bluuebunny/crossref_metadata_2025_split huggingface dataset:
Substituenteneffekte in den 13C‐NMR‐Spektren von diastereomeren Chalkondihalogeniden. V. Synthese, Stereochemie und Spektroskopie von Chalkonfluorhydrinen
Authors: Weber Fritz Gerd , Giese Hartmut , Köppel Hubert , Reinhold Monika , Strobel Rita , Radeglia Reiner , Storek Werner 
Published: December 2004

Substituent Effects in 13C‐ N. M. R. Spectra of Diastereomeric Chalcone Dihalogenides. V. Synthesis, Stereochemistry and Spectroscopy of Chalcone FluorohydrinesChalcone fluorohydrins 1 and diastereomeric pairs of chalcone chlorohydrins 2 as standards are investigated in the i.r., 1H, 19F, and 13C n m. r. spectroscopy field. The substituent dependence of the spectral parameters is discussed.The assignment of conformation and configuration on the basis of vicinal 1H1H, 1H19F, and 1H13C coupling constants is determined.
Methylation of 5‐Aldehydo‐6‐arylpyridazin‐3(2H)‐ones via reaction with dimethyl and pentamethyl cuprates
Authors: Shams Nabil A. 
Published: December 2004

AbstractMe5Cu3Li2 in ether or ether‐pentane mixtures, converts the title compounds efficiently into the corresponding 4‐methyl derivatives (5) via conjugate methylation of either α,β‐unsaturated aldehyde or NCCC system, together with ⋍20% of 1,2 adducts (6 and 7). With Me2CuLi, however, the product contains, as an average, ⋍55% of 1, 2 adducts and ⋍45% of 1,4‐isomer. On the other hand, with MeMgI no 1, 2‐methylation could be observed and the only product obtaind is the 1, 4‐isomer.
Pyryliumverbindungen. XXIX [1] Substituierte Benzophenone aus 2,4,6‐Triaryl‐pyryliumsalzen und Methyl(en)ketonen
Authors: Zimmermann Thomas , Fischer Gerhard W. 
Published: December 2004

Pyrylium Compounds. XXIX. Substituted Benzophenones from 2,4,6‐Triarylpyrylium Salts and Methyl(ene) KetonesIn the presence of piperidine acetate (or similar salts of certain dialkylamines), 2,4,6‐triarylpyrylium perchlorates 5 react with methyl(ene) ketones 6 to give benzophenones 7, the structure of which was proved by spectroscopic methods as well as by independent synthesis. Besides acetone and other acyclic ketones (e. g. alkyl methyl ketones, phenylacetone, desoxybenzoin, dibenzyl ketone) cyclic ketones (e. g. cyclopentanone, cyclohexanone, cycloheptanone, acenaphthenone) can also be used as ketone component 6; acetophenones react differently leading to hydrocarbons of the 1,3,5‐triarylbenzene type 15. The varying efficiency of the diverse amine salts and the mode of incorporation of the unsymmetrically substituted ketones suggest the intermediate formation of enamines 10 as crucial step of the ring transformations observed. This assumption is supported by isolation of the iminium salt 18 on reacting 3,5‐dimethyl‐2,4,6‐triphenylpyrylium perchlorate (16) with acetone/piperidine acetate.
Synthese von N‐Maleoyl‐aminosäuren und ‐peptiden
Authors: Augustin Manfred , Müller Wolfgang 
Published: December 2004

Synthesis of N‐Maleoyl‐aminoacids and ‐peptidesN‐Maleoyl‐aminoacid‐N′‐hydroxysuccinimidesters 3 or N‐maleoyl‐aminobenzoic acids 5 are synthesized from N‐maleyl‐aminoacids 1 on different ways. N‐maleoyl‐aminobenzoic‐4‐nitro‐phenyl‐,‐2‐nitro‐phenyl‐or 2,4‐dinitro‐phenylesters 6, 7 and 8 will be obtained from 1 or 5. o‐Mercapto‐aniline, thiourea or cysteine react with 5 to benzothiazines 9, thiazolidines 10 and 1,4‐thiazines 11. from 5 the peptides 12 are yielded. The pentapeptide 13 are formed from 12 by addition of glutathione.
Radikalreaktionen an N‐Heterocyclen. IV. EPR‐Untersuchung des H‐Transfers zwischen aminischen Antioxidantien und Peroxy‐Radikalen
Authors: Tkáč A. , Omelka L. , Schulz M. , Mögel L. 
Published: December 2004

