bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigations about the Reducing Properties of Dimeric Dihydropyridines
Authors: Pragst F. , Šantrůček M. 
Published: December 2004

AbstractThe reaction of a series of bis‐[1,4‐dihydropyridinyl‐(4)] derivatives P2 with some benzyl halides, trans‐1,2‐dibromoethane and several heteroaromatic cations Q⊕ was investigated in acetonitrile/toluene with electrochemical and kinetic methods. For substrates with a reduction potential between −0.9 and −1.5 V the reaction occurs via the ratedetermining dissociation of P2 into free radicals P. as the real reducing agents, which transform the benzyl halides into the corresponding 1,2‐diarylethanes and Q⊕ into the corresponding dimeric product Q2. For the reduction of trans‐1,2‐dibromocyclohexane to cyclohexene a simultaneous transfer of two electrons to the substrate combined with the dissociation of P2 into two pyridinium ions P⊕ is proposed. In the case of a reduction potential more positive than −0.9 V (e.g. nitro substituted benzyl halides) P2 itself can act as the reducing agent with an increased reaction rate. With pyrylium ions Q⊕ a product P‐Q was detected by voltammetry and mass spectroscopy. In this case an electrophilic attack onto P2 instead of the electron transfer from P2 to Q⊕ cannot be excluded.
β‐Fur‐2‐yl‐α‐halogenacrylonitrile. VII. Reaktionen von β‐(5‐Brom‐fur‐2‐yl)‐α‐bromacrylonitril mit Mercaptan, Thioharnstoff und Thioharnstoffderivaten
Authors: Jähnisch K. , Seeboth H. , Kuban R. J. 
Published: December 2004

β‐Fur‐2‐yl‐α‐halogenacrylonitriles. VII. Reactions of β‐(5‐Bromo‐fur‐2‐yl)‐α‐bromoacrylonitriles with Mercaptans, Thiourea and Thiourea Derivativesβ‐(5‐Bromo‐fur‐2‐yl)‐α‐bromoacrylonitrile 1 reacts with ethylmercaptan to yield β‐(5‐bromo‐fur‐2‐yl) β‐ethylthioacrylonitrile 3. With thiourea β,β′‐thio‐bis[β‐(5‐bromo‐fur‐2‐yl)]‐acrylonitrile 2 is formed. The pyrimidines 4 and 5 have been prepared by the reaction of 1 with s‐methylthiourea and 2‐aminothiazole, respectively. The structure of the new compounds were determined by means of x‐ray analysis, 1H‐n.m.r., 13C‐n.m.r. and mass‐spectroscopy.
Aza‐Enamine. VI. Umsetzungen von N,N‐Dialkylhydrazonen aromatischer Aldehyde mit Sulfonylisocyanaten
Authors: Brehme Rainer , Stroede Bernd 
Published: December 2004

Aza‐enamines. VI. Reactions of N,N‐Dialkylhydrazones of Aromatic Aldehydes with Sulfonyl IsocyanatesThe electrophilic attack of the sulfonyl isocyanates 2 on the arylaldehyde‐N,N‐dialkylhydrazones 1 takes place in dependence upon the substitutents R1 and NR2 at the nitrogen or carbon of the azomethine‐group giving the 5‐amino‐hexahydro‐1,3,5‐triazine‐2,4‐diones 3, the phenylglyoxylic‐acid‐sulfonamide‐N,N‐dialkylhydrazones 4 and/or the imidazolidine‐2,4‐diones 5.The preparation and the u.v.‐, i.r.‐ and n.m.r.‐spectroscopic dates of the compounds 3–5 are reported.
Photochemie von Aminoketonen. X. Darstellung und diastereoselektive Photocyclisierung von N‐(β‐Benzoylethyl)‐N‐tosyl‐glycinamiden
Authors: Walther K. , Kranz U. , Henning H.‐G. 
Published: December 2004

