J. Serb. Chem. Soc. 62(6) 451-454 (1997)
JSCS-2406
UDK 577.17:547.33/.94:547.466.1
Short communication
SHORT COMMUNICATION
16-Dehydropregnenolone acetate from solanidine

KATARINA T. M. PENOV-GASI, EVGENIJA A. DJURENDIC, DUSICA RACKOV-COLIC, MARIJA N. SAKAC, OTTO N. ARCSON, LJUBICA MEDIC-MIJACEVIC* and DUSAN MILJKOVIC

Institute of Chemistry, Faculty of Science, University of Novi Sad,
Trg Dositeja Obradovica 3, YU 21 000 Novi Sad and
*ICN Galenika - Institute, 29. Novembra 111, YU-11000 Belgrade, Yugoslavia

(Received 4 November 1996)
An elegant method for the chemical transformation of solanidine to 16-dehydropregnonolone acetate is proposed. Namely, solanidine was converted to 3b-acetoxy-5,20(22)-solanidiene which was oxidized with sodium periodate-iodide system at pH 7-8 at room temperature for 2 h. The obtained oxidation product, keto-lactame gave 16-dehydropregnenolone acetate after elimination of the lactamic part.

Key words: solanidine, keto-lactame, 16-dehydropregnenolone acetate 



J. Serb. Chem. Soc. 62(6) 455-458 (1997)
JSCS-2408
UDK 547.828.547.781.5
Original scientific paper
 


A modified method for obtaining betahistine hydrochloride

KATARINA M. PENOV GASI, JULIJAN KANDRAC, OTTO N. ARCSON, EVGENIJA A. CURENDIC, MARIJA N. SAKAC, VERA CIRIN-NOVTA and DUSAN MILJKOVIC

Institute of Chemistry, Faculty of Science, University of Novi Sad, Trg Dositeja Obradovica 3, YU 21 000 Novi Sad, Yugoslavia

(Received 10 October 1996, revised 14 March 1997)
The aim of this work was to synthesize betahistine hydrochloride of a satisfactory purity in the highest possible yield. The synthesis consisted of four steps, condensation of paraformaldehyde and 2-methylpyridine yielding 2-(2-pyridyl)ethanol (2) in a yield of at least 26.6%, achieved thanks to a specially developed treatment of the reaction mixture and recycling, dehydration of compound 2 with acetic anhydride under reflyx, rendering 2-vinylpyridine (3) in a yield of 72%, addition of methyl amine to the double bond of compound 3, giving betahistine (4) in a yield of 62.5% and finally, preparation of betahistine hydrochloride from betahistine and gaseous hydrochloride in absolute ethanol in a yield of 73%.

Key words: betahistine hydrochloride, modified synthesis 



J. Serb. Chem. Soc. 62(6) 459-471 (1997)
JSCS-2409
UDK 678.743:537.839.56
Original scientific paper
 


Accelerator ion beam analysis of poly(vinyl chloride)

MAJA CVETKOVSKA, BARRY WILKENS* and JAMES MAYER*

St. Cyril and Methodias University, Faculty of Technology and Metallurgy, Rudjer Boskovic 16,
91000 Skopje, Republic of Macedonia, E-mail: Imad@ereb.mf.ukim.edu.mk and
*Arizona State University, Center for Solid State Sciences, Tempe,
AZ 85287-1704 USA: E-mail: Wilkens@csss.la.asu.edu

