bluuebunny/crossref_metadata_2025 huggingface dataset:
Protonierung und Solvation schwacher organischer Basen. VII. 1H‐NMR‐spektroskopische Bestimmung der Basizität von cyclischen Ketonen
Authors: Freiberg W. , Roth H. , Rautenberg Ute , Kröger C.‐F.
Published: December 2004

Protonation and Solvation of Weak Organic Bases. VII. 1H‐N.M.R. Spectroscopic Determination of the Basicity of Cyclic Ketones

From protonation ratios for cycloalkanones of ring size C4‐C7 in the acid system H2OH2SO4HSO3F, determined by 1H‐n.m.r. spectroscopy, basicity and solvation parameters are estimated by application of extrapolation procedures based on the Hammett acidity function H0 or the excess acidity X. The frequency shifts of the n̈OH stretching vibrations of phenol in hydrogen bonded complexes with cycloalkanones have been measured. The ΔνOH values are related to the basicity parameter (H0)1/2.
Condensation of 4‐phenyl‐3,5‐dicarboethoxycyclopentane‐1,2‐dione with primary amines
Authors: Afsah A. M. , Osman A. I. , Sofan M.
Published: December 2004

Condensation of the title compound (1) with primary aromatic amines gave the dianilides (2), which cyclized to cyclopenta[1,2‐c:4,3‐c′]diquinolines (3). Treatment of 1 with o‐phenylenediamine or 2,3‐diaminopyridine afforded cyclopenta[2,1‐b:3,4‐b′]bis[1,5]benzodiazepine (4) and bis[1,5]pyrido[b]diazepine derivative (5), respectively. Whereas, with o‐aminophenol a mixture of 2c and cyclopenta[2,1‐b:3,4‐b′]bis[1,5]benzoxazepine (7) was obtained. Pechmann reaction of 1 with m‐cresol gave the bis[1]benzopyrane (9). Mannich reaction of 1 with benzylamine afforded the 3‐azabicyclo[3.2.1]octane system (10).
Tetrathiafulvalene. XXIV. Gewinnung von cis‐ und trans‐ Isomeren bei Tetrathiafulvalenen (TTF)
Authors: Fanghänel E. , van Hinh L. , Schukat G. , Patzsch J.
Published: December 2004

Tetrathiafulvalenes. XXIV. Isolation of cis‐ and trans‐Isomers of Tetrathiafulvalenes (TTF)

The synthesis of naphthylsubstituted TTF permits in the case of the α‐naphthyl‐methylsubstituted TTF the isolation of the cis‐ and trans‐isomer by reason of differences in the solubility. The spectroscopical and electrochemical properties of naphthylsubstituted TTF are described.
Tetrazolverbindungen. 4 [1]. Alkylierung von 1‐Aryl‐5‐(2‐dimethylamino‐vinyl)‐1 H‐tetrazolen
Authors: Fischer G. W.
Published: December 2004

Tetrazole Compounds. 4. Alkylation of 1‐Aryl‐5‐(2‐dimethylamino‐vinyl)‐1 H‐tetrazoles

Alkylation of 1‐aryl‐5‐(2‐dimethylamino‐vinyl)‐1 H‐tetrazoles 1 with dialkyl sulfates or alkyl iodides yields mainly 4‐alkyl‐1‐aryl‐5‐(2‐dimethylamino‐vinyl)‐1 H‐tetrazolium salts which can be isolated free from isomers by separation as perchlorates 2. The reaction proceeds with retention of the E configuration of the vinyl group. In contrast to 1 the methyl groups of the dimethylamino substituent in 2 are magnetically non‐equivalent indicating restricted rotation of this residue. On heating 2 with aqueous mineral acids the dimethylaminovinyl moiety undergoes degradation to a methyl group affording 4‐alkyl‐1‐aryl‐5‐methyl‐1 H‐tetrazolium salts 4, the structure of which was confirmed by independent synthesis. With hot aqueous alkali hydroxide 2 reacts under ring cleavage to give aryl azide. — 1H n.m.r. and u.v. spectroscopic data of the tetrazolium salts 2 and 4 are reported.
Chemotherapeutic agents. XII [1]. Synthesis of Pyrimidines and Fused Pyrimidines as leishmanicides and herbicides
Authors: Ram Vishnu Ji
Published: December 2004

Various bicyclic (2, 3) and tricyclic (4, 5) heterocycles were prepared by the reaction of 1a, c with dihaloalkanes and polynitrohalobenzene separately. Electrophilic substitution on 1a–c with different alkyl halides yielded mono and dialkyl pyrimidiens (6–20). Nucleophilic substitution reactions on 18 and 21 with amine and hydrazine separately yielded 22–31, 21a, b and 41c. Reaction of 25a with ethyl ethoxymethylenecyanoacetate and chloroacetyl chloride separately provided bicyclic compounds 32 and 33. Condensation‐cyclization of 25a with formic, acetic and nitrous acid separately yielded 34a, b and 35. Reaction of 26a with ethylthiocylycolate and thiourea separately provided 36a and 39. The latter was alkylated with methyl iodide to 40. An attempt to cyclize 29a and 30a with thionyl chloride provided bicyclic compounds 37a, b and an uncyclic product 38. Some of the compounds were screened for leishmanicidal and herbicidal activities and a few of them exhibited significant activity.

