http://www.cnr.it/ontology/cnr/individuo/prodotto/ID39822

Structural unfreezing and endothermic effects in liquids, beta-D-fructose (Articolo in rivista)

Type

Articolo in rivista (Classe)
Prodotto della ricerca (Classe)

Label

Structural unfreezing and endothermic effects in liquids, beta-D-fructose (Articolo in rivista) (literal)

Anno

2004-01-01T00:00:00+01:00 (literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#doi

10.1021/jp048036r (literal)

Alternative label

Tombari E.; Salvetti G.; Ferrari C.; Johari GP (2004)
Structural unfreezing and endothermic effects in liquids, beta-D-fructose
in The journal of physical chemistry. B
(literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori

Tombari E.; Salvetti G.; Ferrari C.; Johari GP (literal)

Pagina inizio

16877 (literal)

Pagina fine

16882 (literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#url

http://pubs.acs.org/journal/jpcbfk (literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#numeroVolume

108 (literal)

Rivista

?The ?journal of physical chemistry. B (Rivista)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#pagineTotali

6 (literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#numeroFascicolo

43 (literal)

Note

ISI Web of Science (WOS) (literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni

CNR-IPCF, Ist Proc Chim Fis, I-56124 Pisa, Italy (literal)

Titolo

Structural unfreezing and endothermic effects in liquids, beta-D-fructose (literal)

Abstract

Both structural unfreezing and irreversible endothermic change between different molecular states of a material can occur on heating its liquid state and produce a double sigmoid-shaped endotherm in its apparent heat capacity, C-p. In such a case, the usual calorimetry is unable to distinguish between the molecular mechanisms of the two endothermic contributions. We report that this distinction can be made by measuring C-p and the complex heat capacity, C-p(*), simultaneously in a temperature-modulated scanning mode. When a sigmoid- shaped increase is observed in both C-p and C-p* of a liquid, the underlying process is structural unfreezing. P But, when this increase is observed in normal scanning and not in the temperature-modulated mode, the underlying process is either irreversible or too slow, compared to the modulation period. The method has been used for resolving the nature of tautomeric transformation in liquid beta-D-fructose. Simultaneous C-p and C-p(*) measurements show that, for normal scannin, C-p increases in a sigmoid-shaped manner with hysteresis, P 9 but for temperature-modulated scanning, the real component of C-p does not increase in this manner (i.e., the reversible component of the heat flow shows neither a sigmoid-shaped increase nor hysteresis). Therefore, the sigmoid-shaped C-p increase observed in normal scanning indicates an endothermic transformation in the beta-D-fructose liquid at T > T-g and not unfreezing of tautomeric transformation on the time scale of heating. (literal)

Prodotto di