(Received 8 January 1997)
Poly(vinyl chlorida (PVC) has a wide variety of applications and potential applications as a material for the manufacture of medical devices and packaging films. In some fields of application the demands are rigorous and so improvements in the analysis are always of interest. In this work it is shown that Rutherford backscattering spectrometry (RBS) and Forward recoil spectrometry (FRS) can be useful and powerful analytical tools. that complement other methods, for the analysis of PVC foils. By adjusting hr instrumental parameters to minimize he polymer damage, it is possible to obtain the composition, the depth profile of heavy elements in the polymer, and to investigate the segregation of some components to the surfaces or interfaces. It is shown that at a fluence of 2.5x10-14 ions cm-2 (4He2+, 2MeV) it is possible to obtain the correct composition of PVC (including additives, detectable by RBS, in this case Si, with a concentrations of up to 1% w/w). At higher irradiation doses elimination of chlorine and hydrogen atoms begins, but this enables the recognition of elements which could not be identified previously because of their very low concentration. For example, metals from metal salts added as some type of stabilizer. The same effect enables the observation of segregation to the surface of poly(dimethylsiloxane) block from triblock copolymer with poly(caprolactone) present as an additive in PVC, by the appearance of an increased concentration of Si at the surface. The segregation of Si at the surface is proved also y SEM-EDX.

Key words: Rutherfor backscattering spectrometry, Forward recoil spectrometry, composition of PVC, segregation of Si at the surface of PVC foils 



J. Serb. Chem. Soc. 62(6) 473-480 (1997)
JSCS-2410
UDK 678.774:536.4:542.9
Original scientific paper
 


Phase transfer catalysis in polycondensation processes.
XVII. Synthesis and thermal properties of some aromatic polyethers

N. HURDUC, M. GRIGORAS*, A. STOLERU* and NATALIA HURDUC**

Gh. Asachi Technical University - Department of Macromolecules,
Bd. Copou 11A, 6600 Iasi, Romania,
*P. Poni Institute of Macromolecular Chemistry, Alee Gr. Ghica-Voda, 6600 Iasi, Romania and
**A. I. Cuza University, Physical Chemistry Department, Bd. Copou 9, 6600 Iasi, Romania

(Received 2 March 1996)
This paper presents some aspects regarding the synthesis and thermal properties of polyethers based on alpha a,a'-dibromo-p-xylene and various bisphenols. The polymers were characterized by 1H-NMR, thermogravimetry, DSC and optical microscopy. To explain some of the thermal behavior, theoretical conformational studies were performed using a MMX program.

Key words: phase transfer catalysis, aromatic polyethers, synthesis 



J. Serb. Chem. Soc. 62(6) 481-494 (1997)
JSCS-2411
UDK 546.742:541.428.49:547.497.1
Original scientific paper
 


Transition metal complexes with thiosemicarbazide-based ligands.
Part. 34. Synthesis, spectroscopic and voltammetric characterization of Ni(II) and Ni(III) complexes with tetra-and octadentate pentane-2,4-dione-bis(s-methylisothiosemicarbazone)-derived ligands

LJILJANA S. JOVANOVIC, VUKADIN M. LEOVAC, MIRJANA M. POPSAVIN,
VALERIJA I.CESLJEVIC, and LUKA BJELICA

Institute of Chemistry, Faculty of Science, University of Novi Sad, Trg Dositeja Obradovica 3, YU 21 000 Novi Sad, Yugoslavia

(Received 25 November 1996, revised 15 March 1997)
The reaction of a methanolic or ethanolic solution of [Ni(H2L)]I.9.5MeOH(1) (H2L=monoanion of the tetradentate N4 pentane-2,4-dione-bis(S-methylisothiosemicarbazone) in the presence of ammonia yielded [Ni(HL)]MeOH(2), or Ni2(L-L)(3)(L-L = hexaanion of the octadentate N8 3,4-diacetyl-2,5-hexanedione-tetrakis (S-methylisothiosemicarbazone). The formation of complex (3) preceded an oxidative dehydrogenation of the diketone C(3)-H group and a bonding of two monomeric units of (1) into the dimer (3) via the single C(3)-H group and a bonding of two monomeric units of (1) into the dimer (3) via the single C(3)-C(3) bond, and the oxidation of Ni(II) to Ni(III). Complexes (1) and (3) were characterized by their electronic, and complexes (1) and (2) by their NMR spectra. The voltammetric behavior of all the complexes in DMF solutions at a glassy carbon electrode was studied in detail.

