bluuebunny/crossref_metadata_2025_split huggingface dataset:
Die Synthese des ß‐Melanotropins (ß‐MSH) mit der Aminosäurensequenz des bovinen Hormons
Authors: Schwyzer R. , Iselin B. , Kappeler H. , Riniker B. , Rittel W. , Zuber H. 
Published: December 2004

AbstractThe synthesis of an octadecapeptide with the amino‐acid sequence of bovine β‐melanotropin (seryl‐βMSH10) has been accomplished using the same scheme for the protection of amino and carboxyl groups as in the case of α‐melanotropin (αMSH)9), βcorticotropin (ACTH)1)14, and active sequences of β‐corticotropin (e.g. β‐1–24‐corticotropin13) = CIBA 30920‐Ba, Synacthen ®). The compound has been obtained in a very pure state, as shown by thin‐layer chromatography, electro‐phoresis, counter‐current distribution, chromatography on carboxymethyl‐Sephadex ® and amino‐acid analysis. The amino‐acid residues are in the correct (L) configuration, this being ascertained by the methods of synthesis and by enzymic degradation. Synthetic seryl‐βMSH has a distribution coefficient in 2‐butanol/0.5 per cent trichloroacetic acid of 0.56 (1300 transfers) corresponding very closely to that reported for the natural product (same solvents: 0.53; 702 transfers10)) [α] = −57.5° ± 1° (c = 1 in 1 n acetic acid). The product contains 78% peptide, 15.5% water and 6.5% acetic acid (both solvents firmly bound). Its biological activity is 1/10 that of synthetic α‐MSH9).
Chemische Korrelation von Condylocarpin mit Akuammicin
Authors: Schumann D. , Schmid H. 
Published: December 2004

AbstractDurch Erhitzen large sich das aus Tubotaiwin erhältliche Indolenin Condyfolin teilweise in Tubifolin und reversibel in 20‐epi‐Condyfolin um. Tubifolin und Condy‐folin liefern mit Kaliumboranat die selbe Indol VIII, das sich durch Dehydrierung mit Sauerstoff wiederum in Tubifolin und Condyfolin zurückumwandeln lässt. Durch diese Umwandlungen finden die für Condylocarpin und Tubotaiwin aufgestellten Strukturen eine Bestätigung; gleichzeitig ist damit die absolute Konfi‐guration dieser Alkaloide und des Stemmadenins bestimmt. In allen diesen Alka‐loiden besitzt das Zentrum 15 dieselbe absolute Konfiguration. Auf die mögliche Bedeutung des Indols X als Vorläufer für die Biogenese dieser Alkaloide wird hinge‐wiesen.
Organische Phosphorverbindungen VIII. Die direkte Synthese von Alkyl‐ und Aryl‐halogenphosphinen
Authors: Maier Ludwig 
Published: December 2004

AbstractThe reaction of methyl chloride, methyl bromide, methyl iodide, trifluoro‐methyl iodide, ethyl chloride, ethyl bromide, butyl bromide, and phenyl bromide with red phosphorus has been studied under a variety of conditions. In additon, the reaction of white phosphorus with methyl bromide and phenyl bromide is also described. The synthesis and properties of RPX2 (R = CH3, CF3, C2H5, C6H5, C6H5; X = Cl, Br, I) and R2PX (R = CH3, CF3, C6H5; X = Cl, Br) are reported. The reactions of RPX2 and R2PX With sulfur and with dimethylamine are also described.
Die UV‐Spektren des Tropons, des 2,7‐Dimethyl‐4,5‐benztropons und des 2,7‐Dimethyl‐4,5‐naphtotropons
Authors: Weltin E. , Heilbronner E. , Labhart H. 
Published: December 2004

AbstractThe UV, spectra and the polarizationof the individual absorption bands have been measured for tropone, 2,7‐dimethyl‐4, 5‐benzotropone and 2, 7‐dimethyl‐4, 5‐naphtotropone. The positions, relative intensities and polarizations of these bands predicted by a simplified version of the PPP‐method of configuration interaction is in excellent agreement with observation.
Reaktivität von Koordinationsverbindungen IX. Zur Bildung von binuclearen μ‐peroxo‐Kobaltkomplexen
Authors: Bekâroğlu Oezer , Fallab S. 
Published: December 2004

AbstractThe tendency of CoII‐chelates to form binuclear μ‐peroxo‐bridged complexes with O2 has been investigated. The nature of the ligand strongly influences the stability of such complexes. Polyamin chelates obviously fovour the bonding to O2 whereas chelates with aminopolycarboxylic acids do not show any measurable affinity for O2. The solution stability of (Dien)CoO2Co(Dien)4+ has been determined by spectrophotometric methods.
Etudes sur les matières végétales volatiles CLXXXVII. Présence de maaliol et de valéranone dans l'huile essentielle de Spikenard (Nardostachys jatamansi DC.) chinoise
Authors: Naves Yves‐René 
Published: December 2004

AbstractChinese Spikenard oil (from Nardostachys jatamansi DC.) contains, besides sesquiterpenes, maaliol and valeranone (jatamansone).
Die Struktur der 2‐Acylindol‐Alkaloide Vobasin, Dregamin und Tabernaemontanin
Authors: Renner U. , Prins D. A. , Burlingame A. L. , Biemann K. 
Published: December 2004

