Results 151 to 160 of about 12,998 (208)

Correlation between Hammett Substituent Constants and Directly Calculated π-Conjugation Strength

The Journal of Organic Chemistry, 2006
The results of an energy decomposition analysis of ortho-, meta-, and para-substituted benzylic cations and para-substituted benzylic anions H2C-C6H4Rq (R = H, F, CN, Me, OH, NH2, NO2, CHO, CO2H; q = +, -) are presented and discussed. The calculated values for the pi bonding between CH2(q) and C6H4R show for substituents which have pi orbitals a linear
Israel, Fernández, Gernot, Frenking
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Reaction of phenolic acids with Fenton-generated hydroxyl radicals: Hammett correlation

Desalination, 2010
Abstract Hydroxyl radicals generated by Fenton's reagent rapidly oxidize phenolic acids in aqueous solution. Analysis of second-order rate constants for correlations reveals quantitative structure–activity relationships (QSAR). The results were analysed so as to obtain the relation between the chemical structure of the substituted benzene ring and ...
José A. Peres, Joaquín R. Domínguez, Jesus Beltran-Heredia   +2 more
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Hammett correlations ‘beyond the molecule’ 1

Journal of the Chemical Society, Perkin Transactions 2, 1998
The crown ether dibenzo[24]crown-8 (DB24C8) is interpenetrated by a wide range of disubstituted dibenzylammonium cations to generate [2]pseudorotaxane complexes by virtue of, inter alia, hydrogen bonds. 1H NMR spectroscopic measurements indicate that the solution phase binding strengths of the pseudorotaxane complexes can be controlled accurately via ...
Peter R. Ashton, Matthew C. T. Fyfe, Sarah K. Hickingbottom, J. Fraser Stoddart, Andrew J. P. White, David J. Williams   +5 more
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NMR Hammett correlation. A laboratory experiment

Journal of Chemical Education, 1973
A simple NMR experiment to familiarize students with the concept and uses provided by the Hammett equation, as well as introduce them to the use of NMR apparatus, chemical shift tabulation, and the application of linear regression analysis.
Manuel Salmon, Adolfo Jimenez, Ignacio Salazar, Rainer Zawadzki   +3 more
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Hammett Correlations in the Photosensitized Oxidation of 4-Substituted Thioanisoles

The Journal of Organic Chemistry, 2004
Singlet oxygen is quenched by a series of 4-substituted thioanisoles (methoxy to nitro), with rate constant k(t) = 7 x 10(4) to 7 x 10(6) M(-)(1) s(-)(1), close to the value observed for the myoglobin-catalyzed sulfoxidation of the same sulfides. Correlations with sigma (rho = -1.97) and with E(ox) (slope -3.9 V(-)(1)) are evidence for an electrophilic
ALBINI, ANGELO, FAGNONI, MAURIZIO, Bonesi Sergio   +2 more
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Ultrafast Spectroscopy of Arylchlorodiazirines: Hammett Correlations of Excited State Lifetimes

Journal of the American Chemical Society, 2009
Experimental and computational studies suggest that 375 nm excitation of arylchlorodiazirines furnishes their S(1) excited states with lengthened C-N bonds, a positive charge at the para and diazirine carbon atoms, and a negative charge at the nitrogen atoms. These structures rationalize the observed solvent and substituent effects on the excited state
Yunlong, Zhang, Lei, Wang, Robert A, Moss, Matthew S, Platz   +3 more
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Substituent Correlations Characterized by Hammett Constants in the Spiropyran–Merocyanine Transition

The Journal of Physical Chemistry A, 2017
The modification of molecular properties by the use of substituents is a versatile route for molecular design. Here we show for the example of multiresponsive spiropyrans that substituent effects and their correlations can be accurately described by Hammett constants, which in turn can be obtained directly from density functional theory calculations ...
Oliver Brügner, Thomas Reichenbach, Michael Sommer, Michael Walter   +3 more
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The significance of hammett correlations in mass spectral decompositions

Organic Mass Spectrometry, 1970
AbstractAn unexpected correlation of ion intensities with sigma constants was observed for the loss of substituents from biphenyl molecular ions. The observation is more easily reconciled with an argument based upon energy distributions in molecular ions than on interpretation in terms of rates.
Maurice M. Bursey, Peter T. Kissinger
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Reactivity of an ambiphilic carbene - a nonlinear hammett correlation

Tetrahedron Letters, 1982
Abstract Methoxychlorocarbene behaves as an ambiphile in addition reactions with styrene derivatives.
Robert A. Moss, Wenjeng Guo, Karsten Krogh-Jespersen   +2 more
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Hammett Correlations of Electronic Absorption Spectral Parameters of Pyrimidines

Bulletin des Sociétés Chimiques Belges, 1993
AbstractThe wavenumbers of the long‐wavelength electronic absorption band maxima of substituted uracils give good linear correlations (r = 0.945 to 0.992) with the excited‐state Hammett substituent constants, σ*, in several solvents.
Cyril Párkányi, Christian Boniface, Jean‐Jacques Aaron, Mame Diabou Gaye   +3 more
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