Silanization and non-aqueous electrochemistry of two oxide states on platinum electrodes

When the surface of a Pt electrode is oxidized in aqueous 1 M H₂SO₄ at +0.8 to +2.0 V vs. SSCE for a few seconds to 10 min, disconnected, washed and dried, and placed in CH₃CN solvent, a negative potential scan shows that the surface oxide is reduced in two waves at potentials between?1.2 and?1.6 V vs. SSCE. The combined charge of the two waves amounts to 0.3–2.5 layers of oxide, depending on anodization potential and time. The more easily reduced oxide becomes non-reducible after reaction of the electrode with methyltrichlorosilane. The two oxide waves are interpreted as surface and subsurface oxide layers.     

Chrysomelidial by chromyl chloride oxidation: A revised structure for gastrolactone

Non-conjugated $\text{gem}$-dialkylated alkenes were oxidized to aldehydes in the presence of α,β-unsaturated carbonyl functional groups, providing a new synthesis of $\text{1}$ and a synthesis of $\text{2}$ that led to a revised structure for gastrolactone.     

The acid catalysed rearrangement of a diterpenoid epoxide

A study has been made of the principal rearrangement products resulting from formic acid treatment of 19-hydroxy-ent-beyerene epoxide (3). In concentrated solutions 3 has been found to undergo a deep seated rearrangement to the allylic alcohol (14). A mechanism for the formation of 14 is proposed involving a novel 1,4-hydride shift in the bicyclo[3:2:1]octane C/D ring system following cleavage of the C₁₅O bond. Supporting evidence has been obtained from a study of the specifically labelled epoxide (4), the deuterium in 14 appearing exclusively at C₁₂. Four products (7 and 11–13) emanating from the known beyerane → kaurane interconversion have been identified.     

Versatile solid-phase synthesis of secondary amines from alcohols. Development of an N-Boc-(o-nitrobenzene)sulfonamide linker

The development of a versatile amine releasing linker based on the modified o-nitrobenzene sulfonamide protective group is described. This new N-Boc-o-nitrobenzenesulfonamide (Boc-ONBS) linker enables the elaboration on resin of primary and secondary amines by sequential substitution of the sulfonamide moiety using the Mitsunobu reaction. A 16-member array of secondary and Boc protected primary amines was then prepared using this linker.     

X-ray photoelectron spectroscopy and magnetic studies on the effect of pore size, wall thickness, and wall composition on superparamagnetic cobaltocene mesoporous Nb, Ta, and Ti composites

Recent results in our group demonstrated that mixed oxidation state mesoporous niobium oxide cobaltocene composites display superparamagnetism at certain composition ratios. This was the first report of superparamagnetism in nanoscale molecular ensembles. A series of mesoporous niobium oxide materials were synthesized in order to understand the role of pore size and thickness of the walls in the mesostructure on the magnetic properties. Mesoporous Ti oxide and Ta oxide composites were also synthesized in order to investigate the effect of changing the wall composition on the magnetic properties of this new series of materials. All samples were characterized by X-ray diffraction, nitrogen adsorption, ultraviolet spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and superconducting quantum interference device magnetometry. The results of this study showed that variation of wall thickness or pore size in the Nb system had little effect on the properties and that superparamagnetism most likely arises from mixed oxidation state cobaltocene grains residing in the individual pores and not from the free electrons in the mesostructure or much larger domains. The Langevin function was applied to the isothermal magnetic data from the Nb composites and gave mean superparamagnetic particle sizes of ca. 14 nm in each system. The Co(II) to Co(III) ratios in these materials were approximately 1:1. The Ti and Ta materials showed no sign of superparamagnetism and only very low levels of neutral cobaltocene in the pores. This suggests that a critical amount of cobaltocene is required to bring about superparamagnetic behavior.     

Some diels—alder reactions of η1-bonded cyclopentadienylmetal compounds

Bis(cyclopentadienyl)mercury readily undergoes Diels—Alder reactions with RCCR (R = CO₂Me or CF₃), CF₃CFCFCF₃, CF₃CFCF₂, (CF₃)₂CC(CN)₂, C₂(CN)₄ and Ph$\text{NCONNC}$O to give stable adducts characterised by¹H, ¹⁹F and ¹³C NMR, spectroscopy. Similar reactions of CF₃CCCF₃ and CF₃CFCFCF₃ with the cyclopentadiene derivatives Me₃MC₅H₅ and (Me₃M)₂C₅H₄ (M = Si, Sn) are also described.     

