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Thermochemistry of alpha-D-xylose(cr)

Published

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

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 February 27, 2024)
Created December 4, 2012, Updated February 19, 2017