Fluorescence quenching of tryptophan in aqueous solutions by pyruvate

1987 ◽  
Vol 47 (5) ◽  
pp. 1127-1131 ◽  
Author(s):  
G. A. Gachko ◽  
I. L. Zubko ◽  
V. K. Zybel't ◽  
L. N. Kivach ◽  
S. A. Maskevich ◽  
...  
Keyword(s):  
Fluorescence Quenching ◽  
Aqueous Solutions

Enhanced nucleophile selectivity in the photoaddition to styrene. Comparison with the thermal addition

1988 ◽  
Vol 66 (9) ◽  
pp. 2412-2421 ◽  
Author(s):  
Steven W. Anderson ◽  
Keith Yates
Keyword(s):  
Acetic Acid ◽  
Fluorescence Quenching ◽  
Aqueous Solutions ◽  
Irradiation Time ◽  
The Other ◽  
Ring Substituent ◽  
Thermal Addition ◽  
Carbenium Ion ◽  
Medium Acidity

The reactivity–selectivity properties of the sec-phenethyl carbenium ion and its analogues have been examined in binary-aqueous solutions of alcohols (ROH; R = Me, Et, CF3CH2, n-Bu, t-Bu, n-Pr, i-Pr), acetic acid, and in solutions containing external nucleophiles such as thiophenol, ethanethiol, acetate, and benzenesulfinate. Selectivity (S = k(Nuc)/k(H2O)) is observed to be a function of the nucleophile, the ring substituent, thermal or photochemical conditions, irradiation time, and medium acidity. In the case of styrene, the photochemically generated (usually 254 nm, 1 h) species exhibits greater selectivity (up to two orders of magnitude) than its thermal counterpart, generated (usually 80 °C, 2−4 d) in identical media, particularly in aqueous-rich solvent compositions. A rationale for these differences, supported by fluorescence quenching experiments, and the other effects upon selectivity will be discussed.

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