Photochemistry of Aminoketones. X. Preparation and Diastereoselective Photocyclization of N‐(β‐Benzoylethyl)‐N‐tosyl‐glycinamidesThe title compounds 4 were prepared by MICHAEL‐like addition of N‐tosylglycinamides to phenyl‐vinyl‐ketone, generated from ω‐bromo‐propiophenone. 300 nm Irradiation of 4a–c (CO–NH) in benzene and acetone, respectively, causes, n, π*‐excitation and photocyclization to (3‐ref‐2‐cis)‐3‐hydroxy‐3‐phenyl‐N‐tosylprolinamides 5. Under the same conditions 4d–h (CONAlk2) yield (3‐ref‐2‐trans)‐prolinamides 6. The difference in diastereoselectivity is explained by intramolecular dipolar interaction in 4* and intramolecular hydrogen bondings in the intermediate hydroxybiradicals.
Fotochemische Primärprozesse von Xanthenfarbstoffen. VIII. Zum Einfluß von gemischten Mizellen auf die fotochemischen Primärprozesse von Selenopyronin und Erythrosin sowie die sensibilisierte Diazoniumsalzfotolyse
Authors: Ortmann W. , Fanghänel E. 
Published: December 2004

Photochemical Primary Processes of Xanthene Dyes. VIII. Influence of Mixed Micelles on the Photochemical Primary Processes of Selenopyronine and Erythrosine and the Sensitized Photolysis of Diazonium SaltsThe influence of the nonionic detergent dodecyltriglycol (DTG) on the escape rate of dye ions from cationic and anionic micelles is investigated. The rate constant of the escape of selenopyronine ions (Sp⊕) from mixed micelles of sodium dodecylsulfate (NDS) and DTG (1:1) (kA ≈︁ 3,2 · 104 s−1) is, as a result of the lower charge density, higher by the factor 10 than that from clean NDS‐micelles (kA ≈︁; 2,8 · 103 s−1). Erythrosine ions (Et2⊖) are tightly fixed to cetyltrimethylammoniumbromide (CTAB)‐micelles (kA ≈︁; 0,25 · 103 s−1) and to mixed micelles of CTAB and DTG (1:1). This may be a result of the twofold negative charge of the erythrosine ions. Properties of the mixed micelles (polarity, average aggregation numbers) are determined by using the dyes and pyrene as probes. The sensitized photolysis of diazonium salts by electron transfer from photoexited selenopyronine under aerobic conditions is more effective by a factor of 3–5 in the presence of anionic micelles than when in a water solution.
Zur Darstellung und selektiven Reduktion von geschützten Endothiopeptiden
Authors: Ripperger H. 
Published: December 2004

On the Synthesis and Selective Reduction of Protected EndothiopeptidesThe conversion of some protected peptides structurally related to nicotianamine into the corresponding endothiopeptides has been studied, using 2,4‐bis(4‐phenoxyphenyl)‐1,3,2,4‐dithiadiphosphetan 2,4‐disulfide, a modified Lawesson reagent. Regioselectivity was observed. The possibility of selective reduction of the thioamide group in the presence of t‐butyl ester and urethane groups was demonstrated.
Nucleophile Substitutionen an Kohlensäurederivaten. XX. Aminolyse des Bis(trichlormethyl)carbonates
Authors: Cotarca Livius , Bacaloglu R. , Csunderlik C. , Marcu N. , Tarnaveanu A. 
Published: December 2004

Nucleophilic Substitutions at Carbonic Acid Derivatives. XX. Aminolysis of Bis(trichlormethyl)carbonateThe rate constants for the two steps of the reaction of bis(trichlormethyl)carbonate with substituted anilines have been determinated by conductivity measurements.The first relatively fast step of the reaction is the nucleophilic attack of the amine to the bis(trichloromethyl)‐carbonate leading to trichloromethylurethane through a six or four centers transition state in which the carbon‐nitrogen bond is formed parallel with the transfer of the proton. In this reaction a phosgene molecule is also produced, which reacts very fast with amine to form a N,N′‐diarylurea.The second, much slower step, is the nucleophilic attack of the amine to the trichloromethylurethane. Through a similar transition state in which the proton transfer has even a higher importance, a N,N′‐disubstituted urea and an other molecule of phosgene are formed.
Synthese und UV‐spektroskopische Charakterisierung von Carbeniumionen an Aerosil
Authors: Ulbricht Antje , Spange Stefan , Heublein Günther 
Published: December 2004

