bluuebunny/crossref_metadata_2025 huggingface dataset:
Zur Umsetzung von n‐Alkanen mit Aluminiumnitratnonahydrat
Authors: Minkov Dimiter , Lavčieva Dimitrina , Kumanova Bogdana
Published: December 2004

About the Reaction between n‐Alkanes and Aluminium Nitrate‐nonahydrate

The reaction between n‐alkanes (C10C13) and aluminium nitrate‐nonahydrate in the temperature range 353–403 K, time of contact 12 h and mole ratio nitrating agent: hydrocarbon from 1:2 to 2:1 was investigated.

The product obtained was separated on silicagel. The fractions separated by adsorption chromatography were studied by i.r.‐ and combined GC/MS spectroscopy. Only alkyl nitrates were obtained. The oxidation processes yield aldehydes, ketones and nitrate carboxylic acids.

The model reaction with n‐undecane shows that undecyl‐3‐nitrate (5), undecanal (6), undeca‐5‐on (7) and nitrate undecanic acid (8) are obtained.
Fluoreszenzlöschung und Excimerenbildung von Pyren‐3‐sulfonat in wäßrigen Lösungen von Polydimethyldiallylammoniumchlorid
Authors: Becker H. G. O. , Schütz R. , Kuzmin M. G. , Sadovsky N. A. , Soboleva I. V.
Published: December 2004

Quenching of Fluorescence and Excimer Formation of Sodiumpyren‐3‐sulfonate in Aqueous Solutions of Polydimethyldiallylammonium Chloride

The fluorescence spectra and lifetimes of sodium‐pyren‐3‐sulfonate have been measured in the presence of polydimethyldiallylammonium chloride. It is shown, that the excimer formation by static self‐quenching of fluorescence of the pyren‐3‐sulfonate is based on the cooperative effect of the macroion. The association constants of interaction between the aromatic compound and the polycation are determined. Presence of diazoniumcations leads to quenching of fluorescence of pyren‐3‐sulfonate in both the polyelectrolyte and aqueous phases. The quenching constants are discussed.
Reaction of Cyclohexylamine with Formaldehyde: The structure of N′,N″,N″′‐tricyclohexylhexahydro‐symtriazine
Authors: Zangrando Ennio , Poggi Gabriella , Giumanini Angelo G. , Verardo Giancarlo
Published: December 2004

A reported preparation of 1,3‐dicyclohexyl‐1,3‐diazacyclobutane (2) is rebutted: the correct structure is that of N′,N″,N″′‐tricyclohexylhexahydro‐sym‐triazine (5), having a diequatorial‐axial conformation in the solid state, as shown by mass spectrometry and X‐ray diffraction. Theoretical calculations were carried out in order to predict the stabilities of 1,2‐ and 1,3‐diazacyclobutane (14 and 1) and their geometries.
Silylation‐Mediated Oxidation of 2,2′‐Anhydro‐5,6‐dihydro‐5‐azacytidine
Authors: Abbasi M. M. , El‐Wassimi M. T. , Osman F. H. , Kamel M. M.
Published: December 2004

Reaction of 5,6‐dihydro‐5‐azacytidine hydrochloride 1 with 2‐acetoxy‐isobutyryl chloride produced 5′‐O‐(2,5,5‐trimethyl‐1,3‐dioxolan‐4‐on‐2‐yl)‐3′‐O‐acetyl‐5,6‐dihydro‐2,2′‐anhydro‐1‐β‐D‐arabinofuranosyl‐5‐azacytosine hydrochloride 2, which upon partial hydrolysis with EtOH/HCl at 4°C gave 3′‐O‐acetyl‐5,6‐dihydro‐2,2′‐anhydro‐1‐β‐D‐arabinofuranosyl‐5‐azacytosine hydrochloride 3. The hydrolysis of 3 with EtOH/HCl at 25°C gave 2,2′‐anhydro‐5,6‐dihydro‐1‐β‐D‐arabinofuranosyl‐5‐azacytosine hydrochloride 4. Silylation oxidation of 3 and 4 with BSTFA or BSA in acetonitrile produced the N‐substituted derivatives of 1‐β‐D‐arabinofuranosyl‐5‐azacytosine 8 and 7, respectively.
The “normalizing factor” for the tomato mutant chloronerva. XXV. Synthesis of 2‐Epinicotianamine and Nicotianamine
Authors: Ripperger H. , Schreiber K.
Published: December 2004

