmr ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Electron Systems ◽  
Coupling Constant ◽  
Electronic Effects ◽  
Nmr Chemical Shifts ◽  
Monosubstituted Benzenes ◽  
Cis And Trans ◽  
C Nmr

The 13C NMR chemical shifts of fifteen 6 substituted 2,3-dihydro-1,4-diazepinium salts (cis trimethincyanines) (1) and twelve 2 substituted bis(dimethylamino)trimethinium salts (trans trimethincyanines) (2) have been determined. A comparison of the substituentinduced shifts (13C SCS) of 1 and 2 allows no distinction between steric and electronic effects. In the three 6 п-electron systems 1, 2 and monosubstituted benzenes the 13C SCS are similar for the substituent bearing carbon atoms. A surprisingly large 4JFCCNC coupling constant has been observed.

scholarly journals Substituent effects on the spectral behavior and synthesis of mercury 1,5-diarylthiocarbazonates

1981 ◽  
Vol 59 (4) ◽  
pp. 679-687 ◽  
Author(s):  
Nori Y. C. Chu ◽  
Steven A. Goldstein ◽  
Philip M. Keehn
Keyword(s):  
Bathochromic Shift ◽  
Substituent Effects ◽  
Spectral Shift ◽  
Spectral Studies ◽  
Hypsochromic Shift ◽  
Electronic Effects ◽  
Activated State ◽  
Mercury Complexes ◽  
Inductive Effects ◽  
Methoxy Substituent

Symmetric and unsymmetric substituted 1,5-diarylthiocarbazones, and their mono- and bismercury complexes, were synthesized for spectral analysis. The first singlet–singlet transition of the mercury complexes was determined and the spectral shift produced by trifluoromethyl substitution was compared with that caused by different substituents in similar complexes. The large magnitude of the hypsochromic shift produced by the trifluoromethyl substituent can be explained by concerted steric and inductive effects, while the smaller bathochromic shift induced by the methoxy substituent is a result of opposing steric and electronic effects. In the trifluoromethyl substitution, a hypsochromic shift caused by steric influences was found to be 500 cm−1 in the photochromic unactivated state, and 250 cm−1 in the photochromic activated state. A similar shift caused by inductive influences was found to be 750 cm−1 in the photochromic unactivated state, and 600 cm−1 in the photochromic activated state. The smaller spectral shift observed in the photochromic activated state is consistent with the elucidated structure of the unsymmetric 1,5-diarylthiocarbazone, 6d, which was shown that the trifluoromethyl substitution was on the phenylazo portion of the molecule by chemical and spectral studies.

Metal complexes as ligands. X. Investigation of valency and substituent effects in binuclear complexes derived from tetradentate salicylaldimines

1972 ◽  
Vol 25 (1) ◽  
pp. 45 ◽  
Author(s):  
S Kokot ◽  
CM Harris ◽  
E Sinn
Keyword(s):  
Metal Complexes ◽  
Substituent Effects ◽  
Nickel Complexes ◽  
Magnetic Interactions ◽  
Binuclear Complexes ◽  
Electronic Effects ◽  
Metal Chlorides ◽  
Limited Sampling ◽  
Phenyl Rings ◽  
The Difference

A series of binuclear complexes has been formed by using planar copper(11) complexes (CUTSB) of tetradentate Schiff bases (TSB) as ligands to coordinate with metal chlorides. The binuclear complexes, (CuTSB)MCln (M = Cu11, Fe111, Mn11; n. = 2, 3), all exhibit pairwise antiferromagnetic interactions. The nickel complexes (NitsB)Mcln (M = FeIII, MnII) can be formed similarly, but the nickel atoms are diamagnetic so that no significant magnetic interactions are expected. The effect of 5-Cl, 5-Br, and 5,6-benzo substituents in the phenyl rings of the TSB groups on the strength of the antiferromagnetic interactions was examined in the complexes (CUTSB)CuCl2. Although the presence of a substituent usually increases the strength of the interaction, this trend is not systematic and there is no reason to attribute it to electronic effects of ring substituents. In (CUTSB)MCln, the main difference between the complexes with M = Fe111 and M = Mn11 is the difference in the valencies of the two d5 metals. In our limited sampling (one complex of each type), the interaction is stronger between iron(111) and copper(11) than between the manganese(11) and copper(11). These complexes form as hydrates, and since iron(111) and manganese(11) prefer octahedral environments, it is probable that one and two molecules of water respectively are coordinated to these metals. In the case where M = FeIII, N�ssbauer measurements indicate that this is so.

