Simple synthesis of endo-2-bromo-5-thiabicyclo[2.1.1]hexane

A brief synthesis of endo-2-bromo-5-thiabicyclo [2.1.1]hexane ( 9 ) has been developed involving conversion of 3-cyclopentenol ( 6 ) to 3-thioacetoxycyclopentene ( 7 ), bromination of this giving trans-1,2-dibromo-4-thioacetoxycyclopentane ( 8 ), and treatment of the latter with base. Compound 9 is oxidized to its S-oxide 10 and S, S-dioxide 11 . Comparative ¹³C and ¹H NMR data are given for 9–11 .     

Determination of organophosphate pesticides at a carbon nanotube/organophosphorus hydrolase electrochemical biosensor

An amperometric biosensor for oganophosphorus (OP) pesticides based on a carbon nanotube (CNT)-modified transducer and an organophosphorus hydrolase (OPH) biocatalyst is described. A bilayer approach with the OPH layer atop of the CNT film was used for preparing the CNT/OPH biosensor. The CNT layer leads to a greatly improved anodic detection of the enzymatically generated p-nitrophenol product, including higher sensitivity and stability. The sensor performance was optimized with respect to the surface modification and operating conditions. Under the optimal conditions the biosensor was used to measure as low as 0.15 μM paraoxon and 0.8 μM methyl parathion with sensitivities of 25 and 6 nA/μM, respectively.     

Electrostatic fields above individual atoms

This review describes recent field ion microscopic measurements of local electrostatic fields in the immediate vicinity of individual surface atoms. The studies were stimulated and supported by self-consistent theoretical calculations on the field distribution close to single atoms of different electronic structure adsorbed on a metal surface in the presence of high external fields. The experimental and theoretical data establish the existence of strongly varying local field distributions above different surface atoms. New details concerning localized field ionization and image formation processes occurring in the field ion microscope are revealed.     

The carbides RE2MnC4 (RE = Y,Er, Tm) with Er2FeC4-type structure

The title compounds were prepared from coldpressed pellets of the elemental components by arcmelting. They crystallize with the orthorhombic Er₂FeC₄-type structure, which was refined from X-ray data of an Er₂MnC₄ single crystal: Ibam, a = 760.4(1)pm, b = 937.1(1)pm, c = 504.0(1)pm, R = 0.021 for 524 structure factors and 17 variable parameters. Y₂MnC₄ does not become superconducting down to 1.7 K. Chemical bonding in these compounds is briefly discussed.