Reaction cascades initiated by nucleophilic attack of heteropentalene mesomeric betaine and nitrogen-rich mesoionic tetrazolium-5-amides on electron-deficient unsaturated compounds. Synthesis of novel heterocyclic systems.
The reactions of heteropentalene mesomeric betaine 1 and nitrogen-rich mesoionic tetrazolium-5-amides 4, 11 and 16-18 with electron-deficient unsaturated compounds have been studied. Novel heterocyclic systems, tetrazolo[4,5-a][1,7]benzodiazonine inner salt 2 and 3-oxo-3,7-dihydro-2H-pyrazolo[3,4-b]pyridine 5, have been synthesized by the reactions of dimethyl acetylenedicarboxylate with 1 and tetrazolium-5-anilide 4, respectively, and fully characterized by X-ray crystallography. It has been found that the reactions of other tetrazolium-5-amides are also initiated by the nucleophilic addition of the electron-rich amide nitrogen to the electron-deficient unsaturated compounds.
Mesomeric betaines constructed of quinolinium cations and carboxylate anions separated by thiophene-ethynyl spacers as fluorescent dipoles
4- and 5-((1-Methylquinolinium-3-yl)ethynyl)thiophene-2-carboxylates were prepared starting from 3-ethynylquinoline which was subjected to a Sonogashira-Hagihara coupling with ethyl 4- and 5-bromothiophenecarboxylates, respectively. Methylation to give the corresponding quinolinium salts, saponification under basic conditions, acidification to give the carboxylic acids, and basification finally yielded the title compounds. Calculations of the frontier orbital profiles confirm the classification of these mesomeric betaines as cross-conjugated systems, as the HOMO is essentially located in the carboxylate group which is connected to the spacer by a nodal position. Fluorescence spectroscopic investigations were performed.
Enhancement of surface properties on Low Density Polyethylene packaging films using various fluorination routes
Nowadays, packaging market deployment requires an important attention. Influence of treatment with molecular (F2) or atomic (Fradical dot) fluorine on properties of Low Density Polyethylene (LDPE) films was investigated. The films were treated using direct fluorination conditions with F2 or a specific reagent XeF2, which releases atomic fluorine Fradical dot. Changes of LDPE chemical composition were investigated by FTIR and solid state NMR. Surface morphology was studied by several microscopy techniques (SEM and AFM). Finally to further characterize film properties after treatments, surface energy measurements and electron paramagnetic resonance (EPR) analyses were also carried out. An upper fluorinated layer, which contains mainly high amount of single bondCF2single bond, was formed during the direct fluorination conditions (F2). For the process performed with XeF2, specific groups single bondCHFsingle bond were detected not only on the polymer surface but also in the bulk. The final CHF/CF2 ratio depended on the fluorination route. Treatment with Fradical dot (originated from XeF2 decomposition) resulted in single bondCHFsingle bond groups in bulk prevailing formation whereas F2 formed mainly single bondCF2single bond groups. Regardless to the reactive species, radicals (dangling bonds) appeared during the fluorination and reacted with oxygen during the exposition to air after the treatment. Such a process resulted in oxygenated polar groups formation and consequently in the surface energy increase.