ChemInform Abstract: DETERMINATION OF POSITIONAL WEIGHTING FACTORS FOR THE SWAIN AND LUPTON SUBSTITUENT CONSTANTS F AND R

1976 ◽  
Vol 7 (15) ◽  
pp. no-no
Author(s):  
S. G. WILLIAMS ◽  
F. E. NORRINGTON
Keyword(s):  
Weighting Factors ◽  
Substituent Constants

Polarographic and spectrophotometric behaviour of some N-p-phenyl substituted benzamidines

1991 ◽  
Vol 56 (12) ◽  
pp. 2791-2799 ◽  
Author(s):  
Juan A. Squella ◽  
Luis J. Nuñez-Vergara ◽  
Hernan Rodríguez ◽  
Amelia Márquez ◽  
Jose M. Rodríguez-Mellado ◽  
...  
Keyword(s):  
Spectrophotometric Study ◽  
Absorption Bands ◽  
Electrochemical Parameters ◽  
Wide Ph Range ◽  
Group A ◽  
Substituent Constants ◽  
Ph Range ◽  
The Waves

Five N-p-phenyl substituted benzamidines were studied by DC and DP polarography in a wide pH range. Coulometric results show that the overall processes are four-electron reductions. Logarithmic analysis of the waves indicate that the process are irreversible. The influence of the pH on the polarographic parameters was also studied. A UV spectrophotometric study was performed in the pH range 2-13. In basic media some variations in the absorption bands were observed due to the dissociation of the amidine group. A determination of the pK values was made by deconvolution of the spectra. Correlations of both the electrochemical parameters and spectrophotometric pK values with the Hammett substituent constants were obtained.

CuAAC and RuAAC with Alkyne-functionalised Dihydroazulene Photoswitches and Determination of Hammett σ-Constants for Triazoles

2014 ◽  
Vol 67 (3) ◽  
pp. 531 ◽  
Author(s):  
Henriette Lissau ◽  
Søren Lindbæk Broman ◽  
Martyn Jevric ◽  
Anders Ø. Madsen ◽  
Mogens Brøndsted Nielsen
Keyword(s):  
Molecular Electronics ◽  
Ring Closure ◽  
Reference Systems ◽  
Rigid Structure ◽  
Useful Components ◽  
Substituent Constants ◽  
Hammett Σ Constants

Dihydroazulene (DHA)–vinylheptafulvene (VHF) photoswitches have attracted attention as potentially useful components in molecular electronics. The π-conjugated dihydroazulene system is a rigid structure and can be strategically functionalised to place handles for further elaboration. Here we show that alkyne-functionalised dihydroazulenes can be subjected to copper and ruthenium catalysed azide–alkyne cycloadditions (CuAAC and RuAAC) with tolylazide, furnishing 1,4- and 1,5-disubstituted triazoles. The rates of ring-closure of the corresponding vinylheptafulvenes were compared with those of reference systems, which allowed determination of Hammett substituent constants (meta and para) for N-tolyl-substituted 1,2,3-triazoles.

SU-E-T-844: Efficient IMRT Optimization by Appropriate Determination of Weighting Factors Using a New L1-Solver: TFOCS

2011 ◽  
Vol 38 (6Part24) ◽  
pp. 3685-3685
Author(s):  
H Kim ◽  
L Zhu ◽  
T Kim ◽  
L Xing
Keyword(s):  
Weighting Factors

Analysis of substituent and solvent effects on dissociation of N-phenylbenzenesulphonamides

1987 ◽  
Vol 52 (12) ◽  
pp. 2900-2908 ◽  
Author(s):  
Miroslav Ludwig ◽  
Oldřich Pytela ◽  
Helena Javůrková ◽  
Miroslav Večeřa
Keyword(s):  
Factor Analysis ◽  
Hydrogen Bonds ◽  
Model Equation ◽  
Substituent Effects ◽  
Regression Function ◽  
Reaction Centre ◽  
Solvent Dependence ◽  
Substituent Constants ◽  
Reaction Constants

The potentiometric titration in water, methanol, dimethyl sulphoxide, dimethylformamide, and acetonitrile has been used for determination of pK values of 13 N-arylbenzenesulphonamides. The validity of the Hammett and Yukawa-Tsuno models using several sets of substituent constants has been evaluated by the test to check adequacy of the regression function and by the factor analysis. It has been found that the substituent effects in solvents must be interpreted with regard to the experimental method used, solvent, set of the substituent constants, as well as the model equation ETR. The dependence of the Hammett reaction constants on the solvent has been analyzed and reveals a preferred stabilization of the conjugated base through hydrogen bonds. Direct conjugation of the reaction centre with the substituent and with different extent of the solvent-dependence with the 4-CN and 4-NO2 derivatives have been observed.

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