Leishmaniasis is considered to be one of the most devastating diseases and is ominous to tropical countries. The high toxicity of leishmanicidal drugs in current use, aroused considerable interest to develop new safer and effective chemotherapeutic agents. The only drug pyrimethamine [2] is the representative of pyrimidine derivatives, known as leishmanicides but low order of activity at high dose failed to retain in the clinic. Based on our past experiences in rational designing of leishmanicidal pyrimidine analogs, incorporation of levamisole pharmacophore either in flexible or rigid forms is indispensable for potential activity [1,3] against visceral leishmaniasis. These observations induced an impetus to synthesize pyrimidine analogs as potential leishmanicides.
Kinetics and isotope effects of the Dehydrochlorination of 1,1‐dichloro‐2,2‐bis‐(4‐nitrophenyl) ethane with 1,5‐diazabicyclo [4.3.0] non‐5‐ene in aprotic solvents
Authors: Schroeder Grzegorz , Jarczewski Arnold
Published: December 2004

The kinetics of the reaction of 1,1‐dichloro‐2,2‐bis‐(4‐nitrophenyl)ethane (1) with 1,5‐diazabicyclo‐[4.3.0]non‐5‐ene(DBN) in acetonitrile (MeCN), dichloromethane (DCM), tetrahydrofuran (THF), isopropylether (IPE) and hexane (Hex) solvents are reported. The reaction is a simple β‐elimination forming 1‐chloro‐2,2‐bis‐(4‐nitrophenyl)ethane (2) (100% conversion). The rate constants are similar for MeCN, THF, IPE, but lower by a factor of 2 and 7 for DCM and Hex respectively. The deuterium kinetic isotope effects kH/kD are between 10 and 6 for MeCN and Hex solvents. The entropies of activation (ΔS≠) are negative and large and show no correlation with the polarity of the solvents. The free enthalpies of activation (ΔG≠) are rather small (about 68 kJ mol−1). The results are interpreted in terms of E2H with a contribution of (E1cB)I mechanism.
Synthesis of Condensed 4H‐Pyrans: The reaction of 1,1‐dimethyl‐3,5‐diketocyclohexane with cinnamonitriles
Authors: Elnagdi Mohamed Hilmy , Abdel Aal Fatma Abdel Maksoud , Yassin Youssef Mahfouz
Published: December 2004

Cyclohexano‐4H‐pyrans could be prepared by reaction of 1,1‐dimethyl‐3,5‐diketo‐cyclohexane 2 with cinnamonitriles 1 and converted into 2‐amino‐4‐aryl‐1,4‐dihydro‐7,7‐dimethyl‐5‐oxocyclohexanopyridin‐3‐carbonitrile 7a, b; 7,7‐dimethyl‐2,5‐dioxo‐4‐phenyl‐1,2,3,4‐tetrahydro‐cyclohexanopyridin‐3‐carbonitrile 8, 5‐aryl‐1,1‐dicyano‐2‐phenyl‐8,8‐dimethyl‐1,2,3,4,6,7,8,9‐octahydro‐3‐azaacridin‐4,6‐dione 12a, b and 2‐thioxo‐4‐amino‐5‐aryl‐3‐benzoyl‐2,3‐dihydro‐9,9‐dimethylcyclohexano‐[g]‐4H‐pyrano[2,3‐d]pyrimidin‐7‐one 14a, b.
Zur Gasphasenpyrolyse von α, ω‐Phenylalkenen – Gesetzmäßigkeiten und Besonderheiten
Authors: Ondruschka B. , Zychlinski W. , Bach G. , Zimmermann G.
Published: December 2004

On the Gas Phase Pyrolysis of α, ω‐Phenylalkenes — Regularities and Special Features

The thermal conversion of the α, ω‐phenyl alkenes 1 to 4 was studied in the presence of a molar excess of Ar or steam at 500 to 875°C in a labscale tubular reactor. Detailed GC analyses did not establish significant evidences for such molecular rearrangements like, e.g., Di‐π‐methane rearrangement of 2, Ene and Carbo‐Claisen reaction of 3. The decomposition obviously occurs via radical chain processes in the main. Besides them, however, radical cyclizations, Neophyl rearrangements and Retro‐Ene reactions are parts of the complex reaction.
Synthesis of 2,7‐Fluorenone Bisglycidyl Ether and related compounds as potential cytostatics
Authors: Młochowski Jacek , Palus Jerzy
Published: December 2004

The syntheses of fluorenone derivatives having one to three glycidyl groups and related compounds are reported. Their activity against experimental tumors in vitro in relation to the molecular structure is discussed.
Studies on UV/Vis Absorption Spectra of Azo Dyes. 24. The different effect of a 2‐methoxy and a 3‐methoxy group in 4‐N.N‐diethylaminoazobenzenes on colour
Authors: Mustroph Heinz , Gussmann Frank
Published: December 2004

A number of 2‐ and 3‐methoxy‐substituted‐4‐N.N‐diethylaminoazobenzenes have been prepared and their absorption maxima in ethanol and toluene compared with the corresponding 4‐N.N‐diethylaminoazobenzenes. Both the 2‐ and 3‐methoxy groups cause a bathochromic shift, but the bathochromic shift of a 3‐methoxy group depends on the substituents in the diazo component. With increasing electron‐withdrawing strength of the substituents in the diazo component a progressive enhancement of bathochromic shift appears. In toluene all 3‐methoxy‐substituted dyes absorb at longer wavelengths compared with the 2‐methoxy‐substituted dyes.
Azobrücken aus Azinen. X. Ein neuer Weg zu Carbocyclen mit parallel benachbarten NN/CC‐Brücken
Authors: Hünig Siegfried , Kraft Petra
Published: December 2004

Azo‐bridges of Azines. X. A New Way to Carbocyclic with Parallel Neighbouring NN/CC‐Bonds

Nitrogen extrusion from the easily accessible triazoline 11 on acidic solid phases results in the formation of aziridine 13 together with 14, a new system with parallel NN/CC‐bonds. By irradiation 14 undergoes smoothly [2 + 2]‐cycloaddition forming the cage compound 15. Photolysis of 11 does not yield 13 or 14. Instead by loss of the azo‐group either triazoline 16 or aziridine 17 are formed, depending on the band width of the UV‐sources.
Pyrrole aus einem 3‐Amino‐3‐arylazo‐propensäuremethylester und α‐Halogencarbonylverbindungen und die Bildung des Pyrrolo[3.2‐e][1,2,4]‐triazin‐Ringsystems
Authors: Kirschke Klaus , Costisella Burkhard , Ramm Matthias , Schulz Burkhard
Published: December 2004