Key words: nickel(II) complexes, nickel(III) complexes, S-methylisothiosemicarbazide-based ligands, NMR spectra, electronic spectra, cyclic voltammetry 



J. Serb. Chem. Soc. 62(6)495-502 (1997)
JSCS-2412
UDK 543.544.2/.5:530.18
Original scientific paper
 


RM pair linearity and proportionality rules in non-salting-out liquid chromatography

TOMISLAV JANJIC, GORDNA VUCKOVIC and MILENKO CELAP

Faculty of Chemistry, University of Belgrade, Akademski trg,
P.O.Box 158, YU-11001 Belgrade, Yugoslavia

(Received 16 December 1996)
It is shown that the RM pair linearity rule, as well as the Proportionality rule, the validity of which in salting-out chromatography was established earlier, are also often valid in other fields of liquid chromatography.

Key words: liquid chromatography, RM pair linearity rule, proportionality rule 



J. Serb. Chem. Soc. 62(6) 503-508 (1997)
JSCS-2413
UDK 549.67:541.18.044/.045
Original scientific paper
 


Investigation of the effect of novel hydrophobic zeolite types on the pervaporation properties of composite polysiloxane membranes

BORIVOJ ADNACEVIC, JELENA JOVANOVIC* and SPASENKA GAJINOV*

Faculty of Physical Chemistry, University of Belgrade, Studentski trg 12-16,
P.O.Box 137, YU-11001 Belgrade and
*Institute of General and Physical Chemistry, Studentski trg 12/V,
P.O.Box 551, YU-11001 Belgrad, Yugoslavia

(Received 25 October 1996, revised 14 February 1997)
This paper describes investigations of the effect of two different types of novel hydrophobic zeolites (ultrastable zeolite type Y and pentasyl type zeolite) on the pervaporation properties of zeolite-filled polydimethylsiloxane membranes. A procedure of obtaining membranes of various thickness varying in the zeolite content was mastered. Physicochemical characterization of the utilized zeolites was done. The effects of the zeolite type and concentration, as well as the temperature and membrane thickness on the membrane permeability and selectivity were established.

Key words: hydrophobic zeolites, zeolites, zeolite-filled polydimethylsiloxane membranes, pervaporation, permeability, selectivity 



J. Serb. Chem. Soc. 62(6)509-514 (1997)
JSCS-2414
UDK 543.253:547.8.973:546.621/541.428.49/
Original scientific paper
 


Polarographic study of eriochome cyanine R and its aluminum complexes

DESANKA SUZNJEVIC, STEVAN BLAGOJEVIC, MILENKO ERCEG*, DRAGICA DUMANOVIC** and DUSAN VUCELIC***

Institute of General and Physical Chemistry, Studentski trg 12/V,
P.O.Box 551, YU-11001 Belgrade,
*Forensic Institute, Kraljice Ane bb, YU-11000 Belgrade,
**ICN Galenika - Institute, 29. Novembra 111, YU-11000 Belgrade and
***Faculty of Physical Chemistry, University of Belgrade, Studentski trg 12-16,
P.O.Box 137, YU-11001 Belgrade, Yugoslavia

(Received 2 December 1996)
The behavior of the two main cathodic polarographic waves of the dye Eriochhrome cyanine R (ECR), A at -0.45V, and B at -0.1 vs. SCE, were followed from acetate buffer pH 4.8 in the presence of Al3+ ions. Two new waves (E and F) were noticed in the potential region between waves A and B. From amperometric titrations, the mole ratios 1:1 and 2:3 of the formed Al-ERC complexes, which correspond to the waves E and F, were determined. The procedure for indirect analytical determination of aluminum was done by monitoring the variation of the wave A height as a function of the Al3+ ion concentration. A linear response of the wave height vs. the metal-ion of 3% determined for the aluminum ion concentration of 0.1 mg/l (n=10).