2‐Epinicotianamine (6) was synthesized by stepwise reductive alkylation of ethyl (R)‐2‐azetidinecarboxylate (2) with ethyl (S)‐4‐oxo‐2‐(trifluoroacetylamino)butanoate (3); nicotianamine (8) was prepared in an analogous manner from (2S,αS)‐α‐amino‐2‐carboxy‐1‐azetidine‐butanoic acid (7). 2‐Epinicotianamine and nicotianamine showed the same biological activity with regard to the phenotypical normalization of the tomato mutant chloronerva.
Darstellung und Reaktivität von 2,4‐Diamino(bis‐alkylamino)‐1,3,5‐triazin‐6‐yl‐thioharnstoffen
Authors: Freiberg Renate , Bulka Ehrenfried
Published: December 2004

Synthesis and Reactivity of 2,4‐Diamino(bis‐alkylamino)‐s‐triazine‐6‐thioureas

2,4‐Diamino‐s‐triazine‐6‐thiourea (1a) was prepared by treating cyanomelamine with hydrogen sulphide under pressure in aqueous ammonia. Addition was also performed indirectly by the reaction with thioacetamide. This method was further be used to get 2,4‐bis‐alkylamino‐s‐triazine‐6‐thioureas (1b–g). s‐Triazine‐thioureas (1a–g) were S‐alkylated with methyl iodide or benzyl chloride to the compounds 2a–f, 3a. Hantzsch thiazole synthesis of s‐triazine‐thioureas with α‐halocarbonyl derivatives gave 2,4‐diamino(bis‐alkylamino)‐6‐(thiazolamino)‐s‐triazines (5a–j, 6b, d–g, 7a–f).
Exo‐ and endohormones. X. A novel route to an isomer mixture of 7,9‐Dodecadien‐1‐yl Acetate utilizable in field attraction of Lobesia botrana males
Authors: Daradics L. , Oprean I. , Hodosan F.
Published: December 2004

Wittig condensation of (Z)‐2‐pentenylidene triphenylphosphorane (14) and 7‐tert.‐butoxy‐heptanal (13) under conditions of phase transfer catalysis and subsequent conversion into the corresponding acetate afforded a mixture of 28% 7(E),9(Z)‐dodecadien‐1‐yl acetate, the sex pheromone of Lobesia botrana, along with the other geometrical isomers and 30% unidentified by‐products. The synthons 14 and 13 were prepared starting with (Z)‐2‐butene‐1,4‐diol (1) and hexane‐1,6‐diol (9), respectively.
Darstellung neuer substituierter 1,2,4‐Triazin‐6‐carbonsäuren und 1,2,4‐Triazin‐6‐yl‐alkancarbonsäuren
Authors: Heinisch L.
Published: December 2004

Synthesis of New Substituted as‐Triazine‐6‐carboxylic Acids and as‐Triazine‐6‐yl‐alkanoic Acids

New substituted 3‐amino‐, 5‐amino‐ and 3,5‐diamino‐as‐triazine‐6‐carboxylic acids 4a, b, 5a, b and 6 were obtained by the hydrolysis 6‐azalumazine derivatives 3a–e. Corresponding acids of the structure 10a–d, 11a, b and 12 were synthesized from 5‐chlor‐3‐methylthio‐astriazine‐6‐carboxylic‐ester 8. The synthesis of new 3‐alkylthioderivatives of as‐triazine‐6‐yl‐acetic acid 16a–c and ‐propionic acid 18 and its hydrolysis to 3,5‐dioxotetrahydro‐as‐triazine‐6‐yl‐propionic acid 19 is reported.
Bestimmung der Extinktionskoeffizienten der Photoisomeren von 3β‐Hydroxy‐cholest‐5,7‐dien (Provitamin D3)
Authors: Gliesing S. , Reichenbächer M. , Ilge H.‐D. , Fassler D.
Published: December 2004