Pyrroles from Methyl 3‐Amino‐3‐arylazo‐propenoat and α‐Halogenocarbonyl Compounds and the Forming of the Pyrrolo[3.2‐e][1,2,4]‐triazin Ring System

Methyl 3‐amino‐3‐(2,4,6‐trichlor‐phenylazo)propenoat (2) and α‐halogenocarbonyl compounds (4a–c) undergo cyclization to pyrroles on the pattern of the Hantzsch‐pyrrole‐synthesis. The 2‐(2,4,6‐trichlor‐phenylazo)‐3‐pyrrolecarboxylic azide (7) reacts under Curtius rearrangement and cyclization to the ring system of the pyrrolo[3.2‐e][1,2,4]‐triazin (8).
Synthese von Senföloxiden mit unterschiedlichen Substituenten
Authors: Tittelbach Franz
Published: December 2004

Synthesis of Mustard Oil Oxides with Different Substituents

Treatment of N‐alkyl‐N′‐aryl‐thioureas with chlorocarbonylsulfenyl chloride leads to 2‐alkyl‐4‐aryl‐3‐thiono‐1,2,4‐thiadiazolidin‐3‐ones (4). Isomerization of 4 takes place in the presence of strong acids to give 5‐alkylimino‐4‐aryl‐1,2,4‐dithiazolidin‐3‐ones (5). 5‐Arylimino‐4‐aryl‐1,2,4‐dithiazolidin‐3‐ones with different aromatic substituents (13a–e) are accessible by desulfurization of the corresponding 5‐arylimino‐4‐aryl‐1,2,4‐dithiazolidin‐3‐thiones (12) with benzonitril oxide. Structure of 4 follows both from desulfurization to the known 1,2,4‐thiadiazolidin‐3,5‐diones (9) and spectroscopic data.
3‐Alkylated (R)‐2,3‐Dihydroxyalkyl p‐Toluenesulfonates – homochiral building blocks for modified steroid side chains
Authors: Schrötter Eberhard , Luong Tran Thanh , Schick Hans
Published: December 2004

Oxidative cleavage of 1,2:5,6‐di‐0‐cyclohexylidene‐D‐mannitol (2) with lead (IV) acetate yields (R)‐2,3‐0‐cyclohexylideneglyceraldehyde, which was transformed by oxidation and esterification into methyl 2,3‐0‐cyclohexylideneglycerate. Grignard reaction with various alkylmagnesium halides followed by acid‐catalyzed removal of the acetal group and reaction with p‐toluenesulfonyl chloride in pyridine furnished the title compounds (8a–d) in good chemical overall yield and high enantiomeric purity. The compounds were prepared as intermediates for the synthesis of a series of steroids with a modified side chain.
Thiatriazole. VII. 3‐Aroxy‐5‐imino‐1,2,4‐dithiazole aus 5‐Amino‐1,2,3,4‐thiatriazol
Authors: Graubaum H. , Costisella B. , Ramm M. , Schulz D.
Published: December 2004

Thiatriazoles. VII. 3‐Aroxy‐1,2,4‐dithiazole‐5‐imids of 5‐Amino‐1,2,3,4‐thiatriazole

The unstable but isolable 3‐aroxy‐1,2,4‐dithiazole‐5‐imids (2a–d) has been found on chlorothioformate acylation of 5‐amino‐1,2,3,4‐thiatriazole (1) in acetonitril. Further acylation and nucleophilic displacement reactions gave stable 3‐amino‐5‐acylimino‐1,2,4‐dithiazoles (6a–c, 7). The structure of the prepared compounds was inferred from their 1H and 13C‐n.m.r., mass spectra and corroborated by comparison with the data of similar derivates as well as by chemical means.
Vibronic spectral behaviour of molecules. XV. Study on the T1 → S0 Phosphorescence of Isomeric Terphenyls
Authors: Gustav K. , Storch M.
Published: December 2004

Underlying the completely‐optimized S0 and T1 molecular geometries of isomeric terphenyls the corresponding theoretical vibronic T1 → S0 ‘line’ spectra calculated within the CONDON approach, are presented and compared with the experimental phosphorescences. The influence of possible conformations on the vibronic spectral behaviour is studied theoretically. The DUSHINSKY effect is found to be most important to the T1 → S0 phosphorescence of m‐terphenyl. An analysis of the spectroscopically relevant vibrational modes is given.
Zur Chemie der Mucohalogensäuren. V. Reaktionen von 3,4,5‐Trichlor‐2(5H)‐furanon und 3‐Aroxy‐4,5‐dichlor‐2(5H)‐furanonen mit Azid
Authors: Jähnisch Klaus , Ambrosi Horst‐Dieter
Published: December 2004

Chemistry of Mucohalic Acids. V. Reaction of 3,4,5‐Trichloro‐2(5H)‐furanone and 3‐Aroxy‐4,5‐dichloro‐2(5H)‐furanones with Azide

3,4,5‐Trichloro‐2(5H)‐furanone 1 reacts with sodium azide to afford 4‐azido‐3,5‐dichloro‐2(5H)‐furanone 2, whereas 3‐aroxy‐4,5‐dichloro‐2(5H)‐furanones 11 provides under the same conditions 3‐aroxy‐5‐azido‐4‐chloro‐2(5H)‐furanones 12. Reactions of 1 and 11 with two equivalents of azide lead to diazido derivatives 5 and 13. β‐Lactam 9 or pyrimidone 10 were synthesized from 5 and benzanilide.
A Formula for the Shaped Charge Jet Breakup‐Time
Authors: Hirsch E.
Published: December 2004