scholarly journals Carbonyl Addition Reactions: Factors Affecting the Hydrate–Hemiacetal and Hemiacetal–Acetal Equilibrium Constants

1975 ◽  
Vol 53 (6) ◽  
pp. 898-906 ◽  
Author(s):  
J. Peter Guthrie
Keyword(s):  
Aqueous Solution ◽  
Carbonyl Compounds ◽  
Equilibrium Constants ◽  
Substituent Effects ◽  
Steric Effects ◽  
Addition Reactions ◽  
Free Energies ◽  
Electronic Effects ◽  
Factors Affecting ◽  
Analogous Formula

Equilibrium constants for hydrate–hemiacetal interconversion in aqueous solution at 25° have been measured for four fluorinated carbonyl compounds: compound, alcohol, K4 (M−1): CF3CHO, C2H5OH, 2.3; CF3COCH3, CH3OH, 1.0; CF3COPh, CH3OH, 3.5; CF3COCF3, CH3OH, 0.14. These values, combined with values from the literature, permit an examination of substituent effects upon the equilibrium constant for[Formula: see text]The free energy change for this process, corrected for symmetry and steric effects, follows the equation[Formula: see text]Thus electronic effects upon this equilibrium are generally small and in fact are often smaller than steric effects.This analysis permits and justifies the calculation of free energies of formation of [Formula: see text] compounds from the (more generally measurable) free energies of formation of the analogous [Formula: see text] compounds.

Electronic Effects on the Bergman Cyclisation of Enediynes. A Review

2004 ◽  
Vol 69 (5) ◽  
pp. 945-965 ◽  
Author(s):  
Michael Klein ◽  
Thomas Walenzyk ◽  
Burkhard König
Keyword(s):  
Experimental Data ◽  
Metal Ion ◽  
Substituent Effects ◽  
Terminal Alkyne ◽  
Electronic Effects ◽  
Ring Strain ◽  
Clear Cut ◽  
Theoretical Predictions ◽  
Metal Ion Chelation

The thermal cyclisation of enediynes to benzene-1,4-diyl diradicals (Bergman cyclisation) is affected by geometrical and electronic conditions. While the effect of ring strain or conformational constrains on the cyclisation temperature has been investigated in detail, electronic contributions have been less studied. Often geometrical and electronic contributions cannot be clearly distinguished. In most cases metal ion chelation does involve both. In this review we have summarised clear-cut observations of electronic substituents effects on the thermal enediyne reactivity. The effects of substituents in the vinylic and terminal alkyne position, the influence of benzo-fusion and hetarene fusion, as well as the changes induced by heteroatoms in the enediyne skeleton, are within the scope of this review. With the exception of more complex heterocyclic hetarene-fused enediynes the experimental data of electronic substituent effects on the thermal Bergman cyclisation of enediynes follow theoretical predictions. A review with 57 references.

