Use of 1-alkyl-3-methylimidazolium hexafluorophosphate room temperature ionic liquids as chelate extraction solvent with 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione

Possible use of room temperature ionic liquids (RTILs) as chelate extraction solvent was evaluated by using 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF₆]), 1-hexyl-3-methylimidazolium hexafluorophosphate ([hmim][PF₆]) and 1-octyl-3-methylimidazolium hexafluorophosphate ([omim][PF₆]). These RTILs showed high extraction performance for divalent metal cations with 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione (Htta). The extracted metals were back-extracted into 1 mol dm⁻³ nitric acid quantitatively. Furthermore, the extracted species were estimated as neutral hydrated complexes M(tta)₂(H₂O)_n (n= 1 or 2) for M = Ni, Cu and Pb and anionic complexes M(tta)₃⁻ for M = Mn, Co, Zn and Cd.     

Use of dicyclohexano-18-crown-6 to separate traces of silver(I) from potassium thiocyanate in hydrochloric acid media,and determination of the silver by atomic absorption spectrometry

Solvent extraction with 0.05 mol L(-1) dicyclohexano-18-crown-6 (DC18C6) in 1,2-dichloroethane, coupled with flame atomic absorption spectrometry (AAS), has been investigated as a new method for separation of trace amounts of silver(I) from 0.05 mol L(-1) potassium thiocyanate in 1.0 mol L(-1) hydrochloric acid media and quantification of the amount of silver present. The method is based on the formation of an extractable ion-association product, [DC18C6.K](+)[Ag(SCN)(2)](-), with a metal-to-crown ether ratio of 1:1 (as derived from slope analysis data). Stripping of the extracted silver(I) in the 1,2-dichloroethane phase was achieved within 5 min by use of 3.0 mol L(-1) potassium thiocyanate. Reducing the concentration of acid in the sample solution to 0.1 mol L(-1) improved the preconcentration factor severalfold. Excellent tolerance of the proposed method to the presence of foreign ions in solution with silver(I) was demonstrated. A detection limit of 13 ng mL(-1) was derived from the mean value of the blank plus three times its standard deviation. The method was used to determine traces of silver(I) after separation from gold(III), platinum(IV), and palladium(II) matrices on the basis of extractability differences with 18-membered crown ethers under specified conditions. The efficiency of the adopted ion-association mechanism for silver(I) extraction was apparent from the average recovery of 96% for spiked standards by use of the back-washing technique. The proposed extraction procedure was applied to the determination of traces of silver(I) in a selection of chemical reagents.     

Compressed Corannulene in a Molecular Cage

Self‐assembled coordination cages can be employed as a molecular press, where the bowl‐shaped guest corannulene (C₂₀H₁₀) is significantly flattened upon inclusion within the hydrophobic cavity. This is demonstrated by the pairwise inclusion of corannulene with naphthalene diimide as well as by the dimer inclusion of bromocorannulene inside the box‐like host. The compressed corannulene structures are unambiguously revealed by single‐crystal X‐ray analysis.     

Alternate stranded triplex formation of chimeric DNA composed of tandem alpha- and beta-anomeric strands

A chimeric oligoDNA composed of a natural beta-anomeric oligonucleotide portion and an unnatural alpha-anomeric oligonucleotide portion forms an alternate stranded triplex possessing enhanced thermal stability compared to the triplexes composed of the parental oligomers.     

Explosive fragmentation of a thin ceramic tube using pulsed power

This study experimentally examined the explosive fragmentation of thin ceramic tubes using pulsed power. A thin ceramic tube was threaded on a thin copper wire, and high voltage was applied to the wire using a pulsed power generator. This melted the wire and the resulting vapor put pressure on the ceramic tube, causing it to fragment. We examined the statistical properties of the fragment mass distribution. The cumulative fragment mass distribution obeyed the double exponential or power law with exponential decay. Both distributions agreed well with the experimental data. Finally, we obtained universal scaling for fragmentation, which is applicable to both impact and explosive fragmentation.     

Age-dependent plasticity in the superior temporal sulcus in deaf humans: a functional MRI study

Background  

Sign-language comprehension activates the auditory cortex in deaf subjects. It is not known whether this functional plasticity in the temporal cortex is age dependent. We conducted functional magnetic-resonance imaging in six deaf signers who lost their hearing before the age of 2 years, five deaf signers who were >5 years of age at the time of hearing loss and six signers with normal hearing. The task was sentence comprehension in Japanese sign language.     

Efficient synthesis of (±)-γ-lycorane employing stereoselective conjugate addition to nitroolefin

(±)-γ-Lycorane 3 was synthesized in 52% overall yield via seven steps from 5 by employing the highly stereoselective nitro-Michael cyclization of 5 to 9 and diastereoselective conjugate addition of aryllithium to a nitroolefin 10 as two key steps.     

Total synthesis of (+/-)-alpha- and beta-lycoranes by sequential chemoselective conjugate addition-stereoselective nitro-Michael cyclization of an omega-nitro-alpha,beta,psi,omega-unsaturated ester

[reaction: see text] An omega-nitro-alpha,beta,psi,omega-unsaturated ester underwent a chemoselective conjugate addition of a nitroolefin moiety with aryllithium to produce a psi-aryl-omega-nitro-alpha,beta-unsaturated ester, which was then stereoselectively cyclized by intramolecular nitro-Michael reaction giving a functionalized cyclohexane applicable to the total synthesis of (+/-)-alpha- and beta-lycoranes.