bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photochemie von Acylaziden. I. Photo‐ und Thermochemie von 5‐Azidocarbonyldibenz[b, f]azepin und seinem Dimeren
Authors: Abraham W. , Dreher K. , Buck K. , Kreysig D. 
Published: December 2004

Photochemistry of Acylazides. I. Photo‐ and Thermochemistry of 5‐Azidocarbonyldibenz[b,f]azepine and its DimerThe reactions of the title compounds, two new carbamoylazides, by photoexcitation and in the ground state, respectively, were investigated. The photochemistry of compounds 1 und 2 differs from that of other heterocycles of the same type and is determined by the azido group. They exhibit the three known kinds of reactions of carbamoylazides via singlet and triplet nitrene, respectively, and the Curtius‐rearrangement forming an intramolecular insertion product 6, dibenz‐[b,f]azepine 4 and the isocyanate. Products from triplet nitrenes are lacking in the photoreaction of the dimeric azide 2.The decomposition of the azide 1 can be sensitized by triplet energy transfer. Surprisingly, the isocyanate is also formed by triplet sensitization.Photoexcited pyrene reacts with 1 via electron transfer yielding rearrangement and triplet products, respectively. In contrast to diphenylcarbamoylazide, the reaction pathway of the thermally excited compounds leads to nitrene products mainly.
Kinetics and mechanism of isocyanate reactions. II. Reactions of Aryl Isocyanates with Alcohols in the presence ob tertiary amines
Authors: Bacaloglu R. , Cotarcâ L. , Marcu N. , Tölgyi St 
Published: December 2004

AbstractThe reaction of phenyl isocyanate with n‐butanol in the presence of tertiary amines has been kinetically studied as a model process for the polyurethane formation under conditions similar to those of industrial scale production. The rate‐determining step is believed to be the nucleophilic attack of tertiary amine on an associate of isocyanate with alcohol which is then converted into a very reactive uronium salt. This salt reacts fast with alcohol giving the final product, the urethane.
Kinetics and mechanism of isocyanate reactions. III. Reactions of Aryl Isocyanates with Alcohols in the presence of organotin compounds
Authors: Bacaloglu R. , Cotarcâ L. , Marcu N. , Tölgyi St 
Published: December 2004

AbstractA comparative kinetic study for the reaction of aryl isocyanates with alcohols in the presence of organotin compounds has been performed. It has been found that the transfer of an alkoxide ion from tin to isocyanate is the rate‐determining step. This transfer occurs within a complex formed in two rapid preequilibrium processes between either tin compounds and alcohol or isocyanate, respectively.
Chlormethyl‐substituierte Heterocyclen aus Chlortetrolsäuremethylester
Authors: Janietz D. , Goldmann B. , Rudorf W.‐D. 
Published: December 2004

Chloromethyl Substituted Heterocycles from Methyl ChlorotetrolateReaction of amidines, isothioureas or thioureas with methyl chlorotetrolate 1 leads to pyrimidin‐4‐ones 2 and 1,3‐thiazines (3), respectively. Compounds 2 and 3 are starting materials for the synthesis of 6‐chloromethyl‐uracils (4), 1,3‐thiazine‐2,4‐dione 5 and 6‐benzylthiomethyl‐thiazinone (6).2‐Aminothiazoles react with the ester 1 to yield 5‐chloromethyl‐thiazolo[3,2‐a]pyrimidin‐7‐ones (7). The 5‐oxo isomers 8 are obtained by reaction of thiazoles with ethyl γ‐chloroacetoacetate.By reaction of 2‐mercaptoimidazoles and 1 or chlorotetrolic acid the condensed 1,3‐thiazinones (10) result. In the latter case the intermediate 9 is isolated. It can be cyclised to 10 by heating with acetic anhydride and sulphuric acid.
Photochemie und Photophysik von 3‐(2‐Isoxazolinyl)‐phenylketonen
Authors: Timpe H.‐J. , Schmidt M. , Fišera L'. 
Published: December 2004

