The Adsorption and Thermal Decomposition of CH2CO (CD2CO) on Si(111)-7 × 7

The adsorption and thermal decomposition of ketene on Si(l 11)-7 × 7 were investigated using various surface analysis techniques. When the surface was exposed to ketene at 120 K, two CO stretching modes at 220 and 273 meV appeared in HREELS, corresponding to two adsorbed ketene states. After the sample was annealed at ?250 K, the 273 and the 80 meV peaks vanished, indicating the disappearance of one of the adsorption states by partial desorption of the adsorbate. In a corresponding TPD measurement, a desorption peak for ketene species was noted at 220 K. Annealing the sample at 450 K caused the decomposition of the adsorbate, producing CH_x and O adspecies. Further annealing of the surface at higher temperatures resulted in the breaking of the CH bond, the desorption of H and O species and the formation of Si carbide. The desorption of H at 800 K was confirmed by the appearance of the D₂ (m/e = 4) TPD peak at that temperature when CD₂CO was used instead of CH₂CO.     

Synthesis of 9-(2,3-dihydroxy-1-propoxymethyl)guanine - a new potential antiviral agent

Coupling of tris(trimethylsilyl)guanine (4) with 1,2-di-$\text{O}$-acetyl-3-$\text{O}$chloromethyl glycerol (3), followed by removal of the protecting groups afforded 9-(2,3-dihydroxy-1-propoxy)guanine (1). Compound 1 exhibited potent antiviral activity.     

Laser-induced reactions of NO2 in the visible region

The reaction of NO₂ with isobutane, induced by 488 nm laser radiation, to form 2-nitro-2-methylpropane has been investigated and the results computer-modeled according to two possible reaction mechanisms. The first scheme involves the direct abstraction of H from isobutane by vibronically excited NO₂ (NO ₂ ^* ), and the second, abstraction by an intermediate NO₃ radial produced by NO ₂ ^* +NO₂. The modeling results strongly support the NO ₂ ^* scheme as the dominant reaction mechanism.     

The Study on the Thermal Stability of CLA in Egg Yolk

Conjugated linoleic acids (CLA) have been a subject of extensive investigation for their anticarcinogenic, hypolipidemic, antiatherosclerotic and immune-enhancing activities. Stability of CLA in foods has not received much attention by both academics and industry. Although CLA has shown many beneficial effects, its decomposition must be prevented when CLA in foods is processed, stored and transported. However, no study to date has addressed the stability of CLA in foods. The present study was carried out further to examine the stability of CLA in egg yolk during the storage and frying, using gas liquid chromatography (GLC) and silver ion high-performance liquid chromatography (Agt-HPLC). The eggs, containing 4.0% CLA per gramme of egg yolk, were 40s. Either storage for 6 months or frying for 40 s did not significantly change the composition of CLA in egg yolk. However, the degradation of CLA was statistically significant when the CLA components of egg yolk protected CLA from degradation. It is concluded that CLA is well preserved in egg before it is consumed.     

Properties of nanobelts and nanotubes measured by in situ TEM.

Characterizing the physical properties of individual nanostructures is challenging because of the difficulty in manipulating the objects of sizes from nanometers to micrometers. Most nanomeasurements have been carried using scanning probe microscopy. In this article, we demonstrate that transmission electron microscopy can be a powerful tool for quantitative measurements of the mechanical and electrical properties of a single nanostructure. Dual-mode resonance of an oxide nanobelt has been observed, and its bending modulus has been measured. An in situ technique was demonstrated for measuring the work function at the tip of a carbon nanotube. The ballistic quantum conductance of a multiwalled carbon nanotube was observed at room temperature using the setup in TEM. It is concluded that in situ measurement by directly linking structure with property is a future direction of electron microscopy.     

The thermal reaction of HNCO at moderate temperatures

The thermal reaction of HNCO has been studied in a static cell at temperatures between 873 and 1220 K and a constant pressure of 800 torr under highly diluted conditions. The reaction was measurable above 1000 K by FTIR spectrometry. The products detected include CO, CO₂, HCN, NH₃, and the unreacted HNCO. In this moderate temperature regime, the rates of product formation and HNCO decay cannot be accounted for by a previously established high-temperature mechanism, assuming HNCO → NH + CO (1) as the initiation process. Instead, a new bimolecular reaction, 2HNCO → CO₂ + HNCNH (2), has been invoked to interpret the disappearance of HNCO as well as the formation of various products, most importantly CO₂. The concentration profiles of all measured species can be quantitatively modeled, throughout the temperature range analyzed, by varying k₂ using a modified mechanism. The kinetically modeled values of k₂ can be effectively represented by This result agrees closely with that computed with the conventional transition-state theory using the TST parameters predicted by the BAC-MP4 method: The bimolecular reaction takes place via a stable 4-membered ring intermediate which is isoelectronic with diketene; viz.      

Laser desorption of DNA oligomers larger than one kilobase from cooled 4-nitrophenol

A unique matrix system consisting mostly of 4-nitrophenol has shown to be very effective for matrix-assisted laser desorption/ionization time-of-flight mass spectrometric analysis of large DNA oligomers when a cooled sample stage was used to prevent the sublimation of this matrix under vacuum. Using this 4-nitrophenol matrix with UV laser desorption, detection of picomole quantities of DNA oligomers containing up to approximately 800 nucleotides was routinely achieved. The effectiveness of this matrix was further demonstrated by the observation of a double-stranded DNA oligomer larger than 1000 base pairs, seen as a denatured single-stranded species, with a molecular ion mass exceeding 300 000 Da. The potential applications of 4-nitrophenol as a matrix for DNA sizing are discussed.     

Anomalous Nitration Reactions of Halotropones and Tribromotropolone

Nitration of 2-bromo or 2-chlorotropone gave a new compound, 2,7-dinitrotropone: The halegen atom on the 2-position was displaced by the nitro group through an electrophilic substitution reaction. Nitration of 3,5,7-tribromotropolone gave 3,7-dibromo-5-nitropolone: the nitro group again displaced the bromine atom at position 5.     

Novel Phenomenon of Oxygen-to-oxygen Silyl Migration in Directed Aldol Reaction

The phenomenon of migration of the silyl groups from α-oxygen to β-oxygen in sodium aldol reaction was observed for the first time in this paper.     

Dynamic NMR Studies of Some Halo and Mercaptide Bridged Palladium (II) Dimers

Some halo or mercaptide bridged palladium (II) dimers, [Pd(S₂CNR₂)X]₃ (R=ibutyl, X=Cl, Br, I, S-ethyl and S-t-butyl) were studied by variable temperature ¹H nmr spectroscopy. Line shape changes of the chloro and bromo bridged dimers were interpretated by the solvolytic breaking of the Pd-X bond, while mercaptide bridged complexes were explained in terms of slow N-C single bond rotation. The results consist with the strengthness of the class b metal ion with various soft donor ligands.