bluuebunny/crossref_metadata_2025 huggingface dataset:
Liquid-liquid equilibrium in the water-ethanol-toluene system. Experimental results
Authors: Říčná Květuše , Matouš Jaroslav , Novák Josef P. , Kubíček Vladimír
Published: May 2010

Liquid-liquid equilibrium at 5, 25, and 50 °C was measured in the water-ethanol-toluene system. Special attention was paid to the determination of distribution coefficient of ethanol. Besides, the composition and boiling point of azeotropic mixture at normal pressure were determined.
Heat capacities of 4-methyl-2-pentanone, 2,6-dimethyl-4-heptanone, 1-hexanol, 1-heptanol, and 1-octanol in the temperature range 298-318 K
Authors: Veselý František , Barcal Petr , Zábranský Milan , Svoboda Václav
Published: May 2010

Molar heat capacities of 4-methyl-2-pentanone and 2,6-dimethyl-4-heptanone in the liquid state have been measured at a constant pressure over the temperature range 298.15 to 318.15 K. In order that the appropriateness of selection of literature data for correlation of the heat capacity as a function of temperature may be verified, results for three 1-alkanols (1-hexanol, 1-heptanol, and 1-octanol) have been measured over the same temperature range.
Potentiometric and NMR study of ethylenediamine-N,N,N',N'-tetrakis[methylene(phenylphosphinic)] acid and its complexing properties
Authors: Lukeš Ivan , Hermann Petr , Pech Pavel
Published: May 2010

The dissociation constants of ethylenediamine-tetrakis-[methylene(phenylphosphinic)] acid (H4edtmpPh) and its stability constants with Mg2+, Ca2+, Sr2+, Ba2+, Mn2+, Fe2+, Co2+ and Ni2+ have been determined. Study of the dependence of the 1H, 31P and 13C NMR spectra of H4edtmpPh solutions on the pH indicates that it is more similar to H4edta than to analogous phosphonic acids.
Kinetics of quaternization reactions of polymeric amines
Authors: Přádný Martin , Ševčík Stanislav , Dragan Stela
Published: May 2010

The paper deals with kinetics phenomena occurring in the quaternization of some polymeric amines, such as poly[2-(dimethylamino)ethyl methacrylate], poly{N-[3-(dimethylamino)propyl]-acrylamide}, and poly[2-(dimethylamino)ethyl methacrylate-co-2-hydroxyethyl methacrylate], with alkyl halides. The accelerating and slowing-down effects which take place in the alkylation reactions are discussed on the basis of the reaction course, i.e. of the dependence of differential rate constants on the conversion fraction of the reaction. Accelaration of the reaction is affected by the increasing polarity of microsurroundings of the reacting groups, while electrostatic and steric hindrances of the reacted groups slow down the reaction. Conformational effects, chemical and solvation interactions in the polymer-solvent-alkylating agent system and tacticity of the polymer are also operative.
The crystal and molecular structure of tris-butyl-tin(IV)-(1-pyrrolidinecarbodithioato)-3-propionate
Authors: Lokaj Jan , Vrábel Viktor , Kellö Eleonóra , Ratay Vladimír
Published: May 2010

The crystal and molecular structure of Bu3Sn(pyrn-dtc-prop) was solved by the X-ray structural analysis method and refined by the block diagonal least squares method to R = 0.053 for 1 930 observed reflections. The compound crystallizes in the monoclinic system with a space group of P21/c, Z = 4, F(000) = 1 056, with unit cell dimensions of a = 1.4758(5), b = 0.9970(3), c = 1.9166(6) nm; β = 113.90(2)°. The measured and calculated crystal densities were Dm = 1.32 and Dc = 1.31.103 kg m-3. The tin atom is coordinated by three carbon atoms at distances of Sn-C 0.2117(8), 0.2133(8), 0.2158(11) nm and two oxygen atoms O(1) and O(2) at distances of Sn-O 0.2210(5) and 0.2399(5) nm. The coordination polyhedron is a deformed trigonal bipyramid. The S2CN ligand is approximately planar.
Compounds of aziadamantane type: Mass spectrometric study
Authors: Isaev Sergei D. , Karpenko Nataliya F. , Yurchenko Aleksandr G. , Vodička Luděk , Kadentsev Valentin I. , Zachař Pavel
Published: May 2010

Azi and hydrazi derivatives of adamantane,adamantanone and diamantane were studied by mass spectrometry. The EI spectra of azi derivatives lack completely molecular ions; the presence of abundant dehydroadamantane or dehydrodiamantane ions corresponds to elimination of nitrogen molecule from the molecular ion. Comparison of the EI ionization with photolysis or pyrolysis allowed to deduce some analogies and to suggest the mechanism of decomposition of the molecular ion.
Reactions of aromatic amines with 5-nitro-3-furoyl and 5-nitro-2-furoyl isothiocyanates
Authors: Jurášek Adolf , Štetinová Jarmila , Kováč Jaroslav , Žvak Vladimír , Leško Ján , Dandárová Miloslava , Vlniešková Eva
Published: May 2010

5-Nitro-3-furoyl isothiocyanate reacts with 4-X-anilines (X = H, CH3, OH, N(C2H5)2, NHCOCH3, Cl, Br) to give the corresponding N-(5-nitro-3-furoyl)-N'-(4-X-phenyl)thioureas, in contrast to 4-methoxyaniline and 4-nitroaniline, which afford 5-nitro-3-furancarboxylic acid amides in a rather anomalous way. Formation of these amides is discussed and some properties of 2- and 3-substituted thioureas related to 5-nitrofuran are compared.
Studies in Vilsmeier-Haack reaction: Reaction of 3-methyl-1-phenyl-4-arylidene-5-pyrazolone
Authors: Awad Ibrahim M. A. , Hassan Khairy M.
Published: May 2010

The 3-methyl group in Ia, b has been found to undergo diformylation by Vilsmeier reagent to give the aminoacrolein derivatives (IIa, b). Treatment of IIa, b with different reagents affords the related 1-phenyl-4-arylidene-5-pyrazolone derivatives with different heterocyclic systems in the 3-position. The Vilsmeier reaction on pyrazolopyrazole (XIII) have been utilized to prove chemically that new heterocyclic systems are formed only at the 3-position and no addition on the carbon-carbon double bond in the conjugated system O=C-C=C-(B) takes place.
Conformation of ring A in 3-oxotriterpenoids. sofa conformation in 3-oxolupane-28-nitrile crystal
Authors: Klinot Jiří , Podlaha Jaroslav , Podlahová Jana , Malý Karel , Petříček Václav
Published: May 2010

