Experimental and theoretical investigation of the unusual substituent effect of the vinyl group

1980 ◽  
Vol 58 (4) ◽  
pp. 412-417 ◽  
Author(s):  
W. F. Reynolds ◽  
T. A. Modro ◽  
P. G. Mezey ◽  
E. Skorupowa ◽  
A. Maron
Keyword(s):  
Free Energy ◽  
Substituent Effect ◽  
Phenyl Ring ◽  
Linear Free Energy Relationship ◽  
Ion Transfer ◽  
Hydride Ion ◽  
Linear Free Energy ◽  
Substituent Constants ◽  
Vinyl Group ◽  
Hydride Ion Transfer

σ+ Substituent constants for the ortho- and para-vinyl group have been determined by the application of the linear free-energy relationship to the nitration of the β-substituted styrene derivatives.Energy changes (relative to benzene system) for the proton and hydride ion transfer to individual positions in the styrene molecule have been calculated. Both approaches indicate that the vinyl group is capable of stabilizing both positively and negatively charged transition states. The interactions of the vinyl group with other substituents in the phenyl ring are also determined. Again, stabilizing effects with respect to both π-donor and π-acceptor substituents have been demonstrated for the vinyl group.

Half-wave potentials of quinone methides in dimethylformamide: Substituent effects

1981 ◽  
Vol 46 (4) ◽  
pp. 861-872 ◽  
Author(s):  
Josef Krupička ◽  
Bohumír Koutek ◽  
Lubomír Musil ◽  
Libuše Pavlíčková ◽  
Milan Souček
Keyword(s):  
Free Energy ◽  
Substituent Effects ◽  
Linear Free Energy Relationship ◽  
Quinone Methides ◽  
Linear Free Energy ◽  
Diffusion Controlled ◽  
Half Wave ◽  
Substituent Constants ◽  
Series Type ◽  
Spin Densities

Half-wave potentials of two series of quinone methides A have been determined in 0.1M tetrabutylammonium perchlorate in dimethylformamide. the first series (type I; 14 compounds) contained fuchsones substituted in positions 2 and 2,6 of the quinonoid ring, the second series (type II and III; 17 compounds) consisted of 2,6-ditert-butylquinone methides, with substituents at the exocyclic C(7) carbon atom. Properties of the first polarographic wave proved that in both series the reaction is one-electron, reversible, diffusion-controlled process. Linear free energy relationship was found between E1/2 and dual substituent constants σI and σR. Statistical analysis of linear free energy relationship for 2- and 2,6-substituted derivatives proved absence of steric factor in transmission of electronic substituent effect. The experimental results were interpreted on the basis of LUMO energies and spin densities, calculated by the HMO method.

scholarly journals Electrofugality of Some Ferrocenylphenylmethyl Cations

2019 ◽  
Vol 92 (2) ◽  
pp. 307-313
Author(s):  
Sandra Jurić ◽  
Marijan Marijan ◽  
Olga Kronja
Keyword(s):  
Free Energy ◽  
Phenyl Ring ◽  
Positive Charge ◽  
Narrow Range ◽  
Phenyl Group ◽  
Linear Free Energy Relationship ◽  
Methyl Ethyl ◽  
Linear Free Energy ◽  
Ferrocenyl Group ◽  
Complete Set

The electrofugality scale has been extended with new substituted ferrocenylphenylmethyl cations 1-4. Ef values were determined by applying the linear free energy relationship (LFER): log k = sf (Ef + Nf). Due to ability of the ferrocene moiety to efficiently stabilize the positive charge, ferrocenylphenylmethyl cations constitute a group of very powerful electrofuges (Ef > 1). Impact of the phenyl group in ferrocenylphenylmethyl derivatives on stabilization of the positive charge is considerably leveled by the ferrocenyl group, so the rate effect of the alkyl substituents (methyl, ethyl and tert-butyl) on the phenyl ring is suppressed, causing narrow range of Ef parameters. Lack of breakdown of Hammett-Brown plot if the rates for the complete set of substrates 1–5 have been correlated, indicates that the ferrocenyl group in α-position diminishes the stabilizing effects of electron-donating substituents as well.

