bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Existence of Helical Chirality in a Sterically Congested Naphtho [9]annulenone Preliminary Communication
Authors: Anastassiou Apostolos G. , Hasan Misbahul 
Published: December 2004

AbstractThe existence of the naphtho [9]annulenone 1 in two skeletally enantiomeric forms is demonstrated with the use of 1HNMR. spectroscopy in conjunction with a chiral «shift» reagent.
Alkylative amination of non‐enolizable aldehydes with alkyl (dialkyl‐amino)titanium derivatives Preliminary Communication
Authors: Seebach Dieter , Schiess Martin 
Published: December 2004

AbstractThe readily available tris (diethylamino)methyltitanium and related compounds (see 1 in Scheme 2) react with non‐enolizable aldehydes to give tertiary amines 2; these amines result from direct replacement of the carbonyl O‐atom by an alkyl and an amino group (Scheme 3). A tentative mechanism is proposed, according to which the amino group is transferred to the carbonyl C‐atom prior to the alkyl group (Scheme 4).
nucleophilic addition to C,C‐double bonds. VII. Study of proximity effects in olefinic alcohols and amines by photoelectron spectroscopy
Authors: Tombo Gerardo M. Ramos , Ammann Hans Jakob , Müller Klaus , Ganter Camille 
Published: December 2004

The influence of steric compression on electronic structure in polycyclic olefinic alcohols and amines is studied by PE. spectroscopy.The unsubstituted alcohol 2 and amine 7 show PE.‐spectroscopic properties that can be reconciled by postulating a predominance of intramolecularly H‐bonded species in the gas phase.For the alkylated derivatives 5 and 9, in which H‐bonding is precluded, distinct, but only moderate lone‐pair double‐bond interactions are observed.
Zur Synthese sulfonierter Derivate von 2‐Fluoranilin
Authors: Courtin Alfred 
Published: December 2004

Syntheses of Sulfonated Derivatives of 2‐FluoroanilineSynthesis of 4‐amino‐3‐fluorobenzenesulfonic acid (3) was achieved in two ways: reaction of 2‐fluoroaniline (1) with amidosulfonic acid and by first conventionally converting 4‐nitro‐3‐fluoroaniline (8) to 4‐nitro‐3‐fluorobenzenesulfonyl chloride (9) followed subsequently by hydrolysis to 3‐fluoro‐4‐nitrobenzenesulfonic acid (10) and reduction. Hydrogenolysis of 3 gave sulfanilic acid (7). Both, sulfonation of fluorobenzene (6) to 4‐fluorobenzenesulfonic acid (11) followed by nitration and sulfonation of 1‐fluoro‐2‐nitrobenzene (12) led to 4‐fluoro‐3‐nitrobenzenesulfonic acid (13). Reduction of 13 gave the isomeric 3‐amino‐4‐fluorobenzenesulfonic acid (4), which was also obtained both by sulfonation of 1 and by sulfonation of o‐fluoroacetanilide (14) followed by hydrolysis. Selective hydrogenolyses of 2‐amino‐5‐bromo‐3‐fluorobenzenesulfonic acid (15), prepared by reaction of 4‐bromo‐2‐fluoroaniline (16) with amidosulfonic acid, and of 4‐amino‐2‐bromo‐5‐fluorobenzenesulfonic acid (20), obtained by sulfonation of 5‐bromo‐2‐fluoroaniline (19) yielded the isomers 2‐amino‐3‐fluorobenzenesulfonic acid (5) and 3, respectively. The fourth isomer, 3‐amino‐2‐fluorobenzenesulfonic acid (2), was synthesized by sulfur dioxide treatment of the diazonium chloride derived from 2‐fluoro‐3‐nitroaniline (21) to 2‐fluoro‐3‐nitrobenzenesulfonyl chloride (22), followed by hydrolysis to 2‐fluoro‐3‐nitrobenzenesulfonic acid (23) and final Béchamp‐reduction.
Die Synthese von 2,3,4,5‐1H‐Tetrahydroimidazo[2,1‐b]chinazolin‐2,5‐dionen und analogen 2,3,4,5‐1H‐Tetrahydroimidazo[1,2‐a]thieno[2,3‐d] (bzw. [3,2‐d])‐pyrimidin‐2,5‐dionen
Authors: Kienzle Frank , Kaiser Ado , Minder Rudolf E. 
Published: December 2004

