David M. Grant

Fluid Structures ofCO2 andCO2–CH4 Mixture at Supercritical Fluid and Liquid Densities by Nuclear Spin–Lattice Relaxation Measurements

13C nuclear relaxation times were measured by a high‐pressure sapphire NMR cell for neat CO2 and a CO2–CH4 mixture over a wide range that covers gas, liquid and supercritical densities. The nuclear spin–lattice relaxation times at liquid and supercritical densities for the CO2–CH4 mixture were obtained for the first time. Although the spin–rotation interactions still dominate the spin–lattice relaxation processes in CH4, the intramolecular dipolar interaction contributes approximately 5% to the overall relaxation rates at liquid densities for this mixture. The chemical shift anisotropy and the intermolecular contributions to the relaxation rates of CO2 were experimentally determined to be negligible. A movable wall cell model was modified and used to relate the relaxation time data to the fluid structures of the first solvation shell around the central molecules in the liquid and supercritical fluid states. The coordination number in the first shell was found to be 12 for both the neat CO2 and CO2–CH4 mixture at liquid and supercritical fluid densities.

Two Triterpenoid Saponins from Clinopodium chinensis

Abstract Two new triterpenoid saponins, clinopodiside D(1) and E(2) were isolated by further investigation of the plant, Clinopodium chinensis Benth, and their structures were elucidated using chemical evidence and spectral methods, in particular 2D-NMR spectroscopy.

Revision of the structure of a sesquiterpene from Ligularia sagitta

The structure of a new sesquiterpene from the rhizomes of Ligularia sagitta was revised as benzofuranoeremophil-1-ene by 2D NMR and X-ray diffraction.