Crystal structure of 3-oxolupane-28-nitrile (I) has been determined. As usual, the B, C and D rings adopt a chair, and the E ring an envelope conformation. Surprisingly enough, the A ring exists in a sofa arrangement with coplanar C(1) to C(5) and O atoms. The existence of this uncommon and energetically unfavourable conformation is explained by an intermolecular interaction of carbonyl dipoles facilitated by the particular mode of crystal packing. The comparison with crystal structure of 3-oxolupanes II-IV demonstrates that these compounds differ in conformation of the A and E rings whereas the rest of the skeleton remains essentially the same and is remarkably bent about B and C rings. Differences in the effect of 8β-methyl group on the energy of the chair and boat forms of the A ring are tentatively explained on the basis of the B ring deformation. Conformation of the A ring in solution is generally unlike that in the crystal since energy differences between the conformers tend to be effectively overbalanced by crystal packing forces.
Solvolytic rearrangements in 4β,5-cyclopropano-5β-androstane-3β,17β,19-triol 3-acetate 17-benzoate 19-p-toluenesulfonate
Authors: Fajkoš Jan , Joska Jiří
Published: May 2010

The title tosylate V was prepared from the tosylate III by Simmons-Smith methylenation. Its acetolysis afforded three products with modified steroid skeletons: The diene VIII, the olefin XI, and the pentacyclic diacetate XIII. The 3-oxo derivatives XIV, XVI, XVII, and XIX-compounds of potentional biological interest-were prepared as follows: Oxidation of the monoacetate X followed by hydrolysis yielded the testosterone analogue XIV and oxidation of the diol IX gave the dione XVI. Using similar reaction sequence the triol diester XII afforded the oxo compounds XVII and XIX.
Synthesis, conformational features and biological activity of [Pro3] antiarrhythmic peptide
Authors: Kundu Bijoy
Published: May 2010

Synthesis of Gly-Pro-Pro-Gly-Ala-Gly([Pro3]AAP) in solution has been carried out. Solvent dependent conformational distribution of [Pro3]AAP has been studied using CD and NMR spectroscopy. The CD spectra in water, methanol and trifluoroethanol show predominance of the polyproline II-like structure. The CD curve of [Pro3]AAP in aqueous solution suggests an absence of any intramolecular H-bonded conformation whereas in polar organic solvents like methanol and trifluoroethanol, a possible contribution from an intramolecularly H-bonded γ-turn around the Pro3 residue has been proposed. Solvent titration experiments in methanol-water system using 13C NMR suggest that all the carbonyls are exposed and are not involved in any ordered structure. Further, the Δδβγ values for both the prolines corresponded to the dihedral angle of 150° for polyproline II-like structure, thereby suggesting that in solution [Pro3]AAP exists predominantly in polyproline II-like structure. Temperature coefficients of NH chemical shifts in (CD3)2SO also indicate that all the NH's are exposed and are not involved in any intramolecular H-bonded structure. The antiarrhythmic, as well as antithrombotic activity of [Pro3]AAP have also been discussed.
Atriopeptins. II. Synthesis of N-terminal fragments
Authors: Ovchinnikov Mikhail V. , Bespalova Zhanna D. , Molokoedov Aleksandr S. , Revenko Inna V. , Sepetov Nikolai F. , Isakova Olga L. , Titov Mikhail I.
Published: May 2010

Peptides, corresponding to the N-terminal sequence in atriopeptins, were synthesized by classical methods of peptide chemistry in solution. The obtained peptides were characterized by various physicochemical methods. The scheme and methods of the synthesis are discussed.
Atriopeptins. III. Synthesis and biological activity studies of α-r-ANF, AP-II, AP-III and des-Ser5-Ser6-AP-II
Authors: Ovchinnikov Mikhail V. , Bespalova Zhanna D. , Molokoedov Aleksandr S. , Titov Mikhail I. , Revenko Inna V. , Vinogradov Valentin A. , Korobov Nikolai V. , Zhukovskii Sergei V.
Published: May 2010

Starting from previously synthesized atriopeptin fragments, peptides α-r-ANF, AP-II, AP-III and des-Ser5-Ser6-AP-II were prepared using complex F. The acetamidomethyl protecting group on cysteine was removed simultaneously with the cyclization. Biological activity of atriopeptin was evaluated.
Amino acid sequence of cyanogen bromide fragment CB5 of human hemopexin
Authors: Kluh Ivan , Morávek Ladislav , Pavlík Manfred
Published: May 2010

Cyanogen bromide fragment CB5 represents the region of the polypeptide chain of hemopexin between the fourth and fifth methionine residue (residues 232-352). It contains 120 amino acid residues in the following sequence: Arg-Cys-Ser-Pro-His-Leu-Val-Leu-Ser-Ala-Leu-Thr-Ser-Asp-Asn-His-Gly-Ala-Thr-Tyr-Ala-Phe-Ser-Gly-Thr-His-Tyr-Trp-Arg-Leu-Asp-Thr-Ser-Arg-Asp-Gly-Trp-His-Ser-Trp-Pro-Ile-Ala-His-Gln-Trp-Pro-Gln-Gly-Pro-Ser-Ala-Val-Asp-Ala-Ala-Phe-Ser-Trp-Glu-Glu-Lys-Leu-Tyr-Leu-Val-Gln-Gly-Thr-Gln-Val-Tyr-Val-Phe-Leu-Thr-Lys-Gly-Gly-Tyr-Thr-Leu-Val-Ser-Gly-Tyr-Pro-Lys-Arg-Leu-Glu-Lys-Glu-Val-Gly-Thr-Pro-His-Gly-Ile-Ile-Leu-Asp-Ser-Val-Asp-Ala-Ala-Phe-Ile-Cys-Pro-Gly-Ser-Ser-Arg-Leu-His-Ile-Met. The sequence was derived from the data on peptides prepared by cleavage of fragment CB5 by mild acid hydrolysis, by trypsin and chymotrypsin.
Trinucleotide AUA and UAU formation catalyzed by wheat germ RNA polymerase II
Authors: Cvekl Aleš , Horská Květa , Šebesta Karel , Rosenberg Ivan , Holý Antonín
Published: May 2010