The Synthesis of 2,3,4,5‐1H‐Tetrahydroimidazo[2,1‐b]quinazolin‐2,5‐diones and analogous 2,3,4,5‐1H‐Tetrahydroimidazo[1,2‐a]thieno[2,3‐d] (or [3,2‐d])‐pyrimidin‐2,5‐dionesThe syntheses of various imidazo [2, 1‐b]quinazolinediones and their thiophene analogs are described.
13C‐NMR.‐Substituenteninkremente der N3‐Gruppe in Azido‐1,4‐benzochinonen
Authors: Neidlein Richard , Kramer Walter , Leidholdt Rolf 
Published: December 2004

13C‐NMR. Substituent Increments of the Azido‐group in 1,4‐BenzoquinonesThe empirical substituent increments of the azido‐group in 1,4‐benzoquinones have been derived from the 13C‐NMR. chemical shifts of 2‐azido‐5‐chloro‐1,4‐benzoquinone. The validity of the obtained values was tested by comparison of the empirical and computed 13C‐NMR. chemical shifts of other azido‐chloro‐1,4‐benzoquinones.
Synthèse de spirohydantoines dérivées du diphényl‐2,4‐aza‐3‐bicyclo‐[3.3.1]nonane et du diphényl‐7,9‐aza‐8‐bicyclo[4.3.1]decane par réaction de Bucherer dans la N,N‐diméthylformamide: Influence de la température et cours stéréochimique. Communication préliminaire
Authors: Martínez Ernesto , del Campo Carmen , Trigo Gregorio G. 
Published: December 2004

Synthesis of Spyrohydantoines Derivatives of 2,4‐Diphenyl‐3‐azabicyclo[3.3.1]nonane and 7,9‐Diphenyl‐8‐azabicyclo[4.3.1]decane via Bucherer Reaction in N,N‐Dimethylformamide: Influence of the Temperature and Stereochemical PathThe unreactives ketones related to 2,4‐diphenyl‐3‐azabicyclo [3.3.1]nonan‐9‐one to the Bucherer reaction in usuals conditions show excellent reactivity in DMF. as unique solvant. The stereochemical paths of these reactions and the synthetic utility of the temperature modification are described.
Photochromisme des spiropyrannes. Photodégradation d'aza‐, oxaza‐ et thiaza‐cyclopentane‐ et ‐cyclohexanespiropyrannes
Authors: Gaude Didier , Gautron René , Maguet Michel , Guglielmetti Robert 
Published: December 2004

Photochromism of spiropyrans. Photodegradation of aza‐, oxaza‐, and thiaza‐cyclopentane‐ and ‐cyclohexanespiropyransStudy of the photodegradation of saturated azaheterocyclic spiropyrans showed that electron‐donor substituents improve, as in the benzoheterocyclic series, the fatigue properties towards. UV. light. The introduction of oxygen or sulfur in the 5‐ or 6‐membered saturated azacycles or the substitution with an orthofused aromatic nucleus have practically no influence on the results of photodegradation. The indolinospiropyrans allow the greatest number of photochromic cycles before falling to half the initial absorbance on photolysis under accurate conditions.
Über die Dicyanierung der 1,4‐Diaminoanthrachinone und die Reaktivität der 1,4‐Diamino‐9,10‐dihydroanthracen‐2,3‐dicarbonitrile gegenüber nucleophilen Reagenzien 3. Mitteilung über Arylierungen und Heterocyclisierungen von Anthrachinonsystemen
Authors: Adam Jean‐Marie , Winkler Tammo 
Published: December 2004

