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Published August 16, 2006 | Supplemental Material
Journal Article Open

Cooperative Hydration of Pyruvic Acid in Ice


About 3.5 ± 0.3 water molecules are still involved in the exothermic hydration of 2-oxopropanoic acid (PA) into its monohydrate (2,2-dihydroxypropanoic acid, PAH) in ice at 230 K. This is borne out by thermodynamic analysis of the fact that Q_H(T) = [PAH]/[PA] becomes temperature independent below ∼250 K (in chemically and thermally equilibrated frozen 0.1 ≤ [PA]/M ≤ 4.6 solutions in D_2O), which requires that the enthalpy of PA hydration (ΔHH ∼ −22 kJ mol^(-1)) be balanced by a multiple of the enthalpy of ice melting (ΔH_M = 6.3 kJ mol^(-1)). Considering that:  (1) thermograms of frozen PA solutions display a single endotherm, at the onset of ice melting, (2) the sum of the integral intensities of the ^1δ_(PAH) and ^1δ_(PA) methyl proton NMR resonances is nearly constant while, (3) line widths increase exponentially with decreasing temperature before diverging below ∼230 K, we infer that PA in ice remains cooperatively hydrated within interstitial microfluids until they vitrify.

Additional Information

© 2006 American Chemical Society. Received March 24, 2006. L.H. was a SURF student. The present study is supported by the National Science Foundation under grant number NSF-ATM-0228140. We thank Sonjong Hwang, and Peter Babilo, for technical support.

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Supplemental Material - ja062039vsi20060324_021914.pdf

Supplemental Material - ja062039vsi20060620_062357.pdf


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