beta-ionone and citronellal

The use of two new highly viscous binary solvents, DMSO-d6/glycerol (GL) and DMSO-d6/glycerol-d8 (GL-d8), is reported for the first time in order to give access to the individual NMR spectra of mixture components. Their high dissolution power offers a wide range of potential applications to mixture analysis, regardless of polarity. Under particular conditions of viscosity, the tumbling rate of small and medium-sized molecules slows down in solution, so that the longitudinal cross-relaxation regime favors the observation of spin diffusion. As a consequence, all the resonances of the (1)H nuclei within the same molecule tend to correlate together in a 2D nuclear Overhauser effect spectroscopy (NOESY) spectrum, thus opening the way to mixture analysis. This work reports the analysis of a polar mixture composed of Leu-Val, Leu-Tyr, Gly-Tyr, and Ala-Tyr dissolved in DMSO-d6/GL (8:2, v/v) and of an apolar mixture made of β-ionone, (±)-citronellal, (+)-limonene, and flavone dissolved in DMSO-d6/GL-d8 (5:5, v/v) by means of spin diffusion in homonuclear selective 1D NOESY, selective 2D NOESY, NOESY-correlation spectroscopy (COSY), NOESY-total correlation spectroscopy (TOCSY) experiments, and 2D heteronuclear single-quantum correlation spectroscopy (HSQC)-NOESY. DMSO-d6/GL must be preferred to DMSO-d6/GL-d8 for the study of biological active compounds in which labile protons must not be exchanged by deuterium nuclei. DMSO-d6/GL-d8 is more appropriate for organic compounds in which labile protons are not essential to the structure elucidation. DMSO-d6/GL and DMSO-d6/GL-d8 binary mixture solvents seem to be so far the most efficient viscous solvents described in the literature for the resolution of both polar and apolar complex mixtures components by NMR spin diffusion.

Topics: Acyclic Monoterpenes; Aldehydes; Amino Acids; Cyclohexenes; Dimethyl Sulfoxide; Flavones; Glycerol; Limonene; Magnetic Resonance Spectroscopy; Molecular Structure; Monoterpenes; Norisoprenoids; Solvents; Terpenes; Viscosity

A multisniffing system has been developed to allow three panelists to simultaneously participate in a GC-olfactometric analysis. This device, associated with a computerized data treatment, allows shortening CHARM and GC-"SNIF' analyses to less than 1 week and less than 1 day, respectively. The program was developed as an extension of an existing commercial chromatography data system, as usual GC processing functions are suited to the treatment of olfactograms (plots of odor response versus GC elution time). Because of the improved algorithm, the consequences of gaps in coincident responses were minimized, and the systematic use of a panel improved the repeatability of CHARM olfactograms. Comparing both methods, GC-SNIF repeatability appears to be higher than that of CHARM, as the former method uses a larger panel, but in a shorter lapse of time.

Topics: Acyclic Monoterpenes; Aldehydes; Benzyl Compounds; Chromatography, Gas; Cyclohexanols; Equipment Design; Eucalyptol; Hexanols; Humans; Models, Molecular; Monoterpenes; Norisoprenoids; Odorants; Software; Terpenes