Photochemistry and Photophysics of 3‐(2‐Isoxazolinyl)‐phenylketones3‐Benzoyl‐Δ2‐1,2‐oxazolines (1–6) are formed by 1,3‐dipolar cycloaddition between benzoylnitril‐N‐oxide (8) and dihydrofurane 9 or 1,3‐dioxep‐5‐enes (10a–c). The preparative yields are small due to the competitive dimerization of the dipole 8. Two stereoisomers are obtained by using 2‐substituted 1,3‐dioxep‐5‐enes as dipolarophiles. The different steric position of the substituents in 3–6 gives rise to different spectral data. The synthesized ketones possess triplet states with a high degree of charge transfer character. Therefore, the ability to H‐abstraction reaction from alcohols is small. For ketone 2 and methanol as H‐donor a rate constant of k = 4,1 · 102 M−1s−1 is determined. Also by electron transfer reactions with triethylamine and some onium compounds the reactivity of the T1 of the ketones 1–6 is less compared to those of nπ* excited ketones. The photolysis of the ketones takes place very unselectively and leads to a product mixture. The quantum yields for the decay of the ketones are 10−2 to 10−3.
s‐triazolo[4,3‐a][1,3]diazacycloalkans. V. Synthesis of new derivatives of 3‐oxo‐2,3,5,6,7,8‐hexahydro‐s‐triazolo[4,3‐a]pyrimidine
Authors: Kreżel Izabella 
Published: December 2004

Abstract1‐Ethoxycarbonyl‐2‐methylthio‐1,4,5,6‐tetrahydropyrimidine (1) reacting with acylhydrazines, affords 2‐acyl derivatives of 3‐oxo‐2,3,5,6,7,8‐hexahydro‐s‐triazolo [4,3‐a] pyrimidine (2) or 2‐acylhydrazine derivatives of 1. The acylation of 2 and its 2‐phenyl derivative 3 with isothiocyanates give corresponding 3‐oxo‐2,3,5,6,7,8 nexahydro‐s‐triazolo [4,3‐a] pyrimidine 11a, b, 13a, e and 14.
Prostaglandins and prostaglandin intermediates. 22. Synthesis of a Stable Prostacyclin Analogue
Authors: Theil F. , Costisella B. , Hauser A. , Schick H. , Schwarz S. 
Published: December 2004

AbstractAn industrially available prostaglandin intermediate is converted into a new prostacyclin analogue with a cyclic ether instead of the unstable enol ether system. For the construction of the modified alkyl side chain two subsequent Horner olefinations are used. This reaction sequence includes a new methodology for the conversion of an aldehyde into a β,γ‐unsaturated carboxylic acid by a three‐carbon elongation.
Strukturanalytische Untersuchungen an Folgeprodukten aus Sulfonamiden. V. Infrarotspektroskopische und thermoanalytische Untersuchungen an polymorphen Modifikationen von N‐substituierten S‐Methyl‐N′‐tosyl‐isothioharnstoffen
Authors: Reinke H. , Hans M. , Matos E. , Dehne H. 
Published: December 2004

Structure‐Analytical Investigations of Consecutive Products of Sulphonamides. V. Infrared Spectroscopic and Thermoanalytical Studies of Polymorphic Modifications of N‐Substituted S‐Methyl‐N′‐tosyl‐isothioureasFour compounds (1d, 1e, 1h, 1p) out of twelve N‐substituted S‐methyl‐N′‐tosylisothioureas were shown to form polymorphic modifications. Attempts were made to isolate each single specimen and to characterize it by means of differential scanning calorimetry and infrared spectroscopy. The results clearly revealed that both different hydrogen bonding and conformational effects are responsible for the formation of the polymorphic species. With the help of 15N labeled compounds the presence of the sulphonylimino structure in any modification was proved. The v(NH) and δs(SO2) band positions are used to divide the polymorphs into two groups A and B.
Failure of azo coupling by ion pairing of 4′‐Diethylamino‐α‐cyano‐stilbene‐4‐diazonium tetraphenylboranates in water
Authors: Walkow F. , Rehorek D. 
Published: December 2004