Synthesis and UV‐spectroscopic Characterization of Carbenium Ions on AerosilThe interaction of aerosil with various triphenylmethyl derivatives in the cationic vinyl polymerization in 1,2‐dichloroethane was studied. The adsorption of the triphenylmethylium ions onto aerosil surfaces strongly depends on both the type of substituents (R  CH3, OCH3, Cl, H and NO2) and the nature of the counter anion (SbCl6⊖, FeCl4⊖, SnCl5⊖, HSO4⊖, SO42⊖, F⊖, Cl⊖, Br⊖, CF3COO⊖, N3⊖ and SCN⊖). The binding of the triphenylmethylium ions with aerosil occurs via nucleophilic anions such as halides. Counter anions derived from metal halides as MtXn+1⊖ are not able bind on aerosil. Covalent compounds as triphenylmethyl halides are ionized by the acidic aerosil surface. The influence of substituents at the triphenylmethylium ion, the type of counter anions and the influence of water traces on surface — ionization are discussed.
Synthesis of Thiazolo(4,5‐b)‐quinoxalines and related compounds
Authors: Ammar Y. A. , Ismail I. M. , Sh. El‐Sharief A. M. , Mohamed Y. A. , Amer R. M. 
Published: December 2004

AbstractThe reaction of 2,3,7‐trichloroquinoxaline (1) or 2,3‐dichloro‐7‐bromoquinoxaline (2) with thiourea in DMSO gave 6,6′‐dichloro‐ or 6,6′‐dibromodiquinoxalino[2,3‐b:2′:3′‐e]1,4‐dithiien (3 or 4). However, 1 or 2 reacts with thiourea in ethanol to give (3 or 4) beside 7‐chloro‐ or 7‐bromo‐2‐imino‐2,3‐dihydrothiazolo[4,5‐b] quinoxaline (5 or 6) respectively. Interaction of 1 or 2 with acetone thiosemicarbazone gave 7‐chloro‐ or 7‐bromo‐3‐amino‐2‐imino‐2,3‐dihydro‐thiazolo[4,5‐b] quinoxaline hydrochloride (13 or 14) respectively. Cyclization of 7‐chloro‐ or 7‐bromo‐3‐amino‐2‐imino‐2,3‐dihydrothiazolo[4,5‐b]quinoxaline (15 or 16) on treatment with aromatic acid chlorides or isothiocyanates succeeded to give 19—21 or 28 and 29.
New syntheses of pyrazolo[3,4‐d]pyrimidine, pyrazolo[3,4‐d]pyridazine, isoindolinedione and pyrazole derivatives
Authors: Abdelhamid Abdou O. , Negm Abdalla M. , Abbas Ikhlass M. 
Published: December 2004

AbstractPhenacylmalononitriles 2 react with hydrazines, acetic‐hydrochloric acid and with diazotised primary aromatic amines to afford phenacylpyrazole (5a,b), aminofurans (6a,b) and aminopyrazole derivatives (3a,d) respectively. The synthesised derivatives (3d, 6a) were the key materials for the synthesis of isoindolinedione, (7a–c) pyrazolopyrimidine (9, 10), and pyrazolopyridazine derivatives (11). The structures of the newly synthesised heterocycles were established on the basis of elemental analyses and spectral data besides synthesis via other routes.
Chinoxaline. XXVII. Synthese bis‐azolo[a,c]kondensierter Chinoxaline. II. Darstellung aus 4‐Formyl‐azolo[a]chinoxalinen
Authors: Vogel M. , Lippmann E. 
Published: December 2004

Quinoxalines. XXVII. Synthesis of Bis‐azolo[a,c]‐fused Quinoxalines. II. Synthesis from Azolo[a]quinoxaline‐4‐carbaldehydesThe azolo[a]quinoxaline‐4‐carbaldehydes 2a–d were obtained from 4‐methyl azolo‐[a]quinoxalines 1a–d by Kröhnke reaction. 2a exists in the hydrate form. 2a–d react with tosylhydrazide giving the thermally labile compounds 3a–d in good yields. Treatment of 3a–d with a boiling solution of sodium ethoxide (Bamford‐Stevens reaction) leads to the fused quinoxaline systems 4a–d. 4d was also obtained from bis‐tosylhydrazone 10.
Furylvinylhalogenide. X [1]. Reaktionen von β‐Fur‐2‐yl‐β‐chlor‐α‐cyanacrylsäurederivaten mit Hydrazinen
Authors: Jähnisch K. , Schwertner S. 
Published: December 2004

