Synthesis of 1H-naphth[2,3-d]imidazole-4,9-diones by acid catalyzed cyclization of 2-Acylamino-3-amino-1,4-naphthoquinones

The conversion of 2-acylamino-3-amino-1,4-naphthoquinones (II) to the corresponding 2-substituted 1H-naphth[2,3-d]imidazole-4,9-diones (I) under both alkaline and acid catalyzed conditions has been effected and the results compared. Treatment of 3-(4′-chlorobutanonyl-amino)-3-amino-1,4-naphthoquinone (He) with aqueous ethanolic sodium hydroxide solution gives 1,2-butanonaphth[2,3-d]imidazole-4,9-dione (V); whereas, treatment of lie with refluxing formic acid gave 2-(4′-chlorobutyl)-1H-naphth[2,3-d]imidazole-4,9-dione. Treatment of 2-substi-tuted 1H-naphth[2,3-d]imidazole-4,5-diones in DMF with alkyl halides in the presence of potassium carbonate affords the expected 1,2-disubstituted naphth[2,3-d]imidazole-4,9-diones (VI). The spectral properties of I, II, V and VI as well as those of some 2-acylamino-3-chloro-1,4-naphthoquinones IV are discussed.     

The structure of wholly aromatic polyesters with bulky side chains: Poly(phenylene phenyl-terephthalate)

Abstract

The thermotropic polyester prepared from phenyl-terephthalic acid and hydro-quinone is highly crystalline, despite the probable random 2-and 3-disposition of the phenyl substituents. The x-ray pattern of melt-spun fibers contains 18 Bragg reflections that are indexed by a monoclinic unit cell with dimensions a = 28.0 Å. b = 4.89 Å, c = 12.48 Å (fiber axis), and γ = 114.8°, containing monomer units of four chains. In the ac-plane, the chains are arranged in pairs with the phenyl side chains interdigitated; successive pairs of chains are staggered by about c/2. We have used molecular mechanics modeling to simulate arrays of chains with random 2-and 3-disposition of the side chains on the terephthalic acid units and have compared the results with those for a similar structure in which all the substituents were at the 2-position. The refined model for random substitution is distorted, but the average separations of the monomer units are within experimental error of the observed unit cell dimensions, and their standard deviations are very similar to those derived from the line-broadening data. The potential energy of the random substitution model is only about 1 kcal/mol of monomer higher than that for the model with all 2-substitution, indicating the random substitution is not a problem for the formation of an ordered structure.     

Exploiting site-site interactions on solid support to generate dimeric molecules

[structure: see text]. "Intra-site" olefin cross-metathesis on solid support leads to nearly quantitative yields of dimeric molecules.     

Deformation der Mikrofibrillen von Baumwoll-und Bakterien-Cellulose

Ohne Zusammenfassung     

A magic-angle rotor for NMR using a forced gas bearing

A new design for a rotor system to achieve spinning rates of the order of 3 kHz is presented. The design uses a simple cylindrical rotor, and involves a forced air bearing over the whole cylindrical surface. The jets of gas which make this bearing also cause the spinning. Powder-filled hollow rotors spin smoothly, and are convenient to make and use. The whole system is suitable for magic angle rotation, such as is needed to obtain high-resolution NMR spectra of solids. Examples of spectra obtained using the device are illustrated and discussed.     

Amino Acid Sequence of N-Terminal Peptide of Normal Human Serum Albumin

From the peptic digest of normal human serum albumin., the N-terminal peptide comprising 24 amino acid residues was obtained by means of peptide mapping. Combined uses of trypsin, α-chymotrypsin, thermolysin, carboxypeptidase A and Dansyl-Edman technique resulted in the elucidation of amino acid sequence of no. 1 to no. 24 as follows: NH₂-Asp-Ala-His-Lys-Ser-Glu-Val-Ala-His-Arg-Phe-Lys-Asp-Leu-GIy-Glu-Glu-Asn-Phe-Lys-Ala-Leu-Val-Leu-COOH These sequence results agree completely with those recently published by other workers.     

Drilling and operational sounds from an oil production island in the ice-covered Beaufort sea

Recordings of sounds underwater and in air, and of iceborne vibrations, were obtained at Northstar Island, an artificial gravel island in the Beaufort Sea near Prudhoe Bay (Alaska). The aim was to document the levels, characteristics, and range dependence of sounds and vibrations produced by drilling and oil production during the winter, when the island was surrounded by shore-fast ice. Drilling produced the highest underwater broadband (10-10,000 Hz) levels (maximum= 124 dB re: 1 microPa at 1 km), and mainly affected 700-1400 Hz frequencies. In contrast, drilling did not increase broadband levels in air or ice relative to levels during other island activities. Production did not increase broadband levels for any of the sensors. In all media, broadband levels decreased by approximately 20 dB/tenfold change in distance. Background levels underwater were reached by 9.4 km during drilling and 3-4 km without. In the air and ice, background levels were reached 5-10 km and 2-10 km from Northstar, respectively, depending on the wind but irrespective of drilling. A comparison of the recorded sounds with harbor and ringed seal audiograms showed that Northstar sounds were probably audible to seals, at least intermittently, out to approximately 1.5 km in water and approximately 5 km in air.