Radical Reactions of N‐Heterocyclic Compounds. IV. ESR Investigation of H‐Transfer between Aminic Antioxydants and Peroxy RadicalsThe N‐radicals of pyrazole‐, imidazole‐ and indole‐derivatives were prepared in comparatively high concentrations at room temperature in benzene or toluene and their e.s.r. signals were interpreted. In H‐abstraction by free or to Co(III)‐coordinated tert.‐butylperoxy radicals from bifunctional heterocyclic substituted amines 2–9, 11 the following efficiency was ascertained: unhindered OH > aniline‐NH > heterocyclic‐NH, hindered OH‐groups. No radical attack on the exocyclic NH2‐group took place.The splitting constant concerning the heterocyclic nitrogen of nitroxyl radicals 5a, 10a was in the range aNendo = 0.7 to 0.85 mT in contrast to exocyclic nitroxyls 6a, 8a, 9a, 11a possessing aNexo = 1.0 to 1.1 mT. The interruption of the π‐conjugation between the heterocyclic and the aniline groups by insertion of a CH2‐group led to the decrease of the stability of the generated N‐radicals. In the case of anilinebenzimidazole 9 the Co(III)‐complexed endocyclic aminyl radical 9b was observed simultaneously with the exocyclic nitroxyl radical 9a.
Spektralverhalten von Pyrazolin‐5‐on‐Azomethinfarbstoffen – Quantenchemische Beschreibung der Substituenteneinflüsse
Authors: Weise A. , Mustroph H. , Winnig B. , Grossmann N. , Fanghänel E. 
Published: December 2004

Absorption Behaviour of Pyrazoline‐5‐one Azomethine Dyes – Quantumchemical Description of the Influence of SubstituentsThe VIS absorption of the pyrazoline‐5‐one azomethine dyes 1a–h is measured in dependence of the substituents of the amino group.HMO calculations confirm that the „x‐ and y‐bands”︁ have a strong charge transfer character. The absorptions in the visible region correspond to a transition from the HOMO mainly localized at the amino‐substituted phenyl to the complex acceptor 4‐imino‐pyrazoline‐5‐one (“x‐band”) or to the pyrazoline‐5‐one fragment (“y‐band”). The calculated transition energies correlate with the values νmax of the x‐band (r = 0.993). There is also a linear correlation between the square of the LCAO‐MO coefficients in position 7 and 6 of the dye and εmax (r = 0.978).
Umsetzung von (Z/E)‐1‐Aryl‐4‐arylmethylen‐pyrrolidin‐2,3,5‐trionen mit Enaminocarbonylverbindungen
Authors: Augustin M. , Jeschke P. 
Published: December 2004

Reaction of (Z/E)‐1‐Aryl‐4‐arylmethylene‐pyrrolidine‐2,3,5‐triones with Enaminocarbonyl CompoundsTreatment of the α, β‐unsaturated ketones (Z/E)‐1a–e with alicyclic or aliphatic enamines afforded cyclic Michael adducts 2 and 3a–e, respectively. By dehydration of the N,O‐hemiacetals 3b–d the corresponding 1,4‐dihydropyridines 4a–c were obtained.The acid‐catalyzed reaction of aminosubstituted maleimides with (Z/E)‐1e, aldehydes or indan‐1,2,3‐trione led to 5a–c, 6a–c, 7a–c and 8. O‐Methylation of the aryl‐bis(maleinimidyl)methanes 5c, 6c by using diazomethane gave 5d, 6d, whereas 5a cyclized spontaneously to the 1,4‐dihydropyridine 9a. Further 1,4‐dihydropyridines were prepared by cyclocondensation of 6a, b in the presence of ammonium acetate and oxidized to the pyridine derivative 10.
Electrochemistry of Organic Cations. VI. Investigations about the Cathodic Cleavage of Some Pyridinium and Triazolium Ions
Authors: Pragst F. , Henrion A. , Abraham W. , Michael G. 
Published: December 2004

