Nuclear relaxation rates of 13C and 14N have been measured as a function of temperature for neat thiazole and isothiazole. Nuclear Overhauser enhancements, also measured as a function of temperature, were used to separate dipolar and spin rotational contributions to 13C relaxation. 13CH dipolar relaxation rates were combined with quadrupolar 14N relaxation rates to determine the angle between the rotational axes and the principal inertial axes, and the rotational correlation times for motion about each rotational axis. The accuracy of the results were discussed, especially with respect to the 14N coupling parameters. The viscosity has been measured for thiazole and isothiazole as a function of temperature. The temperature and viscosity dependence of the rotational correlation times is compared with those of other planar molecules.

Proton spin lattice relaxation of pyridine-N-oxide-2,6-d2 in dilute solution (0·2 M) with carbon tetrachloride has been measured at -12·6, 6·5, and 26·6°C. Using 2H and 14N decoupling, eight transitions were resolved and recovery was monitored after non-selective inversion. In absence of 14N decoupling, scalar relaxation produced clearly visible effects on the proton recovery curves. Combined with measurements of deuterium relaxation of the 2,6-d2 and 4-d derivatives, proton relaxation data (including effects of dipolar cross correlation) were used to determine all three rotational diffusion constants at each temperature. The in-plane spinning motion was found to be ∼four-fold more strongly dependent on viscosity than predicted by the slip rotational diffusion model, while motion about the other two principal axes proceeds at rates within ∼40 per cent of slip predictions. 14N spin lattice relaxation data were combined with the anisotropic reorientation rates in efforts to determine liquid phase values of the 14N quadrupole coupling parameters. A very small decrease from solid phase values provides the best overall fit to the relaxation data.

Nuclear magnetic resonance lines with relatively short spin-spin relaxation times (T2) may be inverted for the purpose of measuring their spin-lattice relaxation times (T1) by applying a large audio frequency field modulation pulse to a high resolution sideband detection NMR spectrometer. The frequency, amplitude, and length of such a pulse is evaluated and the trajectory of the magnetization as it is inverted is approximately calculated. It is found, in agreement with Anderson's cw result, that the spins invert in a time πγH1 J1 (β), as if a field H1 J1 (β) had been applied, where H1 is the actual rotating rf field amplitude, J1 is the first Bessel function and β equals γHmωm, where Hm is the modulation amplitude and ωm is the modulation angular frequency.

Chemischer InformationsdienstVolume 5, Issue 43 Physical Organic Chemistry ChemInform Abstract: MICROWAVE SPECTRA OF ISOTOPIC PYRAZOLES AND MOLECULAR STRUCTURE OF PYRAZOLE LISE NYGAARD, LISE NYGAARDSearch for more papers by this authorDINES CHRISTEN, DINES CHRISTENSearch for more papers by this authorJ. TORMOD NIELSEN, J. TORMOD NIELSENSearch for more papers by this authorE. PEDERSEN, E. PEDERSENSearch for more papers by this authorOLE SNERLING, OLE SNERLINGSearch for more papers by this authorERIK VESTERGAARD, ERIK VESTERGAARDSearch for more papers by this authorG. OLE SOERENSEN, G. OLE SOERENSENSearch for more papers by this author LISE NYGAARD, LISE NYGAARDSearch for more papers by this authorDINES CHRISTEN, DINES CHRISTENSearch for more papers by this authorJ. TORMOD NIELSEN, J. TORMOD NIELSENSearch for more papers by this authorE. PEDERSEN, E. PEDERSENSearch for more papers by this authorOLE SNERLING, OLE SNERLINGSearch for more papers by this authorERIK VESTERGAARD, ERIK VESTERGAARDSearch for more papers by this authorG. OLE SOERENSEN, G. OLE SOERENSENSearch for more papers by this author First published: October 29, 1974 https://doi.org/10.1002/chin.197443060AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume5, Issue43October 29, 1974 RelatedInformation