The elongation of dinucleotides ApU and UpA to trinucleotides ApUpA and UpApU by wheat germ RNA polymerase II was studied at a medium ionic strength (60 mM-KCl). The catalytic mechanism of the first internucleotide bond formation consists in the binding of the primer dinucleotide followed by the binding of NTP ("ordered bibi" reaction), i.e. by an analogous mechanism as found for RNA polymerase holoenzyme from E. coli. In further experiments phosphonate analogues of dinucleotides ApU and UpA were used as the priming dinucleotides. It was shown that analogues U(c)pA and Up(c)A are very poor primers for the synthesis of corresponding trinucleotides; the elongation of analogues A(c)pU and Ap(c)U was not observed at all. The comparison of kinetic constants Kia, KmA, KmB and Vmax as well as the substrate properties of phosphonate analogues indicates the increased specifity of the wheat germ RNA polymerase initiation binding site in comparison with the E. coli holoenzyme.
Experimental determination of vapour-liquid equilibrium; Normal and low-pressure region
Authors: Hála Eduard
Published: May 2010

Review without abstract.
Oscillations of concentrations in multicomponent diffusion
Authors: Kvasnica Jozef
Published: May 2010

While selfdiffusion coefficients Dii are always positive, the stability conditions admit both signs of the interdiffusion coefficients Dij (i ≠ j). In a multicomponent system (n > 2) with opposite signs of interdiffusion (at least within some range of concentrations and temperatures) there might occur anomalous evolution of concentrations, e.g. the damped oscillations of extremal values for some x2/t.
Copper(II) extraction by alkyl- and alkenyl-substituted 8-quinolinols
Authors: Černý Mirko , Vilímec Jan , Šťastová Jitka , Rod Vladimír , Kraus Miloš
Published: May 2010

The equilibrium and kinetics of copper extraction from water solutions of copper(II) perchlorate into chloroform by 8-quinolinol, 2-methyl-8-quinolinol, six 7-alkenyl-8-quinolinols (with C3 to C12 side chains) and by 7-(p-tert.butylbenzyl)-8-quinolinol were measured. The data were treated by previously derived models which take into account the complex nature of the extraction process. The equilibrium data were expressed as extraction constants Kex, the rate data as the rate parameter Θ and initial extraction rates J0, respectively. The influence of the position, size and structure of the substituents on these parameters is discussed. A strong effect of the position of the double bond C=C in the side chain was found.
A comparison of pyrolytical and oxidative degradation of poly(methyl methacrylate) and methyl methacrylate-styrene copolymer using the capillary GC and GC-MS methods
Authors: Pacáková Věra , Dieckmann Ramona , Leclercq Piet A. , Hoch Karel
Published: May 2010

The thermal degradation of poly(methyl methacrylate) (PMMA) and of a methyl methacrylate copolymer with styrene (MMA-ST) were studied in an inert atmosphere and in the air, under conditions simulating a fire. Tubular furnace and high-frequency pyrolyzers were compared. The combustion products were analyzed using the capillary GC and GC-MS methods.
The effect of systematic errors of the equilibrium distribution concentrations on the number of stages of countercurrent extraction with various consumption of extractant
Authors: Dojčanský Ján , Bafrncová Soňa , Surový Július
Published: May 2010

On using five hypothetical systems differing in the extent of mutual solubility of components, tie-line slope, and type of binodal curve, the effect is evaluated of systematic errors in the form of absolute deviation in the liquid-liquid equilibrium distribution concentrations on the accuracy of calculated number of theoretical stages of isothermal countercurrent extraction under various operating conditions.
Slip velocity and hydrodynamic parameters in liquid-liquid spray columns
Authors: Sovilj Milan
Published: May 2010

An empirical correlation for the prediction of slip velocity in liquid-liquid spray columns, which includes a dimensionless group containing the interfacial tension, is presented. Good agreement between experimental and predicted values of slip velocity is obtained over a wide range of dispersed phase hold-up (0.97–36.2%) and Reynolds number (58-1067).
Synthesis of 4-(N-acetyl-L-tyrosyl)amino-2-iodobenzoic acid
Authors: Protiva Jiří , Křeček Václav , Máca Bohumil , Urban Jiří , Buděšínský Miloš , Procházka Miloš
Published: May 2010

The title compound was prepared by a three-step synthesis from diacetyltyrosine (XV) and 4-amino-2-iodobenzoic acid (I). Syntheses of acid I and 4-amino-3-iodobenzoic acid (II) have been revised and modified. 1H and 13C NMR spectra of the synthesized compounds are discussed.
7-Methanesulfonyloxy-3α,5-cyclo-5α-cholestanes
Authors: Kohout Ladislav
Published: May 2010

Acetolysis and hydrogenolysis of 7-methanesulfonyloxy-3α,5-cyclo-5α-cholestanes was studied. The 7β-methanesulfonyloxy derivative VI is hydrogenolyzed more readily than its 7α-isomer III. The acetolysis gives products of elimination, substitution and rearrangement with participation of the cyclopropane ring. Whereas the 7α-derivative III predominantly reacts with elimination, the 7β-derivative VI is more susceptible to the participation reaction.
Mannich and Grignard reaction of some N-(2-propynyl)azaheterocycles
Authors: Šilhánková Alexandra , Hoskovec Michal , Liboska Radek , Ferles Miloslav
Published: May 2010

1,4-Disubstituted butynes IV-VII were prepared by Mannich reaction of N-(2-propynyl) derivatives of 1,2,3,4-tetrahydroquinoline, 1,2,3,4-tetrahydroisoquinoline, piperidine and azacycloheptane with polyoxymethylene and another heterocyclic amines. Reaction of 3-(1-piperidinyl)-1-propynylmagnesium bromide or 3-(1-azacycloheptyl)-1-propynylmagnesium bromide afforded alcohols X-XIII.
Synthesis of isoxazolylimidazolin-5-ones
Authors: Prameela B. , Rajanarendar E. , Murthy A. Krishna
Published: May 2010

1-(3-Methyl-5-styryl-4-isoxazolyl)-2-styryl-4-benzylideneimidazolin-5-ones (III) have been synthesized by the interaction of isoxazole Schiff bases (I) with 4-benzylidene-2-methyloxazol-5-one (II).
New semisynthetic anthracycline glycosides
Authors: Jizba Josef V. , Sedmera Petr , Přikrylová Věra , Vokoun Jindřich , Mikulík Karel , Vaněk Zdenko
Published: May 2010