It was found that the breakup‐time of jets formed by shaped charges of cylindrical symmetry is given very accurately by the formula:

This formula is obtained from a general principal applied here for the first time which says that the breakup‐time of homogeneous ductile metals under very high strain rates is equal to the smallest initial dimension of the elongating metal divided by VPL. When applied to simple configurations such as a pipe which expands due to internal explosion this principal leads to a correct prediction of the average formed fragment dimensions. This principal provides for the first time an explanation to the experimental fact that metals' ductility can increase by an order of magnitude when the strain rate increases from 10−2 to 105 pro second.
On the Burning Rate Characteristics of CMDB Propellants
Authors: Swaminathan V. , Soosai Marian M.
Published: December 2004

The object of this paper is to obtain expressions for the burning rate pressure exponent and the temperature sensitivity of AP‐based and HMX‐based CMDB propellants in terms of the respective physical constants on the basis of a recently developed model of combustion for CMDB propellants and to examine the effects, if any, on these two parameters, of the changes in propellant composition, AP particle size and pressure. Computer programs were developed for this purpose and the results obtained for typical sets of input data presented in the paper. While the results of the calculation indicate a markedly strong dependence of the pressure exponent and the temperature sensitivity on pressure and composition for both AP‐based and HMX‐based CMDB propellants, the parameters are characterized by far lesser dependence on AP particle size for the AP‐based propellant.
Studies on the Synthesis of 2,2′,4,4′,6,6′‐Hexanitrostilbene
Authors: Golding P. , Hayes G. F.
Published: December 2004

The synthesis of 2,2′,4,4′,6,6′‐hexanitrostilbene by oxidative coupling of 2,4,6‐trinitrotoluene in the presence of metal catalysts has been studied. The effects of reaction parameters on product yields have been evaluated and mechanisms for the reaction are proposed.
Relation entre La Structure Electronique et la Sensibilité au Choc des Explosifs Secondaires Nitrés. Critère Moléculaire de Sensibilité II. Cas des esters nitriques
Authors: Delpuech A. , Cherville J.
Published: December 2004

Dans cet article, nous avons étendu aux esters nitriques l'étude de la relation entre structure électronique et sensibilité au choc, déjà effectuée sur les nitroaromatiques et les nitramines. On y vérifie la validité du critère moléculaire de sensibilité au choc précédemment établi. Ce travail permet, en outre, de proposer une échelle de sensibilité au choc englobant les explosifs organiques des primaires aux secondaires les moins sensibles.
EXTEST international study group for the Standardization of the Methods of Testing Explosives. (Formerly European commission for the standardization of the tests of explosives). Official report on the 8th meeting, EXTEST 78, held at Tatrânska Lomnica, Czechoslovakia, October 2–7, 1978
Authors: Persson P. A.
Published: December 2004

The present issue of “Propellants and Explosives” contains the Secretary's official report of the meeting, the individual Session and Working Group reports written by the session Chairmen, and the full texts of the technical papers presented and accepted for publication.

The meeting discussed the following topics:

deflagration and transition from deflagration to detonation

initiation and stability of detonation of slurry and watergel explosives

sensitivity of slurry and watergel explosives

the underwater explosion test

testing of blasting fumes

test detonators

Steps towards standardization were taken in the field of deflagration and underwater explosion testing. There was also an exchange of views from different countries on the subject of methods of testing permissible explosives.
Sensibilité des bouillies
Authors: Michot C. , Bigourd J.
Published: December 2004

Dans les exploitations à ciel ouvert des mines et carrières, le chargement des cartouches en chute libre et le chargement de l'explosif en vrac par gravité dans les mines verticales sont réglementés en France par deux arrêtés. Le second arrêté s'applique aussi au chargement des bouillies en vrac par pompage.

Les règles relatives aux conditions spéciales d'emploi s'appliquaient jusqu'à présent essentiellement aux explosifs nitrate‐fuel et aux premières bouillies expérimentées en France. Ces explosifs ayant une sensibilité faible, il suffisait d'en limiter l'aptitude à la détonation.

Récemment sont apparues de nouvelles bouillies se distinguant des premières par une sensibilité plus grande ou par une aptitude à la détonation plus importante. Une révision des règles s'avérait par conséquent indispensable.

Pour l'élaboration de nouvelles règles, il a été tenu compte des observations faites ces dernières années sur les bouillies et surtout des informations obtenues sur les explosions survenues en Amérique du Nord en 1975 et 1976, au pompage des bouillies. Ainsi, suivant les risques propes liés au mode de chargement et plus spécialement au matériel utilisé (pompe, appareil de chargement pneumatique), il est proposé de limiter la sensibilité de l'explosif d'autant plus que son aptitude à la détonation est importante. Les nouvelles règles élaborées ont été présentées à l'Administration compétente et sont maintenant en vigueur en France.
A Test Site for Shotfiring Fumes Experiments
Authors: Lindqvist K. , Johnson N. O.
Published: December 2004

The Västra Sund test site for shotfiring fumes experiments is presented and the experimental method is described. Study of fumes emission as a function of charge confinement and package. Demonstration of steel tubes being used to replace bore‐holes as a charge confinement.
Studies on Curing of Polyurethane Propellant Binder System
Authors: Govindan G. , Athithan S. K.
Published: December 2004

Solid propellant rocket technology makes use of polyurethane propellant system based on hydroxy terminated polybutadiene as binder. Processability of the propellant is determined by viscosity build‐up after unloading from the mixer, which in turn depends on rate of curing reaction between alcohols and isocyanate. For a typical binder system consisting of alcohols and isocyanate as in propellant composition, rate of curing has been studied using IR spectroscopy are carried out in solution phase. In this study, unaltered binder system was studied as such for the progress of the reaction as a function of time. Concurrently, viscosity studies were also carried out to study the rate of viscosity build‐up with time as reaction proceeds. With these studies two distinct phases have been brought out for the cure reaction of binder, first phase involving a linear reduction in concentration of the isocyanate groups followed by the second phase tending to equilibrium.
Conception, synthèse et caractérisation d'un nouvel explosif insensible et énergétique : Le DANTNP
Authors: Wartenberg Ch. , Charrue P. , Laval F.
Published: December 2004

