Vapor Pressures and Enthalpies of Sublimation ofd-Glucose,d-Xylose, Cellobiose, and Levoglucosan

The vapor pressures of α- d -glucose (or dextrose), d -xylose, d -cellobiose (or 4-β- d -glucopyranosyl- d -glucopyranose), and levoglucosan (or 1,6-anhydro-β- d -glucopyranose) have been measured using the Knudsen effusion technique, in the range of temperatures from 344 to 488 K. The measurements were all made in the solid sublimation regime, and enthalpies of sublimation were calculated from the Clausius−Clapeyron equation. The vapor pressures may be correlated by ln( P /Pa) = A − B / ( T /K), where A = 53.16, B = 23 382 (±600) for d -glucose (395−406 K), A = 46.29 and B = 19 006 (±375) for d -xylose (370−395 K), and A = 70.30 and B = 36 264 (±5220) for cellobiose (474−488 K). Levoglucosan displayed a solid phase transition at approximately 386 K, and its vapor pressure was affected accordingly. For this material, A = 38.96 and B = 15 049 (±123) in the temperature range 344−386 K and A = 31.19 and B = 12 066 (±709) in the temperature range 386−405 K.