Determination of the Molar Absorptivity (ε) of the Photoisomers of 3β‐Hydroxy‐cholest‐5.7‐diene (Provitamin D3)

A method is described which allows the determination of the molecular absorptivity (ε) of all components in a four‐component system and is applied to the ε‐determination of the photoisomers of provitamin D3 (1): prävitamin D3 (2), lumisterol3 (3), and tachysterol3 (4). By means of irradiation with appropriate wavelengths the four‐component system is reduced to a two‐ and a three‐component system, respectively, and the unknown molar absorptivities are evaluated numerically or graphically.
13C‐NMR‐Untersuchungen an 4‐Amino‐2,6‐dialkyl‐pyrimidinen und ihren Sulfonamidderivaten
Authors: Gründemann E. , Niclas H.‐J. , Zeunter F.
Published: December 2004

Carbon‐13 N.M.R. Studies on 4‐Amino‐2,6‐dialkyl Pyrimidines and Their Sulfonamide Derivatives

Carbon‐13 n.m.r. studies on 4‐amino‐2,4‐dialkyl pyrimidines and their sulfonamide derivatives have shown that the known additivity rules for the assignment of signals are not valid. The reason is a tautomerism as demonstrated by changes of the chemical shifts of the alkyl groups. The electronic influence of substituents at the amino group on the alkyl C‐atoms are neglegible compared to changes due to tautomerism.
Revisitation of the reaction between aniline and formaldehyde. VI. The accumulated amide ester function from Addition of Carboxylic Anhydrides to N‐methyleneamines or their trimers
Authors: Giumanini Angelo G. , Verardo Giancarlo , Cauci Sabina
Published: December 2004

Some aliphatic carboxylic anhydrides gave excellent yields of the novel addition products to both aliphatic and aromatic N‐methyleneimines, starting from their aliphatic and aromatic trimeric cyclic oligomers. A preliminary positive ion mass spectrometric study is here reported. They hydrolyze surprisingly faster than the corresponding acid amides, making necessary the intervention of a special mechanism. The reduction of the acetylamideester of cyclohexylmethyleneimine (3c) with LiAlH4 was also “abnormal”, as it yielded N‐methyl‐N‐ethylcyclohexylamine in quantitative yield.
Synthesis of Schizokinen, Homoschizokinen, Its Imide and the detection of imide with 13C‐N.M.R.‐spectroscopy
Authors: Milewska Maria J. , Chimiak Andrzej , Głowacki Zdzisław
Published: December 2004

A new method for the synthesis of homoschizokinen 1 and schizokinen 2 is described. 2‐tert‐Butyl‐1,3‐di‐N‐hydroxysuccinimidyl citrate has been applied as the key substrate. The method excludes the possibility of imide formation. The imide of compound 1 has been obtained analogously from the active ester of the 1,3‐dioxolan‐4‐one derivative 5. It has been stated that 13C‐n.m.r. signals of the C‐3 carbon atoms enable the detection of traces of homoschizokinen 17.
Exo‐ and endohormones. XII. Synthesis of 7(E),9(Z)‐Dodecadien‐1‐yl Acetate, the sex pheromone of european grape vine moth Lobesia botrana, involving phase transfer technique
Authors: Daradics L. , Oprean I. , Hodosan F. , Serban N.
Published: December 2004

The synthesis of 7(E), 9(Z)‐dodecadien‐1‐yl acetate using for the olefination steps Wittig and Horner reactions under phase transfer conditions is reported. The 7(E) double bond was prepared by Horner coupling of 7‐tert‐butoxy‐heptanal (1) with 0,0‐diethylphosphonoacetate (2) in a two phase system.

