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@article{693983,
author = {Heger, Dominik and Klánová, Jana and Klán, Petr},
article_location = {USA},
article_number = {3},
keywords = {Photochemistry; ice; cresol red; spectroscopy},
language = {eng},
issn = {1089-5639},
journal = {Journal of Physical Chemistry B},
title = {Enhanced Protonation of Cresol Red in Acidic Aqueous Solutions Caused by Freezing},
volume = {110},
year = {2006}
}
TY - JOUR
ID - 693983
AU - Heger, Dominik - Klánová, Jana - Klán, Petr
PY - 2006
TI - Enhanced Protonation of Cresol Red in Acidic Aqueous Solutions Caused by Freezing
JF - Journal of Physical Chemistry B
VL - 110
IS - 3
SP - 1277-1287
EP - 1277-1287
PB - The American Chemical Society
SN - 10895639
KW - Photochemistry
KW - ice
KW - cresol red
KW - spectroscopy
N2 - The protonation degree of cresol red (CR) in frozen aqueous solutions at 253 or 77 K, containing various acids (HF, HCl, HNO3, H2SO4, and p-toluenesulfonic acid), sodium hydroxide, NaCl, or NH4Cl, was examined using UV/Vis absorption spectroscopy. CR, a weak organic diacid, has been selected as a model system to study the acid-base interactions at the grain boundaries of ice. The multivariate curve resolution alternating least-squares method was used to determine the number and abundances of chemical species responsible for the overlaying absorption visible spectra measured. The results showed that the extent of CR protonation, enhanced in the solid state by 2-4 orders of magnitude in contrast to the liquid solution, is principally connected to an increase in the local concentration of acids. It was found that this enhancement was not very sensitive to either the freezing rate or the type of acid used and that CR apparently established an acid-base equilibrium prior to solidification. In addition, the presence of inorganic salts, such as NaCl or NH4Cl, is reported to cause a more efficient deprotonation of CR in the former case and an enhanced protonation in the latter case, being well explained by the theory of Bronshteyn and Chernov. CR thus served as an acid-base indicator at the grain boundaries of ice samples. Structural changes in the CR molecule induced by lowering the temperature and a presence of the constraining ice environment were studied by the absorption and 1H NMR spectroscopies. Cryospheric and atmospheric implications concerning the influence of acids and bases on composition and reactivity of ice or snow contaminants were examined.
ER -
HEGER, Dominik, Jana KLÁNOVÁ a Petr KLÁN. Enhanced Protonation of Cresol Red in Acidic Aqueous Solutions Caused by Freezing. \textit{Journal of Physical Chemistry B}. USA: The American Chemical Society, 2006, roč.~110, č.~3, s.~1277-1287. ISSN~1089-5639.
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