AbstractThe influence of chloride and five tetracoordinated boron anions on the light absorption and azo coupling of the 4′‐diethylamino‐α‐cyano‐stilbene‐4‐diazonium ion 1 in formamide, dimethylformamide and water, respectively, is reported. In highly diluted solutions, no ion pairing of 1 occurs in polar organic solvents. Except for tetraphenylboranates, this applies also to water. Here, tetraphenylboranates produce a large bathochromic shift of the intramolecular CT‐band of 1 due to the formation of contact ion pairs. This ion pairing is strongly favoured by hydrophobic interaction between 1 and the complex anion.In contrast to the free diazonium 1, its ion pairs with tetraphenylboranates fail in azo coupling in water. This is shown on coupling with 2‐naphthol.
A novel efficient approach to the Synthesis of 6‐Oxo Ethinylestradiol and its 3‐isopropanesulfonate
Authors: Weber Gisela , Schaumann J. , Carl Constanze , Schwarz S. , Leisner Rosemarie 
Published: December 2004

AbstractEthinylestradiol (1) was converted into the corresponding 6‐oxo derivative 7 by a short and simple procedure involving acetate 10 and ketone 11. Phase transfer catalyzed esterification of compound 7 with propane‐2‐sulfonyl chloride gave sulfonate 12.
Studies on the oxidation of enamines with molecular oxygen. I. Oxidation of Some Piperidino Alkenes
Authors: Blau Karla , Voerckel V. 
Published: December 2004

AbstractIn the autoxidation of 1‐piperidinocyclohex‐1‐ene (1), 1‐piperidinobut‐1‐ene (2), 3‐piperidinopent‐2‐ene (3), and 1‐piperidino‐2‐methyl‐prop‐1‐ene(4) only products of an oxidative attack at the CC‐double bond are formed.Both α‐aminoketones, the products of the rearrangement of primarily formed epoxides, and products of the oxidative session of the CC double bond are obtained. As a side reaction some hydrolysis of the starting enamines takes place. This hydrolysis proves that some water must be formed during the enamine oxidation.
Pyryliumverbindungen. 41. 7aH‐Cyclopenta[b]pyran‐7‐one durch Ringtransformation von 2,4,6‐Triaryl‐pyryliumsalzen mit acyclischen 1,2‐Diketonen
Authors: Zimmermann T. , Fischer G. W. , Kutschabsky L. 
Published: December 2004

Pyrylium Compounds. 41. 7aH‐Cyclopenta[b]pyran‐7‐ones by Ring Transformation of 2,4,6‐Triarylpyrylium Salts with Acyclic 1,2‐DiketonesReaction of 2,4,6‐triarylpyrylium salts 1 with acyclic 1,2‐diketones 2 (CH3COCOR, R = Me, Ph) in the presence of an appropriate condensing agent (e.g. piperidine acetate, triethyl‐amine/acetic acid, sodium acetate) yields the hitherto unknown 2,4,5,7a‐substituted 7aH‐cyclopenta[b]pyran‐7‐ones 3 as a result of a new type of ring transformation (2,5‐[C4O+C]/2,3‐[C2+C3]). A characteristic feature of compounds 3 is their ability to undergo electrophilic substitutions. Thus, stepwise bromination of the 7a‐methyl derivative 3a in acetic acid affords 6‐bromo‐7a‐methyl‐2,4,5‐triphenyl‐cyclopenta[b]pyran‐7‐one (4) and 3,6‐dibromo‐7a‐methyl‐2,4,5‐triphenyl‐cyclopenta[b]pyran‐7‐one (5); analogously, nitration of 3a leads to 7a‐methyl‐6‐nitro‐2,4,5‐triphenyl‐cyclopenta[b]pyran‐7‐one (6), indicating that position 6 is the favoured position for electrophilic substitutions. Contrary to the 3,5‐unsubstituted pyrylium salts 1, the 3,5‐dimethyl‐2,4,6‐triphenyl‐pyrylium perchlorate (13) reacts with 1,2‐diketones 2 through a 2,6‐[C5+C] transformation to give arylsubstituted 1,2‐diones 14. The structure of the new compounds was determined by spectroscopic methods and by a single crystal X‐ray analysis of the dibromo derivative 5.
Determination of the Dipole Moment of the Charge‐Shift Triplet Exciplex from zinc phthalocyanine tetrasulfomorpholide and p‐methoxy‐benzenediazonium tetrafluoroborate
Authors: Becker H. G. O. , Kehlen H. , Krüger R. 
Published: December 2004