Wittig olefination was used to build up the 9(Z) double bond by reacting 9‐tert‐butoxy‐2‐nonen‐1‐yl‐triphenyl‐phosphonium bromide(13) with propionaldehyde under phase transfer catalytic conditions.
Experimentelle und theoretische Untersuchungen an Kohlenwasserstoffen der Formel C5H6: Pyrolyse von Cyclopenta‐1,3‐dien
Authors: Gey E. , Ondruschka B. , Zimmermann G.
Published: December 2004

Experimental and Theoretical Investigations on Hydrocarbons of the Formula C5H6: Pyrolysis of 1,3‐Cyclopentadiene

The details of high temperature chemistry of the conversion of 1,3‐cyclopentadiene (CPD) are unknown. Therefore the pyrolysis of CPD was studied under various reaction conditions in labscale dimension. The attempt to interpret the composition of the reaction products only on the basis of convenient axiomes does not seem satisfactory. For that reason heats of formation and relative stabilities for 25 closed and open shell hydrocarbons of the formula C5H6 were calculated using the MINDO/3 procedure. These enthalpy values were used to estimate heats of reactions for selected start steps of the pyrolysis of CPD. The molecular‐assisted hydrogen transfer under formation of cyclopentadienyl and cyclopentenyl radicals ought to be one of the most important reaction steps.
Nachbargruppenbeteiligung bei durch N‐Bromsuccinimid initiierten Elektrophilen Additionen
Authors: Haufe Günter , Gierscher Fritz , Köhler Günther , Schulze Klaus
Published: December 2004

Neighbouring Group Participation in Electrophilic Additions Initiated by N‐Bromosuccinimide

Starting from endo‐5‐hydroxymethyl‐norbornene as well as 5‐(hydroxymethyl)‐methyl‐cyclohexene the methoxybromination procedure gives cyclic ethers by participation of the hydroxymethyl group. Unsaturated formyl compounds or their acetals, respectively by contrast, gave methoxybromination products. After oxidation of the functional groups bromo methoxy methyl carboxylates are formed depending on the molar ratio of the substrate to NBS.
Partialsynthesen von Cardenoliden und Cardenolid‐Analogen. XII. Synthese 21‐substituierter Cardenolide durch Oxidation von 17β ‐ (Fur‐3‐yl)‐Steroiden und nukleophile Substitution
Authors: Lindig Claus , Repke Kurt R. H.
Published: December 2004

Partial Syntheses of Cardenolides and Cardenolide‐Analogues. XII. Synthesis of 21‐Substituted Cardenolides by Oxidation of 17β ‐ (3‐Furyl)‐Steroids and Nucleophilic Substitution

Oxidation of 17β‐(3‐furyl)‐5β, 14β‐androstane‐3β, 14β‐diol 3‐acetate (2b) with chromic acid yielded the 14,21‐epoxy‐cardenolide 4. After elimination of the 14β‐hydroxy group of 2b the unsaturated furyl derivative 5, when treated with chromic acid, gave a mixture of the diastereomeric unsaturated 21ξ‐hydroxy‐cardenolides 8a which were converted with N‐bromoacetamide to a mixture of the 14β, 15β‐epoxy‐21ξ‐hydroxy‐cardenolides 9a.

The hydroxy‐cardenolides 8a and 9a were acetylated to the 21ξ‐acetoxy‐cardenolides 8b/8c and 9b/9c, respectively, and they reacted with primary and secondary amines to give the corresponding N‐substituted 21ξ‐amino‐cardenolides 11a‐‐11c and 12b, respectively. When reacted with p‐toluenesulfonyl chloride both 8a and 9a yielded the 21ξ‐chloro‐cardenolides 11d/11e and 12c/12d, respectively, the chlorine of which could easily be substituted by SN1‐ and SN2‐reactions.
Oligosiloxane mit funktionellen Gruppen. II Reaktion von 1,4‐Bis(trimethylsiloxy)‐but‐2‐en mit H‐Silanen in Gegenwart von Hexachloroplatin‐säure
Authors: Engelbrecht L. , Sonnek G. , Ždanov A. A. , Makarova L. I.
Published: December 2004

Oligosiloxanes with Functional Groups. II. Reaction of 1.4‐Bis(trimethylsiloxy)‐but‐2‐ene with H‐Silanes in the Presence of Hexachloroplatinic Acid

The synthesis of silicon‐modified butane‐1.4‐diol derivatives by the hydrosilylation of 1.4‐bis (trimethylsiloxy) but‐2‐ene (1) is described. Under the conditions of the hydrosilylation 1 is isomerized with high selectivity. At a temperature above 150°C hydrosilylation and isomerization take place simultaneously.
Substituierte 5‐Imino‐3,3‐pentamethylen‐1,2,4‐thiadiazolidine durch Aminierung von Thioharnstoffderivaten
Authors: Andreae Siegfried , Schmitz Ernst
Published: December 2004

