Solvolysis of isothiazole analogs of cumyl chloride. Determination of the Brown electrophilic substituent constants for isothiazole derivatives

1975 ◽  
Vol 40 (23) ◽  
pp. 3381-3383 ◽  
Author(s):  
Donald S. Noyce ◽  
Bonnie B. Sandel
Keyword(s):  
Chloride Determination ◽  
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.

Comparison of Laboratory Techniques for the Determination of Pesticide Residues in Milk

1963 ◽  
Vol 46 (2) ◽  
pp. 209-215
Author(s):  
J Lloyd Henderson
Keyword(s):  
Gas Chromatography ◽  
Electron Capture ◽  
Pesticide Residues ◽  
Colorimetric Method ◽  
Laboratory Techniques ◽  
Test Electron ◽  
Chloride Determination ◽  
Low Levels ◽  
Organic Chloride

Abstract Of the techniques available for specific pesticide residues, fly bioassay is non-specific and not very sensitive; total organic chloride determination also lacks specificity; the AOAC colorimetric method produces variable results, lacks sensitivity for low levels of residues, and does not cover the range of residues likely to be present in milk. Chromatographic tests are most satisfactory. Microcoulometric gas chromatography has many advantages but requires a skilled analyst. Electron-capture gas chromatography is promising but has not been fully developed. The Mills test, which combines column cleanup with identification by paper chromatography, is a rapid, practical screening test. In a collaborative comparison of the chromatographic procedures, microcoulometry tended to give higher results than the Mills test; electron-capture gave lower results than the other two methods. Details of all tests must be followed closely for good results.

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