Molecular composites in thermosets

The synthesis of molecular composites where rigid polymer molecules are reinforcing elements in a thermoset bisimide matrix has been investigated. The approach has been designed to avoid phase separation by selecting systems where reaction of amine-terminated rigid and semiflexible oligomers with maleimide unsaturation occurs prior to crosslinking of the thermoset. This objective has been met for some compositions. The concentration and molecular weight of the rigid oligomers have been varied. The structure of the reinforcing polymer, the reactivity of the maleimide and the conditions for composite synthesis are variables of critical importance, and further work must determine the promise and limitations of this approach.     

Analytical characterisation of pigments on pre-Roman pottery by means of spectroscopic techniques Part I: white coloured shards

This paper is part of a systematic archaeometric investigation aimed at the characterisation of the pigments and related materials (ligand, colour substrate) used in decoration of pottery excavated in the archaeological zone of Canosa (Puglia, Italy). Shards found in thirteen different tombs have been analysed; in this paper samples exhibiting a white colouration have been selected. Both surface (XPS) and bulk (FT-IR) spectroscopies were used which gave complementary information and enabled white pigments to be divided into two groups. Moreover, X-ray diffraction was used in some cases to further support some spectral assignments. The molecular specificity of FT-IR, when applied to the analysis of both pigments and ceramic body, allowed the identification of the various constituents and, hence, provided indirect information on the end-use of the original wares. The potential of the combined use of different spectroscopies to obtain valuable information on both painting materials and technical aspects is shown.     

Synthesis of new 1,2,3-triazolo[1,2-a]benzotriazole derivatives or substituted 2,3-benzo-1,3a,6,6a-tetraazapentalenes. II

This paper continues the synthesis of new 1,2,3-triazolo[1,2-a]benzotriazoles or 2,3-benzo-1,3a,6,6a-tetrazapentalenes to submit to biological assays. The derivatives were obtained by deoxycyclization reactions of appropriate nitrophenyl-1,2,3-triazole derivatives and by thermal decomposition of appropriate azidophenyl-1,2,3-triazoles (Schemes 1 and 2). Some attempts to extend these synthetic routes to the preparation of 1,2,4-triazolo[1,2-a]benzotriazoles (Scheme 3) and 1,2,3-triazolo[1,2-b]-4H-1,2,3-benzo-triazines (Scheme 4) completely failed.     

New 1,2,3‐triazolo[4,5‐e]1,2,4‐triazolo[4,3‐c]pyrimidine derivatives II

The 7‐chloro‐3‐(2‐chlorobenzyl)‐ and 7‐chloro‐3‐(2‐fluorobenzyl)‐1,2,3‐triazolo[4,5‐d]pyrimidines ( 1 and 4 ), by nucleophilic replacement with some hydrazides, gave the corresponding 7‐hydrazidoderivatives ( 2a‐e and 5a‐e ). These, by heating in Dowtherm, underwent an intramolecular cyclization to form the new tricyclic 7‐substituted‐3‐(2‐chlorobenzyl)‐ and 3‐(2‐fluorobenzyl)‐1,2,3‐triazolo[4,5‐e]1,2,4‐triazolo[4,3‐c]pyrimidines ( 3a‐d and 6a‐d ). The 7‐hydrazino‐3‐(2‐chlorobenzyl)‐ and 7‐hydrazino‐3‐(2‐fluorobenzyl)‐triazolo‐pyrimidines ( 9a and 9b ) were also prepared via the corresponding mercapto ( 7a and 7b ) and thiomethyl ( 8a and 8b ) derivatives.     

Transition metal-catalysed sequences of nucleophilic addition

Summary In presence of nickel or palladium catalysts, nucleophiles can attack vinylcyclopropanes with concomitant ring cleavage. With palladium catalysts in presence of appropriate substituents the terminal carbon atom of the resulting open chain is able to add to two molecules of a conjugated diene giving rise to long-chain unsaturated compounds.     

Synthesis of some 3,7-disubstituted quino[3,2-c][1,8]naphthyridines

The preparation of some 3,7-disubstituted-5,6-dihydroquino[3,2-c][1,8]naphthyridines ( 6 ) by the condensation of 7-substituted-2,3-dihydro-1,8-naphthyridin-4-(1H)ones ( 5 ) with o-aminoacetophenone or o-aminobenzophenone is described. All the 5,6-dihydroderivatives 6 were transformed into the fully aromatic compounds 7 by heating with nitrobenzene. Only a few quino[3,2-c][1,8]naphthyridines were previously described.     

1,2,3-Triazolo[4,5-d]-1,2,4-triazolo[4,3-b]pyridazines

Some new 1,2,3-triazolo[4,5-d]-1,2,4-triazolo[4,3-b]pyridazines were prepared starting from the corresponding 1,2,3-triazolo[4,5-d]pyridazines via the formation of the 1,2,4-triazole ring, by condensation of an appropriate monocarbon fragment with the 4-hydrazino substituent and the nitrogen atom in the 5 position of the heterocycle. Condensation of 4-phenylhydrazino substituted derivatives with formic acid gave zwitterionic compounds.     

A first theoretical study on the origin of the metal-mediated regioselective opening of 2,3-epoxy alcohols

Hybrid density functional theory (B3LYP) method allows the study of the role of metal ions (Li(+)) in the regioselective opening of 2,3-epoxy alcohols with lithium halides (Cl, Br, I) to the corresponding halohydrins. The theoretical results largely confirm the experimental results, especially with regards to the regioselectivity observed in the opening of the oxirane ring. The C3 halogen attack is always preferred to the C2 attack, with a significant difference in the TS structures with the reaction pathway under kinetic control. The central role of the lithium cation, linked to the oxygen atoms of the epoxy alcohol, is well documented in the reaction mechanisms presented. The energy differences between the two structures of the proposed TS appear to be ascribed to the different contribution of the X-H-O hydrogen bond between the hydroxyl groups of the reactant and the incoming halogen nucleophile.     

Probing plume protection problems in the health care environment

This paper presents pragmatic particulars pertaining to plume protection problems with special emphasis on the health care environment. Practical approaches to optimizing protection are discussed with an eye toward facilitating the safety of personnel and the general health care environment from particulates, parasites, viruses and other undesirable entities, elements and compounds.     

Optimizing separation conditions for riboflavin,flavin mononucleotide and flavin adenine dinucleotide in capillary zone electrophoresis with laser-induced fluorescence detection

DNA sequencing is performed in a multiplexed capillary electrophoresis system by UV absorption detection. Four individual electropherograms are obtained by simultaneously running the unlabeled DNA products of the four ddNTP-terminated reactions in the capillary array. The sequence of the template used in the cycle-sequencing reaction can be determined by overlaying the four electropherograms. Two internal standards are employed to adjust for the variance in migration times among the capillaries. After applying the correction algorithm, base calling can be done at a high level of confidence.