AbstractThe electrochemical reduction of some N‐acylamino‐, N‐amino‐, N‐benzyl‐ and N‐phenacyl‐substituted pyridinium and triazolium ions is investigated in acetonitrile by voltammetric methods and potentiostatic electrolyses. The acylaminopyridinium ions 1 and the arylaminopyridinium ions 3 are cathodically cleaved into the pyridine derivative and the carboxylic amide or the aromatic amine. In the case of the 1‐benzyl‐4‐acylaminotriazolium ions 5 the reductive formation of hydrogen from the acidic N‐acylamino group is preferred and the corresponding ylide is formed, which reacts at more negative potential by splitting off the benzyl group. The reduction of the N‐phenacylpyridinium ion 7d occurs with splitting off the phenacyl radical, which dimerizes to 1,2‐dibenzoylethane in a good yield. In the case of N‐benzyl‐ and N‐p‐cyanobenzylpyridinium ions the cathodic dimerization to the corresponding bisdihydropyridines was found, whereas the electrolysis of the N‐nitrobenzylpyridinium ions occurs with cleavage of the N‐substituent‐bond, which is initiated by the primary formation of the nitrophenyl anion radical. It follows from electrogenerated chemiluminescence experiments that the cleavage of the cations 1 and 5 occurs with the uptake of one electron.
Dithiocarbonsäuren, Dithiocarbonsäureester oder Thiocarbonsäureamide aus methylenaktiven Chlormethylverbindungen und Schwefel
Authors: Thiel W. , Mayer R. 
Published: December 2004

Dithiocarboxylic Acids, Dithiocarboxylic Esters, or Thiocarboxylic Amides by Reaction of Methylene‐active Chloromethyl Compounds with SulfurWith a mixture of sulfur and amine in DMF at room temperature halomethyl compounds (1, 5–10) can be oxidized to give thiocarboxylic acids (2, 11–16) and their derivatives (3, 4, 17–35). We studied this reaction in detail especially with chloroacetic derivatives (11–15) or chloromethyl heterocycles (16) formally derived from chloroacetic acid.The resulting thiooxalic acid derivatives (11–27) represent activated acids and very useful C2‐synthons, especially for the synthesis of heterocycles.Oxidation in the presence of triethyl amine leads to dithiocarboxylates (11–16) which can be alkylated to dithioesters (17–27) in high yields.As a rule, with different primary and secondary amines instead of tertiary amines these dithiocarboxylates or dithiocarboxylic esters can be transformed already at low temperatures to thioamides (28–35).
Bromination of pyridines. II. Bromination of Aminopicolines
Authors: Dunn A. D. , Currie A. , Hayes L. E. 
Published: December 2004

AbstractThe bromination of all ten possible aminopicolines 1–10 was investigated. In general, the major brominated product was that corresponding to electrophilic attack at the sites para or ortho to the amino group.
Kristallin‐flüssige 1,3,4‐Thiadiazole. II [1]. 1,3,4‐Thiadiazole mit Cyclohexanstrukturfragmenten
Authors: Schäfer W. , Rosenfeld U. , Zaschke H. , Stettin H. , Kresse H. 
Published: December 2004

Liquid Crystalline 1,3,4‐Thiadiazoles. II. 1,3,4‐Thiadiazoles with CyclohexanefragmentsPreparation and liquid crystalline properties of disubstituted 1,3,4‐thiadiazoles (1 and 2) are described. The mesomorphic behaviour of the title compounds is compared with their benzoate analogues. The dielectric anisotropy of these compounds is negative.
Thiohydrazide und 1,3,4‐Thiadiazole durch Hydrazinolyse von Dithioestern
Authors: Thiel W. , Mayer R. 
Published: December 2004

