Large-scale separation of metallic and semiconducting single-walled carbon nanotubes

In the applications of single-walled carbon nanotubes (SWNTs), it is extremely important to separate semiconducting and metallic SWNTs. Although several methods have been reported for the separation, only low yields have been achieved at great expense. We show a separation method involving a dispersion-centrifugation process in a tetrahydrofuran solution of amine, which makes metallic SWNTs highly concentrated to 87% in a simple way.     

Asymmetric lithiation of 2-alkynyl aryl sulfides—Enantio- and diastereoselective formation of allenyl aryl sulfides and their application in nickel-catalyzed cross-coupling reactions

The enantio- and diastereoselective synthesis of allenyl aryl sulfides by asymmetric lithiation of 2-alkynyl (2-hetero)aryl sulfides is described. A dynamic thermodynamic resolution by selective crystallization of the intermediate lithium complexes derived from deprotonation, applying a bis(oxazoline) ligand, was achieved to give enantioselectivities up to 85% ee. Subsequent stereospecific nickel-catalyzed cross-coupling reactions with arylzinc reagents established a versatile access to threefold carbon-substituted allenes.     

Copolymerization of 2-methylene-4-phenyl-1,3-dioxolane with electrophilic vinyl monomers through zwitterionic mechanism

Spontaneous copolymerization of cyclic ketene acetal, 2-methylene-4-phenyl-1,3-dioxolane ( I ) with common electrophilic vinyl monomers, such as methyl α-cyanoacrylate (MCA), acrylonitrile (AN), and methyl methacrylate (MMA) were investigated to further explore zwitterion polymerization method with cyclic ketene acetals. In the reaction of I with MCA and AN, spontaneous copolymerization took place at ambient temperature. The copolymers of I with MCA gave low molecular weight polymers, but copolymers obtained with I and AN were high molecular weight polymers. In the reaction of I and MMA, high molecular weight copolymer was obtained only at temperatures above 80°C. Thus, obtained polymers were not the alternating copolymers and possessed high I content in all the cases. From the above results, macrozwitterionic mechanism was suggested as discussed.     

Synthetic studies on oxindole spiro-lactones with thalliumd(III) trinitrate: A formal total synthesis of (±)-tryptoquivaline G

(±)-Tryptoquivaline G was formally synthesized through shortened steps from tryptophan, in which oxidation with thallium(III) trinitrate(TTN) was effected at the crucial stage. The present work also constitutes the first synthesis of oxindole lactones carrying 2-alkyl quinazolinones.     

Planar chiral cyclic ether: asymmetric resolution and chirality transformation

Remarkably stable planar chirality was found in a nine-membered diallylic cyclic ether. Enantiomerically enriched ether was prepared by a kinetic resolution of a racemic one, which is valuable as a novel type of chiral building block.     

Cationic ring-opening transfer polymerization of spiro ortho esters initiated by carbon black

The ring-opening transfer polymerization of spiro ortho esters (SOE) initiated by carbon black was investigated. In the absence of carbon black, no polymerization occurred at all. In the presence of channel black containing carboxyl group, the ring-opening transfer polymerization of SOE was initiated at 50-70°C. to give polyether ester, namely alternating copolymer of epoxide and lactone. The rate of polymerization of 1,4,6-trioxaspiro[4.4]nonane and 1,4,6-trioxaspiro[4.5]decane was considerably small compared with that of 1,4,6-trioxaspiro[4.6]undecane. The activation energy of the polymerization of 2-chloromethyl-1,4,6-trioxaspiro[4.6]undecane was estimated to be 6.0 kcal/mol. The initiating activity of carbon black increased with an increase in carboxyl group content of carbon black. Furnace black that contained no carboxyl group was unable to initiate the polymerization. Furthermore, the carbon black lost the initiating ability of the polymerization upon the blocking of carboxyl group on the surface by the treatment with potassium hydroxide or diazomethane. Based on these results, it was concluded that carboxyl group on carbon black plays an important role in the initiation. During the polymerization, a part of the polymer formed was grafted onto carbon black: the grafting ratio was 10–30%. The mechanisms of initiation and grafting were discussed.     

Mechanism and elimination of interferences in flame photometry

Summary The mechanism of the suppressing effects of aluminium, borate, phosphate, sulphate upon calcium radiation has been investigated. A very stable long flame was used with a specially designed Meker Burner. Variations in the interferences were observed when Ca and those interfering substances were separately atomized into one and same flame, and also when the point in the flame from which the light was drawn was changed by the use of a specially designed optical system attached to a Hitachi-EPU-2 A spectrophotometer. It is concluded that the suppression of Ca radiation is caused by hindering of the vaporization process because of the formation of non-volatile compounds of Ca with those interfering substances.A method of eliminating the suppressing effects of borate, phosphate and sulphate on alkaline earth radiations has been suggested.

