An improved synthesis of [2.2.3]cyclazines from 3H-pyrrolizines

[2.2.3]Cyclazines are obtained in moderate yields by reaction of 3$\text{H}$-pyrrolizines bearing conjugative substituents (Ph or CO₂Me) with vinamidinium salts in the presence of strong bases. Syntheses of the previously unknown 2-phenyl-3$\text{H}$-pyrrolizine and 1-methoxycarbonylcyclopenta [$\text{h}$] [2.2.4] cyclazine are also described.     

An effective synthesis method for secondary fluorinated alcohols via the reaction of esters of polyfluorinated acids with trialkylalanes

Unlike nonfluorinated analogs, complex esters of polyfluorinated acids in reactions with trialkylalanes produce only polyfluorinated secondary alcohols.Department of Fine Organic Synthesis, Institute of Organic Chemistry, Urals Branch, Russian Academy of Sciences, 450054 Ufa. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 2339–2341, October, 1992.     

Determination of potassium by an automatic ultraviolet absorptiometric method

An automatic ultraviolet absorptiometric method has been developed for the determination of potassium. The method involves precipitation of potassium by addition of a known excess of sodium tetraphenylborate, removal of the potassium tetraphenylborate precipitate by filtration, and measurement of the excess of sodium tetraphenylborate in the filtrate by means of its absorbance at 254 mμ;. Most of the apparatus, including a continuous filter, is standard AutoAnalyzer equipment but a Uvicord ultraviolet absorptiometer replaces the conventional colorimeter. Build-up of precipitate in the system is eliminated by immersing the mixing coils in an ultrasonic bath which is actuated intermittently by a simple timing mechanism. The method is especially suitable for potassium analysis in production plant where flame photometer results are sometimes affected by fertilizer dust in the air surrounding the burner.     

Microcalorimetric studies of dodecacarbonyl(diiron)ruthenium and dodecacarbonyl(iron)diruthenium. Enthalpy contribution of heterometallic metal—metal bonds

Microcalorimetic measurements at 520–550 K of the heats of thermal decomposition of Fe₂Ru(CO)₁₂, FeRu₂(CO)₁₂ and Ru₃(CO)₁₂ lead to values of the standard enthalphy of formation (ΔH^o_f, c/kJ mol^-1) as follows: Fe₂Ru(CO)₁₂  (1820 ± 14); FeRu₂(CO)₁₂  (1891 ± 16); Ru₃(CO)₁₂  (1903 ± 18). Enthalpies of sublimation are estimated and the ironruthenium bond enthalpy contribution is derived as E(FeRu)  (95 ± 20) kJ mol^-1.     

Infrared and Raman line shapes of dilute HOD in liquid H2O and D2O from 10 to 90 degrees C

A combined electronic structure/molecular dynamics approach was used to calculate infrared and isotropic Raman spectra for the OH or OD stretches of dilute HOD in D2O or H2O, respectively. The quantities needed to compute the infrared and Raman spectra were obtained from density functional theory calculations performed on clusters, generated from liquid-state configurations, containing an HOD molecule along with 4-9 solvent water molecules. The frequency, transition dipole, and isotropic transition polarizability were each empirically related to the electric field due to the solvent along the OH (or OD) bond, calculated on the H (or D) atom of interest. The frequency and transition dipole moment of the OH (or OD) stretch of the HOD molecule were found to be very sensitive to its instantaneous solvent environment, as opposed to the isotropic transition polarizability, which was found to be relatively insensitive to environment. Infrared and isotropic Raman spectra were computed within a molecular dynamics simulation by using the empirical relationships and semiclassical expressions for the line shapes. The line shapes agree well with experiment over a temperature range from 10 to 90 degrees C.     

Inferring wettability of heterogeneous surfaces by ToF-SIMS

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) has been examined as a possible predictive tool for surface wettability. Heterogeneous surfaces were prepared with hydrophilic and hydrophobic regions of known surface coverage using self-assembled monolayers. The surface coverage of each component was then correlated with ToF-SIMS fragmentation of the hydrophobic and hydrophilic surface groups and static contact angle measurements. From these measurements, a clear relationship between the surface wettability and relative intensity of characteristic secondary ions was identified. Moreover, our results for planar surfaces can be extrapolated to predict the wettability of particulate samples for which direct contact angle measurements are not straightforward. The ability to infer particle wettability by ToF-SIMS is well suited to mineral characterization and in particular, the prediction of mineral flotation efficiencies.     

A mode-coupling theory of vibrational line broadening in near-critical fluids

We present a fully microscopic mode-coupling theory of near-critical line broadening. All the structural and dynamical input required by the theory is calculated directly from intermolecular potentials. We compute vibrational frequency time-correlation functions and line shapes as the critical point is approached along both the critical isochore and the liquid-gas coexistence curve. Theory is shown to be in good agreement with simulation.     

Non-symmetric 2-designs modulo 2

Necessary conditions are obtained for the existence of a 2 – (v, k, ) design, for which the block intersection sizess ₁,s ₂, ...,s _n satisfys ₁ s ₂ ... s _n s (mod 2 ^e ), wheree is odd. These conditions are obtained by combining restrictions on the Smith Normal Form of the incidence matrix of the design with some well known properties of self-orthogonal binary codes with all weights divisible by 4.Research done at AT&T Bell Laboratories.