Thiohydrazides and 1,3,4‐Thiadiazoles by Hydrazinolysis of Dithiocarboxylic EstersThe reaction of 1,1‐dithiooxalicesters1and heteroaryldithiocarboxylicesters2with excess hydrazine yields stable thiohydrazides3and4, respectively. If the hydrazinolysis is carried out with only 0,5 equivalent hydrazine 1,3,4‐thiadiazoles6and7, equally substituted in position 2 and 5, result. 1,3,4‐Thiadiazoes are also formed by heating the isolated thiohydrazides3and4. The thiohydrazides3and4are also excellent starting compounds for the synthesis of unsymmetrically substituted 1,3,4‐thiadiazoles (8,9), especially for derivatives with carbamoyl or heteroaryl residues.
Ignition of composite propellant at subatmospheric pressures by means of carbon dioxide laser
Authors: Sofue T. , Iwama A. 
Published: December 2004

AbstractIgnition behavior of solid propellant composed of 25 wt% polybutadiene and 75% ammonium perchlorate under subatmospheric conditions has been studied using a carbon dioxide laser whose radiant flux is uniformalized. Data of ignition time in Ar, N2 and He atmospheres, and critical radiant flux and pressures over which ignition might be achieved, were obtained. Moreover, the data were compared with theoretical values, taking account of variable heat conductivity for the ambient gases with a surface ignition hypothesis.It is concluded that these ambient gases participate in the pre‐ and post‐ignition reactions and the ignition preventive behavior of He atmosphere is not predictable merely based on its high transport properties. The detailed observation of the ignition transient near the critical pressure revealed that the ignition in Ar atmosphere occurs in gas phase under less than 100 torr whereas in He atmosphere it occurs always at the condensed phase surface.
Investigation of the Explosive Properties of HMX/Al 70/30
Authors: Langen P. , Barth P. 
Published: December 2004

AbstractThe production of HMX/Al 70/30 and the investigation of the characteristic properties are described and a comparison to RDX/Al 70/30 properties made. According to first test results, the possibility of an increased performance compared to RDX/Al 70/30 may not be ruled out.
Gap‐Test‐Untersuchungen an gewerblichen Sprengstoffen
Authors: Trimborn F. 
Published: December 2004

AbstractDas Prüfverfahren “Gap‐Test” ist bisher bei gewerblichen Sprengstoffen nicht in größerem Umfang eingesetzt worden. Dabei scheint es sowohl von seiten der Sicherheit als auch der Funktionsfähigkeit interessant zu sein. Dieses Prüfverfahren wird anhand einer speziellen Ausführung „Gap‐Test des BICT”︁ vorgestellt. Es wird über Ergebnisse an 24 gewerblichen deutschen Sprengstoffen berichtet. Die gefundene Empfindlichkeitsskala ist in guter Übereinstimmung mit der Erfahrung. Bei gelatinösen Sprengstoffen und Wettersprengstoffen wurden Besonderheiten beobachtet. Möglichkeiten und Grenzen der speziellen Versuchsanordnung werden erörtert.
Technical Improvements for SEC Studies
Authors: Su F. H. , Bien D. M. , Perng H. C. , Hu David , Wu Sam 
Published: December 2004

AbstractAn on‐line system to measure hoop‐strain of strain evaluation cylinders (SECs) has been developed. The experimental results compared with the data measured by intermicrometer are acceptable. A modified mathematical equation to calculate thermal expansion coefficient of propellant is proposed and gives excellent agreement in comparing with the data measured by thermomechanical analysis (TMA).
Flame Temperature Calculations at High Temperature and Pressure
Authors: Vladimiroff T. , Carignan Y. P. , Chiu D. S. , Macpherson A. K. 
Published: December 2004

AbstractIn the past, real gas effects on the flame temperature were evaluated using the virial equation of state. Usually, the virial expansion was truncated after the third term. In this work the equation of state for dense gases proposed by Haar and Shenker is considered. The implementation developed for H2O, CO, CO2, H2, and N2 by Powell, Wilmot, Haar and Klein is used. The contribution of all minor species is assumed to be approximated by a Lennard‐Jones gas with ϵ/k = 100 K and σ = 3.0 Å. It is found that the more conventional approach is valid up to a loading density of 0.2 g/cm3. As density increases real gas effects cause the calculated flame temperature to decrease and the calculated pressure to increase. A computer program to perform the calculations has been devised for a personal computer.
Heat of Fusion for 1,3,5,5‐ Tetranitrohexahydropyrimidine (DNNC) and its DNNC‐d6 deuterium labelled analogue
Authors: Shackelford Scott A. , Goldman Jeffrey F. 
Published: December 2004

