On travelling-wave solutions to systems of conservation laws with singular viscosity

Abstract. The method of vanishing artificial viscosity is used to obtain smooth, largedata travelling-wave solutions to a class of conservation laws with semidefinite viscosity. The one-dimensional Navier-Stokes equations serve as an illustrating example.     

Infrared vibration-rotation spectrum and structure of OCS dimer

Direct observations of infrared absorption in the weakly bound dimer of carbonyl sulphide, produced in pulsed molecular beams, have been made. Diode laser spectra in the 5 micron, carbonyl stretching, wavelength region were recorded with FWHM linewidths of approximately 100 MHz. All of the observations are consistent with OCS dimer having a C _2h , centrosymmetric geometry, with the centres of mass of the monomers nearly opposite one another. This essentially perpendicular structure places the S atoms close to the centre of the complex. The perpendicular distance between the monomer axes is 3·64 Å. Intermolecular potential functions containing dispersion and electrostatic contributions are discussed.     

Palladium‐Catalyzed Regioselective C‐Benzylation via a Rearrangement Reaction: Access to Benzyl‐Substituted Anilines

An unprecedented C‐benzylation rearrangement reaction, catalyzed by palladium, is reported. The reaction proceeds by rearrangement leading to the direct synthesis of para or ortho benzyl‐substituted N‐methylanilines. The product is obtained in high regioselectivity, without the need to use a ligand for the catalytic process.     

Preparative access to medicinal chemistry related chiral alcohols using carbonyl reductase technology

Libraries of highly enantioenriched secondary alcohols in both enantiomeric forms were synthesised by enzymatic reduction of their parent ketones using selectAZyme? carbonyl reductase (CRED) technology. Commercially available CREDs were able to reduce a range of substrate classes efficiently and with very high enantioselectivity. Matching substrate classes to small subsets of CREDs enabled the fast development of preparative bioreductions and the rapid generation of 100–1500 mg samples of chiral alcohols in typically >95% ee and the majority in ?99.0% ee. The conditions for small scale synthesis were then scaled up to 0.5 kg to deliver one of the chiral alcohols, (S)-1-(4-bromophenyl)-2-chloroethanol, in 99.8% ee and 91% isolated yield.     

Characterization of the Reaction of Chloroacetaldehyde with Single and Double Stranded DNA

Chloroacetaldehyde reacts with viral M13mp18 single and double stranded DNA to form the highly fluorescent adducts, etheno-AMP and etheno-CMP.

Absorbance and fluorescence spectroscopy can be used to monitor and characterize these reactions. Both single and double stranded DNA showed increases in the absorbance following reaction with the aldehyde. The fluorescence also increased in these two groups and continued to rise with increasing time of incubation until a point of saturation was reached. The fluorescence of the double stranded moiety was considerably enhanced following reaction with the aldehyde while that of the single stranded population was not, making this method appropriate for the separation of small quantities of the two populations of DNA.     

A Benzylation Study of 2,3-Dichloronaphthazarin

Depending on different reaction time and temperature employed, benzylation of 2,3-dichloronaphthazarin (I) using silver oxide as the catalyst can form either exclusively 5,8-dibenzyloxy-6,7-dichloronaphthalene-1,4-dione (II), or exclusively 5-benzyloxy-2,3-dichloro-8-hydroxynaphthalene-1,4-dione (IV); or a mixture of II and 5,8-dibenzyloxy-2,3-dichloronaphthalene-1,4-dione (III). Structures of these compounds were identified by nmr analysis.