Carbon-13 nuclear magnetic resonance in solid ammonium tartrate

Journal Article · Thu Aug 01 04:00:00 EDT 1974 · J. Chem. Phys.; (United States)

DOI:https://doi.org/10.1063/1.1681970· OSTI ID:6231913

Pines, A; Chang, J J; Griffin, R G

Chemical shielding tensors have been determined for /sup 13/C in single crystals of ammonium D-tartrate using proton-enhanced NMR. The unit cell contains two molecules, and in some orientations eight lines are resolved from the eight magnetically inequivalent carbon nuclei. Details of the experimental approach, equipment, and analysis are provided, and results are presented for three determinations on two single crystals. These indicate a precision of +- 2 ppM in the determination of the principal values of +- 3/sup 0/ in the orientation of the principal axes for the carboxyl groups, with lower precision for the hydroxyl groups. The orientations of the principal axes of the tensors are related to the crystallographic (a, b, c*) axes by employing orientation data from x-ray precision work in this study. The most plausible assignment of the tensors to particular /sup 13/C nuclei in the unit cell indicates that the heaviest shielding for /sup 13/C in the carboxyl groups occurs when H/sub 0/ is perpendicular to the carboxyl plane and the lightest shielding when H/sub 0/ is in the carboxyl plane bisecting the C-O bond. The average principal shielding values are, for the carboxyl /sup 13/C, sigma/sub 11/ = -110.5, sigma/sub 22/ = -61.7, sigma/sub 33/ = 21.6; and for the hydroxyl /sup 13/C, sigma/sub 11/ = 41.9, sigma/sub 22/ = 48.0, sigma/sub 33/ = 74.0 in parts per million (+-2) relative to an external reference of liquid benzene. The effects of hydrogen bonding on the tensors are discussed briefly. 10 figures, 4 tables.

• Research Organization: Univ. of California, Berkeley
• OSTI ID: 6231913
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 61:3; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400301* -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
AMMONIUM COMPOUNDS
CARBON 13
CARBON ISOTOPES
CARBOXYLIC ACID ESTERS
COMPARATIVE EVALUATIONS
CRYSTALS
ESTERS
EVEN-ODD NUCLEI
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
MONOCRYSTALS
NUCLEAR MAGNETIC RESONANCE
NUCLEI
ORGANIC COMPOUNDS
ORIENTATION
POWDERS
RESONANCE
SHIELDING
STABLE ISOTOPES
TARTARIC ACID ESTERS
TENSORS