JSCS Vol 68, No. 7
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Impresum |
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J.Serb.Chem.Soc.
68(7)515–524(2003) |
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The kinetics of the reactions of 2-substituted nicotinic acids with
diazodiphenylmethane in various alcohols
SASA Z. DRMANIC, BRATISLAV Z. JOVANOVIC,
ALEKSANDAR D. MARINKOVIC and MILICA M. MISIC-VUKOVIC
Department of Organic
Chemistry, Faculty of Technology and Metallurgy, University of Belgrade
Karnegijeva 4, P. O. Box 3503, 11001 Belgrade, Serbia and Montenegro
(Received 15 November
2002)
The rate constants of 2-substituted nicotinic acids in reaction with
diazodiphenylmethane (DDM) in eight alcohols at 30ºC have been determined. In
order to explain the obtained results through solvent effects, the second order
reaction rate constants (k) of the exAMined acids were correlated using
the appropriate solvent parAMeters by the equation:
log k = log k0 + af(e) + bs* + c ngH
where f(e) is the measure of
solvent ability as a dielectric to stabilize the separation of opposite charges
in the activated complex, s* is the measure of
solvent ability to stabilize proton in the initial state and ngH represents the ability of protic solvents to form hydrogen bond
with the negative end of the ion-pair intermediate. These constants were
correlated also by using solvatochromic equation of the form:
log k = log k0 + sp* + aa + bb
where p* is the measure of the solvent polarity, a represents the scale of the solvent hydrogen bond donor acidities
(HBD) and b represents the scale of the solvent hydrogen
bond acceptor basicities (HBA). The correlations of the kinetic data were
carried out by means of multiple linear regression analysis. The results
obtained for 2-substituted nicotinic acids were compared with the results for ortho-substituted
benzoic acid under the sAMe experimental conditions.
Keywords: 2-substituted nicotinic acids, kinetic measurements, protic
solvents, solvent parAMeters, diazodiphenylmethane.
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J.Serb.Chem.Soc.
68(7)525–534(2003) |
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Effect of substituents on the 1H-NMR chemical
shifts of 3-methylene-2-substituted-1,4-pentadienes
NATASA V. VALENTIC and GORDANA S. USCUMLIC
Faculty of Technology
and Metallurgy, University of Belgrade, Karnegijeva 4, P. O. Box 3503,
11120 Belgrade, Serbia and Montenegro, E-mail: naca@elab.tmf.bg.ac.yu
(Received 26 November
2002, revised 21 February 2003)
The principle of linear free energy relationships was applied to the 1H
chemical shifts of the b-vinyl proton atoms of
3-methylene-2-substituted-1,4-pentadienes. The correlations of the proton
chemical shifts with Swain and Lupton substituent parAMeters provide a mutually
consistent picture of the electronic effects in these compounds. The overall pattern
of proton chemical shifts can be largely accounted for by a model of
substituent effects based on field, resonance and p polarization effects. Owing to the particular geometric
arrangement of the vinyl group in 3-methylene-2-substituted-1,4-pentadienes,
the b-vinyl protons HB and HC
have different sensitivities to polar and resonance effects. The different
sensitivities of the 1H chemical shifts to resonance effects reveals
some effects not predicted by the model outlined above. Evidence is presented
that demonstrates that both the 1H and 13C chemical shifts for these compounds reflect their ground-state
charge densities.
Keywords: cross-conjugated trienes, ring substituted a-(s-cis-2-butadienyl)styrenes, b-vinyl proton chemical
shifts, substituent effects.
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J.Serb.Chem.Soc.
68(7)535–542(2003) |
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Kinetics and mechanism of cetyltrimethylAMmonium
bromide catalyzed oxidation of diethylene glycol by chlorAMine-T in acidic
medium
V. W. BHAGWAT, J. TIWARI, A. CHOUBE* and B.
PARE**
School of Studies in Chemistry, VikrAM University, Ujjain-456010, India,
*IPCA Laboratories, RatlAM, India, and
**Madhav Science College, VikrAM University, Ujjain-456010, India
(Received 15 October
2002, revised 18 February 2003)
The kinetics and mechanism of the C16TAB catalyzed oxidation of
diethylene glycol (2,2’-oxydiethanol) by chlorAMine-T in acidic medium has been
studied. The reaction has a first-order dependence on chlorAMine-T. With excess
concentrations of other reactants, the reaction rate follows fractional order
kinetics with respect to [diethylene glycol]. The micellar effect due to
cetyltrimethylAMmonium bromide, a cationic surfactant, has been studied. The
reaction is catalyzed by chloride ions as well. The small salt effect and
increase in the reaction rate with increasing dielectric constant suggest the
involvement of neutral molecules in the rate determining step. Addition of p-toluenesulfonAMide
retards the reaction rate. On the basis of product analysis, a pertinent
mechanism is proposed.
