Cooperative hydration of pyruvic acid in ice.
J Am Chem Soc
; 128(32): 10621-4, 2006 Aug 16.
Article
en En
| MEDLINE
| ID: mdl-16895430
ABSTRACT
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 QH(T) = [PAH]/[PA] becomes temperature independent below approximately 250 K (in chemically and thermally equilibrated frozen 0.1 < or = [PA]/M < or = 4.6 solutions in D2O), which requires that the enthalpy of PA hydration (DeltaHH approximately -22 kJ mol(-1)) be balanced by a multiple of the enthalpy of ice melting (DeltaHM = 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 1deltaPAH and 1deltaPA methyl proton NMR resonances is nearly constant while, (3) line widths increase exponentially with decreasing temperature before diverging below approximately 230 K, we infer that PA in ice remains cooperatively hydrated within interstitial microfluids until they vitrify.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Agua
/
Ácido Pirúvico
/
Hielo
Idioma:
En
Revista:
J Am Chem Soc
Año:
2006
Tipo del documento:
Article
País de afiliación:
Estados Unidos