The magnetic moment of103Ru

The nuclear magnetic moment of¹⁰³Ru has been determined using the technique of low-temperature nuclear orientation on¹⁰³Ru as a dilute impurity in Fe. The Fe lattice was cooled to 1.7 mK using a PrNi₅ enhanced nuclear demagnetisation stage precooled with a³He–⁴He dilution refrigerator. The¹⁰³RuFe system was observed to have a long nuclear spin-lattice relaxation time, but analysis of the relaxation indicates that the¹⁰³Ru nuclei are close to thermal equilibrium with the Fe lattice at times>200 min after demagnetising. From the near thermal equilibrium anisotropy of the 497 keV -ray in¹⁰³Rh we have deduced the nuclear magnetic moment as |(¹⁰³Ru)|=0.18(2)_N. This value is almost independent of the choice of spinI=3/2 or 5/2 for the nucleus, but is only consistent with systematics ifI(¹⁰³Ru)=3/2 and <0. UsingI=3/2 we obtain the E2/M1 mixing ratio of the 497 keV -ray as =–0.42(4). The sign of the anisotropy of the 610 keV -ray from the 650 keV level in¹⁰³Rh is only consistent with an allowed -decay to the state ifI(650 keV,¹⁰³Rh)=5/2. The E2/M1 mixing ratio of the 610 keV -ray is then =+0.15(3) or +60( _–40 ⁺ ), <–80. From the initial rise in -ray anisotropy following demagnetisation we determine the Korringa constant for¹⁰³RuFe to beC=5.7(5) K·s.     

Reciprocity principles associated with the general linear gravity wave problem

Summary Reziprocity principles are presented which hold for the general problem of small amplitude wave motion on the surface of an incompressible liquid. The effects of viscosity, surface tension, irrotationality, free surface sources and solid boundary geometry at liquid-solid intersections are discussed.

---

Zusammenfassung Reziprozitätsprinzipien, die für das allgemeine Problem der Wellenbewegung mit kleinen Amplituden auf der Oberfläche einer inkompressiblem Flüssigkeit gelten, werden angegeben. Die Einflüsse von Viskosität, Oberflächenspannung, Wirbelfreiheit, Quellen an der freien Oberfläche un die Geometrie fester Ränder bei flüssig-festen Übergängen werden diskutiert.

     

A SIFT ion-molecule study of some reactions in Titan's atmosphere. reactions of N(+), N(2)(+), and HCN(+) with CH(4), C(2)H(2), and C(2)H(4)

The results of a study of the ion-molecule reactions of N(+), N(2)(+), and HCN(+) with methane, acetylene, and ethylene are reported. These studies were performed using the FA-SIFT at the University of Canterbury. The reactions studied here are important to understanding the ion chemistry in Titan's atmosphere. N(+) and N(2)(+) are the primary ions formed by photo-ionization and electron impact in Titan's ionosphere and drive Titan's ion chemistry. It is therefore very important to know how these ions react with the principal trace neutral species in Titan's atmosphere: Methane, acetylene, and ethylene. While these reactions have been studied before the product channels have been difficult to define as several potential isobaric products make a definitive answer difficult. Mass overlap causes difficulties in making unambiguous species assignments in these systems. Two discriminators have been used in this study to resolve the mass overlap problem. They are deuterium labeling and also the differences in reactivities of each isobar with various neutral reactants. Several differences have been found from the products in previous work. The HCN(+) ion is important in both Titan's atmosphere and in the laboratory.     

Enantioselective synthesis of alpha-methyl-D-cysteine and lanthionine building blocks via alpha-methyl-D-serine-beta-lactone

[reaction: see text] We report here the enantioselective synthesis of Boc-alpha-methyl-d-cysteine(PMB)-OH and lanthionine building blocks through the regioselective ring opening of key intermediate Boc-alpha-methyl-d-serine-beta-lactone.