Nematic lyotropic phases have been prepared using mixed detergents with the decyl sulfate anion. The phases have been studied by observing Li-7, Na-23, Cs-133, and D-2 nuclear magnetic resonance (NMR) spectra. The NMR signals all show first-order quadrupole splittings. The studies of the nematic phases were designed to investigate the influence of the counterion and temperature variation. The ternary phase sodium decyl sulfate-decanol-D20 was modified by substituting the cations Li+, K+, Rb+, Cs+, NH4+, and C2HsNH3+ for Na+ in varying proportion, but sustaining the mole fractions of detergent, decanol, and D20. Phase changes do occur as a result of counterion effects and two types of nematic phase can be distinguished. A type I nematic phase is slow to respond to orienting forces in a magnetic field, but does form a single liquid crystalline sample with the uniaxial nematic axis aligned parallel to the magnetic field direction. The second type II phase observed, is more mobile and orients much more rapidly in a magnet but with the nematic axis perpendicular to the field direction. At certain temperatures and compositions of counterions the two types of nematic phase can coexist. Type I nematic phases do not preserve their orientation while spinning about an axis perpendicular to the magnetic field direction but remain oriented when the spinning axis coincides with the field axis. They are suitable as orienting media for solutes to be investigated in NMR spectrometers with superconducting solenoids. Type II nematic phases, after a short initial period in the magnetic field, retain their single liquid crystalline properties while spinning in both parallel and perpendicular arrangements to the field. Nematic phases have been prepared with three different cations Li+, Na+, and Cs+. Variation of the lithium decyl sulfate content of these nematic media induces the type I to type II phase transition. The changes in quadrupole splitting and the rates of change of quadrupole splitting with concentration at the phase change type I to type II indicate that relatively small changes in microdegree of order near the ions accompanies the perpendicular change in alignment. The temperature dependence of phase changes with the pure ternary phase sodium decyl sulfate-decanol-D20 contrasts with that of a phase prepared with added sodium sulfate and ethylene carbonate. These differences indicate a type I phase without additives and a type II phase with the additives.

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Vapor absorption spectra have been measured for naphthalene, anthracene, and pyrene using a modified Beckman DU Spectrometer. Vapor concentrations were determined using published vapor pressure data, and oscillator strengths were computed for a total of five transitions in the three molecules. It was found that the vapor oscillator strengths are considerably lower than in solution by a factor greater than that predicted by classical theory. An absorption region at about 41,000 cm.−1 in anthracene is tentatively assigned as the 1B2u+ state calculated by Pariser to lie at 42,400 cm.−1.

The amplitude of the nuclear induction signal is calculated for pulsed nuclear magnetic resonance experiments for systems in which chemical exchange takes place between two sites of different Larmor frequency. General expressions are given, within the scope of first order rate theory for one and two pulse experiments as well as multiple pulse (Carr—Purcell) sequences. It is proven that for a Carr—Purcell sequence the decay is always expressible as a sum of two exponentials. The two time constants are derived for the general case and some special cases are discussed in detail. The theory makes possible the measurement of exchange rate constants using spin-echo techniques without the use of computers and seems relatively easy to generalize to more complicated systems.

In order to study the effect of association with π-donors, the proton resonance signal of chloroform in the aromatic solvents benzene, toluene, mesitylene, chlorobenzene, o-dichlorobenzene, bromobenzene, nitrobenzene and in the olefinic solvents 1-hexene, cyclohexene, and cyclohexadiene was measured as a function of concentration. The observed shifts of the resonance signal are indicative of specific complex formation. In the aromatic solvents benzene, toluene, and mesitylene, complex formation results in an anomalous shift of the chloroform resonance to high field, which can be attributed to a large induced diamagnetism resulting from the circulation of π-electrons in the aromatic ring. An approximate calculation indicates that the chloroform molecule in the complex is oriented with the hydrogen atom near the six-fold axis above the plane of the aromatic ring and the chlorines directed away from the ring. In nitrobenzene this type of association with chloroform gives way to n-donor association with the oxygen atom of the nitro group. This type of association also occurs to some extent in the halogenated benzenes. A small shift of the chloroform signal to low field is observed with the olefinic solvents, which is attributable to weak π-donor association. Analysis of the freezing-point diagrams of the binary systems with chloroform provide further evidence of complex formation.