Keywords: diethylene glycol, chlorAMine-T, micellar catalysis.
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J.Serb.Chem.Soc.
68(7)543–547(2003) |
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SHORT COMMUNICATION
Experimental study of physical parAMeters
significant in fullerene synthesis
B. TODOROVIC-MARKOVIC, Z. MARKOVIC, M.
MARINKOVIC and T. NENADOVIC
Vinca Institute of
Nuclear Sciences, P. O. Box 522, Belgrade, Serbia and Montenegro
(Received 29 October
2002, revised 8 March 2003)
In this work, the effect
of physical parAMeters on the yield of fullerene, synthesized in a hollow
cathode plasma reactor is investigated. The experimental investigations done
previously have shown that the fullerene yield depended on tehcnical parAMeters
- the current intensity, inert gas pressure, type of gas and interelectrode
gap. The aim of this work was to show that the fullerene yield depends on
physical parAMeters - carbon concentration, carbon flow rate from the
interelectrode gap, axial temperature and temperature gradient between the arc
channel and the chAMber walls as well. It was found that fullerene synthesis
occurs in an inert heat bath with dimensions determined by the temperature
gradient. The lower temperature limit is around 2000 K and the value of the
upper limit is the value of the axis temperature which depends on the discharge
conditions. The synthesis of fullerenes is more effective if the carbon
concentration in the heat bath is large and the carbon flow rate from that zone
to colder parts of chAMber is small.
Keywords: fullerene, carbon arc, carbon
concentration, temperature.
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J.Serb.Chem.Soc.
68(7)549–555(2003) |
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Equiseparable chemical trees
IVAN GUTMAN, BILJANA ARSIC* and BORIS FURTULA
Faculty ov Science, University of Kragujevac, P. O. Box 60, 34000 Kragujevac
and
*Faculty of Science, University of Nis, Visegradska 33, 18000 Nis, Serbia and
Montenegro
(Received 21 February
2003)
Abstract: Let n1(e|T) and n2(e|T)
denote the number of vertices of a tree T, lying on the two sides of the
edge e. Let T1 and T2 be two trees with
equal number of vertices, let e be an edge of T1 and f
an edge of T2. Then e and f are said to be equiseparable if
either n1(e|T1) = n1(e|T2)
or n1(e|T1) = n2(e|T2).
If all edges of T1 and T2 can be chosen so
as to form equiseparable pairs, then T1 and T2
are equiseparable trees. A number of molecular structure-descriptors of
equiseparable chemical trees coincide, implying that the corresponding alkane
isomers must have similar physico-chemical properties. It is shown how
equiseparable chemical trees can be constructed in a systematic manner.
Keywords: Wiener index, variable Wiener index, chemical trees, alkanes,
equiseparability.
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J.Serb.Chem.Soc.
68(7)557–564(2003) |
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Gas chromatograpic retention indices for
N-substituted AMino s-triazines on capillary columns.
Part IV. Influence of column polarity on retention index
DUSAN Z. MIJIN, DUSAN G. ANTONOVIC, GORDANA BONCIC-CARICIC, BRATISLAV Z.
JOVANOVI, and OLGA S. RAJKOVIC*
Department of Organic
Chemistry, Faculty of Technology and Metallurgy, University of Belgrade, P. O.
Box 3503, 11001 Belgrade and
*High Chemical School, 37001 Krusevac, Serbia and Montenegro
(Received 29 July,
revised 26 November 2002)
The retention index increment for the addition of a methylene group to the
alkyl group of an analyte molecule is shown to be lower than 100 i.u. for
N-substituted AMino s-triazines. In temperature progAMmed gas chromatography, a
linearly interpolated retention index I, determined from the linear
regression equation, I = AZ + (GRF)z, with the number of
atoms (Z) in the molecule as variable, was used to describe the
retention of 25 N-substituted AMino s-triazines, on DB-1, DB-5 and
DB-WAX capillary columns, divided into five series according to the similarity
of the alkyl groups in the particular series. In the above equation, A
is the linear regression coefficient or the retention index increment per atom
addition, Z the number of C, N and Cl atoms in the molecule, and (GRF)z
the group retention factor or functionality constant for functional groups in
the molecule, based on the number Z. It is possible to estimate the
retention indices of an unknown member of the series from the Z, A
and (GRF) values.
