Thermochemistry of alpha-D-xylose(cr)

Published

December 4, 2012

Author(s)

Robert N. Goldberg, Manuel A. Ribeiro da Silva, Maria D. Ribeiro da Silva, Ana I. Lobo Ferreira, Quan Shi, Brian F. Woodfield

Abstract

The thermochemistry of alpha-D-xylose(cr) was studied by means of oxygen bomb calorimetry and a Physical Property Measurement System (PPMS) in zero magnetic field. The sample of -D-xylose(cr) used in this study was one well-characterized by HPLC, Karl Fischer analysis, NMR, and by carbon dioxide analysis. The standard molar enthalpy of combustion was found to be ΔcH = -(2342.2 ± 0.8) kJ∙mol-1 at T = 298.15 K and at the standard pressure po = 0.1 MPa. The standard molar heat capacities for alpha-D-xylose(cr) were measured with the PPMS over the temperature range 1.9001 K ≤ T ≤ 303.66 K. At T = 298.15 K, Cpo = (178.1 ± 1.8) J∙K-1∙mol-1. The values of were fit as a function of T by using theoretical and empirical models for appropriate temperature ranges. The results of these fits were used to calculate values of , the entropy increment ∆ S , ∆ H , and Ф = (∆ S - ∆ H /T) from T = 0.5 K to T = 300 K. Derived quantities for alpha-D-xylose(cr) are the standard molar enthalpy of formation ΔfH = -(1054.5 ± 1.1) kJ∙mol 1, the third law standard molar entropy S = (175.3 ± 1.9) J∙K 1∙mol-1, and the standard molar Gibbs energy of formation ΔfG = -(750.5 ± 1.0) kJ∙mol-1. A comparison of values of ΔcH and So for the five-carbon aldoses demonstrated a striking similarity in the values of these respective properties for alpha-D-xylose(cr), D-ribose(cr), and D-arabinose(cr). Thermochemical network calculations were performed that led to values of the standard formation properties at T = 298.15 K for a variety of biochemical substances: D-xylose(aq), D-xylose-(aq), D xylose2-(aq), D-lyxose(cr and aq), D-lyxose-(aq), D-xylulose(aq), xylitol(aq), 1,4-- D-xylobiose(am and aq), and 1,4-alpha-D-xylobiose(am and aq).

Citation

Journal of Chemical Thermodynamics

Volume

58

Pub Type

Journals

Keywords

calorimetry, combustion, enthalpy, entropy, heat capacity, thermochemistry, ¿-D-xylose

Citation

Goldberg, R. , Ribeiro, M. , D., M. , Lobo, A. , , Q. and Woodfield, B. (2012), Thermochemistry of alpha-D-xylose(cr), Journal of Chemical Thermodynamics (Accessed April 19, 2024)