Kinetics and thermodynamics of sucrose hydrolysis from real-time enthalpy and heat capacity measurements
Anno: 2007
Autori: Tombari E., Salvetti G., Ferrari C., Johari G.P.
Affiliazione autori: Istituto per i Processi Chimico-Fisici del CNR, via G. Moruzzi 1, 56124 Pisa, Italy; Department of Materials Science and Engineering, McMaster University, Hamilton, Ont. L8S 4L7, Canada
Abstract: We report a real time study of the enthalpy release and heat capacity during the course of HCl-catalyzed hydrolysis of sucrose to fructose and glucose. Measurements were performed during both isothermal conditions and during slow heating and then cooling at a controlled rate. The reaction rate constant of the first-order kinetics follows an Arrhenius relation with activation energy of 109.2 kJ/mol of sucrose. On hydrolysis, the enthalpy decreases by 14.4 kJ/mol of sucrose at 310 K, and the heat capacity, C-p, increases by 61 J mol(-1) K-1 of sucrose in the solution. The enthalpy of hydrolysis decreases with increase in the temperature and Delta C-p on hydrolysis increases. The effects are attributed to change in the configurational and vibrational partition functions as one covalent bond in sucrose breaks to form two molecules, which then individually form additional hydrogen bonds and alter the water’s structure in the solution. C-p of the solution increases with temperature less rapidly before sucrose hydrolysis than after it. This may reflect an increase in the configurational contribution to C-p as the hydrogen bond population changes.
Giornale/Rivista: JOURNAL OF PHYSICAL CHEMISTRY B
Volume: 111 (3) Da Pagina: 496 A: 501
Parole chiavi: INVERSION; CALORIMETRY; RELAXATIONDOI: 10.1021/jp067061pCitazioni: 36dati da “WEB OF SCIENCE” (of Thomson Reuters) aggiornati al: 2024-04-21Riferimenti tratti da Isi Web of Knowledge: (solo abbonati) Link per visualizzare la scheda su IsiWeb: Clicca quiLink per visualizzare la citazioni su IsiWeb: Clicca qui