Nous présentons dans cet article la stratégie de recherche développée pour la définition de mouvelles molécules explosives. L'application de notre déarche théorique à la conception d'un explosif insensible est illustrée par l'exemple du 5‐nitro‐4,6‐bis(5‐amino‐3‐nitro, 1H‐ 1,2,4‐triazole‐ 1‐y1)pyrimidine ou DANTNP. Le mode opératoire de synthése et les principales caractéristiques physico‐chimiques du matériau sont discutés. Le comportement expérimental de ce nouvel explosif est confronté aux prévisions issues de la méthodologie de conception.
On the extended method of calculation of atomic structures
Authors: Jucys Adolfas Pranaitis
Published: December 2004

The extended method of calculation of atomic structures is characterized. This method is understood as the use of as many radial orbitals as there are electrons in the atom under consideration. The process of passing from the ordinary method of calculation to the extended one is described. In the method proposed the additional complications appear within the confines of dealing with radial variables only. The general rules for carrying out the calculations, in applying the extended method, are formulated.
Variational principle for the intensity of forbidden transitions
Authors: Dmitriev Y. Y. , Yuriev M. S.
Published: December 2004

A new variational principle for the probability of forbidden transitions is derived. Upper and lower bounds for the corresponding matrix element are given.
Wellenmechanische Absolutrechnungen an Molekülen und Atomsystemen mit der SCFMOLC(LCGO) Methode. II. Das Benzol (C6H6)
Authors: Diercksen G. , Preuss H.
Published: December 2004

Das C6H6 wurde im Gleichgewichtsabstand der Zentren unter Berücksichtigung aller 42 Elektronen ab initio mit dem Allgemeinen Programmsystem/SCFMOLC(LCGO) Methode berechnet. Es ergab sich eine Gesamtenergie von −227.27 a.E. und eine Ionisierungsenergie von 8.5 eV. Ferner wurde gefunden, dass den Einelektronen π‐Zuständen in energetischer Reihenfolge σ‐Zustände eingelagert sind.
Two‐particle density functions for a spin‐projected single Slater determinant
Authors: Mestechkin M. M.
Published: December 2004

The two‐particle density functions introduced by McWeeny are calculated for a spin‐projected Slater determinant.
Free‐electron model for the inelastic collision of fast electrons with benzene
Authors: Sen Purnendra Nath , Basu Sadhan
Published: December 2004

Using a free‐electron wave function the cross section for the excitation of the first excited state and that for the ionization of benzene in the inelastic collision with fast electrons have been estimated. In the ionization process the cross section has been found to be maximum when the secondary electron moves away with a kinetic energy of about 3 eV. For incident‐electron energy above 20 eV the cross section for ionization is larger than that for excitation, while below it the reverse is the case.
The polarization phenomena of spherical molecules
Authors: Boyle L. L.
Published: December 2004

The calculation of the polarizabilities of spherical molecules is discussed in the light of the average excitation energy approximation to perturbation theory. It is shown that whilst information about the energy in external fields can always be obtained from polarization phenomena, some information about the unperturbed wave function also can be obtained from magnetic susceptibility and Cotton–Mouton effect measurements. In the case of argon such information was found to agree with the results of self‐consistent‐field calculations. Predictions of the Cotton–Mouton constants of krypton and xenon are made.
Mechanism of photooxidation: Interpretation of the substituent effects in the photooxidation of acenic derivatives
Authors: Chalvet O. , Daudel R. , Ponce C. , Rigaudy J.
Published: December 2004

It has been observed that some substituents introduced in acenic derivatives are able to change the site of the fixation of oxygen during photooxidation. It is not possible to interpret this phenomenon by calculating the paralocalization energies. However, if an intermediate complex is introduced, which corresponds to an extension of the delocalized bond, a satisfactory explanation of the experimental results is possible.
The kinetic energy of molecular charge distributions and molecular stability
Authors: Bader R. F. W. , Preston H. J. T.
Published: December 2004

This paper examines the relationship between the topographical features of a molecular charge distribution and the kinetic energy of the system. Specifically, the spatial contributions to the kinetic energy are related to the Laplacian of the total charge density and to the gradients of the natural‐orbital densities. It is concluded that a necessary requirement for molecular stability is the existence of a net negative curvature for the molecular charge distribution in the internuclear region. It is shown that the charge density accumulated in the internuclear region of a stable molecule is distributed in such a way as to keep the accompanying increase in the kinetic energy to a minimum. A comparison of the contributions to the kinetic energy from the atomic and molecular charge distributions indicates that in the formation of a stable molecule the contribution from the molecular charge density in the binding region is decreased relative to that of the atoms.
Theorie quantique du pouvoir rotatoire magnetique des molecules diamagnetiques. I. Formalisme general
Authors: Smet P.
Published: December 2004

The quantum theory of the Faraday effect or magnetic rotatory power is set up for diamagnetic molecules and is based upon a variation‐perturbation method which, unlike the usual Dirac perturbation theory, needs only the knowledge of the wave function ψ of the ground state of the non‐perturbed molecule. The principle of this theory includes in the expression of the perturbed wave function, vectors which characterize the contribution of the different fields of perturbation. The quantities which descríbe the Faraday effect, obtained from the calculation of the electric and magnetic macroscopic dipole moments, are expressed from ψ and the vectors precedently introduced. They are determined by a variation calculus.
On the projection of many‐electron spin eigenstates
Authors: Kouba Joseph , Öhrn Yngve
Published: December 2004