The Dicyanation of 1,4‐Diaminoanthraquinones and the Reactivity of 1,4‐Diamino‐9,10‐dioxo‐9,10‐dihydroanthracene‐2,3‐dicarbonitriles towards Nucleophilic ReagentsThe reaction of 1‐amino‐9, 10‐dioxo‐4‐phenylamino‐9,10‐dihydroanthracene‐2‐sulfonic acid (1, RC6H5) with cyanide in water yields a mixture of 1‐amino‐9,10‐dioxo‐4‐phenylamino‐9,10‐dihydroanthracene‐2‐carbonitrile (3, R  C6H5) and 1‐amino‐4‐(phenylamino)anthraquinone (4, R  C6H5) under the usual reaction conditions (Scheme 1). In dimethylsulfoxide, however, a second cyano group is introduced, and 1‐amino‐9,10‐dioxo‐4‐phenylamino‐9,10‐dihydroanthracene‐2,3‐dicarbonitrile (7) is formed (Scheme 2). The cyano groups are very reactive towards nucleophiles. The cyano group in 2‐position can be substituted by hydroxide and aliphatic amines (Schemes 5 and 6). The cyano group in 3‐position can be eliminated by aliphatic amines and hydrazine (Scheme 7). Nucleophilic attack at the cyano C‐atom of the 2‐cyano group by suitable reagents leads to ring formation, yielding e.g. 2‐(Δ2‐1, 3‐oxazolin‐2‐yl)‐, 2‐(benz[d]imidazol‐2‐yl)‐ and 2‐(1H‐tetrazol‐5‐yl)anthraquinones (Schemes 8 and 10).
Das Carotinoidspektrum der Hagebutten von Rosa pomifera: Nachweis von (5Z)‐Neurosporin; Synthese von (3R, 15Z)‐Rubixanthin
Authors: Märki‐Fischer Edith , Marti Urs , Buchecker Richard , Eugster Conrad Hans 
Published: December 2004

Carotenoids from Hips of Rosa pomifera: Discovery of (5Z)‐Neurosporene; Synthesis of (3R, 15Z)‐RubixanthinExtensive chromatographic separations of the mixture of carotenoids from ripe hips of R. pomifera have led to the identification of 43 individual compounds, namely (Scheme 2): (15 Z)‐phytoene (1), (15 Z)‐phytofluene (2), all‐(E)‐phytofluene (2a), ξ‐carotene (3), two mono‐(Z)‐ξ‐carotenes (3a and 3b), (6 R)‐ϵ, ψ‐carotene (4), a mono‐(Z)‐ϵ, ψ‐carotene (4a), β, ψ‐carotene (5), a mono‐(Z)‐β, ψ‐carotene (5a), neurosporene (6), (5 Z)‐neurosporene (6a), a mono‐(Z)‐neurosporene (6b), lycopene (7), five (Z)‐lycopenes (7a–7e), β, β‐carotene (8), two mono‐(Z)‐β, β‐carotenes (probably (9 Z)‐β, β‐carotene (8a) and (13 Z)‐β, β‐carotene (8b)), β‐cryptoxanthin (9), three (Z)‐β‐cryptoxanthins (9a–9c), rubixanthin (10), (5′ Z)‐rubixanthin (=gazaniaxanthin; 10a), (9′ Z)‐rubixanthin (10b), (13′ Z)‐ and (13 Z)‐rubixanthin (10c and 10d, resp.), (5′ Z, 13′ Z)‐ or (5′ Z, 13 Z)‐rubixanthin (10e), lutein (11), zeaxanthin (12), (13 Z)‐zeaxanthin (12b), a mono‐(Z)‐zeaxanthin (probably (9 Z)‐zeaxanthin (12a)), (8 R)‐mutatoxanthin (13), (8 S)‐mutatoxanthin (14), neoxanthin (15), (8′ R)‐neochrome (16), (8′ S)‐neochrome (17), a tetrahydroxycarotenoid (18?), a tetrahydroxy‐epoxy‐carotenoid (19?), and a trihydroxycarotenoid of unknown structure.Rubixanthin (10) and (5′ Z)‐rubixanthin (10a) can easily be distinguished by HPLC. separation and CD. spectra at low temperature. The synthesis of (3 R, 15 Z)‐rubixanthin (29) is described.The isolation of (5 Z)‐neurosporene (6a) supports the hypothesis that the ϵ‐end group arises by enzymatic cyclization of precursors having a (5 Z)‐ or (5′ Z)‐configuration.
Synthesis and X‐Ray Analysis of a Nickel Triphenyl‐Cyclopropenyl Complex. A mo‐interpretation of the geometry and bonding in the (C3H3)ML3‐type of complexes
Authors: Mealli Carlo , Midollini Stefano , Moneti Simonetta , Albright Thomas A. 
Published: December 2004