Keywords: retention indices, retention index increment, s-triazines, group
retention factors.
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J.Serb.Chem.Soc.
68(7)565–579(2003) |
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Investigation of the compatibility between
one-dimensional system parAMeters and the multi-dimensional Solvation
parAMeter model in RP liquid column chromatography
TOMISLAV J. JANJIC, GORDANA VUCKOVIC, and MILENKO B. CELAP
Faculty of Chemistry, University of Belgrade, P. O. Box 158, 11001 Belgrade,
Serbia and Montenegro
(Received 21 November
2002)
Abstract: It has been established that in many cases the system constants used
in the Solvation parAMeter model as well as the corresponding log k
values can be linearized in the sAMe NSP and NSP’ scale,
respectively, which shows the compatibility of both models. NSP and
NSP’ are one-dimensional system parAMeters adapted to the chromatographic
system used over the phase equilibrium constant.
Keywords: system parAMeters, NSP parAMeter, NSP’ parAMeter, Solvation
parAMeter model, log k linearization, system constants.
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J.Serb.Chem.Soc.
68(7)581–591(2003) |
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Extraction and separation studies of Ga(III),
In(III) and Tl(III) using the neutral organophosphorous extractant, Cyanex-923
S. D. PAWAR and P. M. DHADKE
Inorganic Chemical
Laboratory, Institute of Chemical Technology Uninversity of Mumbai, Matunga,
Mumbai-400 019 India
(Received 5 November
2002, revised 27 January 2003)
The neutral extractant, Cyanes-923 has been used for the extraction and
separation of gallium(III), indium(III) and thallium(III) from acidic solution.
These metal ions were found to be quantitatively extracted with Cyanex-923 in
toluene in the pH range 4.5–5.5, 5.0–6.5 and 1.5–3.0, respectively, and from
the organic phase they can be stripped with 2.0 mol dm-3 HNO3,
3.0 mol dm-3 HNO3 and 3.0 mol dm-3 HCl,
respectively. The effect of pH equilibration period, diluents, diverse ions and
stripping agents on the extraction of Ga(III), In(III) and Tl(III) has been
studied. The stroichiometry of the extracted species of these metal ions was
determined on the basis of the slope analysis method. The reaction proceed by
solvation and the probable extracted species found were [MCl3.
3Cyanex-923] [where M = Ga(III) or In(III) ] and [HTlCl4.
3Cyanex-923]. Based on these results a sequential procedure for the separation
of Ga(III), In(III) and Tl(III) from each other was developed.
Keywords: solvent extraction, Cyanex-923, Ga(III), In(III), Tl(III),
stripping, separation.
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J.Serb.Chem.Soc.
68(7)593–598(2003) |
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SHORT COMMUNICATION
Radiolytic splitting of water molecules in the
presence of some suprAMolecular compounds
ALEXANDRU CECAL, ANDREI PARASCHIVESCU, KARIN POPA, DAN COLISNIC, GRIGORE TIMCO*
and LIDIA SINGEREAN*
Faculty of Chemistry, “Al. I. Cuza” University, 11, B-dul Carol I, 6600
Iasi, Romania and
*Institute of Chemistry, Academy of Science, Kishinew, Republic of Moldova
(Received 5 June 2002)
This paper deals with the study of the hydrogen output during the catalyzed
radiolysis of water in the presence of the suprAMolecular compounds Fe2NiO(TMAc)6·3HTMAc,
FeCoO (TMAc)6·3HTMAc, [Cr3O(C6H5COO)6]·ClO4,
Fe3Ni2O(OH)(TMAc)7(Aacet)3, Ni2(H2O)
(TMAc)4(HTMAc)4, [Cr3O(TMAc)·3H2O](TMAc),
and Cr8F8(TMAc)16. A 60Co g-source of 5.1×1014 Bq activity at a rate dose of 8.038 kGy h-1
was used. The radiolysis products were determined by mass spectrometry. For a
given irradiation time, it was found that quantity of hydrogen obtained by
water radiolysis is 6 – 18 times greater in the presence of the suprAMolecular
compounds as catalysts than in their absence from the irradiated system.
Keywords: hydrogen evolution, radiolysis, suprAMolecular catalysts,
radioactive waste.
Copyright &AMp; copy; SHD
2003.
October 21, 2003.
For more information contact: SHD@tmf.bg.ac.yu