A translation is made of spin projection methods into the language of second quantization. This leads to a new formula for the Sanibel coefficients and expressions convenient to use for automatic calculation of spin projections.
The calculation of matrix elements for valence bond functions
Authors: Shull Harrison
Published: December 2004

Pauling's formulas for the calculation of matrix elements for valence bond functions are derived using a simple substitutional process. The results generalize and simplify the formulas. In particular, the formulas do not depend upon orthogonality of atomic orbitals nor upon the nature of the choice of bond structures (canonical or not). The results are particularly adaptable to automatic computation.
On uncoupled approximation with approximate form of the Hartree–Fock operator
Authors: Malinowski S.
Published: December 2004

It is shown that the uncoupled approximation of Dalgarno with the approximate form of the Hartree–Fock operator gives no bound for the second order energy.
LCAO–MO studies on hydrogen bonding: The interaction between carbonyl and hydroxyl groups
Authors: Schuster Peter
Published: December 2004

Potential curves that show the energy dependence of hydrogen bonds between carbonyl and hydroxyl groups on the OH bond length, on the distance between the molecules, and on the angle between the functional groups have been calculated with the CNDO/2 method. The results are presented for a small model system–formaldehyde/water—and for the dimer of formic acid. Good agreement is obtained with the available experimental data. The influence of the molecular geometry on the calculated results is discussed.
Wellenmechanische untersuchungen am 2‐buten unter berücksichtigung aller elektronen
Authors: Janoschek R. , Preuss H.
Published: December 2004

2‐butene has been investigated for different nuclear positions taking all 32 electrons into account, using the SCF–MO–LC(LCGO) method. The calculations show that the energy of the trans‐form is 1.1 kcal/mol lower than that of the cis‐form. The potential curve between these two forms is shown graphically. The ionization energy was estimated to be 9.0 eV.
Extended method of calculation for two shells of atomic electrons having the same orbital quantum number
Authors: Jucys A. P. , Našlenas E. P.
Published: December 2004

An extended method of calculation for two shells of atomic electrons, based upon the use of non‐orthogonal radial orbitals, is presented. The rules for going over from the radial integrals of the ordinary method of calculation to the linear combinations of radial integrals of the extended method of calculation are given. The numerical calculations are carried out for the ground states of lithium‐ and beryllium‐like atomic systems.
Theoretical study of isoelectronic systems: Diazomethane, ketene and allene
Authors: André J.‐M. , André M. Cl. , Leroy G. , Weiler J.
Published: December 2004

All‐electron SCF–LCAO–MO computations for diazomethane, ketene and allene are presented. The basis functions are contracted Gaussian orbitals. Theoretical results are discussed and related to available experimental data.
Increased‐valence formulae and the bonding of oxygen to haemoglobin
Authors: Harcourt R. D.
Published: December 2004

The molecular orbital configuration for the ground‐state of O2 generates the valence formula . “Increased‐valence” formulae for triatomic and polyatomic molecules have been developed recently. In them, more electrons participate in bonding than is possible for the familiar valence‐bond formulae. Using oxyhaemoglobin as an example of an oxygen carrier, various increased‐valence formulae are generated for the FeO2 groups. In the low‐energy formulae, the iron is bonded to the above valence formula for O2. Therefore, in contrast to the bonding schemes of Pauling and Coryell, Griffith and Weiss, little reorganization of O2 need occur on formation of HbO2. This conclusion is independent of the mode of co‐ordination of iron to the O2.
Self consistent molecular orbital calculations on polyatomic molecules: Gaussian approximation for two‐electron integrals
Authors: Bendazzoli G. L. , Bernardi F. , Palmieri P.
Published: December 2004

A MO–LCAO–SCF treatment is performed on water, ammonia and methane using a recently proposed approximate method.

The procedure is found capable of predicting total and orbital energies in close agreement with the results of accurate computations using double ζ basis sets of Slater type orbitals.

A comparison is made with the results of similar approximate ab initio procedures.
On the complete set of functions in the Heitler–London method for two‐electron problem
Authors: Abarenkov I. V.
Published: December 2004

It is shown that under certain restrictions the system of determinants φi(x1)φk(x2) − φk(x1)ψi(x2) constructed from two different sets of orbitals ψk and φk will be the complete set of functions for antisymmetrical two‐electron wave functions if the condition i < k is imposed.
A change of variable for the perturbation parameter in rayleigh–Schrödinger perturbation theory
Authors: Amos A. T.
Published: December 2004

The Feenberg–Goldhammer change of scale, whereby the H0 in perturbation theory is replaced by (1/μ)H0 with μ a scaling parameter, is shown to be equivalent to a change of variable for the perturbation parameter. A more general change of variable is shown to lead to a perturbation series with perturbation energies E3, …, E2n+1 equal to zero. The resulting energy through (2n + 1)th order has the same form as that found from the Brillouin–Wigner series by different methods.
On the validity of Hamilton‐Jacobi mechanics in the mean in quantum mechanics
Authors: Taylor W. J. , Levine R. D.
Published: December 2004

It is shown that under certain conditions the time‐dependent Hamilton–Jacobi equation (TDHJE) is satisfied in the mean in quantum mechanics provided the classical action is replaced by Dirac's complex quantal action. This may be regarded as the equivalent of Ehrenfest's theorem for the TDHJE. Expectation values of operators are discussed in a similar manner.
The general theory of the extended method of calulation of atomic structures
Authors: Jucys A. P. , Naŝlėnas E. P. , Žvirblis P. S.
Published: December 2004

A general theory of the extended method of calculation of atomic structures having complex configurations is presented. It is based on the correspondence between the radial integrals of the ordinary method and the linear combinations of those of the extended method. The rules for going over from the ordinary method to the extended one are given.
The spherical limit of H: A symmetry dilemma
Authors: Katriel J.
Published: December 2004