AbstractTriplet exciplexes are known to have usually relatively low polarities, in contrast to singlet exciplexes. It is shown that triplet quenching rate constants of the title system can be used to determine the exciplex dipole moment if it is (plausibly) assumed that the dissociation rate constants of charge‐shift exciplexes only depend on the viscosity but not on the polarity of the solvent.The quenching rate constants kq of the title system in various acetonitrile/acetone or acetonitrile/ethylacetate mixtures are determined and treated by an adapted McRAE equation developed for UV‐VIS absorption spectroscopic data.The dipole moment of p‐methoxy‐benzenediazonium tetrafluoroborate necessary for the solution of the McRAE equation is estimated by a Hammett correlation of known data which gives by extrapolation μ(p‐MeOC6H4N2⊕BF4⊖) = 31.4 × 10−30 Cm (9.4 Debye). Using this value and a cavity radius of 3.7 × 10−10m (cp. [1]) μex3(ZnPcTSM…p‐MeO–C6H4N2⊕BF4⊖)* = 16.0 × 10−30 cm (4.8 Debye) is obtained. According to this value the triplet exciplex studied has a lower polarity than the starting diazonium salt.
Heterocyclisch substituierte Arendiazoniumsalze mit erweiterter spektraler Empfindlichkeit. II. 4‐(1‐Heterocycliden‐2,3‐diaza‐prop‐2‐en‐3‐yl)‐benzendia‐zoniumtetrafluoroborate
Authors: Fanghänel E. , Tschötsch C. K. J. , Richter A. M. 
Published: December 2004

Heterocyclic Substituted Arenediazonium Salts with a Long‐wave‐length Range of Sensitivity. II. 4‐(1‐Heterocycliden‐2,3‐diaza‐prop‐2‐en‐3‐yl)‐arenediazonium tetrafluoroboratesThe title compounds (3) are obtained by reaction of aromatic bis‐diazonium salts with substituted 2‐benzylidene‐1,3‐dithioles and 2‐benzylidene‐1,3‐diselenole, respectively. The maximum of the long wave‐length absorption band of 3 varies from 580 nm up to 665 nm depending on the structure of the compound.The quantum yields of the photolysis of the diazonium salts 3 are low (1 · 10−4 to 7 · 10−3). The azo dyes obtained from 3 with usual azo‐couplers absorb in a shorter wave‐length range than the corresponding diazonium salts themselves (hypso‐coupling effect).
Deflagration to detonation Transition Behavior of Aluminized HMX
Authors: Price D. , Clairmont A. R. 
Published: December 2004

AbstractThe effect of fine (5 μm) and coarse (95 μm) aluminum on the deflagration‐to‐detonation transition (DDT) behavior of HMX, in charges pressed to 90% theoretical maximum density (TMD), was studied. It was found that Al slows down the DDT process increasingly as the content of Al increases; that is, it increases predetonation column length and the relative times to detonation. Fine Al is more effective than coarse in delaying DDT, at a given content, but both are inferior to wax in this respect.
A method for Determining the Deflagration Behaviour of Explosives
Authors: Tamchyna V. , Mošťàk P. 
Published: December 2004

AbstractThe deflagration behaviour of explosives, in particular of permissible explosives, was investigated under various experimental conditions. The initiation of a methane/air mixture was provoked by a deflagrating explosive in a gallery under conditions of low resistance stemming. The results indicate that the initiation probability of an explosive methane/air mixture depends on the chemical reactivity (ignition ability) of the explosive which is low for permissible explosives under the conditions given.
A Design Criterion for Permissible Watergel Explosives
Authors: Mohan V. Krishna , Srinivas M. A. 
Published: December 2004

