Molecular Dynamics of Polycrystalline Cellobiose Studied by Solid-State NMR

✍ Scribed by H.R. Tang; P.S. Belton

• Publisher: Elsevier Science
• Year: 2002
• Tongue: English
• Weight: 362 KB
• Volume: 21
• Category: Article
• ISSN: 0926-2040
• DOI: 10.1006/snmr.2002.0052

✦ Synopsis

Molecular motions of polycrystalline cellobiose have been investigated by measuring proton spin-lattice relaxation times, T1 and T1rho, and the second moment, M2, in both protonated and D2O exchanged forms over the temperature range 120-380 K. T1 relaxation is dominated by the motions of hydroxyl groups between 150 and 380 K, characterised by an activation energy of about 8.74 kJ/mol, whereas T1rho relaxation is driven by the motions of the same groups between 120 and 300 K. T1rho results suggest that hydroxyl groups have a distribution of dynamics. Motion of methylene groups was detected in the second-moment experiments at about 350 K, characterised by activation energy of about 40 kJ/mol. Consideration of the calculated and observed rigid-lattice second moments suggests that the reported X-ray data are incorrect for the inter-proton distance on C6'. 13C CPMAS spectra of both protonated and deuterated cellobiose have also been measured. Spectra of the deuterated material showed the existence of a second crystalline form in addition to the normal form.