3-Trifluoroacetamido-4-O-trifluoroacetyl-2,3,6-trideoxy-α,β-L-lyxopyranosyl chloride (VII) was coupled under Koenigs-Knorr glycosidation conditions to (7S)-O-(2-hydroxyethyl)daunomycinone (IV), (7R)-O-(2-hydroxyethyl)daunomycinone (V), and (7S)-O-(4-hydroxy-2-butynyl)daunomycinone (VI). The deprotection of isolated N-trifluoroacetyl derivatives of α- and β-glycosides XVI, XVII, XX, XXI, and XXIV yielded free glycosides XVIII, XIX, XXII, XXIII, and XXV. Their anomeric configuration was determined by NMR spectroscopy. Reaction of 3,4-di-O-acetyl-2,6-dideoxy-α,β-L-arabinopyranosyl chloride (II) with IV gave glycosides XII and XIII. Their deacetylation provided free glycosides XIV and XV. An analogueous reaction with 3-acetamido-4-O-acetyl-2,3,6-trideoxy-α,β-L-lyxopyranosyl chloride (III) with IV lead to the N-acetyl glycoside IX only.
The ingfluence of temperature, pH and aeration on the ethanolic fermentation of glucose by Pachysolen tannophilus
Authors: Camacho Rubio F. , Bravo Rodríguez V. , Sánchez Villasclaras S. , Castro Vico M.
Published: May 2010

The ethanolic fermentation of 25 g l-1 solutions of glucose in batch cultures of Pachysolen tannophilus has been studied experimentally in terms of three environmental variables: initial pH from 1.5 to 6.5, temperatures of 25 °C, 30 °C and 35 °C and aeration values of Q = 0.150 v/v/min, Q = 0.075 v/v/min and Q = 0 v/v/min (i.e. with air entering through the stirring vortex alone). Using the values for the concentrations of biomass, residual glucose and ethanol produced at intervals throughout the experiments, the maximum specific rates of growth, glucose consumption and ethanol production, together with the biomass and ethanol yields, have been calculated. The most favourable conditions for ethanol production are an initial pH of about 3, temperature of 30 °C and Q = 0 v/v/min. Under these conditions the ethanol yield is approximately 0.36 (g ethanol) (g glucose)-1 and the maximum specific production rate is 1.2 (g ethanol) (g biomass)-1 h-1.
Cationic modifications of polyalkenes II. Effect of a single or continuous supply of Co-initiator
Authors: Kučera Miloslav , Kimmer Dušan , Majerová Karla , Fiala Zdeněk
Published: May 2010

For an effective modification of polyalkenes leading to the formation of block and/or graft copolymers, the presence of co-initiating water is absolutely necessary. We have compared two procedures used in the co-initiation of cationic reactions on polymers. Gradually supplied air moisture raises the efficiency of modification of isotactic polypropylene with poly(oxyethylene) several times, compared with a single addition of co-initiating water.
Light scattering size estimation of nearly monodisperse spherical particles in the multivalued region: A reminiscence
Authors: Sedláček Blahoslav
Published: May 2010

For the size estimation of large, nearly monodisperse spherical particles, the forward angle dissymmetry technique (FAD) has been used and the results compared with data obtained by the transmission electron microscopy (TEM) and integral turbidity ratio (ITR) methods. Starting with a certain relative particle size which depends on the chosen angle pair, the FAD functions go through several extremes and become multivalued. The possibility of the particle size estimation under such conditions and, also, without the knowledge of actual particle concentration (but knowing the relative refractive index), is discussed in this paper.
Reaction of 6-azauridine with thionyl chloride in hexamethylphosphoramide
Authors: Drašar Pavel , Beránek Jiří
Published: May 2010

Reaction of 6-azauridine (I) with a mixture of thionyl chloride and hexamethylphosphoramide afforded 5'-chloro-5'-deoxy-6-azauridine (II) and a mixture of SR- and SS-isomers of 5'-chloro-5'-deoxy-2',3'-O-sulfinyl-6-azauridine (IIIa and IIIb) which were separated by column chromatography on silica gel; compounds IIIa and IIIb also arose in the reaction of compound II with diphenyl sulfite. Removal of the cyclic sulfinyl group from the isomeric sulfites IIIa and IIIb gave compound II; reaction of IIIa and IIIb with imidazole in dimethylformamide afforded the 5'-chloro-5'-deoxy-2,2'-anhydro derivative IV.
Kinetics of methanolysis of 1-(2-halogeno and 2,6-dihalogenobenzoyl)-3-(4-chlorophenyl)ureas
Authors: Kaválek Jaromír , Kacetl Lubomír , Kaválková Marcela
Published: May 2010

The methanolysis kinetics has been measured of 1-(2,6-difluorobenzoyl)-3-(4-chlorophenyl)urea (a larvicidal insecticide Dimilin) and of four other mono- and dihalogenobenzoyl derivatives. Polar and steric effects of halogen on the rate and dissociation constants is discussed.
Some approaches to the synthesis of sulbactam
Authors: Husinec Suren , Dragović Deana , Stokić Zdenka , Kojić Josipa
Published: May 2010

A study on the synthesis of penicillanic acid 1,1-dioxide, Sulbactam, was carried out. Two reliable convergent synthetic routes to this β-lactamase inhibitor starting from penicillin G potassium salt and 6-aminopenicillanic acid have been developed.
Some further 2-(4-substituted 1-piperazinyl)acetamides derived from 6,11-dihydrodibenzo[b,e]thiepin. Transformations of 6,11-dihydrodibenzo[b,e]thiepin derivatives into anthraquinones, anthrones and anthracenes
Authors: Hulinská Hana , Ryska Miroslav , Koruna Ivan , Holubek Jiří , Taimr Jan , Svátek Emil , Protiva Miroslav
Published: May 2010

Reactions of the secondary amines I and VIII with chloroacetyl chloride gave the 2-chloroacetamides II and IX affording by substitution reactions with 1-methylpiperazine, 2-(1-piperazinyl)ethanol and 3-(1-piperazinyl)propanol in the title compounds III-V and X-XII. The starting amine VIII was prepared from the ketone XIV via XVII and VII. The product of 1,6-addition and the following dehydrogenation XVIII was obtained as a by-product of the reaction of XIV with 1-methyl-4-piperidylmagnesium chloride. Reaction of 2-fluorodibenzo[b,e]thiepin-11(6H)-one (XV) with sodium hydride in dimethylformamide and the following hydrolysis gave 2-fluoroanthraquinone (XXVII). An attempt at trapping the presumed dianion of the type B by treatment with methyl iodide and the following hydrolysis resulted in a mixture of XXVII and the anthracenes XXXI and XXXII. A similar reaction sequence starting from the ketone XIV gave the anthrones XXX and XXXIV, 9-methoxy-10-(methylthio)anthracene (XXXIII) (main product) and anthraquinone (XXVIII). Oxidation of XXXIII with m-chloroperbenzoic acid or hydrogen peroxide gave either the sulfone XXXV or XXXVI.
Synthesis and CD characteristics of position 3 analogues of antiarrhythmic peptide
Authors: Kundu Bijoy
Published: May 2010