Substituted 5‐Imino‐3,3‐pentamethylene‐1,2,4‐thiadiazolidines by Amination of Thiourea Derivatives

N‐Acylthioureas 2a–b and thiosemicarbazones of aldehydes, ketones, and esters 4a–g are aminated at the potential SH‐group by 3,3‐pentamethyleneoxaziridine yielding substituted 5‐imino‐3,3‐pentamethylene‐1,2,4‐thiadiazolidines 3 and 6 the latter via the intermediates 5.

The reaction of the thiosemicarbazones 4 is a very general one, but only two acylthioureas 2 could be converted into the title compounds.
1,2,3‐Triazabutadiene. XX. Untersuchungen zur Fotoisomerisierung, Fotolyse, Protonierung und sauren Spaltung von 1‐Aryl‐3‐[3‐methyl‐benzthiazolinyliden‐(2)]‐triazenen in mizellaren Lösungen
Authors: Fanghänel E. , Ortmann W. , Hennig A.
Published: December 2004

1,2,3‐Triazabutadienes. XX. Investigations of the Photochemical Z‐E‐Isomerization, Photolysis, Protonation and Acidic Cleavage of 1‐Aryl‐3‐3‐methylbenzthiazolinyliden‐(2)‐triazenes in Micellar Solutions

The E‐isomers of the 1‐Aryl‐3‐[3‐methylbenzthiazolinyliden‐(2)]‐triazenes are soluble in aqueous micellar solutions of sodium dodecylsulfate (NDS) and cetyltrimethylammoniumbromide (CTAB). They are fixed in the Stern region of the micelles. The Z‐isomers decompose in aqueous micellar solutions by acidic cleavage. They can be stabilized by the use of alkaline buffer solutions. The concentration of protons is higher by the factor 103 in the Stern region of NDS‐micelles than in the Stern region of CTAB‐micelles. This difference is explained by electrostatic attraction and repulsion between the protons and the micelles. The quantum yields of the photochemical isomerization in micellar solutions and in organic solvents are the same. Water soluble ionic dyes with relatively low triplet energies sensitize the photoisomerization in micellar solutions and the photostationary state is on the side of the E‐isomer.
Zur Nitrierung von 2‐Methylaminopyridin‐N‐oxid‐Derivaten
Authors: Talik Tadeusz , Talik Zofia
Published: December 2004

Nitration of Some Derivatives of 2‐Methylaminopyridine N‐Oxides

The only stable products obtained from nitrations of 2‐methylaminopyridine N‐oxide and some derivatives, are those resulting from nitration of the pyridine ring. Thus, 2‐methyl‐aminopyridine N‐oxide 8 is nitrated under mild conditions to yield 2‐methylamino‐5‐nitropyridine N‐oxide 9, but not 2‐methylnitraminopyridine‐N‐oxide 10 is obtained.

2‐Methylamino‐4‐nitropyridine N‐oxide 1 yields 2‐methylamino‐4,5‐dinitropyridine N‐oxide 2 upon nitration.

Chemical reactions which relate known compounds to the new compounds obtained, confirm the assigned structures.
Untersuchungen zum UV/Vis‐Spektralverhalten von Azofarbstoffen. XX. Zum unterschiedlichen Substituenteneinfluß auf die Absorptionsmaxima von Hydrazonen und Benzendiazoniumionen
Authors: Mustroph H.
Published: December 2004

Studies on UV/Vis Absorption Spectra of Azo Dyes. XX. On the Different Substituent Effects on the Absorption Maxima of Hydrazones and Benzenediazonium Ions

PMO theory predicts that substituent effects on the absorption maxima of benzenediazonium ions are partly contrary to those in hydrazones. Therefore, it seemed likely that azo coupling products absorbing at shorter wavelengths than the parent diazonium ions should exist. This is confirmed experimentally. The hydrazones 4c and 5c absorb significantly hypsochromic than the diazonium ion 3c.
Untersuchungen zur Gegenionenstruktur bei der Kationischen Polymerisation von Isobutylvinylether mit iodhaltigen Initiatoren
Authors: Spange Stefan , Heublein Günther , Taeger Frank
Published: December 2004

Investigations on the Counter Ion Structure of the Cationics Polymerization of Isobutylvinylether with Iodine Based Systems

The structure of counter ions of iodine based initiators for the cationic polymerization of isobutylvinylether is elucidated by means of u.v.‐spectroscopy using as model system:
equation image

Increasing electrophilicity of the cation causes a decrease of the counter ion stability. High concentrations of iodine lead to the formation of polyiodides, as I and I, respectively.