AbstractThe reaction of [(C3Ph3)Ni(PPh3)2]ClO4 with P(CH2CH2PPh2)3(pp3) and NaBPh4 yields the [(C3Ph3)Ni(pp3)]BPh4‐complex. After long exposure of the solution of this compound in acetone/butanol to the air a new derivative [(C3Ph3)‐Ni(pp2po)]BPh4· 0.5 C4H9OH, where pp2po is (Ph2PCH2CH2)2P(CH2 CH2POPh2), is obtained. Complete X‐ray analysis has been carried out for the latter complex: a=18.303 (5); b=29.445 (6), c=13.305 (5) Å, β=112.70 (9)°; space group monoclinic, P21/a, Z=4. Disorder problems were encountered in the refinement of the structure. The best R is 0.093. One of the arms of the parent pp3‐molecule, not coordinated to the metal, undergoes oxidation. The Ni‐atom, coordinated by the three remaining P‐atoms of the ligand, is also linked in a roughly η3‐mode to the cyclopropenium ligand. The geometry of the molecule is examined in detail. Extended HMO‐calculations were performed to interpret how the variation of PNiP angles affects the bonding between the NiP3‐ and C3H3‐fragments. The conclusion is that the overall energy of the complex may be lowered in spite of a weakening of the Ni‐cyclopropenium linkage. Extensions are made to other systems containing a linkage between a metal and a X3‐ring (X=P,As).
Synthesen des Analgetikums 2‐[1‐(m‐Methoxyphenyl)‐2‐cyclohexen‐1‐yl]‐N,N ‐dimethyl‐äthylamin
Authors: Bruderer Hans , Bernauer Karl 
Published: December 2004

Syntheses of the Analgesic 2‐[1‐(m‐Methoxyphenyl)‐2‐cyclohexen‐1‐yl] ‐N,N‐dimethyl‐ethylamineThree principal routes to 2‐[1‐(m‐methoxyphenyl)‐2‐cyclohexen‐1‐yl]‐ N,N‐dimethyl‐ethylamine (13), a compound with interesting analgesic properties, are described. In the first, derivatives of [1‐(m‐methoxyphenyl)‐2‐cyclohexen‐1‐yl]acetic acid (10) (alternatively the ethyl ester 29, the dimethylamide 32 or the nitrile 34) serve as crucial intermediates. All three can be synthesized from 2‐(m‐methoxyphenyl)cyclohexanone (1) by sequences comprising successively C‐alkylation (1→2,4,5; Scheme 1), reduction of the ketone carbonyl group (2→6;4→18;5→19; Scheme 1 and 2) and elimination (16→29; 18→32; 19→34; Scheme 2). The relative configuration of the cyclohexanols 16, 18, 19 and of a series of related compounds is established by chemical correlation with the lactone 30 the structure of which follows from 1H‐NMR. data (Scheme 2). The second route creates the intermediates 29 and 32 by ester‐ or amide‐enolate‐Claisen‐type‐rearrangement reactions starting from 3‐(m‐methoxyphenyl)‐2‐cyclohexen‐1‐ol (39; Scheme 3). Compounds 29, 32 and 34 are transformed into the target molecule 13 by standard reactions. A Hofmann elimination of the quaternary ammonium fluoride 50 (X=F), derived from the known cis‐perhydroindoline 48, is the essential step in the third approach to 13 (Scheme 4).
Polarographische Untersuchungen an symmetrischen Triazacarbocyaninen in Methanol
Authors: Hellrung Bruno 
Published: December 2004