AbstractThis paper presents an analysis of the relationship between oxygen balance, inert content, computed detonation parameters and incendivity for several watergel explosives. A mathematical technique has been developed for correlating compositional details and the permissibility test results for a number of existing compositions. The analysis covers two types of explosive compositions and three categories of permissibility tests. Using energy of detonation, oxygen balance, and percentage of water and sodium chloride in the composition, this technique is able to consistently predict the permissibility test result with less than 10% exceptions. It is felt that this method will facilitate the design of new explosive formulations which have a high probability of success in permissibility tests.
Wellenmechanische Absolutrechnungen an Molekülen und Atomsystemen mit der SCFMOLC(LCGO) Methode. XI. Das Hydroxylanion (OH)−
Authors: Janoschek R. , Preuss H. , Diercksen G. 
Published: December 2004

AbstractDas (OH)− wurde unter Berücksichtigung aller 10 Elektronen mit dem Allgemeinen Programmsystem/SCFMOLC(LCGO) Verfahren für 4 verschiedene Kernabstände berechnet. Es ergab sich ein Energieminimum bei einem Abstand von R = 1,82 a.E. mit einer Gesamtenergie von ϵ = −75,305 a.E. Für die Ionisierungsenergie des (OH)− (Elektronenaffinität des OH) ergab sich ein Wert von 2,29 eV. Die Kraftkonstante wurde zu k = 7,47 mdyn/Å bestimmt, die zugehörige Frequenz beträgt ω = 3655 cm−.
Magneto‐optical rotation in molecules. IV. The Verdet constant for the nitrogen molecule
Authors: I'Haya Y. 
Published: December 2004

AbstractThe theory of magneto‐optical rotation is applied to the calculation of the Verdet constant for the nitrogen molecule. Only two excited states, 1∑ and 1Πu, are considered to take part in the magneto‐optical rotation. Using the SCF wave functions, the verdet constant at 5780 Å is calculated to be 5.325 μmin/cm Oe which compares well with the experimental value of 6.273 μmin/cm Oe. The relation with the normal Verdet constant is also discussed.
The spin degeneracy problem in the AMO method
Authors: Tamir Ilana , Pauncz Ruben 
Published: December 2004

AbstractThe use of different spin functions in the AMO method was investigated for benzene, the ring of six H atoms, and fulvene. The additional improvement in the energy obtained by the use of a linear combination of different spin functions is quite small for the singlet ground state. It is pointed out that there are great differences in energy between functions having the same spatial function but different spin functions.
Recent developments in the theory of one‐ and two‐electron molecules
Authors: Kołos W. 
Published: December 2004

AbstractRecent theoretical work dealing with one‐ and two‐electron molecules is reviewed. Results obtained using both the variational method and the perturbation theory are discussed for the ground states as well as for excited states of the molecules. Emphasis is placed on those results which are sufficiently accurate to yield definite conclusions with regard to either the system or the method.
Dimeres composes de molecules dont l'excitation electronique entraine un deplacement de la configuration nucleaire d'equilibre accompagne d'un changement de constante de force
Authors: Sucre M. García 
Published: December 2004

AbstractWe have studied the validity of the traditional model of a dimer that has been treated exactly by Merrifield and Fulton and Gouterman, solving the vibronic coupled equations by a numerical method. This model takes into account the modification of the nuclear equilibrium configuration, but it neglects the variation of the force constant when the monomer is electronically excited from the fundamental to a given excited state (the corresponding electronic potentials are both considered as harmonic). We have shown by inspection of the absorption and fluorescence spectra calculated by solving the vibronic equation exactly that the variation force constant cannot be neglected, even if it is weak, particularly in the weak coupling region. The weak, intermediate and strong coupling criteria have been deduced, for the model studied, by examination of the dimeric electronic potential surfaces for different cases of intermolecular interactions.
Symmetry adapted functions belonging to the dirac groups
Authors: Deepak Adarsh , Dulock Victor , Thomas Billy S. , McIntosh Harold V. 
Published: December 2004