The spherical limit of H is studied as an example of the occurrence of a symmetry dilemma of a kind which is a general characteristic of truncated one centre expansions. At internuclear distances just somewhat larger than the equilibrium distance the best spherical approximation turns out to be centred off the molecular midpoint and is thus a mixture of σg and σu. Rather detailed insight into the situation is gained by an analysis based on the electrostatic Hellmann‐Feynman theorem.
Two‐electron theory of non‐interacting surface and impurity states
Authors: Davison S. G. , Tan W. K.
Published: December 2004

Some earlier results in the Davison‐Cheng two‐electron theory of surface and impurity states are corrected. Although the surface spin state findings are only slightly modified, it is found that the inner and outer impurity spin states no longer always occur separately, but can in fact co‐exist. After discussing the connection between the two‐electron theory of monatomic crystals and the one‐electron theory of diatomic crystals, the paper concludes by briefly outlining the recent developments in the one‐electron theory of surface and impurity state interaction.
SCF perturbation theory and intermolecular interactions
Authors: Basilevsky M. V. , Berenfeld M. M.
Published: December 2004

A self‐consistent perturbation theory is derived in the framework of Roothaan's MOLCAO procedure for closed shell systems. Contrary to previous investigations which have considered only one particle perturbations, two particle perturbation operators are considered. Expressions for the first‐order density matrix and first‐ and second‐order energy corrections are obtained. A diagram formulation of the complete perturbation expansion is presented.

The results are applied to the treatment of the intermolecular interaction problem. The interaction energy is represented as a sum of several contributions: Coulomb, exchange, resonance, polarization and exchange repulsion. A semi‐empirical version of the theory is suggested which explicitly involves all the physically significant energy terms and may be useful for the investigation of complex systems.
PCILON. perturbative configuration interaction using localized orbitals and numerical integration. I. Numerical integration techniques for the calculation of Hamiltonian matrix elements between localized orbitals
Authors: Daudey J. P. , Diner S.
Published: December 2004

Modern techniques for multidimensional numerical integration, Korobov's and Sobol's formulas namely, are used for the direct computation of matrix elements between the localized molecular orbitals needed for a configuration interaction calculation by a perturbation method. A minimal orbital basis of Slater functions is used for formaldehyde and ethylene taken as example. The resulting precision is satisfactory.
Convergence of the completely separated bipolar expansion of r
Authors: Salmon Lydia S.
Published: December 2004

A proof of the convergence of the double infinite series form of the radial factor in the bipolar expansion of r is given. It consists of demonstrating the validity of the required term‐by‐term integrations.
Direct minimization of the energy functional in LCAO–MO calculations
Authors: Kari R. , Sutcliffe B. T.
Published: December 2004

In this paper we obtain formulae useful in methods for the direct minimization of the energy functional in the LCAO‐MO‐MC‐SCF approach. The formulae are appropriate for dealing with variations in both the linear and nonlinear parameters. We include formulae for the usual closed‐ and open‐shell problems as special cases.
A study of the AMO method as applied to the lithium metal. I. Review, results, and discussion
Authors: Calais Jean‐Louis , Sperber Gunnar
Published: December 2004

The total electronic energy per atom in the lithium metal has been calculated for three different Fermi surfaces as a function of the internuclear distance. In each case the optimized AMO energy as well as the total energy corresponding to doubly filled molecular orbitals (MO) has been calculated. For densities around the equilibrium density the spherical Fermi surface yields the lowest energy whereas a cubic Fermi surface is preferred for low densities. For densities around the equilibrium there is no band splitting: the AMO energy coincides with the MO energy. The computations have been carried out within an LCAO approximation with overlap and multicenter‐integrals calculated accurately.
A study of the AMO method as applied to the lithium metal. II. The first‐order density matrix and the shape of the fermi surface
Authors: Sperber Gunnar , Calais Jean‐Louis
Published: December 2004

Alternant molecular orbitals for the lithium metal are constructed in different ways. The corresponding first‐order density matrix is calculated for different shapes of the Fermi surface. Numerical methods to calculate the first‐order density matrix are described.
A note on Löwdin orthogonalization and the square root of a positive self‐adjoint matrix
Authors: Scofield D. F.
Published: December 2004

A quadratically convergent process using a continued fraction method for finding the square root of the overlap matrix used in Löwdin orthogonalization is presented. The continued fraction method is compared to several other methods for finding the square root of a matrix. The method is found to be more efficient than the other methods when high accuracy is desired.
Decoupled Hartree‐Fock methods. II. Calculation of the potential curves of diatomic molecules
Authors: Náray‐Szabó G.
Published: December 2004

Applying an extended form of the Mulliken approximation and a monopole approximation for the Coulomb integrals the Hartree‐Fock nonorthogonal energy expression is decoupled. Thus, the total energy splits into a sum of one‐electron increments. The increments are minimized directly with respect to the linear coefficients and orbital exponents. Further, the ZDO approximation is used in the decoupled energy expression to avoid difficulties arising in connection with the evaluation of multicenter integrals. “Rigid core” calculations were carried out for the valence electrons of first‐row diatomics. In case of nonpolar molecules good results are obtained for equilibrium distances and force constants. The method fails for molecules with atoms having very different nuclear charges.
Representable reference density matrices induced by information theory
Authors: Larson Everett G.
Published: December 2004

A class of reference full density matrices and their reduced density matrices is presented. These density matrices are designed to be of value as references from which to describe and measure the effects of electron correlation in atoms, molecules, and solids. A given reference full density matrix is constructed to contain the least possible information consistent with having the (recognized) symmetry properties of—and reducing to the 1‐matrix of—a given “true” full density matrix (which in a typical application is constructed from a correlated variational wave function). Therefore, the reduced density matrices derived from are representable and depend only upon the 1‐matrix of and the (recognized) symmetry properties of for their construction. Furthermore, the property of containing the least possible information consistent with the given constraints makes these reference density matrices ideally suitable as references from which to describe the electron correlation contained in the “true” full density matrix magnified image.
Ab initio valence bond calculations. I. Methylene
Authors: Tantardini Gian Franco , Raimondi Mario , Simonetta Massimo
Published: December 2004