Polarographic Investigations on Symmetrical Triazacarbocyanine Dyes in MethanolThe reduction mechanism of eleven symmetrical triazacarbocyanine dyes with different heterocycles in methanol (containing lithium chloride or lithium acetate/acetic acid) has been investigated by means of polarography, cyclic oscillopolarography and coulometry.The reduction occurs in a reversible to irreversible two electron transfer step, followed by an irreversible chemical step. Reduction potentials, transfer coefficients and specific currents have been measured and compared with properties measured in acetonitrile.The effect of substituents X has been studied on the compounds 1‐ethyl‐2‐[3‐(1‐ethyl‐6‐X‐1,2‐dihydroquinolin‐2‐ylidene)‐1‐triazeno]‐6‐X‐quinolinium tetrafluoroborate 1f(X) and 3‐ethyl‐2‐[3‐(3‐ethyl‐5‐X‐Δ4‐1, 3‐thiazolin‐2‐ylidene)‐1‐triazeno]‐5‐X‐1, 3‐thiazolium tetrafluoroborate 1g(X), and ρ‐values of 0.20 and 0.40 V, respectively, have been found.
Synthesis of 2‐Oxo‐2H‐[1,2,4]oxadiazolo‐[2,3‐c]pyrimidine‐5‐carbamates
Authors: Hengartner Urs , Muller Jean‐Claude , Ramuz Henri 
Published: December 2004

AbstractThermal cyclization of the pyrimidine‐N‐oxide dicarbamate 2 gives a 95:5 mixture of the 2‐oxo‐2H‐[1,2,4]oxadiazolo[2,3‐a]‐ and [2,3‐c]pyrimidinecarbamates 3 and 4. An efficient procedure for the conversion of 3 to 4, and vice versa, is described.
Synthesis of (5R)‐ and (5S)‐5‐Methyl‐5, 6‐dihydrouridine Derivatives
Authors: Škarić Vinko , Matulić‐Adamić Jasenka 
Published: December 2004

AbstractThe hydrogenation of 2′, 3′‐O‐isopropylidene‐5‐methyluridine (1) in water over 5% Rh/Al2O3 gave (5 R)‐ and (5 S)‐5‐methyl‐5, 6‐dihydrouridine (2), separated as 5′‐O‐(p‐tolylsulfonyl)‐ (3) and 5′‐O‐benzoyl‐ (5) derivatives by preparative TLC. on silica gel and ether/hexane developments. The diastereoisomeric differentiation at the C(5) chiral centre depends upon the reaction media and the nature of the protecting group attached to the ribosyl moiety.The synthesis of iodo derivatives (5 R)‐ and (5 S)‐4 is also described. The diastereoisomers 4 were converted into (5 R)‐ and (5 S)‐2′, 3′,‐O‐isopropylidene‐5‐methyl‐2, 5′‐anhydro‐5, 6‐dihydrouridine (7).
Structural Detail and Thermal Bond Relocation of a Sterically Strained Cyclononatetraene Preliminary Communication
Authors: Anastassiou Apostolos G. , Kasmai Hamid S. , Sabahi Mahmood 
Published: December 2004

AbstractThe X‐ray crystallographic molecular dimensions and thermal response of the 5, 13‐diphenyl‐cyclonoa [b]naphthalene 1a, are described.
Singlet Oxygen and Superoxide: Experimental Differentiation and Analysis
Authors: Maurette Marie‐Thérèse , Oliveros Esther , Infelta Pierre P. , Ramsteiner Klaus , Braun André M. 
Published: December 2004

AbstractSuperoxide produced by either pulse radiolysis or from KO2 undergoes no reaction with furfuryl alcohol competitive to the corresponding endo‐peroxide formation with singlet oxygen. Thus, furfuryl alcohol can be used as a specific chemical quencher of singlet oxygen.Superoxide can be quantitatively analyzed by its electron transfer reaction with 1, 4‐benzoquinone.The differentiation of the two activated species of oxygen has been realized in microemulsions. Singlet oxygen is known to penetrate the interfaces of surfactant aggregates and may be analyzed in the hydrophobic core by known methods. Charged surfaces on such aggregates, specially those formed by anionic surfactants, prevent the passage of superoxide and restrict its presence and the need for analysis to the bulk aqueous phase.Hydrated electrons may penetrate the interface depending on the dose per pulse applied. 2, 5‐Di (t‐butyl)‐1, 4‐benzoquinone has been taken as an acceptor for electron transfer reactions within the hydrophobic core.
Optisch aktive C5‐Bausteine zur Synthese von natürlich vorkommenden Terpenen
Authors: Dumont Raymond , Pfander Hanspeter 
Published: December 2004

