Polyfluorobicyclo(2,2,1)heptanes Part VIII. Bis(undecafluorobicyclo(2,2,1)heptan-1-yl)- and bis(4H-decafluorobicyclo(2,2,1)heptan-1-yl)-mercury

The title compounds were prepared from 1-lithio-undecafluorobicylco(2,2,1)-heptane, and from 1H,4-lithio-decafluorobicyclo(2,2,1)heptane and 1H-decafluorobicyclo(2,2,1)hept-4-yl magnesium iodide with mercuric chloride. With sulphur and caesium fluoride in dimethyl formamide, both mercurials gave the corresponding thioxides and these on hydrolysis gave the known bridgehead thiols. With sulphur alone, the undecafluoro mercurial gave mainly the disulphide and a range of polysulphides, under conditions which left the 4H-decafluoro mercurial unchanged. Conventional d.c. polarography of the mercurials indicated an inconsistency in the use of this method for determining the acidities of highly fluorinated hydrocarbons.     

High-capacity method for purification of human liver hexosaminidase B using hydrophobic chromatography

Hydrophobic chromatography was investigated as a purification procedure for human liver hexosaminidases. Both phenyl-Sepharose and valine-Sepharose have a high binding capacity for hexosaminidases. A degree of resolution between the A and B isozymes is achieved with phenyl-Sepharose.Both hydrophobic supports myst be used close to their capacity in order to recover the applied enzyme.Two purification procedures for human liver hexosaminidase B were employed, which resulted in recoveries of approximately 48 and 24% with final specific activities of 33,400 and 4840 nmole/min·mg, respectively.     

Kinetics of the metathetical reaction between carbon tetrachloride and toluene

A metathetical reaction between carbon tetrachloride and toluene to give benzyl chloride and chloroform occurs at temperatures above 200°C (k = 4.8 × 10¹⁰ e^?32,900/RT cc mole^?1sec^?1). The reaction does not involve free radicals, as is shown by the kinetic behavior of the system, by the lack of effect of added free-radical chain inhibitors, and by the absence of the expected chain termination product, hexachloroethane. The reaction is one of a general type between carbon tetrachloride and alkanes or alkylaromatics, but at the temperatures required it is often obscured by dehydrohalogenation of the product to the highly reactive olefin. At high temperatures, benzyl chloride reacts with toluene to give bibenzyl and hydrogen chloride, apparently also by a metathetical reaction. The transition state is postulated to be four-center, in which the carbon-chlorine and carbon–hydrogen bonds are broken and reformed: The experimental preexponential factor is in good agreement with that calculated from transition-state theory.     

Laser-excited fluorescence of CSCl2

Resonance fluorescence spectra of the $\text{A}\text{?}{}^1\text{A}{}_2\text{→}\text{X}\text{?}{}^1\text{A}{}_1$ system of CSCl₂ are excited by an Ar⁺ laser operated at 5145 Å. The radiation is selectively absorbed by the 2₀¹3₀¹4₀¹ transition of the ³⁵Cl₂CS isotope. About 55 fluorescence bands have been measured and assigned, and the vibrational constants of the ground state have been calculated from the observed displacements.     

Supercooling of the disordered vortex lattice in Bi(2)Sr(2)CaCu(2)O(8+delta)

Time-resolved local induction measurements near the vortex lattice order-disorder transition in optimally doped Bi(2)Sr(2)CaCu(2)O(8+delta) crystals show that the high-field, disordered phase can be quenched to fields as low as half the transition field. Over an important range of fields, the electrodynamical behavior of the vortex system is governed by the coexistence of ordered and disordered vortex phases in the sample. We interpret the results as supercooling of the high-field phase and the possible first-order nature of the order-disorder transition at the "second magnetization peak."     

Direct detection of discharge products in lithium-oxygen batteries by solid-state NMR spectroscopy

A closer look: Solid-state (7) Li and (17) O?NMR spectroscopy is a valuable tool in the characterization of products formed in the lithium-oxygen battery, a necessary step in the development of a viable cell. Since lithium peroxide, the desired discharge product, has a unique (17) O?NMR signature, it can be clearly identified.