Key words: eriocherome cyanine R, Al3+ complexes, polarography, mole ratio, determination 



J. Serb. Chem. Soc. 62(6) 515-521 (1997)
JSCS-2415
UDK 661.634:541.183,546.923:541.573
Preliminary communication
 


PRELIMINARY COMMUNICATION
The electrosorption valence of adsorbed phosphoric acid anions on the Pt(111) surface

B. Z. NIKOLIC and R. R. ADZIC*

Faculty of Technology and Metallurgy, Karnegijeva 4, P.O.Box 494, YU-11001 Belgrade and
*ICTM - Institute of Electrochemistry, Njegoseva 12, P.O.Box 815, YU-11001 Belgrade, Yugoslavia

(Received 16 January, revised 5 March 1997)
The adsorption of phosphoric acid anions on the Pt(111) face has been studied using cyclic voltammetry. It is shown that the adsorption of H3PO4 anions is stronger than that of H2SO4 or HClO4. From the voltammetry curves obtained for the Pt(111) upon addition of H3PO4 solution with different concentrations into 0.01 M HClO4 the electrosorption valence of H3PO4 on the Pt(111), g = -1 has been calculated. The voltammetric curves for Pt(111) in concentrated H3PO4 and H2SO4 solutions show a sharp peak in the hydrogen region, which is caused by anion adsorption and possibly by ordering of the adsorbed anions.

Key words: electrosorption valence, adsorption, phosphoric acid, voltammetry curve, Pt(111) face, charge 



J. Serb. Chem. Soc. 62(6) 523-530 (1997)
JSCS-2416
UDK 546.47.815:622.765:543.51
Original scientific paper
 


Precipitate flotation of lead and zinc and their determination by atomic absorption spectrometry

KATARINA CUNDEVA and TRAJCE STAFILOV

Institute of Chemistry, Faculty of Science, St. Cyril and Methodius University,
P.O.Box 162, 91001 Skopje, Macedonia

(Received 30 October 1996, revised 15 February 1997)
A preconcentration flotation procedure has been developed to extend the range of conventional atomic absorption analysis to trace concentration of lead and zinc in natural waters. The optimal conditions for the preconcentration and separation of these metals from fresh water by precipitate flotation with hydrated iron(III) oxide (Fe2O3xH2O) were studied. All important parameters necessary for the successful flotation, like optimal mass of collector, pH of the medium, induction time etc., were checked. Under the same conditions Pb and Zn were floated quantitatively (100% for lead and 95.16% for zinc) with 30 mg Fe(III). The possibility of the usage of atomic absorption spectrometry was determined of the colligend levels in fresh water samples. The quantitative determination of lead was carried out by electrothermal atomic absorption spectrometry, while zinc was determined by flame atomic absorption spectrometry. The results obtained by atomic absorption spectrometry were compared with the results obtained by inductively coupled plasma-atomic emission spectrometry. The detection limit for lead is 0.50 g/L and for zinc is 0.85 g/L.

Key words: lead, zinc, determination, precipitate flotation, atomic absorption spectrometry 



J. Serb. Chem. Soc. 62(6) 531-533 (1997)
JSCS-2417
UDK 633.88:66.066.1/:536.44
Note
 


NOTE
Dependence of the camomile flower yield on the carbon dioxide quantity during isothermal supercritical extraction

BRANISLAV PEKIC, ZORAN ZEKOVIC and ALEKSANDAR TOLIC

Faculty of Technology, Department of Pharmaceutical Engineering, University of Novi Sad,
Cara Lazara 1, YU-21000 Novi Sad, Yugoslavia

(Received 2 July 1996, revised 27 January 1997)
The dependence of the total extract yield of camomile flowers by isothermal supercritical extraction on the carbon dioxide quantity, at different pressures (80, 160 and 240 bar) at a temperature of 313 K, was investigated. A dynamic method was used. The experimentally obtained results were described by equations which fitted the experimental results rather well. The equations obtained in this way represent a contribution to defining the quantitative dependence of yield on the carbon dioxide quantity used in the extraction.

Key words: camomile flowers, supercritical extraction, carbon dioxide



 


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