Six analogues of the antiarrhythmic peptide (Gly-Pro-Hyp-Gly-Ala-Gly), in which Hyp at position 3 has been replaced with other amino acids such as Gly, Ala, D-Ala, Ser, Thr and Lys have been synthesized. The compounds were obtained by a stepwise peptide coupling strategy in solution. A relationship between antiarrhythmic activities and CD spectra has been discussed.
Study of dipole moments of phenylsulphonyl isothiocyanates
Authors: Suchár Gejza , Danihel Ivan , Jasovská Antónia
Published: May 2010

The dipole moments of 4-substituted phenylsulphonyl isothiocyanates have been measured in benzene at 20 °C. The steric arrangement of SO2NCS group is discussed on the basis of comparison of the dipole moment values measured with those calculated by vectorial addition of bond moments for the conformers formed by rotation around the S-N bond.
Reinvestigation of dipole moments of para substituted phenyl isocyanates and determination of dipole moment of NCO group by optimization procedure
Authors: Danihel Ivan , Barnikol Falk , Kristian Pavol
Published: May 2010

The values of dipole moments of a series of p-substituted phenyl isocyanates have been determined by the method of Halverstadt and Kumler. The experimental dipole moments measured have been used for determination of magnitude and direction of the group dipole moment of NCO group bound to a benzene ring (7·93.10-30 C m, 21 °C) by means of a simple optimization procedure.
The conductance behaviour of NaI and NaBPh4 in acetone and in isopropanol at 10, 15, 20, 25, and 30 °C
Authors: Papadopoulos N. , Ritzoulis G.
Published: May 2010

Molar conductivities at the limit of zero concentration have been evaluated for NaI and NaBPh4 in acetone and in isopropanol at 10, 15, 20, 25, and 30 °C. The experimental data have been analysed by means of the Lee-Wheaton equation. The thermodynamic parameters of the non-coulombic interaction have been evaluated.
Electrochemical reduction of benzenediazonium salts in aprotic medium
Authors: Janderka Pavel , Cejpek Igor
Published: May 2010

DC polarography, TAST polarography, differential pulse polarography, polarography with superimposed alternating current, slow cyclic voltammetry with a hanging Hg drop electrode and a Pt electrode, rapid cyclic voltammetry with a hanging Hg drop, and coulometry were used to study the electrochemical reduction of p-methoxy- and p-nitrobenzenediazonium cations in aprotic medium. A reduction mechanism involving two separate one-electron steps is proposed, the first of which being complicated by adsorption and follow-up chemical reaction leading to evolution of nitrogen. The basicity of the aprotic solvents, expressed by donor numbers according to Gutman, influences the reduction mechanism of these cations.
Power input of screw rotors and agitators: Theory of calculation of power input of screw rotors
Authors: Rieger František
Published: May 2010

A method has been proposed of the calculation of screw rotors. The calculation starts from the equation for the power input for the flow between two plates corrected by correction coefficients.
Liquid circulation in a cylindrical vessel with radial baffles and inclined blade impeller
Authors: Fořt Ivan , Hošťálek Miloslav , Medek Jaroslav
Published: May 2010

Liquid circulation was studied in a cylindrical vessel with radial baffles under the turbulent flow regime of liquid agitated gradually with the following types of four inclined blade impellers: impeller with plane blades inclined at the angle of 25°; impeller with asymmetrically profiled blades at the angle of 30°-17°; impeller with strength-profiled blades. By solving the turbulent (vortex) analogy of the Stokes equations for the creeping (non-inertial) laminar flow, the streamline distribution (the Stokes stream function) in the bulk of agitated charge was obtained for each of impellers studied (relative size d/D = 1/3, relative distance from the bottom H2/D = 1/3, relative vessel filling H/D = 1), placed axisymmetrically in the vessel and pumping the liquid towards its flat bottom. The zero values of the Stokes stream function at the bottom, walls, and charge liquid level, and further the radial profiles of axial and radial component of mean velocity in the cross sections under and above the impeller obtained experimentally by the laser-doppler anemometry on the assumption of axial symmetry of the agitated system studied were set as the boundary conditions for the solution of the partial differential equation considered. It follows from the results obtained that the homogenous circulation of agitated charge at the relatively lowest value of the impeller power input is reached when agitating with the asymmetrically profiled blade impeller which therefore can successfully replace the propeller mixer with airfoil profiled blades.
Millisecond pyrolysis – Mathematic model and parametric sensitivity
Authors: Valášková Zina , Horák Josef
Published: May 2010

Ethane-water vapour pyrolysis and the influence of the system parameters on the pyrolysis furnace behaviour were studied using mathematical model describing the reactor constructed from Field's pipes. The parameters under discussion are following: reaction mixture feed rate, inlet pressure, heat transferrer temperature (furnace temperature), addition of overheated water vapour, thickness of coke layer on the reactor walls and radiation heat transfer inside the reactor. All parameters were found to be important. For feed rate, furnace temperature and ethane-water ratio an optimum values set can be evaluated. Coke formation on the reactor walls in case the coke layer is very thin can improve the heat transfer due to surface emissivity increasing. Otherwise the coke layer effect is negative.
Photochemical generation of porphyrin. ESR and absorption spectroscopic studies
Authors: Stopka Pavel , Wagnerová Dana M.
Published: May 2010

Irradiation by a high-pressure mercury arc of a mixture containing pyrrole, benzaldehyde, and Fe(III) in the medium of glacial acetic acid results in the formation of Fe(III)-meso-tetraphenylporphyrin and some amount of free meso-tetraphenylporphyrin. The products were identified by means of ESR and absorption spectra. When irradiated for long periods of time, the products undergo photochemical degradation. Since the photochemical incorporation of Fe(III) into the free meso-tetraphenylporphyrin ligand yields a complex with a structure different from that in the previous case, it may be concluded that Fe(III) acts as a template in laboratory synthesis from the above starting substances.
The molecular and crystal structure of 4,4-dimethyl-6,6-diphenyl-tetrahydro-2H-pyran-2-one
Authors: Novotný Jiří , Ondráček Jan , Schwarz Marián , Kratochvíl Bohumil
Published: May 2010