AbstractAn earlier analysis of the canonical form of a pair of invertible operators obeying the exchange rule

is extended to cover a set of operators, between each pair of which a relation of this type exists; and for which a power of each operator is the unit matrix. Such relations define a system which may be regarded as a generalization of the Dirac matrices of relativistic quantum mechanics. We concentrate upon the group theoretic aspects of such a system and its matrix representations. Applications arise from the fact that all projective representations of finite abelian groups take the form of a Dirac Group. In particular, the representations of the magnetic space groups, which are projective representations of the lattice groups, arise in this manner.
Laplace transform wave functions
Authors: Farmer Christine M. 
Published: December 2004

AbstractThe wave function defining a quantum‐mechanical system is considered as the Laplace transform of some distribution and the consequent form of the Variational Principle derived; an integral equation defines the eigenfunctions of a certain subclass. The model of the hydrogen‐like atom is used to test the theory; the eigenfunctions and associated energy levels of the ground and excited states are obtained for arbitrary values of the orbital quantum number.
The mechanism of binding of polycyclic aromatic hydrocarbons to nucleic acids: A theoretical investigation
Authors: Umans Robert S. , Pullman Bernard 
Published: December 2004

AbstractA kinetic model employing calculated atom and bond localization energies to approximate relative activation energies of reaction is used to analyse previously obtained experimental results for in vitro and in vivo chemical binding of polycyclic aromatic hydrocarbons to nucleic acids. It is found that in vitro linkage of hydrocarbons to DNA induced by a microsomal hydroxylating system is compatible with mechanisms involving either attack at the most reactive hydrocarbon center or attack at the most reactive hydrocarbon bond. Independent evidence leads us to favor the former mechanism. Further, the limited experimental data for in vivo linkage of hydrocarbons to DNA is found to be consistent with a model involving attack at the most reactive bond of the molecule: the “K region”. This model is supported by a close parallelism found between extent of hydrocarbons bound to DNA in vivo and the experimentally determined relative reactivities of their K regions.
Variable electronegativity SCF‐MO calculations on the electronic structure and spectra of some substituted benzenes I. Monosubstitutions
Authors: Mishra P. C. , Rai D. K. 
Published: December 2004

Abstractπ‐electron SCF‐MO theory in its variable electronegativity formalism has been applied to some monosubstituted benzenes. Calculated charge densities and bond orders for the ground and the first excited electronic states are correlated with chemical reactivity and the changes in molecular geometry on electronic excitation. The calculated results for spectra are compared with those obtained using the PPP method and also with the available experimental data.
Partitioning schemes for the 2‐matrix and the pair density
Authors: Morrison Robert C. , Smith Darwin W. , Larson Everett G. 
Published: December 2004

AbstractSeveral schemes are discussed for partitioning the second‐order reduced density matrix Γ into two parts, Γ0 and Γ′.The Γ0s are based on the independent particle model and the Γ′s are corrections due to electron correlation. The difficulties of choosing a Γ0 that will serve as a suitable reference point for studying electron correlation are discussed.In order to compare alternative partitioning schemes, an atomic wave function for the 1S ground state of the Be atom in the configuration‐interaction approximation was selected. A fifty‐two configuration wave function was computed and contour graphs were made of the total pair density Γ(1 2) and of the “correlation pair density” Γ′(1 2) for several choices of the reference Γ0.
Electronic correlation studies. II. Self‐correlated field method. Application to ground state and first 1P, 3P excited states of two‐electron atomic systems
Authors: Guerillot C. R. , Lissillour R. 
Published: December 2004

AbstractAn antisymmetric pair function can be built upon two kinds of monoelectronic functions, the former ones being correlated local functions and the second ones nonlocal functions taking external effects into account. This function, brought into the generalised product function procedure by means of the density matrix formulation, makes possible the study of correlation within N‐electronic systems. The results of a first application of this method to the fundamental and to 1P and 3P excited states of two‐electron systems are given.