Furylvinylhalides. X. Reactions of β‐Fur‐2‐yl‐β‐chloro‐α‐cyanoacrylic Acid Derivatives with Hydrazinesβ‐Fur‐2‐yl‐β‐chloro‐α‐cyanoacrylic acid derivatives 3 react with hydrazines yielding 3‐fur‐2‐yl‐5‐aminopyrazoles 5 or 3‐fur‐2‐yl‐4‐cyanpyrazolin‐5‐ones 6. In some cases the β‐hydrazino‐α‐cyanoacrylic acid derivatives 4, could be isolated.
Phosphororganische Antioxidatien. X [1]. Über die hydroperoxidzersetzende Wirkung von Phosphiten, Phosphoniten und Thiophosphiten
Authors: Köunig T. , Habicher W. D. , Schwetlick K. 
Published: December 2004

Organophosphorus Antioxidants. X. The Hydroperoxide Decomposing Action of Phosphites, Phosphonites and ThiophosphitesThe kinetics and mechanism of reactions of phosphites, phosphonites, thiophosphites and hydrogenphosphites with cumyl (CHP), t‐butyl (TBHP) and α‐tetralyl (THP) hydrogenperoxides has been studied by means of 31P‐n.m.r. spectroscopy, high performance liquid chromatography and iodometric titration.All three valent phosphorus compounds studied initially react with hydroperoxides stoichiometrically to give the corresponding PO products and alcohol. Some species are able to decompose cumyl hydroperoxide catalytically to form phenol and aceton.Acyloin phosphites decompose CHP catalytically after a stoichiometric reaction as thiophosphites do. Tetramethylpiperidinyl phosphites (“HALS‐phosphites”) react with hydroperoxides only stoichiometrically but with high velocity.Phosphonites react with hydroperoxides in the same way as the corresponding phosphites. Their reactivity, however, is much higher.Hydrogenphosphites are less reactive than phosphites in the reaction with hydroperoxides. They are able to act catalytically.
Some Aspects of Underwater Testing Method
Authors: Satyavratan P. V. , Vedam R. 
Published: December 2004

AbstractSome of the interesting results obtained in the course of a large number of experiments carried out at IDL Chemicals Hyderabad are discussed in this paper:

A linear correlation was found between underwater energies and Trauzl lead‐block values. The correlation of the total energy was found to be better than the correlation of shock and bubble energies individually.

Variation of underwater energies with depth was observed. The shock energy decreased with depth and the bubble energy increased with depth, for three different types of explosives.

The effect of firing explosives with and without boosters were studied. In the case of an aluminized slurry explosive there was a slight increase in shock energy and no change in the bubble energy, when initiated with boosters. In the case of a powder explosive, the shock energy was found to decrease by 15% and the bubble energy by 4.7%, when initiated with boosters.

An attempt was made to study the statistical behaviour of underwater testing. The shock energy distribution appeared to be non‐normal. It indicated the possibility of the presence of two modes. The bubble energy distribution was normal and its variability was found to be very low. The total energy distribution was also non‐normal on account of shock energy distribution.

The need for standardization of various testing parameters such as the depth of the charge, the distance between the charge and the transducer, the geometry of the cartridge and the type of initiation, to get repeatable and internationally comparable results, is discussed. There is a need to develop complementary theory and additional measurements (if possible) to make the system more complete and acceptable for measuring the strength of explosives.
Synthesis of N,N′‐Bis(2‐Nitro‐Benzodifuroxanyl)‐1,3,5‐Trinitro‐2,6‐Diaminobenzene
Authors: Naixing Wang , Boren Chen , Yuxiang Ou 
Published: December 2004

AbstractN,N′‐Bis(2‐nitro‐benzodifuroxanyl)‐1,3,5‐trinitro‐2,6‐diaminobenzene has been synthesized from 1,3‐diaminobenzene and trinitrotrichlorobenzene. The molecular structure of this compound has been determined by elemental analysis, IR, 1HNMR, and MS spectroscopies.
High Energetic High Density Materials: A BASIC Program (FCALC) for the design and selection of efficient high energetic materials containing nitro and azido groups
Authors: Senthilkumar Udayampalayam P. , Vijayalakshmi Rajagopalan , Jeyaraman Ramasubbu 
Published: December 2004

