Solid State Nucl Magn Reson. 1998 Aug;12(1):21-30. doi: 10.1016/s0926-2040(98)00041-1.

Molecular motions of D-alpha-galacturonic acid (GA) and methyl-D-alpha-galacturonic acid methyl ester (MGAM) in the solid state-A proton NMR study.

Solid state nuclear magnetic resonance

P S Belton, H R Tang

PMID: 9808293 DOI: 10.1016/s0926-2040(98)00041-1

Abstract

The molecular motions of D-alpha-galacturonic acid monohydrate (GA) and its derivative methyl-alpha-D-galacturonic acid methyl ester monohydrate (MGAM) in the solid state have been studied using 1H NMR. Both protonated and deuterium exchanged samples have been used. Spin-lattice relaxation times in the laboratory and rotating frames as well as second moments have been measured over the temperature range 90-370 K. Analysis of results has shown that in GA spin-lattice relaxation is chiefly by hydroxyl groups and water of crystallization. In MGAM, methyl groups dominate spin-lattice relaxation in the laboratory frame at the low temperature. Hydroxyl groups and water of crystallization contribute to the spin-lattice relaxation in the laboratory frame in the high temperature region. In the rotating frame motion of hydroxyl groups and water of crystallization provide the main relaxation pathway. Changes in the static second moment with temperature can be reasonably well predicted using values of correlation time and motionally averaged second moments obtained by fitting the spin-lattice relaxation data. 13C CPMAS spectra for GA and MGAM are also described.

Substances

• Carbon Isotopes
• Hexuronic Acids
• Protons
• methylgalacturonic acid methyl ester
• galacturonic acid

MeSH terms

• Carbon Isotopes
• Crystallization
• Hexuronic Acids / chemistry*
• Magnetic Resonance Spectroscopy / methods*
• Models, Molecular
• Motion
• Protons
• Rotation
• Stereoisomerism

Publication Types

• Journal Article
• Research Support, Non-U.S. Gov't

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