The influence on chain propagation by iodine and monomer concentration as well have been followed by GPC and u.v.‐spectroscopy. Both influences, strongly affects the propagation reaction.

Triphenylmethylbromide in conjunction with iodine is a convenient initiating system, realizing a long living and transfer suppressed propagation, when solvents of higher polarity are used. An activated carbon‐halide bond is concluded to be the active species.
Untersuchungen zur Synthese und den Eigenschaften von amphiphilen Polymeren
Authors: Behrmann K. , Richter C. , Fanghänel E.
Published: December 2004

Investigations of the Synthesis and Properties of Amphiphilic Polymers

By reaction of propylene/maleic anhydride copolymers with the sodium salt of α‐dodecyl‐ω‐hydroxy‐trioxyethylene ionic polymers with different shares of long aliphatic side chains were prepared. The properties of these amphiphilic polymers were studied. Like micelles they are able to solubilize nonpolar probe molecules (N,N‐dimethyl‐aminoazobenzene). Viscosity measurements show the dependence of the conformation of the polymeric chain in solution on the share of aliphatic side chain and the degree of protonation. The polymers from micelle‐like aggregates. It is supposed that the polymer with a high share of aliphatic side chains froms several local aggregates per polymer chain, while the polymer containing only few side chains seems to form intermolecular aggregates between different polymer chains. These investigations were performed with pyrene as probe molecule. Pyrene was also used to examine the micropolarity of the aggregates. Like polyelectrolytes the amiphilic polymers are able to cause the aggregation of opposite charged dyes (thionine).
Furylvinylhalogenide. IX. Reaktionen von β‐Fur‐2‐yl‐β‐chlor‐α‐cyanacrylsäureestern mit Aminen
Authors: Jähnisch K. , Schwertner R. S. , Seeboth R. H.
Published: December 2004

Furylvinylhalides. IX. Reactions of β‐fur‐2‐yl‐β‐chloro‐α‐cyanoacrylates with amines

β‐Fur‐2‐yl‐β‐chloro‐α‐cyanoacrylates 4 react with amines to yield β‐Fur‐2‐yl‐β‐amino‐α‐cyanoacrylates 5. The 1H‐n.m.r. spectra of 5 are discussed.
Zur Übertragung von Substituenteneffekten in Fluorenen und Fluorenonen
Authors: Hauser A. , Thurner J.‐U. , Hinzmann B.
Published: December 2004

On the Transmission of Substituent Effects in Fluorenes and Fluorenones

A series of 2‐ and 2,7‐substituted fluorenes (1) and fluorenones (2) were prepared either by electrophilic substitution (1c–f, h–j; 2c, d, j), reduction (1, 2k, l) or nucleophilic exchange (1g, m, n; 2m) via respective diazonium compounds as well as by oxydation (2e–h, n) of the hydrocarbons (1).

The carbon‐13 n.m.r. spectra for the fluorene (1a–n) and fluorenone (2a–n) derivatives was analyzed using a dual substituent parameter (DSP) equation. The substituent chemical shifts (SCS) of the carbon atoms 4a, 4b, 7 and 4a, 4b, 7, 9 of eleven fluorenes and nine fluorenones, respectively, correlate with the 𝒻, 𝓇 substituent constants and with σI, σ ones in a satisfactory manner. The comparison indicates that the correlation with the 𝒻, 𝓇 constants yields always a higher resonance contribution than the calculation with σI, σ constants. The DSP analysis reveals that transmission of the substituent effect to the substituted ring is primarily resonance controlled while the transmission to the second ring involves a π‐bond polarization mechanism. For C‐4b in the unsubstituted ring a reversed substituent effect was found. In contrast to fluorenes in fluorenones the transmission of the substituent effect involves the carbon atom 9.
Preparative vis‐laser photochemistry. Qinghaosu‐type 1,2,4‐Trioxanes by molecular oxygen trapping of paterno‐büchi triplet 1,4‐diradicals derived from the bicyclic enol lactones Δ1,6‐ and Δ1,10‐2‐oxabicyclo[4.4.0]decen‐2‐one and p‐benzoquinone
Authors: Adam W. , Kliem Ulrike , Peters Eva‐Maria , Peters K. , von Schnering H.‐G.
Published: December 2004