The molecular and crystal structure of 4,4-dimethyl-6,6-diphenyl-tetrahydro-2H-pyran-2-one was solved by direct methods and anisotropically refined by the least squares method. The final R-factor value was 0.065 for 2 181 observed reflections (I > 1.96σ (I)) and 272 refined parameters. The symmetry of the structure corresponds to the P21/c space group with lattice parameters a = 11.207(2), b = 8.168(1), c = 16.896(3) Å, β = 90.05(1)°. The unit cell contains four formula units. A lactone structure was found for this geminally substituted heterocyclic compound and was also demonstrated by 1H and 13C NMR spectroscopy. The lactone ring assumes the boat conformation.
Preparation of 3-cyano-4-(R-vinyl)-5,5-dimethyl-Δ3-butenolides and substituent effects on their infrared spectra
Authors: Perjéssy Alexander , Avetisyan Aida Avetisovna , Aknazaryan Anna Alexandrovna , Melikyan Gagik Surenovich
Published: May 2010

Twenty nine 3-cyano-4-(R-vinyl)-5,5-dimethyl-Δ3-butenolides were prepared by condensation of 3-cyano-4,5,5-trimethyl-Δ3-butenolide with aliphatic and aromatic aldehydes. The wave numbers of C=O, C=N and C=C stretching vibrations of synthesized compounds were measured in trichloro- and tetrachloromethane. The spectral data were correlated with substituent conotants using Hammett-Brown and the improved and extended Seth-Paul-Van Duyse equation. The statistical results of correlations were compared with those of ethyl α-cyanocinnamates, ethyl benzoates and benzonitriles. The transmission factors for one and two C=C bonds were determined in the regions of π' = 0.46-0.57 and 0.27-0.37, respectively. In 3-cyano-4-(arylvinyl)-5,5-dimethyl-Δ3-butenolides a considerable conjugation exists between the arylvinyl moiety and both the C=O and C=N groups. On the other hand, in 3-cyano-4-(alkylvinyl)-5,5-dimethyl-Δ3-butenolides probably only the endocyclic C=C bond takes part in a marked resonance interaction with alkylvinyl group. A generally valid relationship was found between the slopes of ν(C=O) vs σ+ and ν(C=N) vs σ+ correlations for different types of compounds measured in CHCl3 and CCl4.
Large-scale synthesis of racemic “Corey lactone”
Authors: Veselý Ivan , Kozmík Václav , Dědek Václav , Paleček Jaroslav , Mostecký Jiří , Stibor Ivan
Published: May 2010

Very convenient synthesis of Corey lactone–(3aα,4α,5β,6aα)-5-(1,1'-biphenyl-4-carbonyloxy)-hexahydro-4-hydroxymethyl-2H-cyclopenta[b]furan-2-one (VI) was developed. The title compound was obtained in five steps starting from 7-anti-hydroxymethyl-5-exo-chloro-bicyclo[2.2.1]-heptan-2-one (I) in a very good overall yield.
Condensation reactions of 2,4- and 2,6-dimethylpyridines and their 1-oxides
Authors: Šilhánková Alexandra , Hulvová Jana , Trška Petr , Ferles Miloslav
Published: May 2010

Using the reactions of 2,4- and 2,6-dimethylpyridine-1-oxides with aromatic and heteroaromatic aldehydes under catalysis with potassium tert-butoxide (E)-aryl- and (E)-heteroarylethenylpyridine-1-oxides IIIa-IIIe, IVa-IVc, Va, Vb respectively, were prepared. 1-Oxides IIIg, IVd, IVe and Vc were obtained from the appropriate pyridine bases by oxidation with peracetic acid. Condensation of 2,4- and 2,6-dimethylpyridines with 3-pyridinecarbaldehyde gives a mixture of bases VIa and VIc, and VIb and VId, respectively. On Claisen condensation of 2,6- or 2,4-dimethylpyridine-1-oxide with diethyl oxalate in the presence of sodium hydride and potassium tert-butoxide lactone XIIa and XIIb is formed in addition to α-keto ester XIa and XIb, respectively. From esters XIa and XIb amides XId and XIe were prepared.
Potential antidepressants: 1-(4-Aminoalkoxy)phenyl)-2-propylamines
Authors: Kmoníček Vojtěch , Vejdělek Zdeněk , Holubek Jiří , Valchář Martin , Protiva Miroslav
Published: May 2010

1-(4-Hydroxyphenyl)-2-propylamine (X) and its N-monomethyl (XI) and N,N-dimethyl (XII) derivatives were O-alkylated with six tert.aminoalkyl chlorides to aminoalkyl ethers Ia-VIc. In cases of X and XI the reactions were complicated by O,N-dialkylation leading to isolation of triamino ethers XVI and XVII. 1-(4-Hydroxyphenyl)propan-2-one was alkylated with 2-dimethylaminoethyl chloride and the ether XIII was obtained. An attempt to transform 4-(2-dimethylaminoethoxy)benzaldehyde to the 1-aryl-2-nitropropene XIV by heating with nitroethane in acetic acid in the presence of ammonium acetate resulted in the formation of 4-(2-dimethylaminoethoxy)benzonitrile (XV). In the form of salts the amino ethers prepared were tested for antidepressant activity but proved little active or inactive.
New synthesis of oxime-type beta-lactam antibiotics
Authors: Mandel Martin , Novák Ludvík , Rajšner Miroslav , Holubek Jiří , Holá Vladislava
Published: May 2010

Reaction of anhydrous acids II with phosphorus pentachloride afforded hydrochlorides of chlorides III which were used in acylations of N,O-bis(trimethylsilyl) derivatives of 6-aminopenicillanic and 7-aminodeacetoxycephalosporanic acid. Change of the (Z)-configuration of the alkoxyimino group during the synthesis was observed only in the methoxyimino series. The prepared penicillins IV are effective against gram-positive as well as gram-negative bacteria.
Synergism in hydrodearomatization over Ni-Mo/Al2O3 catalyst
Authors: Novák Michal , Zdražil Miroslav
Published: May 2010