An ab initio valence bond (VB) method for calculating energies and wave functions for simple electronic systems is described and the results of its application to methylene are given together with extensive comparisons with previous theoretical results.
Détermination des Orbitales Moléculaires par Minimisation Directe de L'Energie de L'Etat Fondamental et des Etats Excités des Molécules
Authors: Benard Marc , Julg André
Published: December 2004

Un procédé de minimisation directe de l'énergie d'une molécule par rapport aux coefficients des orbitales atomiques des fonctions moléculaires est utilisé en vue de déterminer les fonctions de l'état fondamental et des états excités. L'orthogonalité entre les divers états est obtenue par des conditions moins restrictives que celles de Roothaan, si bien que l'énergie obtenue pour la première transition électronique est abaissée: de 0,1 à 0,2 eV pour les transitions π → π* des polyènes.
A configuration interaction study of the spin dipole‐dipole parameters for formaldehyde and methylene
Authors: Langhoff Stephen R. , Elbert Stephen T. , Davidson Ernest R.
Published: December 2004

The electron spin dipole‐dipole contribution to the zero field splitting has been evaluated for the 3A2 (n → π*) and 3A1 (π → π*) states of formaldehyde using a CI wave function constructed from contracted Gaussian‐lobe functions. The values D = 0.539 cm−1 and E = 0.031 cm−1 were obtained for the 3A2(n → π*) state and D = −0.588 cm−1 and E = 0.058 cm−1 were obtained for the 3A1 (π → π*) state using the CI wave function constructed from SCF orbitals of the respective parent configurations. An analysis of the effect of CI on the parameters is given for the 3A2 (n n → π*) state of formaldehyde and the 3B1 ground state of methylene. Numerical results are given which show that internally consistent self‐consistent field orbitals (ICSCF) are superior to canonical SCF orbitals as a starting point for a CI calculation. Our CI wave function for the 1A1 ground state gave an energy of −114.13658 hartrees which is significantly lower than any previously reported energy calculation. This wave function gives a dipole moment of 2.22 Debye (C+O−) in good agreement with the experimental value of 2.33 ± 0.02 Debye.
Symmetry in the Heitler‐London method. II. The determination of the allowed molecular multiplets
Authors: Ledovskaya E. M. , Petrashen M. I.
Published: December 2004

In the framework of the Heitler‐London method, a method for determining the allowed molecular multiplets is proposed. The method is based on the connection of the total molecular spin with the permutation symmetry of the coordinate wave function and on the isomorphism of the molecular point group with a certain subgroup of the electron permutation group. The method does not depend on the approximation in which the molecular ions are considered.
Integral transform functions and separable potentials
Authors: Bandrauk A. D.
Published: December 2004

General forms for asymptotic wave functions are derived from properties of the relevant Green's function. The use of separable potentials constructed from the asymptotic functions is described and the relation with integral transform functions is discussed.
Symmetries of n‐electron wave functions under various spatial groups
Authors: Gallup G. A.
Published: December 2004

A new method is used to arrive at Kotani's formula (vide infra) for the character of the representation of the group of spatial symmetry provided by functions which are eigenfunctions of the total spin operator. An alternative form involving determinants of the symmetric functions is also given. The results are applied to some cases which were untreated before and have particular interest in valence‐bond calculations. The problem of the construction of bases functions of the given symmetry is also discussed, and a solution with a wide range of applicability is given.
A variational perturbation treatment of the hydrogen molecular ion using the green function method on the united atom
Authors: Corsaro Felicia A. , Solenberger Françoise R. , Hameka Hendrik F.
Published: December 2004

We calculated the second‐order perturbed energy and the first‐order perturbed wave function of the hydrogen molecular ion by the Green function method based on a united atom with effective nuclear charge, Z. Since the perturbation is given by (Z/r) — (1/rA) — (1/rB), its magnitude depends on the parameter Z. We obtain an analytical expression for the second‐order perturbed energy as a function of Z and the internuclear distance R. We discuss a variety of methods to determine the best values for Z and to derive the potential energy curve and the force constant for H; these methods vary in the accuracy of their results.
Spin projected EHF method: Calculations for a four‐electron model system
Authors: Mayer I.
Published: December 2004

The spin projected extended Hartree‐Fock equations for successive optimization of the orbitals are derived for the four‐electron case and applied to butadiene in the PPP approximation. The method shows an excellent convergence and gives 91.4% of the correlation energy for the given model‐Hamiltonian.
The self‐consistent symmetrized OPW method with an application to crystalline selenium
Authors: Boehm Juhani Von , Krusius Peter
Published: December 2004

A review of the nonrelativistic self‐consistent symmertrized orthogonalized‐plane‐wave (SCSOPW) method used for determining electronic energy bands in periodic solids is given. Working equations based on the full use of group theory at all stages are presented for elemental crystals. As an example the method is applied to the trigonal selenium crystal.
Spin‐orbit interaction in polyatomic molecules: Ab initio computations with Gaussian orbitals
Authors: Bendazzoli G. L. , Palmieri P.
Published: December 2004

Standard sets of Gaussian atomic orbitals (STO‐3G, STO‐4.31G) are used to evaluate spin‐orbit coupling constants in linear molecules (CO, NNN) and spin‐orbit effects on singlet–triplet transition intensities in formaldehyde. All spin‐other orbit effects have been included. In all cases spin‐other orbit interactions form a large fraction of the matrix elements. Simple formulae to evaluate spin‐orbit one‐ and two‐electron integrals over atomic orbitals are presented. Standard molecular integral programs can be used for the computation of spin‐orbit integrals.