Calorimetric studies on the phenolic glycoside D(-)-salicin.
A pure orthorhombic phase sample of D(-)-salicin was purified and characterized for calorimetric measurements. From differential scanning calorimetry (DSC) measurements it was found that the onset and maximum temperatures of the fusion peak were T(on) = (473.30 +/- 0.05) K and T(max) = (474.74 +/- 0.05) K, respectively, and that the corresponding standard enthalpy of fusion was Delta(cr)(l) H(m)(o) = (55.5 +/- 0.4) kJ mol(-1). From the last two values the standard entropy of fusion is calculated as Delta(cr)(l) S(m)(o) = (116.9 +/- 0.4) J mol(-1) K(-1). The standard molar enthalpy of formation of orthorhombic D(-)-salicin at T = 298.15 K, was determined as Delta(f) H(m)(o) (C(13)H(18)O(7), cr, orthorhombic) = -(1366.9 +/- 3.2) kJ mol(-1), by combustion calorimetry. From the results of solution calorimetry obtained in this work and some auxiliary values taken from the literature the enthalpy of reaction of hydrolysis of D(-)-salicin to produce beta-glucose and o-hydroxybenzyl alcohol was found marginally thermoneutral, if the uncertainty interval was considered. Additionally, specific heat capacity measurements on the orthorhombic phase, glass and liquid-quenched glass obtained by DSC was reported.
Pinto
Susana S
SS
Centro de Química Estrutural, Complexo Interdisciplinar, Instituto Superior Técnico da Universidade Técnica de Lisboa, 1049-001 Lisboa, Portugal.
Diogo
Hermínio P
HP
D001592:Benzyl Alcohols / Q000737:chemistry*; D002152:Calorimetry, Differential Scanning / Q000379:methods*; D005960:Glucosides; D009682:Magnetic Resonance Spectroscopy; D013816:Thermodynamics; D014961:X-Ray Diffraction
D001592:Benzyl Alcohols; D005960:Glucosides; C005696:salicin