Optically Active C5‐Synthons for the Synthesis of Naturally Occurring TerpenesThe optically active synthons (S)‐22, (R)‐23, (R)‐25 and (R)‐26 were prepared from L‐serine. Furthermore the tertiary alcohol 6 was synthesized from L‐serine (→(S)‐6) and D‐mannitol (→(R)‐6). These compounds are suitable for the synthesis of optically active natural products.
Nitrocyclopropyl‐Anion: A Triplet Ground State Molecule??
Authors: Wagner Hans‐Ulrich , Boche Gernot 
Published: December 2004

AbstractSTO‐3G calculations show that the nitrocyclopropyl anion prefers a triplet ground state with a tetrahedral C(α)‐atom and a perpendicular orientation of the three‐membered ring and the NO2‐group, 1–90° (Table 1). This unusual result is in agreement with recent experimental findings of Kai et al. (Helv. Chim. Acta 65, 137 (1982)). Other NO2‐anions as well as all CHO‐, COOH‐ and CN‐substituted anions 2–12, have singlet ground states 2–0°–12–0° (Table 1), in agreement with copious experimental data (Wagner & Boche, Z. Naturforsch. 37b, 1339 (1982)).
The Carbon Zip Reaction: A Method for Expanding Carbocycles
Authors: Nakashita Yoshihiko , Hesse Manfred 
Published: December 2004

AbstractA general method for enlargement of carbocyclic rings by the so called zip reaction is given. The Michael adducts of 2‐nitrocycloalkanones with 3‐oxo‐4‐pentenoates in the presence of tetrabutylammonium fluoride give in high yield compounds with the ring enlarged by four C‐atoms. By this method 7‐, 8‐, and 12‐membered cycloalkanones were converted respectively to 11‐, 12‐, and 16‐membered functionalized carbocycles (see Scheme 2 and 3).
Absolute Konfiguration von Loroxanthin (=(3R, 3′R, 6′R)‐β, ϵ‐Carotin‐3, 19, 3′‐triol)
Authors: Märki‐Fischer Edith , Bütikofer Pierre‐André , Buchecker Richard , Eugster Conrad Hans 
Published: December 2004

Absolute Configuration of Loroxanthin (=(3R, 3′R, 6′R)‐β, ϵ‐Carotene‐3, 19, 3′‐triol)‘Loroxanthin’, isolated from Chlorella vulgaris, was separated by HPLC. methods in two major isomers, a mono‐cis‐loroxanthin and the all‐trans‐form. Solutions of the pure isomers easily set up again a mixture of the cis/trans‐isomers. Extensive 1H‐NMR. spectral measurements at 400 MHz allowed to establish the 3′, 6′‐trans‐configuration at the ϵ‐end group in both isomers and the (9E)‐configuration in the mono‐cis‐isomer. The absolute configurations at C(3) and C(6′) were deduced from CD. correlations with synthetic (9Z, 3R, 6′R)‐β, ϵ‐carotene‐3, 19‐diol (5) and (9E, 3R, 6′R)‐β, ϵ‐carotene‐3, 19‐diol (6), respectively. Thus, all‐trans‐loroxanthin (3) is (9Z, 3R, 3′R, 6′R)‐β, ϵ‐carotene‐3, 19, 3′‐triol and its predominant mono‐cis‐isomer is (9E, 3R, 3′R, 6′R)‐β, ϵ‐carotene‐3, 19, 3′‐triol (4). Cooccurrence in the same organism and identical chirality at all centers suggest that loroxanthin is biosynthesized from lutein (2).
The Radical Anions of Some Benzo‐Derivatives of Dehydrocyclooctatetraenes
Authors: Gerson Fabian , Heckendorn René , Wong Henry N. C. 
Published: December 2004