Synergism in hydrodearomatization activity of the Ni-Mo/Al2O3 system was studied using the hydrogenation of naphthalene to tetraline at 300 or 350 °C and 2.0 or 1.5 MPa as model reaction. The catalysts were either reduced or presulphided and the feed was either sulphur-free or contained small amount of benzothiophene. Two main conclusions are important for the theory of synergism in the hydrorefining catalysis: a) the Ni-Mo catalyst does not exhibit synergism in hydrodearomatization in the absence of sulphur in the system, b) in the presence of sulphur in the system, the synergism in hydrodearomatization occurrs probably only under special conditions and is less general and less pronounced than in the hydrodesulphurization.
Hydrogenation activity of homogeneous and heterogenized cyclopentadienyl titanium complexes
Authors: Čapka Martin , Reissová Alena
Published: May 2010

Hydrogenation of alkenes and cycloalkenes catalyzed by a reduced bis(cyclopentadienyl)dichlorotitanium(IV) complex and by its immobilized analogue coordinately bound to silica has been studied. With both catalytic systems, the rate constants and reaction orders to individual components were determined in 10-60 °C temperature region and at a pressure of 0.1 MPa and mechanism of the reaction has been proposed. Kinetic measurements and EPR spectra proved that the immobilized catalysts remain firmly bound to the support during whole catalytic cycle, which made their reuse possible.
The crystal and molecular structure of thiocyanatocopper(II) complexes with 3-methylpyridine and 3,4-dimethylpyridine
Authors: Kabešová Mária , Kožíšková Zlatica
Published: May 2010

Crystals of the complexes [Cu(3,4-diMepy)3(NCS)2] (I) and [Cu(3-Mepy)3(NCS)2] (II) (Me = methyl, py = pyridine) possess the monoclinic symmetry, Pc, with the unit cell parameters of I and II: a = 0.9825(7) and 0.9027(7) nm, b = 0.9740(7) and 0.9021(7) nm, c = 1.4130(60) and 1.4958(50) nm, β = 108.8(4)° and 114.08(4)°, Z = 2 in both cases, d0 = 1.32.103 and 1.37.103 kg m-3, and dc = 1.30.103 and 1.37.103 kg m-3, respectively. The central atom in the complexes exhibits tetragonal pyramidal coordination. The thiocyanate ligands are coordinated by the nitrogen atoms in the equatorial as well as axial positions of the coordination polyhedron. The three heterocyclic ligands are bonded in the equatorial plane. The arrangement of the ligands and the interatomic distances are the same in the two complexes. The crystals were prepared by reacting an ammoniacal solution of CuSO4 with an ethanolic solution of the heterocyclic ligand L and an aqueous solution of NH4NCS so that the c(Cu):c(NH3):c(L):c(NCS) ratio was 2:8:5:4.
Comparison between the classical and QELSS determination of diffusion coefficients. Sharp polymer fractions
Authors: King Simon , Sundelöf Lars-Olof , Porsch Bedřich
Published: May 2010

Simple modification of the method of cumulants for an evaluation of QELSS data within the error limit of 2% in the case of narrow polymers is suggested. Model calculations of the deviations from the exponential decay due to polydispersity are presented, criteria of applicability of the 1st and 2nd cumulant fit at a given accuracy are derived and verified experimentally. The required agreement between the classical and QELSS diffusion constant is achieved if the QELSS measurements are made at concentrations where the effect of concentration dependence of the diffusion constant may be neglected.
Solid phase cosolvents: Polymer analogs of N,N-dialkylamides based on polystyrene
Authors: Janout Václav , Hrudková Hana , Valter Bohumír , Čefelín Pavel
Published: May 2010

Polymers of styrene of various type can be readily amidomethylated by a reaction with N-(hydroxymethyl)amides. Analogs of N-methyl-2-pyrrolidone, N-methyl-6-hexanelactam, N-methyl-8-octanelactam, and N,N-dimethylacetamide were prepared by the polymeranalogous amidomethylation. The reaction between poly(styrene-co-divinylbenzene) and N-(hydroxymethyl)-2-pyrrolidone proceeds by an acceleration mechanism. The extent of the reaction depends on the structure of the polymer and N-(hydroxymethylamide), on the concentration of the catalyst (trifluoroacetic acid) and on the way in which the polymer swells before the reaction. Polymers with bound residues of N-methylamide as solid cosolvents are catalysts of the model nucleophilic substitution reaction between sodium phenoxide and 1-bromooctane. A distinct polymer effect was recorded with polymer analogs of N-methyl-2-pyrrolidone in this reaction.
The influence of alkali metal halides on the butadiene cyclotrimerization catalyzed by (benzene)titanium(II) complexes
Authors: Poláček Jindřich , Petrusová Lidmila , Antropiusová Helena , Mach Karel
Published: May 2010

Addition of alkali chlorides (MCl) to (η6-C6H6)Ti(AlCl4)2 (Ia) decreases the catalytic activity of Ia while the selectivity of the (Z,E,E)-1,5,9-cyclododecatriene formation is improved only when NaCl is used at the optimum molar ratio NaCl/Ia ~ 5. The alkali chlorides remove free AlCl3, which is present in the system as an admixture, probably in the form of MAlCl4 complexes; however, an excess of MCl brings about the decomposition of catalytic trinuclear Ti(II) complexes during the butadiene cyclotrimerization. In addition to inactive TiCl2, this decomposition yields some AlCl3 which induces the formation of cationic byproducts, 1-phenylbut-2-ene and (E)-1,4-poly(butadiene), before it is deactivated or quenched with MCl.
Reaction of organolithium compounds with 1-substituted 2,4,6-triphenylpyridinium perchlorates
Authors: Schwarz Marián , Kuthan Josef
Published: May 2010

The reaction of organolithium compounds with 1-substituted 2,4,6-triphenylpyridinium perchlorates Ia-Ic produces mixtures of 1,4-dihydropyridines IIa-IIe and 1,2-dihydropyridines IIIa-IIIe. Analogous reactions of phenylmagnesium bromide with compounds Ia-Ic proceed with very low conversions (less than 1%). Photochromism in visible range is observed only with the compounds II which have two aromatic substituents at 4-position, whereas compounds III and IId show no visible photochromism. The molecular spectra of the compounds newly prepared are discussed.
Sesquiterpene lactones of Cephalophora aromatica (HOOK.) SCHRADER and their deterrent activity. The stereostructure of geigerinin
Authors: Błoszyk Ełżbieta , Dudek Aleksandra , Kosturkiewicz Zofia , Rychłewska Urszula , Daniewski Włodzimierz M. , Gulumka Maria , Nawrot Jan , Buděšínský Miloš , Vašíčková Soňa , Holub Miroslav
Published: May 2010