AbstractA program named “FCALC” has been developed in BASIC language to calculate the detonation volumes (through a factor F) for various explosives as well as for any new organic structure. The number and kind of substiments that need to be incorporated into an unsubstituted organic compound in order to achieve maximum F factor, and thus maximum detonation velocity, can also be predicted. The program calculates F factors for a user‐defined set of combinations of substituents.
A New Kinetics and the Simplicity of Detonation
Authors: Walker Franklin E. 
Published: December 2004

AbstractA review is presented of three experiments, as well as a number of molecular dynamics and quantum mechanics calculations. which cast in serious doubt the validity of some concepts and theories of detonation. This doubt led to numerous studies in search of more satisfying concepts, and the results of several of those studies are given. Particularly, a new concept of the kinetics of shock‐induced chemical reaction is presented. This process, designated as physical kinetics, is described as a nonequilibrium, nonthermal process in which chemical reaction rates are determined and regulated by the averaged vibrational velocities of the bonded atoms in condensed systems under the influence of high velocity shock waves. These velocities control the advance of the kinetic energy which leads to the very high impact velocities of the molecules and atoms which cause massive bond fracture in the molecules in extremely short times. It is shown that a detonation model based on the new kinetics model, with the major reactions occurring in times of the order of tenths of picoseconds and in distances on the order of tens of angströms ‐ in the shock or detonation front ‐ can provide a precise and satisfying mathematical and physical description of detonation phenomena.
Wellenmechanische Absolutrechnungen an Molekülen und Atomsystemen mit der SCFMOLC(LCGO) Methode. V. Bindungsbeteiligung der Inneren Elektronen des C‐Atoms
Authors: Preuss H. , Diercksen G. 
Published: December 2004

AbstractDurch Vergleichen der “1s‐Einteilchenenergien” an den C Atomen in den Verbindungen C6H6, C5H, C3H6 (Cyclopropan), C2H4 sowie am freien C Atom wird im Rahmen von ab initio—Rechnungen gezeigt, dass die inneren Elektronen von den Bindungsvorgängen wesentlich beeinflusst sind. Die Ursachen werden diskutiert und eine Erklärung dafür angegeben. Der Zusammenhang dieser Energieänderungen mit den Bindungsverhältnissen, sowie die Bedeutung dieser Tatsache für gewisse Modellvorstellungen werden besprochen.
L'Etude Théorique des Systèmes Périodiques. I. La Méthode LCAOHCO
Authors: André Jean‐Marie , Gouverneur Louis , Leroy Et Georges 
Published: December 2004

AbstractOn décrit la méthode des orbitales cristallines, combinaisons linéaires d'orbitales atomiques (LCAOHCO), inspirée des procédés classiques de la chimie quantique et permettant d'étudier théoriquement les systèmes périodiques. On déduit la forme explicite de quelques grandeurs caractéristiques dans l'approximation de Hückel. La méthode est comparée à l'approximation dite des électrons “quasi‐atomiques” et appliquée aux polyènes, aux polyacènes, et au graphite. La validité générale du procédé est discutée dans la conclusion.
L'Étude Théorique des Systèmes Périodiques. II. La Méthode LCAOSCFCO
Authors: André Jean‐Marie , Gouverneur Louis , Leroy Et Georges 
Published: December 2004

AbstractOn décrit le formalisme de la méthode LCAOSCFCO permettant d'étudier les propriétés des systèmes périodiques conjugés et un procédé semi‐empirique pour évaluer les intégrales intervenant dans les éléments de matrice de l'operateur du champ autocohérent de ces systèmes.
The perturbation theory of the extended Hartree–Fock approximation for two‐electron atoms
Authors: Brown W. Byers , Nazaroff G. V. 
Published: December 2004