AbstractThe heat of fusion for DNNC (1,3,5,5‐tetranitrohexahydropyrimidine) and its DNNC‐d6 analogue compound have been determined using differential scanning calorimetry analysis. No significant difference in the DNNC and DNNC‐d6 heat of fusion values was detected at the 95 and 99 percent student t confidence levels. Melting points were also determined for the subject compounds using this analysis technique. These melting points are compared to literature values obtained by conventional methods.
Study on Thermal Decomposition of Composite Propellants containing PCP polymer or PCP‐HTPB copolymer as a binder
Authors: Hung Chen‐Chia , Hwu Wen‐Hwa , Cheng Chin‐Sheng , Shyy Iou‐Ning , Yang Kuo‐Kai 
Published: December 2004

AbstractA modified manometric vacuum stability test (MVST) apparatus as well as a differential thermal analyzer (DTA) and a thermogravimetric analyzer (TGA) were used to study thermal decomposition of a series of propellants. The solid propellants contained polycaprolactone (PCP) prepolymer or PCP‐HTPB copolymer as binder, ammonium perchlorate (AP) and a nitramine (RDX or HMX) as oxidants, aluminum as fuel, and bis(2,2‐dinitropropyl)acetal/formal (BDNPA/F) as plasticizer. The mixtures were cured with an isocyanate (Desmodur N‐100). It is found from MVST examinations that propellants containing PCP polymer are more stable than ones containing PCP‐HTPB copolymer. The PCP propellants were still stable after 40 hours heating at 135°C. The thermal decomposition reactions of prepared propellants during dynamic heating were indicated by two major stages of weight loss in the TGA traces.
Wellenmechanische Absolutrechnungen an Molekülen und Atomsystemen mit der SCFMOLC(LCGO) Methode. VI. Das Methan (CH4)
Authors: Janoschek R. , Diercksen G. , Preuss H. 
Published: December 2004

AbstractDas CH4 wurde unter Berücksichtigung aller 10 Elektronen mit dem Allgemeinen Programmsystem/SCFMOLC(LCGO) Methode für 4 verschiedene Abstände RCH und für die Verdrillung eines Dreieckes HCH gegenüber der Gleichgewichtslage (s. Abbildung 1) berechnet. Es ergab sich im Minimum eine Gesamtenergie von −40.06 a.E., eine Bildungsenergie von 17.0 eV und eine Ionisierungsenergie von 14.8 eV. Der Bindungsabstand wurde zu RCH = 2.053 a.E. bestimmt. Die sich ergebenden Kraftkonstanten lieferten die Frequenzen ω1 = 3139 cm−1 und ω2 = 1865 cm−1.
The projection operator for a space spanned by a linearly dependent set
Authors: Berrondo Manuel , Löwdin Per‐Olov 
Published: December 2004

AbstractThe explicit form of a projection operator constructed from a linearly dependent set is found. The relationships with canonical orthonormalization and with the cofactor matrix of the set's metric matrix are discussed. Similar expressions are obtained for the inner projection of a positive definite operator using a linearly dependent set.
Poisson equation for molecular exchange, hybrid and coulomb electron repulsion integrals
Authors: Silver David M. 
Published: December 2004

AbstractThe various multicenter exchange, hybrid and Coulomb electron repulsion integrals that occur in molecular quantum mechanics are shown to satisfy a Poisson equation in which an overlap integral plays the role of a source distribution function. Two‐, three‐and four‐center exchange integrals arise from four‐center source functions; two‐ and three‐center hybrid integrals arise from three‐center distributions; and one‐ and two‐center Coulomb integrals have two‐center sources.
Conjugated molecules in strong magnetic fields
Authors: Labzowsky L. N. , Lozovik Yu. E. 
Published: December 2004