AbstractThe radical anions of 5,6‐didehydrobenzocyclooctene (3), 5,6,9,10‐tetradehydrobenzocyclooctene (4) and 1,4,7,10‐tetramethyl‐5,6‐didehydrodibenzo[a, e]‐cyclooctene (6) were prepared in situ from dibromo‐precursors and have been characterized by ESR and ENDOR spectroscopy.
The Photochemical Behaviour of 5,5‐Dimethyl‐2(5H)‐furanone
Authors: Anklam Elke , Margaretha Paul 
Published: December 2004

AbstractThe photochemical behaviour of the title compound 2c was investigated in various solvents. In benzene and t‐butanol photodimerization affords the cis‐anti‐cis HH‐ and HT‐dimers (H = head, T = tail). In acetonitrile, cyclohexane and 2‐propanol, photoreduction competes with photodimerization. The photoreduction products are hydrodimers, solvent adducts and the saturated lactone (the 2H‐reduction product). In acetonitrile and cyclohexane H‐abstraction by the β‐C‐atom of the CC bond is the predominant reduction process. In 2‐propanol, solvent adducts to the α‐ and β‐C‐atoms are formed in equal amounts. In xanthone‐sensitized irradiations the ratio of HH‐ to HT‐dimer is the same as on direct irradiation and the relative rates of conversion of 2c to products in different solvents are also similar under both conditions.
Electronic Absorption Spectra of Planar, Conjugated Biradicals in the Lowest Triplet State
Authors: Gisin Markus , Wirz Jakob 
Published: December 2004

AbstractThe semiempirical PPP‐SCF‐SCI method has been adapted to even‐electron, open‐shell π‐systems by performing the SCF calculation on the lowest triplet configuration and choosing a limited set of single electronic excitations from the latter for configuration interaction. The basic approximations and parameters of the standard PPP model were retained. The results were compared with experimental triplet‐triplet absorption spectra of aromatic hydrocarbons and with more elaborate calculations available for selected systems. The reliability of the model was found to be comparable to its well‐known performance in predicting the absorption spectra of closed‐shell π‐systems and of conjugated radicals. Triplet‐state absorption spectra for various planar, conjugated biradicals were calculated and, where possible, compared with experimental data.
The Distortion of Electrically Conducting, Thermodynamically Stable Microphases by an Electric Field
Authors: Eicke Hans‐Friedrich 
Published: December 2004

AbstractO'Konski's considerations regarding the distortion of spherical droplets by electric fields in binary two‐phase systems has been extended to three‐component water/surfactant/oil systems with so‐called ultra‐low interfacial tensions, i.e. spherically aqueous microphases. It is shown that the deformation is almost negligible for fields up to about 5 105 Vm−1 such as those applied in electro‐optical Kerr‐effect measurements with microemulsions if only perturbations of the mean orientation of the surfactants in the interface are considered.
Zur Stabilität der Metallkomplexe von Methantriessigsäure und cis, cis‐1,3,5‐Cyclohexantricarbonsäure
Authors: Wu Yi‐He , Kaden Thomas A. 
Published: December 2004

The stabilities of the Mn2+‐, Co2+‐, Ni2+‐, Cu2+‐ and Zn2+‐complexes with 2‐(carboxymethyl)glutaric acid (2) and cis,cis‐1,3,5‐cyclohexanetricarboxylic acid (3) were measured potentiometrically at 25° and I = 0.5 (KNO3). Beside the complexes ML− protonated species MLH and MLH are also formed. Their stability constants are given in Table 1. A comparison between the stabilities of 2 or 3 and those of acetate, as a model for a monocarboxylate, or succinate and glutarate, as examples for dicarboxylates, indicates that in all species only one carboxylate is strongly bound whereas the second and third ones are probably not.The observation that Δlog K1 = log K − log K as well as Δlog K2 = log K − log K are practically constants with values of 0.34 ± 0.05 and 0.49 ± 0.07, respectively, for both ligands and the five metal ions studied is also in line with the proposed monodentate structures of the complexes ML−, MLH and MLH.