No abstract

Deuterium nuclear magnetic resonance (NMR) powder spectra and spin-lattice relaxation times (T(1)) are used to measure the deuterium quadrupolar coupling constants (QCCs) chi(BD) and chi(ND) and to investigate the molecular reorientation of the BD(3) and ND(3) groups in solid deuterated borane monoammoniate, BD(3)NH(3) and BH(3)ND(3), respectively. In the high-temperature, tetragonal, phase (above 225 K) the following Arrhenius parameters are obtained from the temperature-dependent T(1): E(a) = 5.9 +/- 0.5 kJ/mol and tau(infinity) = 1.1 x 10(-)(13) s for BD(3)NH(3); E(a) = 7.3 +/- 0.8 kJ/mol and tau(infinity) = 4.4 x 10(-)(14) s for BH(3)ND(3). In the low-temperature, orthorhombic, phase the following parameters are obtained: E(a) = 26.4 +/- 1.4 kJ/mol and tau(infinity) = 1.2 x 10(-)(17) s for BD(3)NH(3); E(a) = 13.7 +/- 0.9 kJ/mol and tau(infinity) = 5.7 x 10(-)(15) s for BH(3)ND(3). Here tau(infinity) is proportional to the inverse of the usual Arrhenius preexponential factor, A. Deuterium line shape measurements for the low-temperature phase of BD(3)NH(3) yield E(a) = 25 +/- 2 kJ/mol and tau(infinity) = 4.7 x 10(-)(19) s. These dynamic factors indicate that the molecule is probably undergoing whole molecule rotation above the phase transition but the BH(3) and NH(3) groups are undergoing uncorrelated motion in the low-temperature phase. Deuterium quadrupolar coupling constants of 105 +/- 10 and 200 +/- 10 kHz were determined for BD(3)NH(3) and BH(3)ND(3), respectively. Molecular orbital (MO) calculations (CI(SD)/6-31G(d,p)//MP2/6-31G(d,p)) for the isolated molecule yield values of 143 and 255 kHz. MO calculations also show that the deuterium quadrupolar coupling constants chi(BD) and chi(ND) are relatively insensitive to all molecular structural parameters except the B-H and N-H bond lengths, respectively. It is suggested that the large decrease in the QCC on going from the gas phase to the solid state may be due to a slight lengthening of the B-H and N-H bonds, possibly a result of attractive B-H.H-N interactions.

In this study the (109)Ag NMR spectra of the following solid inorganic silver-containing compounds were investigated: AgNO(3), AgNO(2), Ag(2)SO(4), Ag(2)SO(3), AgCO(3), Ag(3)PO(4), AgCl, AgBr, AgI, AgSO(3)CH(3), silver p-toluenesulfonate, NaAg(CN)(2), KAg(CN)(2), K(3)Ag(CN)(4), Me(4)NAgCl(2), silver diethylthiocarbamate, silver lactate, silver acetate, silver citrate, and bis[(N,N(1)-di-tert-butylformamidinato)silver(I)]. The magic angle spinning (MAS) spectra of all compounds were obtained. In some cases, when protons were available, the (1)H to (109)Ag cross-polarization (CP) technique was used to enhance the signal and shorten the experimental relaxation delay. It was possible to obtain slow MAS (or CP/MAS) or nonspinning spectra for 10 samples, allowing the determination of the principal components of the (109)Ag chemical shift (CS) tensors. The isotropic chemical shifts and the CS tensors are discussed in light of the available crystal structures. The need for an accepted standard for referencing (109)Ag chemical shifts and the use of AgSO(3)CH(3) as a CP setup sample are also discussed.