AbstractThe spin rearrangement of π‐electrons in the ground state of a conjugated molecule in a strong magnetic field H is discussed. The spin S of the molecule increases as the field H increases (intramolecular paramagnetism). The dependence S(H) for linear and cyclic conjugated molecules in the free‐electron model and in the Hückel‐London approximation is derived. For the cyclic molecules the diamagnetic effects are taken into account.
Potential energy integrals in semiempirical MO methods
Authors: Coffey Patrick 
Published: December 2004

AbstractThe two‐center core‐electron attraction integral VAB in zero‐differential overlap semiempirical MO methods is examined. It is concluded that core‐valence orthogonality and valence symmetrical orthogonalization effects must be considered, and that these effects provide justification for the CNDO/2 approximation VAB = ZBγAB.
Irreducible tensor operator methods in intermediate‐field coupling
Authors: König E. , Kremer S. 
Published: December 2004

AbstractThe algebra of irreducible tensor operators is developed in the intermediate‐field coupling case. The Wigner‐Eckart theorem is formulated for a simple irreducible tensor operator as well as for the Kronecker and scalar products of these operators. The expressions required for the calculation of Coulomb repulsion, crystal field splitting, spin‐orbit interaction, and Zeeman effect are given in detail. Recent applications to various problems in spectroscopy and magnetism of transition metal compounds are referred to.
A density functional representation of quantum chemistry. II. Local quantum field theories of molecular matter in terms of the charge density operator do not work
Authors: Primas H. , Schleicher M. 
Published: December 2004

AbstractA comprehensive review of the attempts to rephrase molecular quantum mechanics in terms of the particle density operator and the current density or phase density operator is given. All pertinent investigations which have come to our attention suffer from severe mathematical inconsistencies and are not adequate to the few‐body problem of quantum chemistry. The origin of the failure of these attempts is investigated and it is shown that a realization of a local quantum field theory of molecular matter in terms of observables would presuppose the solution of many highly nontrivial mathematical problems.
Direct minimization of the energy by simultaneous variation of parameters in nonorthogonal basis functions. II. Real STOS for first row atoms
Authors: Weltin E. E 
Published: December 2004

AbstractThe parameter optimization method of Part I is applied to the exponents of real STOS of first row atoms. In addition to minimum basis ground states, some independently optimized excited states are discussed in the case of Be. Local minima on the energy versus parameter surface are found in 4‐configuration functions for the ground state of N. They are not present in either the simpler minimum basis function or in a more complete 8‐configuration function.
A non‐empirical molecular orbital study of valence tautomers of C2H3N
Authors: Hopkinson Alan C. , Lien Min H. , Yates Keith , Csizmadia Imre G. 
Published: December 2004

AbstractThe valence tautomers of C2H3N have been examined by non‐empirical molecular orbital calculations using two split‐valence shell basis sets. All geometries were fully optimized using the 4–31G basis set and these structures were then used in 6–31G basis set calculations. The order of stability of the three possible cyclic isomers is 1‐azirine > cyclic carbene > 2‐azirine. The profiles for conversion of vinylmethylene into cyclopropene, vinylnitrene into 1‐arizine, and iminomethylene into 2‐azirine have all been shown to have barriers.
Branching diagram and serber‐type spin functions. Algorithms for their construction and special properties
Authors: Pauncz Ruben 
Published: December 2004

AbstractBranching diagram and Serber‐type spin functions are ordered according to their diagrams. The method of Graebenstetter et al. is slightly modified; it provides an effective algorithm for the construction of genealogical spin functions. A counterpart of the method is developed for Serber‐type spin functions. Special properties of branching diagram functions and Serber‐functions are established.
Comments on excited state polarizabilities of molecules
Authors: Barnett Gene 
Published: December 2004

AbstractA comparison of experimental and theoretical values for Δα = αe ‐ αg, assuming no sigma‐electron contribution, shows a great distortion by π‐electron calculations. We analyze existing electrochromic data, using this assumption, and report Δα values of 44 Å3 for coronene and 43 Å3 for triphenylene. Some general properties of Δα are discussed in terms of potential energy curves which suggest interesting calculations to relate excited matrix elements with experimental measurements.