Substituenteneinflüsse auf Synthese und Eigenschaften von Hexakis[phosphanaurio(I)]methanium(2+)bis(tetrafluoroboraten) / Substituent Effects in Synthesis and Properties of Hexakis[phosphineaurio(I)]methanium(2 +) Bis(tetrafluoroborates)

1992 ◽  
Vol 47 (12) ◽  
pp. 1725-1735 ◽  
Author(s):  
Hubert Schmidbaur ◽  
Benno Brachthäuser ◽  
Siegfried Gamper ◽  
Annette Schier ◽  
Oliver Steigelmann
Keyword(s):  
Nmr Spectra ◽  
Room Temperature ◽  
Substituent Effects ◽  
Reaction Times ◽  
Phosphine Ligands ◽  
Electronic Effects ◽  
X Ray ◽  
Magnetic Resonance Parameters ◽  
Interstitial Carbon Atom ◽  
C Nmr

Polyaurated carbon complexes of the type [(L–Au)6C]2+ with functionalized phosphine ligands have been prepared by the reaction of the phosphinegold(I) chlorides R(Ph)2PAuCl (R = p-C6H4-Cl 2a,p-C6H4-Br 2b,p-C6H4-CH3 2c,p-C6H4-OCH3 2d,p-C6H4-COOH 2e, p-C6H4–N(CH3)2 2f), R2(Ph)PAuCl (R = p-C6H4-N(CH3)2 2g) and R3PAuCl (R = p-C6H4-N(CH3)2 2h) with tetrakis(dimethoxyboryl)methane in HMPT at room temperature. Clearly depending on the different inductive and mesomeric effects, the preparation of the clusters with substituents like –CH3 3c, –OCH3 3d and –N(CH3)2 3f needs shorter reaction times and the products show better solubility in organic solvents than those with functional groups like –Cl 3a, –Br 3b and –COOH 3e. The 31P magnetic resonance parameters are correlated with electronic effects of the substituents, but the chemical shift of the interstitial carbon atom in the 13C-NMR spectra is largely independent of the coordinating ligands. For the phosphinegold(I) chlorides 2f–h X-ray structure analyses have been performed.

scholarly journals Substituent Effects on Transient, Carbodiimide-Fueled Geometry Changes in Diphenic Acids

2021 ◽  
Author(s):  
Isuru Jayalath ◽  
Madelyn Gerken ◽  
Georgia Mantel ◽  
Scott Hartley
Keyword(s):  
Conformational Changes ◽  
Steric Hindrance ◽  
Substituent Effects ◽  
Biological Behavior ◽  
Chemical System ◽  
Structure Property ◽  
Electronic Effects ◽  
Cell Functions ◽  
Diphenic Acid ◽  
Simple Chemical

Nucleotide-fueled conformational changes in motor proteins are key to many important cell functions. Inspired by this biological behavior, we report a simple chemical system that exhibits carbodiimide-fueled geometry changes. Bridging via transient anhydride formation leads to a significant reduction of the twist about the biaryl bond of substituted diphenic acids, giving a simple molecular clamp. The kinetics are well-described by a simple mechanism, allowing structure–property effects to be determined. The kinetic parameters can be used to derive important characteristics of the system such as the efficiencies (anhydride yields), maximum anhydride concentrations, and overall lifetimes. Transient diphenic anhydrides tolerate steric hindrance ortho to the biaryl bond but are significantly affected by electronic effects, with electron-deficient substituents giving lower yields, peak conversions, and lifetimes. The results provide useful guidelines for the design of functional systems incorporating diphenic acid units

Reactivity of phenylsulfonyl isothiocyanates and transfer of substituent effects through the sulfonyl group

1991 ◽  
Vol 56 (12) ◽  
pp. 2872-2878 ◽  
Author(s):  
Gejza Suchár ◽  
Oľga Hritzová ◽  
Ján Imrich ◽  
Antónia Jasovská
Keyword(s):  
Spectroscopic Method ◽  
Substituent Effects ◽  
Stopped Flow ◽  
Nucleophilic Additions ◽  
Reaction Centre ◽  
Electronic Effects ◽  
Sulfonyl Group ◽  
Electronic Effects Of Substituents ◽  
Kinetics Of

Kinetics of nucleophilic additions of butylamine to phenylsulfonyl isothiocyanate was investigated by the stopped-flow UV spectroscopic method and the transfer of electronic effects of substituents on the reaction centre through the SO2 group was examined. The structure and the polar character of SO2NCS, NCS and SO2 groups is discussed.

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