Synthesis and characterization of a series of 1-methyl-4-[2-aryl-1-diazenyl]piperazines and a series of ethyl 4-[2-aryl-1-diazenyl]-1-piperazinecarboxylates

2004 ◽  
Vol 82 (8) ◽  
pp. 1294-1303 ◽  
Author(s):  
Vanessa Renée Little ◽  
Keith Vaughan
Keyword(s):  
Free Energy ◽  
Chemical Shifts ◽  
Linear Free Energy Relationship ◽  
Piperazine Ring ◽  
Linear Free Energy ◽  
In Series ◽  
Methylene Groups ◽  
Diazonium Coupling ◽  
The Difference

1-Methylpiperazine was coupled with a series of diazonium salts to afford the 1-methyl-4-[2-aryl-1-diazenyl]piperazines (2), a new series of triazenes, which have been characterized by 1H and 13C NMR spectroscopy, IR spectroscopy, and elemental analysis. Assignment of the chemical shifts to specific protons and carbons in the piperazine ring was facilitated by comparison with the chemical shifts in the model compounds piperazine and 1-methylpiperazine and by a HETCOR experiment with the p-tolyl derivative (2i). A DEPT experiment with 1-methylpiperazine (6) was necessary to distinguish the methyl and methylene groups in 6, and a HETCOR spectrum of 6 enabled the correlation of proton and carbon chemical shifts. Line broadening of the signals from the ring methylene protons is attributed to restricted rotation around the N2-N3 bond of the triazene moiety in 2. The second series of triazenes, the ethyl 4-[2-phenyl-1-diazenyl]-1-piperazinecarboxylates (3), have been prepared by similar diazonium coupling to ethyl 1-piperazinecarboxylate and were similarly characterized. The chemical shifts of the piperazine ring protons are much closer together in series 3 than in series 2, resulting in distortion of the multiplets for these methylenes. It was noticed that the difference between these chemical shifts in 3 exhibited a linear free energy relationship with the Hammett substituent constants for the substituents in the aryl ring. Key words: triazene, piperazine, diazonium coupling, NMR, HETCOR, linear free energy relationship.

scholarly journals Kinetics and Mechanism of the Oxidation of Substituted Benzaldehydes by Oxo(salen)manganese(v) Complexes

1999 ◽  
Vol 23 (8) ◽  
pp. 480-481
Author(s):  
Varsha Bansal ◽  
Pradeep K. Sharma ◽  
Kalyan K. Banerji
Keyword(s):  
Hydrogen Atom ◽  
Hydrogen Atom Transfer ◽  
Kinetics And Mechanism ◽  
Atom Transfer ◽  
Ion Transfer ◽  
Hydride Ion ◽  
Substituted Benzaldehydes ◽  
Hydride Ion Transfer

The oxidation of benzaldehyde by oxo(salen)manganese(v) complexes proceeds via either a hydride-ion transfer or a hydrogen-atom transfer from the aldehyde to the manganese(v) complex.

Absorption Spectra of Substituted 2-Phenylindan-1,3-Dion-2-YL Radicals in Solution

1983 ◽  
Vol 38 (12) ◽  
pp. 1337-1341
Author(s):  
J. Zechner ◽  
N. Getoff ◽  
I. Timtcheva ◽  
F. Fratev ◽  
St. Minchef
Keyword(s):  
Free Energy ◽  
Absorption Spectra ◽  
Flash Photolysis ◽  
Bathochromic Shift ◽  
Substitution Effects ◽  
Linear Free Energy Relationship ◽  
Linear Free Energy

Abstract Flash photolysis of a series of 2-phenylindandione-1,3 derivatives substituted in the 4′ position results in both the formation of stable benzylidenephthalides and of phenylindan-1,3-dion-2-yl radicals. The u. v. absorption maxima of these radicals are dependent on the solvent and show a bathochromic shift upon substitution. These substitution effects were correlated by means of a linear free energy relationship. Attempts were made to draw conclusions concerning the changes in the gap of the states involved and their curvature due to substitution.

Correlation of Human and Animal Air-to-Blood Partition Coefficients With a Single Linear Free Energy Relationship Model

2008 ◽  
Vol 27 (9) ◽  
pp. 1130-1139 ◽  
Author(s):  
Laura M. Sprunger ◽  
Jennifer Gibbs ◽  
William E. Acree ◽  
Michael H. Abraham
Keyword(s):  
Free Energy ◽  
Partition Coefficients ◽  
Linear Free Energy Relationship ◽  
Linear Free Energy ◽  
Relationship Model
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