From species Cephalophora aromatica (HOOK.) SCHRADER the authors isolated a series of previously described sesquiterpene lactones I-V and newly the lactone geigerinin (VI). Its structure was confirmed by X-ray analysis and its absolute configuration was determined on the basis of the CD spectra of its complex with Pr(thd)3. The lactones I-VII were tested for antifeedant activity against main crop pests.
Preparation, spectral and physicochemical characteristics of methylamide Nα-phenylthiocarbamoyl derivatives of naturally occurring amino acids
Authors: Pavlík Manfred , Kluh Ivan , Pavlíková Františka , Vašíčková Soňa , Kostka Vladimír
Published: May 2010

The methylamide Nα-phenylthiocarbamoyl derivatives of encoded amino acids II were prepared either by the addition of phenylisothiocyanate to amino acid methylamides or by the treatment of amino acid phenylthiohydantoins (5-alkyl-3-phenyl-2-thioxo-4-imidazolinones) I with methylamine. The derivatives were prepared of 19 amino acids and their melting points, 1H NMR, 13C NMR, mass, ultraviolet and infrared spectra were measured.
Potential antidepressants: 2-(Phenylthio)aralkylamines
Authors: Jílek Jiří , Urban Jiří , Taufmann Petr , Holubek Jiří , Dlabač Antonín , Valchář Martin , Protiva Miroslav
Published: May 2010

Reactions of 2-(phenylthio)benzyl chloride with dimethylamine, diethylamine, pyrrolidine, piperidine, morpholine, and 1-methylpiperazine afforded the title compounds VI-XI. Reaction of 2-(phenylthio)benzaldehyde with nitromethane gave the nitrostyrene XIV which was reduced with lithium aluminium hydride to 2-(2-(phenylthio)phenyl)ethylamine (XVI). This was transformed to the N-methyl and N,N-dimethyl derivatives XVIII and XIX. The Claisen reaction of (2-(phenylthio)phenyl)acetonitrile with ethyl acetate afforded compound XXI which was cleaved by phosphoric acid to (2-(phenylthio)phenyl)acetone (XX). The Leuckart-Wallach reaction afforded the formamide XXIII which was used as starting material for preparing the amines XXIV-XXVI. The alternative approach to these compounds starting by reaction of the aldehyde XII with nitroethane was complicated by the fact that in addition to the nitropropene XV 2-(phenylthio)benzonitrile was also formed. The synthetic use of the inhomogeneous XV resulted then in mixtures of amines XXIV-XXVI with IV-VI which was followed by means of mass and 1H NMR spectra. The amines XXIV-XXVI were oxidized to the sulfoxides XXVII-XXIX. The oily bases were transformed to crystalline salts and spectra of all homogeneous bases were recorded. Pharmacological testing showed the amine VI (VÚFB-15 370) to be a promising potential antidepressant. The amines XI and XXV showed also pharmacological profile of potential antidepressants.
Alkaloids from Corydalis nobilis (L.) PERS. and C. intermedia (L.) MÉRAT
Authors: Slavík Jiří , Slavíková Leonora
Published: May 2010

Rhizomes of Corydalis nobilis (L.) PERS. (3% of alkaloids) contain (+)-tetrahydropalmatine, (+)-bicuculline and (+)-corytuberine as the main constituents of the tertiary alkaloid fraction. Protopine, (+)-corypalmine and (+)-stylopine, which also belong to the dominant alkaloids, were isolated in lesser amounts. As minor alkaloids were isolated (±)-tetrahydropalmatine, (+)-corydaline, allocryptopine, cryptopine, (-)-scoulerine, (+)-adlumidine, (+)-sinactine, (±)-corlumine, isoboldine, (+)-corybulbine, (±)-stylopine and (-)-isocorypalmine. The fraction of quaternary protoberberine alkaloids afforded coptisine dehydrocorydaline, palmatine, corysamine jatrorrhizine and cis-N-methylstylopinium hydroxide. Aobamidine (Z-adlumidiceine enol lactone), isolated as the principal alkaloid of aerial parts (0.3% of alkaloids), is obviously an artifact arising from bicuculline N-metho salt during the isolation process. Further dominant alkaloids of the tertiary fraction were adlumidine, bicuculline, protopine, (±)-tetrahydropalmatine and (±)-corlumine; as minor alkaloids were isolated corytuberine, scoulerine, corypalmine, cryptopine, isocorypalmine, corybulbine, (+)-corydalizine, and unidentified alkaloids CN 1 (C23H25NO5, m.p. 211 °C) and CN 2 (m.p. 261 °C). Quaternary protoberberine fraction afforded coptisine and palmatine. Nineteen of the mentioned alkaloids were isolated from this species for the first time. Tubers of C. intermedia (L.) MÉRAT (0.70% of alkaloids) afforded protopine, tetrahydropalmatine and corydaline as the main alkaloids and allocryptopine, canadine stylopine, palmatine, dehydrocorydaline, berberine, coptisine as minor alkaloids, together with traces of bicuculline and magnoflorine. Dominant alkaloids of the aerial part (0.73% of alkaloids) were bicuculline, bulbocapnine, protopine, stylopine and an unidentified phenolic base, m.p. 258 °C. Isoboldine, scoulerine, allocryptopine, corydaline, canadine, coptisine, palmatine and berberine were identified as the minor alkaloids.
Ce(IV)-mediated formation of benzenediazonium ion from a non-aminoazo dye, 1-phenylazo-2-hydroxy-naphthalene (Sudan I) and its binding to DNA
Authors: Stiborová Marie , Asfaw Befekadu , Anzenbacher Pavel
Published: May 2010

Ce(IV) ions in acidic medium convert a carcinogenic non-aminoazo dye, 1-phenylazo-2-hydroxy-naphthalene (Sudan I) into an ultimate carcinogen, which binds to calf thymus DNA. The principal product of Sudan I oxidation by the Ce(IV) system is the benzenediazonium ion. A minor product is the dihydroxyderivative of Sudan I, 1-(4-hydroxyphenylazo)-2,6-dihydroxynaphthalene. Other minor coloured products (yellow and brown) were not identified. The principal product (the benzenediazonium ion) is responsible for the carcinogenicity of Sudan I, as it covalently binds to DNA. Ce(IV) ions in acidic medium represent a suitable model system, which imitates the activation route of carcinogenic azo dyes.