---

Zusammenfassung Die durch Aluminium, Borat, Phosphat und Sulfat hervorgerufene Intensitätsminderung der durch Calcium bedingten Flammenfärbung wurde untersucht. Bin besonders konstruierter Meker-Brenner wurde zur Erzeugung einer sehr konstanten und langen Flamme verwendet. Versprüht man das Calcium und die erwähnten Störstoffe in dieselbe Flamme oder wechselt man die zur Lichtmessung gewählte Flammenregion unter Verwendung eines dafür geeigneten, an einem Hitachi-EPU-2 A-Spektrophotometer angebrachten optischen Systems, so zeigen sich jeweils verschieden starke Störungen. Daraus ergibt sich, daß die Unterdrückung der Calcium-Strahlung durch eine Beeinträchtigung des Verdampfungsvorganges infolge Bildung nichtflüchtiger Verbindungen verursacht wird, die sich aus Calcium und den angeführten Störstoffen bilden.Ein Verfahren zur Beseitigung des durch Borat, Phosphat und Sulfat herbeigeführten Unterdrückungseffektes auf alkalische Erden wurde vorgeschlagen.

---

Résumé Recherche sur le mécanisme des effets de suppression de l'aluminium, des borates, des phosphates, des sulfates sur la radiation du calcium. A cette fin, l'auteur a employé une flamme longue, trés stable d'un brûleur Meker spécialement prévu. Des variations de ces effets ont pu être constatées lorsque le calcium et les substances gênantes étaient atomisés séparément dans un flamme unique et lorsqu'on faisait varier le point de la flamme émetteur de la lumière observée; ces mesures ont été rendues possibles par l'emploi d'un système optique spécialement conçu fixé à un spectrophotomètre Hitachi-EPU-2 A. La conclusion de ce travail est que la suppression de la radiation du calcium est dûe à un processus d'empêchement de la vaporisation inhérent, à la formation de composés non volatils du calcium avec les substances gênantes.L'auteur suggère une méthode permettant l'élimination des effets de suppression des borates, des phosphates et des sulfates sur les radiations des alcalino-terreux.

---

---

This work was precented before The Eleventh Annual Meeting of The Chemical Society of Japan, in Tokyo, April, 1958.     

Synthesis of a novel bridged nucleoside bearing a fused-azetidine ring, 3′-amino-3′,4′-BNA monomer

A novel bridged nucleic acid monomer, 3′-amino-3′-deoxy-5-methyl-3′-N,4′-C-methyleneuridine, was successfully synthesized via a useful and convenient azetidine ring formation under Staudinger's conditions. A ¹H NMR experiment and a PM3 calculation revealed that the sugar moiety of the novel bridged nucleic acid monomer, 3′-amino-3′,4′-BNA, was restricted to S-type conformation.     

Preparation of enol ethers by carbonyl olefination utilizing an alkoxymethyl chloride-titanocene(II) system

Aldehydes, ketones, esters and lactones are transformed into enol ethers or 1,2-dialkoxy-1-alkenes by treatment with organotitanium species prepared from alkoxymethyl chlorides and a titanocene(II) complex.     

A novel scheme of heterogeneous polymerization of ethylene

The heterogeneous polymerization of ethylene initiated by radiation in tert-butyl alcohol was studied. The polymerization was carried out in a 100-ml reactor at 25–100°C and pressures of 200–300 kg/cm² in the presence of 50 ml of tert-butyl alcohol containing 7 wt-% water. The amounts of polymerized monomer, the average molecular weight of polymer formed, and the molecular weight distribution of polymer were measured at various stages of reaction and at various temperatures. The molecular weight distribution was found to be very much dependent on the reaction time and temperature. For the polymer formed at 50–60°C in the very early stages of reaction, the molecular weight distribution is unimodal, and in the intermediate stage a shoulder appears at a molecular weight higher than the first peak which increases as the polymerization proceeds; eventually a bimodal curve is formed. The bimodal distribution curves were analyzed to determine the fractions and average molecular weights of the each peak. On the basis of these data for the molecular weight distribution and kinetic behavior, a new scheme for the heterogeneous polymerization is proposed which indicates that the polymerization proceeds via propagating radicals in two different physical states, namely, loose and rigid states.