The VIS‐laser irradiation of enol lactones 1a, b and benzoquinone in an argon atmosphere led to the fenestrane‐type oxetane 2a and the propellane‐type oxetane 2b, with regioselective preference for the acetal structure. Under an oxygen atmosphere both regioisomeric fenestrane‐type 1,2,4‐trioxanes 4a and 5a were obtained from enol lactone 1a, while no oxygen trapping to the propellane‐type trioxanes was observed with 1b. Significant quantities of photooxygenation products were obtained from both enol lactones 1a, b due to singlet oxygen derived from oxygen quenching of benzoquinone triplets. The present study demonstrates that Qinghaosu analoga are accessible via trapping of Paterno‐Büchi triplet 1,4‐diradicals by molecular oxygen.
Untersuchungen zur Reaktion von Pyrazolon‐Azomethin‐Farbstoffen mit 2‐Pyrazolin‐5‐on‐Derivaten
Authors: Kucybala Z. , Gaca J.
Published: December 2004

Investigations on the Reaction of Pyrazolone Azomethine Dyes with 2‐Pyrazolin‐5‐one‐Derivatives

The reaction between pyrazolone azomethine dyes 1 and different 2‐pyrazolin‐5‐ones 2 was investigated. Among the reaction products compounds 5 {3,3′3″‐trimethyl‐1,1′1″‐triphenyl‐[4,4′4″‐tri‐(2‐pyrazolin‐5‐on)]} was isolated, which hitherto was unknown as a product of this reaction. A new reaction pathway is proposed.
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 Dimer

The 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

The 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

A 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 Chlorotetrolate

Reaction 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)‐phenylketones

3‐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

1‐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

An 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‐isothioureas

Four 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

The 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

Ethinylestradiol (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

In 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‐Diketones

Reaction 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

Triplet 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 tetrafluoroborates

The 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

The 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

The 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

This 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

Das (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

The 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

The 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

Recent 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

We 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

An 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.
Note on two‐center Fourier transforms
Authors: Laurenzi Bernard J.
Published: December 2004

A method for the evaluation of the Fourier transform of two‐center functions is presented.
Laplace transform wave functions
Authors: Farmer Christine M.
Published: December 2004

The 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

A 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

π‐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

Several 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

An 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.
Spin‐Projected extended Hartree–Fock equations. II. Odd‐electron systems
Authors: Mayer I.
Published: December 2004

The spin‐projected extended Hartree–Fock equations discussed in Part I for an even number of electrons are given here for the odd‐electron case.
Applications of an optimization technique in submolecular biology
Authors: Sundaram K.
Published: December 2004

Some applications of an optimization technique due to Levenberg in theoretical submolecular biology are described. This technique has proved a very useful tool for the generation of three‐dimensional structures of molecules having cyclic components or other constrained regions. The generated molecular structures provide the starting point for quantum chemical calculations of great value in solving problems of biological interest. The mechanism of transport of alkali metal cations by valinomycin is one such example and this paper describes briefly how various conformations of valinomycin were obtained using the optimization technique. A variant of the same method has been suggested as a new technique for the detection of topographical similarities between apparently dissimilar molecules which are substrates for the same enzyme or receptor site. The technique is illustrated with a comparison of a tricyclic antidepressant with norepinephrine both of which have been postulated to compete for a common receptor site in the “amine pump” of peripheral adrenergic nerve cell membranes. Another area in which the optimization technique has proved useful is in developing an optimum separable localized bond function method designed for rigorous calculations on large saturated molecules. This method is briefly described.