AbstractThe first‐order 1/Z perturbation theory of the extended Hartree–Fock approximation for two‐electron atoms is described. A number of unexpected features emerge: (a) it is proved that the orbitals must be expanded in powers of Z−1/2, rather than in Z−1 as expected; (b) it is shown that the restricted Hartree–Fock and correlation parts of the orbitals can be uncoupled to first order, so that second‐order energies are additive; (c) the equation describing the first‐order correlation orbital has an infinite number of solutions of all angular symmetries in general, rather than only one of a single symmetry as expected; (d) the first‐order correlation equation is a homogeneous linear eigenvalue‐type equation with a non‐local potential. It involves a parameter μ and an eigenvalue ω(μ) which may be interpreted as the probability amplitude and energy of a virtual correlation state. The second‐order correlation energy is 2μ2ω.Numerical solutions for the first‐order correlation orbitals, obtained variationally, are presented. The approximate second‐order correlation energy is nearly 90% of the exact value.The first‐order 1/Z perturbation theory of the natural‐orbital expansion is described, and the coupled first‐order integro‐differential perturbation equations are obtained. The close relationship between the first‐order extended Hartree–Fock correlation orbitals and the first‐order natural correlation orbitals is discussed. A comparison of the numerical results with those of Kutzelnigg confirms the similarity.
Eine Rechenzeitsparende Programmierung des Wellenmechanischen Self‐Consistent‐Field Verfahrens für Moleküle (SCFMOLCGO–Verfahren)
Authors: Preuss H. , Diercksen G. 
Published: December 2004

AbstractEs wird eine rechenzeitsparende Programmierung eines SCF–Verfahrens für Moleküle (SCFMOLCGO–Verfahren) angegeben, die auf einer rationellen Behandlung der Zweielektronen‐Mehrzentrenintegrale beruht.
Symmetry components analysis of nuclear spin–spin coupling constants
Authors: Barbier Claudette , Berthier Gaston 
Published: December 2004

AbstractMolecular symmetry properties are used to define “normal” spin–spin coupling constants corresponding to some irreducible representations of the symmetry point group of the molecule. The relationship between these normal coupling constants and the measured ones is established in closed form for the most common cases. The Ramsey perturbation formula is analysed into symmetry components by means of the Winger–Eckart theorem. Both contributions predicted by the molecular‐orbital method, i. e. direct coupling via σ electrons and indirect coupling via σ–π interaction are studied. Numerical calculations for the coupling constants of ethane, ethylene and acetylene were carried out without the mean excitation energy approximation by using SCFMO wave functions; overlap between atomic orbitals is systematically taken into account by calculating coupling constants. Theoretical and experimental results are compared in terms of symmetry components.
A theoretical consideration of the spectral properties of flavin tautomers and imino flavins
Authors: Song Pill‐Soon 
Published: December 2004

AbstractThe Hückel MO and semiempirical SCF–ASMO–CI methods have been employed to calculate transition energies of seven possible flavin tautomers and two imino flavins (Schiff bases). The calculated spectral transition energies indicate that the tautomerism and Schiff base formation are accompanied by a bathochromic shift with reference to the absorption spectrum of riboflavin. This shift is especially pronounced in the case of the 4‐enol forms of the isoalloxazine molecule. The 4‐enolic tautomers also have lowest triplet levels well below the triplets of other tautomers. The significance of the results has been discussed.
Expansion of linear combinations of slater‐type orbitals in eigenfunctions of the three‐dimensional isotropic harmonic oscillator
Authors: Lesk Arthur M. 
Published: December 2004

AbstractSeveral classes of functions related to the Gaussian have been used with success as basis sets for the representation of atomic and molecular orbitals.We have compared the representation of a hydrogen 1s orbital by a sum of Gaussian lobe functions with its expansion in eigenfunctions of the three‐dimensional isotropic harmonic oscillator. The lobe functions are shown to achieve better expectation values of the energy, with fewer terms. The lobe functions have the further computational advantage of not containing high powers of the radius.It is concluded that the lobe functions are a superior basis set for use in calculations of the electronic structure of atoms and molecules.
On the behaviour of the wave function for the 23S state of the two‐electron atom in the region where both electron–nuclear distances are small
Authors: Sochilin G. B. 
Published: December 2004

AbstractThe expansion of the wave function for the 23S state of the two‐electron atom in the neighbourhood of the singularity at r1 = r2 = 0 is considered. The restrictions imposed on the variational functions by this expansion are discussed. For the 23S state of He, Li+, N5+ the behaviour of the variational function based on the Fock expansion in the neighbourhood of this singularity is investigated. The agreement of the variational coefficients with the theoretical coefficients is satisfactory. The calculated values of E and 〈δ(r2)〉 for He, Li+, N5+ are given.