György Deák

Interaction between iron(II) and hydroxamic acids: oxidation of iron(II) to iron(III) by desferrioxamine B under anaerobic conditions

Interaction between iron(II) and acetohydroxamic acid (Aha), alpha-alaninehydroxamic acid (alpha-Alaha), beta-alaninehydroxamic acid (beta-Alaha), hexanedioic acid bis(3-hydroxycarbamoyl-methyl)amide (Dha) or desferrioxamine B (DFB) under anaerobic conditions was studied by pH-metric and UV-Visible spectrophotometric methods. The stability constants of complexes formed with Aha, alpha-Alaha, beta-Alaha and Dha were calculated and turned out to be much lower than those of the corresponding iron(II) complexes. Stability constants of the iron(II)-hydroxamate complexes are compared with those of other divalent 3d-block metal ions and the Irving-Williams series of stabilities was found to be observed. Above pH 4, in the reactions between iron(II) and desferrioxamine B, the oxidation of the metal ion to iron(III) by the ligand was found. The overall reaction that resulted in the formation of the tris-hydroxamato complex [Fe(HDFB)]+ and monoamide derivative of DFB at pH 6 is: 2Fe2+ + 3H4DFB+ = 2[Fe(HDFB)]+ + H3DFB-monoamide+ + H2O + 4H+. Based on these results, the conclusion is that desferrioxamine B can uptake iron in iron(III) form under anaerobic conditions.

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.

Identification of silymarin constituents: An improved HPLC-MS method

A high-performance liquid chromatographic/tandem mass spectrometric method was developed for the determination of the major bioactive flavonolignans in silymarin, a herbal remedy extracted from the milk thistle Silybum marianum. In this study, eight active components of silymarin with the same elemental composition, including silychristins A and B, silydianin, silybin A and B, isosilybin A and B and an unknown compound were completely separated. Furthermore, three additional components were detected and partly separated; presumably two silybin stereoisomers and one isosilybin stereoisomer. The collision-induced dissociation (CID) MS/MS spectra of these silymarin constituents were studied: the spectral similarity values of the component pairs were determined, and simple criteria were found for distinguishing the components.

Bimetallic silver-gold clusters by matrix-assisted laser desorption/ionization

Pure gold clusters (Aun+) were produced up to the cluster size of n = 100 by matrix-assisted laser desorption/ionization (MALDI). The mass spectrum of the resulting clusters showed alteration in the ion intensity at odd-even clusters size. On the other hand, intensity drops at cluster size predicted by the jellium model theory was also observed. Positively and negatively charged bimetallic silver-gold clusters were produced under MALDI conditions from the mixture of HAuCl4/silver trifluoroacetate and the 2-(4-hydroxyphenylazo)benzoic acid (HABA) matrix. A linear correlation was found between the intensity ratio of AunAgm+ to Aun+1Agm−1+ cluster ions and the molar ratio of the gold to silver salt. It was observed that the composition and the distribution of the clusters can be varied with the molar ratio of the silver and gold salts. It was also found that the resulting cluster sizes obey the lognormal distribution.

MALDI-TOF MS characterization of dihydroxy telechelic polyisobutylene

Communication: MALDI-TOF MS characterizations of dihydroxy telechelic polyisobutylene is reported. Dichloro telechelic polyisobutylene (Cl-PIB-Cl) was synthesized by means of living cationic polymerization using p-dicumyl chloride/BCl 3 /DMSO initiating systems. The resulting polymer was functionalized by polymer analogous reactions to yield dihydroxy telechelic polyisobutylene (HO-PIB-OH). It was then investigated by MALDITOF MS in the cation mode using 1,8-dihidroxy-9(10H)-anthracenone (dithranol)/CF 3 COOAg matrix. The MALDI TOF MS spectra showed an increase in mass by 56 amu units attributed to the isobutylene monomer increment. The endgroups of HO-PIB-OH were determined. A good agreement was also found between the calculated isotope distributions and the isotope distributions determined by means of MALDI.

High temperature copolymerization of styrene and maleic anhydride in propagating polymerization front

The synthesis of poly(styrene-maleic anhydride) copolymers by frontal polymerization is reported. The propagating front can be achieved if the mole fraction of styrene (St) is 0.3 ≤ St ≤ 0.7 in the feed. Depending on the St/MA mole ratio alternating St-MA-St-MA copolymers (St/MA ≤ 1) or (St-MA)n-(St-St-St)m block copolymers (St/MA > 1) are formed. The microstructure of the copolymers obtained was estimated by means of 13C NMR spectroscopy.

Matrix-assisted laser desorption/ionization mass spectrometric study of bis(imidazole-1-carboxylate) endfunctionalized polymers

A detailed Matrix-Assisted Laser Desorption/Ionization Mass Spectrometric (MALDI-TOF MS) investigation of polyethylene glycol (PEG), polypropylene glycol (PPG) and polyisobutylene (PIB) bis(imidazole-1-carboxylate) esters is reported. The MS spectra of PPG and PIB bis(imidazole-1-carboxylate) esters recorded in the reflectron mode showed the presence of two additional series of peaks compared to those recorded in the linear mode, while in the case of PEG bis(imidazole-1-carboxylate) only one additional peak series appeared in the reflectron MS spectra. These additional series were attributed to the formation of fragment ions by the loss of one and two endgroups in the first field-free region of the instrument. The neutral losses for the three polymers were also supported by using the post-source decay method (PSD). The observation of decreasing mass difference between the adjacent peaks from two series of polymeric ions with the increase of oligomer mass indicates the presence of PSD ions in a reflectron MALDI spectrum. The relationship between the mass of the precursor ions and those of the PSD ions and neutral loss are also discussed.

Star-shaped micelles of polyisobutylene–polystyrene–polyisobutylene triblock copolymer in hexane solution

Abstract Polyisobutylene–polystyrene–polyisobutylene (PIB–PS–PIB) triblock copolymer was synthesized and studied in dilute hexane, toluene and tetrahydrofuran solution by the laser dynamic light scattering method. Star-shaped micelles were observed in hexane which is a good solvent for the PIB segments but a bad solvent for the PS segments. The diameters of the hard core and the micelle were estimated and the size and the size distribution of micelles were also determined by dynamic light scattering.

Carbocationic polymerization in suprecritical CO2

The polymerization of isobutylene (IB) in supercritical carbon dioxide (SC·CO2) has been investigated in the temperature range from 32.5 to 47.5 °C at 139±3 bar. The in Mn of polyisobutylene (PIB) versus 1/T plot gave ΔH‡Mn, PIB=−14.1±1.5 kcal/mol (-59.1±6.3 kJoule/mol) and ΔS‡Mn, PIB=−31.1±6.2 cal/mol·deg (-130.2±26.0 Joule/mol·deg). These quantities are quite different from those obtained in conventional liquid systems. The ceiling temperature (Tceil) was determined by linear extrapolation of the In Mn versus 1/T plot to the molecular weight of the monomer. According to this procedure the Tceil of IB polymerization in SC·CO2 in about one molar solution at 139±3 bar is 88±9 °C.

Head to head polymers—38. An improved synthesis of head to head polystyrene

Abstract A greatly improved and very reliable synthesis of head to head polystyrene (HHPS) was worked out. HHPS was prepared in a sequence of four steps starting with a reductive photodimerization of acetophenone. The resultant 2,3-diphenyl-2,3-butanediol was dehydrated in vacuum to 2,3-diphenyl-1,3-butadiene, which was polymerized to 1,4-poly(2,3-diphenyl-1,3-butadiene) (PDPBD). PDPBD was then hydrogenated (reduced) with potassium and ethanol to HHPS.