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Mesomorphic properties are studied on the title compounds where substituents are F, Cl, Br, I, NO2, and CN. Besides the known mesophases, nematic and smectic Ad, in CN and NO2 homologues, stable smectic A and B phases were observed in either of the Cl and Br derivatives. Metastable nematic and smectic A phases were found in F derivative. The effects of terminal polar substituents, stabilization of the smectic A phase by moderately polar substituents, and of the nematic phase by strongly polar substituents, were confirmed.

Proton magnetic relaxation times T1, T1ρ, and T1D were measured on a single crystal of α-form oxalic acid dihydrate in two modes: temperature dependence at one or two specific crystal orientations, and angular dependence at several temperatures. Results were compared with the calculation based on an isolated three proton system for the assumed modes of motions. The temperature dependence of T1 and that of T1ρ and T1D in the low temperature range are reasonably accounted for by the 180°-flip of the water molecule. The activation energy for the motion of 43.6 kJ mol−1 is obtained. T1ρ and T1D above about 35 °C decreased as the temperature was raised. The comparison of the observed results in this temperature range with the calculated ones suggests that there is exchange motion among the three spins. An activation energy for this motion of 80.8 kj mol−1 is obtained. This three spin exchange motion may be considered as a combination of a jump of carboxyl proton to a higher potential trough corresponding to th...

The quadrupole spectra of deuteron magnetic resonance were observed on single crystals of (ND4)2C2O4D2O. The quadrupole coupling tensors for stationary deuterons were determined at −110°C. eqQ⁄h and η are 163.7–172.8 kHz and 0.005–0.015 for the ammonium deuterons and 213.3 kHz and 0.090 for the water deuteron. The eqQ values and principal axis directions of EFG tensors are consistent with the structure deduced from the diffraction studies with the exception that the z principal axes of D in the ammonium ion deviate appreciably from the NH directions derived from neutron diffraction. From the change in the line-width with the temperature, the rate of the C3 reorientation of ammonium ions and that of the 180° flip of water molecules were estimated at various temperatures. The ammonium-ion reorientation is found to be quite isotropic. The temperature dependence of the proton T1 and T1ρ and the deuteron T1 were measured on (NH4)2C2O4H2O and (ND4)2C2O4D2O powers. The T1 values were then compared with the calcu...

A deuteron magnetic resonance study has been made on a single crystal of urea-d4. At room temperature deuteron quadrupole coupling corresponding to a stationary molecule is obtained. The eqQ and η values determined are: eqQ⁄h=210.8±1.0 kc./sec. and η=0.139±0.010 for D1, and eqQ⁄h=210.7±1.0 kc./sec. and η=0.146±0.010 for D2 at room temperature, and eqQ⁄h=206.3±1.2 kc./sec., η=0.138±0.010 for D2 at 117°C. In both cases the maximum field gradient component and the N–H direction are in good agreement. The onset of reorientational motion about the C=O bond of a whole molecule has been concluded from the line-width change at high temperatures. Above 110°C the effect on the line-width of the reorientation about C–N bond has also been observed. The barrier heights for these motions are estimated to be 11±2 kcal./mol. for the reorientation about the C=O bond and 15±3 kcal./mol. for that about the C–N bond. The temperature dependence of the quadrupole splitting and that of the dipole coupling between 14N and D have...

Deuteron magnetic resonance study was made on single crystals of NiSiF6·6D2O and NiSnCl6·6D2O. Deuteron quadrupole coupling tensors were determined at various temperatures. In NiSiF6·6D2O, the quadrupole coupling at −116°C is that of stationary D2O, at 23°C and at 70°C that of D2O under rapid 180°-flip motion and at 150°C that of rapid Ni(D2O)62+ reorientation. The eqQ⁄h values at −116°C, 238.3±1.3 kc and 235.7±1.9 kc do not appear to show marked effect of strong coordination. In NiSnCl6·6D2O, the quadrupole coupling corresponding to D2O under 180°-flip motion is observed at −53°C, at 25°C, and at 55°C. Spectra corresponding to a stationary D2O are not observed even at 77 °K. From the orientation of quadrupole tensors probable crystal structures of these compounds are proposed. Line width transitions were observed from which the reorientation rate was derived. The estimated activation energies of the 180°-flip motion of D2O are 7.6 and 4.3 kcal/mol in the fluosilicate and chlorostannate, respectively, and...

