Preferential solvational effects on the Cr(VI) oxidation of benzylamines in benzene/2‐methylpropan‐2‐ol mixtures

Thirumoorthi, A.; Bhuvaneshwari, D. S.; Elango, K. P.

doi:10.1002/kin.20464

Cited by 9 publications

(4 citation statements)

References 22 publications

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“…V-shape correlations obtained with Hammett constants are not uncommon, there are many reports of V-or U-shaped curves linking Hammett constant with other physical parameters, including kinetic constants and degree of substitution. [38][39][40][41] The Hammett constant is a value composing of a mixture of electronic effects including polar and resonance effects. 42 Since polar effects which is incorporated in the Hammett constant represents a similar effects as electronegativity of the Gordyscale group electronegativity, it is proposed that the V-shape presumably comes from the resonance effect incorporated in the Hammett constant.…”

Section: Research Articlementioning

confidence: 99%

Electronic effects of group fragments on the XPS of Fe 2p and 3p photoelectron lines of ferrocenyl-containing chalcones

Erasmus

2017

S.Afr.j.chem.

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A series of ferrocenyl-containing chalcones, Fc-CO-CH=CH-C 6 H 4 R, with the R-group on the para-position on the phenyl ring and R = OCH 3 (1), CH 3 (2), C 6 H 5 (3), tBu (4), H (5), Br (6) and CF 3 (7) were subjected to an X-ray photoelectron spectroscopy (XPS) study. The linear relationships obtained between the Gordy-scale group electronegativity of molecular fragment R, ÷ R , and the maximum binding energies of the Fe 2p 3/2 and the Fe 3p 3/2 photoelectron lines, confirmed communication between the iron atom of the ferrocene moiety and the molecular fragments, R, of 1-7. These relationships illustrated that the influence of the electronic properties of the molecular fragments are more pronounced in the Fe 3p photoelectron lines than in the Fe 2p photoelectron lines.

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Section: Research Articlementioning

confidence: 99%

Electronic effects of group fragments on the XPS of Fe 2p and 3p photoelectron lines of ferrocenyl-containing chalcones

Erasmus

2017

S.Afr.j.chem.

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“…In general, the non‐linear Hammett correlation is diagnostic of a change in the reaction mechanism or free radical mechanism or a change in the rate determining step with change in the nature of substituents. The involvement of free radical like transition state in the oxidation of alcohols by ruthenate and perchlorate ions, the change in the relative importance of bond formation and bond fission in the Cr(VI) oxidation of benzylamines and competition between the rates of complex formation and its decomposition in the oxidation of benzaldehydes by quinolinium chlorochromate have been given as explanation for the observed V‐shaped Hammett plots. V‐shaped Hammett plots observed in manganese(V) oxocorrolazine and manganese(V) (imido)(corrole) complexes towards organic sulfur compounds were rationalized by change in mechanism from electrophilic to nucleophilic attack of complexes.…”

Section: Resultsmentioning

confidence: 99%

A paradigm shift in rate determining step from single electron transfer between phenylsulfinylacetic acids and iron(III) polypyridyl complexes to nucleophilic attack of water to the produced sulfoxide radical cation: a non‐linear Hammett

Subramaniam¹,

Rose

Rathinakumari

2016

J of Physical Organic Chem

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Mechanism of oxidative decarboxylation of phenylsulfinylacetic acids (PSAAs) by iron(III) polypyridyl complexes in aqueous acetonitrile medium has been investigated spectrophotometrically. 3+ is rationalized on the basis of coordination of a water molecule at the carbon atom adjacent to the ring nitrogen of the metal polypyridyl complexes by nucleophilic attack at higher concentrations. Electron-withdrawing and electron-releasing substituents in PSAA facilitate the reaction and Hammett correlation gives an upward 'V' shaped curve. The apparent upward curvature is rationalized based on the change in the rate determining step from electron transfer to nucleophilic attack, by changing the substituents from electron-releasing to electron-withdrawing groups. Electron-releasing substituents in PSAA accelerate the electron transfer from PSAA to the complex and also stabilize the intermediate through resonance interaction leading to negative reaction constants (ρ). Conversely, electron-withdrawing groups, while retarding the electron transfer exert an accelerating effect on the nucleophilic attack of H 2 O which leading to low magnitude of ρ + compared to high ρ À values of electron-releasing groups. Marcus theory is applied, and a fair agreement is seen with the experimental values.

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“…In the oxidation of alcohols by ruthenate and perruthenate ions [84] the appearance of concave upward Hammett plot was explained by the involvement of free radical like transition state. In the Cr(VI) oxidation of benzylamines [85] the observed Ushaped Hammett plot was indicated by a change in the relative importance of bond formation and bond fission in the transition state. Because of the competition between the rate of complex formation by electron-releasing groups and its rate of decomposition by electron-withdrawing groups, V-shaped Hammett plots are seen in the oxidation of benzaldehydes by quinolinium chlorochromate [76].…”

Section: Discussionmentioning

confidence: 99%

Electrophilic and nucleophilic pathways in ligand oxide mediated reactions of phenylsulfinylacetic acids with oxo(salen)chromium(V) complexes

Subramaniam¹,

Devi

Anbarasan³

2016

Polyhedron

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a b s t r a c tThe mechanism of oxidative decarboxylation of phenylsulfinylacetic acids (PSAA) by oxo(salen)Cr(V) + ion in the presence of ligand oxides has been studied spectrophotometrically in acetonitrile medium. Addition of ligand oxides (LO) causes a red shift in the k max values of oxo(salen) complexes and an increase in absorbance with the concentration of LO along with a clear isobestic point. The reaction shows first-order dependence on oxo(salen)-chromium(V) + ion and fractional-order dependence on PSAA and ligand oxide. Michaelis-Menten kinetics without kinetic saturation was observed for the reaction. The order of reactivity among the ligand oxides is picoline N-oxide > pyridine N-oxide > triphenylphosphine oxide. The low catalytic activity of TPPO was rationalized. Both electron-withdrawing and electrondonating substituents in the phenyl ring of PSAA facilitate the reaction rate. The Hammett plots are non-linear upward type with negative q value for electron-donating substituents, (q À = À0.740 to À4.10) and positive q value for electron-withdrawing substituents (q + = +0.057 to +0.886). Non-linear Hammett plot is explained by two possible mechanistic scenarios, electrophilic and nucleophilic attack of oxo(salen)chromium(V) + -LO adduct on PSAA as the substituent in PSAA is changed from electrondonating to electron-withdrawing. The linearity in the log k vs. E ox plot confirms single-electron transfer (SET) mechanism for PSAAs with electron-donating substituents.

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Preferential solvational effects on the Cr(VI) oxidation of benzylamines in benzene/2‐methylpropan‐2‐ol mixtures

Cited by 9 publications

References 22 publications

Electronic effects of group fragments on the XPS of Fe 2p and 3p photoelectron lines of ferrocenyl-containing chalcones

Electronic effects of group fragments on the XPS of Fe 2p and 3p photoelectron lines of ferrocenyl-containing chalcones

A paradigm shift in rate determining step from single electron transfer between phenylsulfinylacetic acids and iron(III) polypyridyl complexes to nucleophilic attack of water to the produced sulfoxide radical cation: a non‐linear Hammett

Electrophilic and nucleophilic pathways in ligand oxide mediated reactions of phenylsulfinylacetic acids with oxo(salen)chromium(V) complexes

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