Jenö Borda

Fast microwave-mediated bulk polycondensation of D,L-lactic acid

The polycondensation of D,L-lactic acid upon microwave irradiation was studied. The results of polycondensation by means of microwave were compared to those obtained from conventional heating of lactic acid at 100°C, and it was found that the reaction proceeds with much higher rate upon microwave irradiation. The oligomer mixtures formed were investigated by means of matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS). The molecular mass of the poly(lactic acid) formed under microwave irradiation was found to increase with irradiation time, and the formation of cyclic oligomers after 20 min of reaction time was also revealed.

Recycled polyurethane elastomers: a universal adhesive

The practical application of the glycolysis mixture of polyurethane wastes is reported. It was found that in the presence of 4,4′-diphenylmethane diisocyanate (MDI) both the separated upper phase of the glycolysis mixture and the complete two-phase reaction mixture could be used as components of the urethane adhesive mixtures for bonding woods, metals, plastics, glass, ceramics, paper and leather. The adhesive properties were determined by tensile-cutting, cutting- and bending strengths, as well as peel resistance measurements. The method to use the complete glycolysis mixture is also reported. The reaction mechanism of bonding is also discussed.

The reactions of chromone and 2-hydroxychromanone with hydroxylamine

Abstract Chromone and 2-hydroxychromanone react with hydroxylamine to give several products through attack at Ca2. The aldoxime 2 is transformed to dioxime 4 or to isoxazole 3 . The dioxime exists as a tautomer mixture; it reacts in several ways, giving chromoneoxime 8 , isoxazole 10 and a new isoxazoline 9 .

Reactive propylene oligomers - II. Propylene oligomers with primary-OH, tertiary-OH and α, β-di-OH end groups

SummaryPropylene oligomers with primary-OH, tertiary-0H andα,β-di-OH end groups have been prepared by converting the isopropenyl-ended oligomers with hydroboration-oxydation, oxymercuration-demercuration and performic acid hydroxylation reactions, respectively.

Reactive propylene oligomers. I: propylene oligomers with isopropenyl end group by thermolysis

SummaryPropylene oligomers containing isopropenyl end group have been prepared by thermolysis of atactic polypropylene.The chain-end structures and the number-avarage isopropenyl chain end functionality was determined in the product by C-13 NMR spectroscopy. Molecular weight of the oligomers were between 300 and 1000, as characterized by GPC.Conditions leading to the formation of propylene oligomers with number-average isopropenyl chain end functionality of 1.0, have been worked out.

Highly functionalized polystyrene by direct metalation—carboxylation

SummaryPolystyrene was directly metalated using 1:1 mixture of n-butyllithium (n-BuLi) and potassium-t-butoxide (t-BuOK) in cyclohexane/hexanes at ambient temperature. The metalated polymer on reaction with solid carbon dioxide followed by a metal-proton exchange gave a carboxylated polymer containing 6.38–6.57 mmol acid/g polymer which corresponds to the introduction of carboxyl groups on 94–97% of the repeat units of polystyrene.Based on 13C nMR spectra meta, para and ortho aromatic ring substitution was proposed. No detectable backbone carboxylation occurs. the distribution of carboxylated sites on the aromatic ring: 9% ortho, 58% meta and 33% para. Quantitative 13C NMR analyses indicates essentially quantitative functionalization.

High-performance liquid chromatography of chromonoid compounds

Abstract Synthetic chromones and isoflavones have been investigated by high-performance reversed-phase partition chromatography on C8 and C18 stationary phases in the isocratic mode, using methanol—water and acetonitrile—water eluents. The effect of various substituents on the retention time and capacity ratio was studied. It has been shown that methyl and methoxyl groups increase, whereas a hydroxyl substituent decreases the value of retention time. The effects of these groups on the retention time and on the degree of separation can be predicted for chromones. Of the other substituents the 2-trifluoromethyl, 6-chloro and cyclic groups (e.g. phenyl, benzyl, thiazolyl etc.) increased the retention time while the opposite effect was observed in the case of certain nitrogen-containing (tetrazolyl, cyano, carboxamido) functions.