The temperature dependence of the dipole moment was investigated on monochloromethyl ether (I), sym-dichloromethyl ether (II) and monobromomethyl ether (III) in the gaseous state, and (III) and sym-dibromomethyl ether (IV) in heptane solution. The moment of (I), (II) and (IV) increases with temperature, while that of (III) does not. From the observed data the energy difference between the gauche and the trans position is 0. 7 kcal./mol. in (I), and zero in (III) Similarly ΔE’s between t,g- and g,g-form of (II) and (IV) are estimated to be 1.3 kcal. and obtained to be 0.9 kcal./mol. respectively from the observed results.

Deuteron quadrupole coupling tensors in Co(ND3)6Cl3 were determined at various temperatures. The observed quadrupole coupling shows that Co(ND3)63+ ions execute a rapid isotropic reorientation at high temperatures (above 320°K for one of the sites (the 4f sites) and above 190°K for another (the 2e sites), while at low temperatures (below 190°K for the 4f sites, and 170°K for the 2e sites), only a C3 axis reorientation of the ligand ND3 groups is present. The deuteron resonance spectra clearly show that Co(ND3)63+ ions in the 4f sites begin to reorient about one of the three C4 axes at intermediate temperatures (about 240°K). On the basis of the orientation of quadrupole tensors, probable orientations of Co(ND3)63+ ions in the 4f sites in the crystal are proposed. Additional measurements of the proton resonance on a single crystal of Co(NH3)6Cl3support the results obtained from the deuteron resonance. To obtain the reorientation rates and the activation energies of these reorientational motions, the deuter...

The dipole moments of propargyl chloride, bromide and monochlorobutyne in the gaseous state are measured to be 1.65D,1.52D and 2.17D respectively. The moment of propargyl chloride and bromide are considerably smaller than the saturated one even though the correction of C≡C—C skeletal moment is taken into account. This is consistent with the —CH2Cl group moment of dichlorobutyne obtained in the preceding work. These results are inconsistent with the resonance scheme presented by Pauling et al. for propargyl halide. The anomaly is considered as a characteristic feature of the molecules having triple bonds of this kind. By taking all of the moments of dichloro- and monochlorobutynes and propargyl chloride into account, the bond moments, the induction moments and the direction of the resultants, are predicted as shown in Fig. 1.

The dipole moment measurement was made at various temperatures on ethyl, i-propyl and t-butyl nitrites. Observed moments are 2.41D for ethyl, 2.57D for i-propyl, 2.70D for t-butyl nitrite at room temperature. The moment of the latter two compounds decrease slightly with temperature while ethyl compound remains constant. These esters are considered to consist of two isomers: the trans and the cis separated by a barrier of several kcal. due to a resonance effect. The energy difference ΔE between the two isomers is found to be zero in ethyl

An apparatus for the measurement of dielectric constant in the gaseous state is constructed. The electrical circuit is a heterodyne double-beat type, the oscillators with a remarkably high frequency stability are constrcuted. By testing several types of gas cell, it was found that one of them (cell D) can be used satisfactorily for the present purpose. For the gas filling system, a modification of Groves’ method is employed. Using this apparatus dielectric constant measurement with an error of less than 0.5 per cent can be obtained. The dipole moment of 1,1-dichloroacetone was measured in this apparatus. The moment was found to increase with temperature. This increase is attributed to the increase of the more polar isomer (b), which coexists with the form (a). The energy difference of the two isomers was found to be about 800 cal./mole. This value is smaller than that of monochloroacetone, and the lowering of ΔE was considered to be due mainly to the reduced moment of the C-Cl bonds by mutual induction. I...

The dipole moment of acenaphthene (I) was measured in the gaseous phase as 0.93D. Measurement in benzene solution at 25°C gave the following moment values: acenaphthene (I) 0.85D; 5-chloroacenaphthene (II) 2.50D ; and 5,6-dichloroacenaphthene (III) 3.85D. By the comparison with the moments of naphthalene derivatives it was shown that the moments of (II) and (III) are approximately equal to the sums of the moment of (I) and the moments arising from one and two C–Cl bonds, respectively.