A precise analysis of the 'H nmr spectrum of toluene as a dilute solution in carbon disulfide yields a revised set of spectral parameters. The chemical shift of the para proton lies 12.6 ppb to low frequency of that of the ortho protons at 300 K. The ring proton chemical shifts are discussed and compared with 'H and 3H shifts observed in carbon tetrachloride. The long-range couplings between methyl and ring protons can be said to be quantitatively understood in terms of a and u-a electron transmitted mechanisms. The changes observed in these three couplings in phenylacetaldehyde can be quantitatively reproduced in terms of these mechanisms and also illustrate how these changes are direct measures of the conformational preferences in this molecule.TED SCHAEFER, RUDY SEBASTIAN et GLENN H. PENNER. Can. J. Chem. 63, 2597(1985.Une analyse prCcise des spectres rmn du 'H du tolukne, en solution diluCe dans le disulfure de carbone, a permis d'obtenir un nouvel ensemble de paramktres spectraux. A 300 K, le dCplacement chimique du proton para se situe ?I une frkquence de 12,6 ppb plus basse que celle des protons ortho. On discute des dCplacements chimiques des protons du cycle et on les compare avec les dCplacements des 'H et 3~ qui ont Ct C determinks en solution dans le tetrachlorure de carbone. On peut dire que I'on peut expliquer quantitativement les couplages ti longue distance entre les protons du cycle et ceux du groupement mCthyle en faisant appel ?I des mkcanismes impliquant que les Clectrons sont transmis par les liaisons u et u-a. On peut reproduire quantitativement les changements observks dans ces trois couplages du phCnylacCtaldChyde en faisant appel ?I ces mkcanismes; de plus, on peut illustrer comment ces changements sont des mesures directes des prCfCrences conformationnelles dans cette moltcule.[Traduit par le journal] !

5121 (23) Clegg, H. P.; Rowlinson, J. S. Faraday SOC. Tram. 1955,51,1333. (24) Gugnoni, R. J.; Eldrige, J. w.; Okay, V. C.; Lee, T. J. AIChE J. 1974, (25) Aftienjew, J.; Zawisza, A. J. Chem. Thermodyn. 1977, 9, 153. (26) Haselden, G. G.; Newitt, D. M.; Shah, S. M. Proc. R. SOC. A 1951, (19) Prausnitz, J. M.; Lichtenthaler, R. N.; Gomes de Azevedo, E.Deuterium nuclear magnetic resonance (NMR) spectra and spin-lattice relaxation times are used to investigate the guest and host molecular dynamics of solid 1 ,4-di-terr-butylbenzene-d4 (DTBB-d4), l,4-di-tert-butylbenzne-dl* (DTBB-d18), the thiourea/ 1 ,4-di-tert-butylbenzene-d4 inclusion compound (TUIDTBB-d4), the thiourea/ 1,4-di-tert-butylbenzene-d~ inclusion compound (TU/DTBB-dz2), the thiourea-d4/ 1,4-di-tert-butylbenzene inclusion compound (TU-d4/DTBB), and thiourea-d4 (TU-d4). X-ray crystallographic studies of TU/DTBB-d4 have been carried out at 291 K. In solid DTBB the phenyl ring is essentially static whereas the rert-butyl groups are undergoing rapid reorientation of both methyl and rert-butyl groups.Attempts to analyze the ' H spectra and Tl data for DTBB-dls suggest that the dynamics of the methyl and tert-butyl groups are nearly equivalent, and as a result, a satisfactory analysis, yielding methyl and tert-butyl rotational activation energies, was not possible. X-ray diffraction results for TU/DTBB-d4 suggest that, at 291 K, the phenyl ring is occupying three nearly equivalent sites. The ZH NMR line shapes between 186 and 392 K were interpreted using a model in which the phenyl ring is rapidly flipping between three positions, with one position less favored. At 296 and 186 K the populations are 0.81:1.00.1.00 and 0.201.00.1 .OO, respectively. Relaxation times obtained between 1 1 1 and 322 K show no mini", supporting the assumption of very rapid phenyl ring reorientation. For TU/DTBB-d2z a high-temperature T1 minimum is well-defined, and a second minimum, corresponding to tert-butyl group rotation, is reached at the lowest attainable temperatures. Lineshape simulations of the spectrum at 77 K yield methyl and tert-butyl group rotational rates of 1.0 X lo3 and 2.0 X 106 s-l, respectively. Analysis of the higher temperature spectra (109-172 K) and T1 data (167-300 K) yield methyl rotation activation energies of 12.7 and 12.3 kJ/mol, respectively. Deuterium line-shape studies of the thiourea dynamics in TU-d4 and TU-d4/DTBB yield activation energies for 180' flips about the C-S bond of 47 and 46 kJ/mol, respectively.Starting from the PY-like integral equation of RISM-1 type and using the Kirkwood-Buff theory, we evaluated the differences in the partial molar volumes of solute V : of cis and trans isomers. The system investigated consists of a tetratomic A-B-B-A fused hard sphere and a single hard sphere both of which are considered as solvent or solute. To compare the evaluated values with the actual values, the VTs were determined for cis-and trans-decahydronaphthalene dissolved in such solvents as carbon tetrachloride, hexane, and benzene, etc., as well as ...