AbstractA detailed account of the structure determination of the 2‐acylindole alkaloids vobasine (XI11 c), dregamine (XX) and tabernaemontanine (XXI) is presented. The relationship of these compounds to other indole alkaloids is discussed, and brief reference is made to their apparent implication in the formation of voacamine type alkaloids.
α‐Substituierte Dopacetamide als Hemmer der Catechol‐O‐methyl‐transferase und der enzymatischen. Hydroxylierung aromatischer Aminosäuren. In den Catecholamin‐Metabolismus eingreifende Substanzen. 2. Mitteilung
Authors: Carlsson A. , Corrodi H. , Waldeck B. 
Published: December 2004

AbstractA series of α‐substituted 3,4‐dihydroxyphenylacetamides (dopacetamides) was synthesized and screened for catechol‐O‐methyl‐transferase (COMT) inhibiting activity. The α‐propyl‐3,4‐dihydroxyphenylacetamide (H 22/54) was found to be most potent. 4‐Tropolone‐acetamide was also shown to be a potent inhibitor of COMT. The dopacetamides also block the biosynthesis of catecholamines and 5‐hydroxytryplamine, most probably by inhibiting enzymatic hydroxylation of L‐phenylalanine, L‐tyrosine and L‐tryptophan.
Recherches sur les arômes. 7e communication. Analyse de l'arôme des framboises III. Les acides et esters inférieurs
Authors: Palluy E. , Sundt E. , Winter M. 
Published: December 2004

AbstractThe acidic fraction of raspberry oil has been found to contain propionic, n‐ and iso‐butyric, n‐ and iso‐valeric‐, 2‐ and 3‐hexenoic acids, besides formic, acetic, caproic and octanoic acids which have already been reported.
Nachbarǵruppeneffekte bei der Hydrolyse von Acetonyl‐Estern
Authors: Schätzle Elsbeth , Urheim Hans , Thürkauf Max , Rottenberg Max 
Published: December 2004

AbstractKinetic studies revealed that esters of hydroxyacetone undergo alkaline hydrolysis with participation of neighbouring groups, its rate being higher by a factor of at least 20 than could have been anticipated on the basis of inductive effects alone. The mechanism is discussed in terms of either nucleophilic or electrophilic intra‐molecular catalysis.
Neue Umlagerungen von Aryl‐allyl‐äthern und Allylphenolen. (Vorläufige Mitteilung)
Authors: Borgulya J. , Hansen H.‐J. , Barner R. , Schmid H. 
Published: December 2004

AbstractIn position 3 (and 5) substituted phenyl‐γ‐methyl (and phenyl)‐allylethers when subjected to the thermal CLAISEN‐rearrangement not only yield the expected o‐allyl‐phenols but in addition considerable amounts of the P‐allylated phenols. Migration to the para‐position is favoured by non‐polar solvents. This para‐migration of the substituted allylgroup is attributed mainly to steric factors. With sterically hindered, in ortho‐ or para‐position allylated phenols there was furthermore found an allyl‐phenol‐rearrangement: on sufficient heating to 200° these substances are transformed to the thermodynamically more stable para‐ resp. ortho‐allylphenols with inversion of the allyl group.
Verteilung der Radioaktivität in der Ratte nach Verabreichung von [14C]‐d,l‐α‐Tocopheryl‐acetat
Authors: Gloor U. , Weber F. , Würsch J. , Wiss O. 
Published: December 2004

Abstract1. The radioactivity in various organs of rats was determined after peroral administration of 2 and 5 mg of [14C]d,lα‐tocopheryl acetate at intervals of half an hour to 88 days.
Synthese des 17,18‐Diornithin‐β‐corticotropin‐(1–24)‐tetracosapeptides, eines biologisch aktiven Analogons des adrenocorticotropen Hormons
Authors: Tesser G. I. , Schwyzer R. 
Published: December 2004

Abstractβ‐Corticotropin (ACTH) possesses a striking sequence of basic amino‐acids‐Lys‐Lys‐Arg‐Arg‐ (No. 15–18) which is apparently necessary for the corticotropic activity: synthetic N‐terminal peptides containing this sequence are active, those lacking for example the two arginines as in the hexadecapeptide II [2] [3] [4] are essentially inactive. We have synthesized 17,18‐diornithine‐β‐corticotropin‐(1–24)‐tetracosapeptide (III), an analogue of the highly active β‐corticotropin‐(1–24)‐tetracosapeptide (I), in which the arginine residues 17 and 18 are replaced by ornithine. Quite unexpectedly this analogue is as highly potent in vitro (SAFFRAN & SCHALLY) and in vivo (s.c. application, SAYERS test) as the tetracosapeptide with the ‘natural’ sequence. This equal potency holds also for lipotropic and melanotropic activity. We may conclude that the two guanidino groups of the arginines in pos. 17 and 18 are not essential for biological activity, but that they may be replaced by amino groups, as in ornithine. Due to the replacement of the guanidino groups by the more easily protectable amino group, the diornithine analogue III is more readily synthesized than the original diarginine polypeptide I.
Komplexometrische Mikrobestimmung von Schwermettallen mit Kobalt‐60 als radioaktivem Indikator
Authors: Fuchs A. 
Published: December 2004

AbstractNanogrammengen von Kobalt und anderen Schwermetallen können komplexometrisch bestimmt werden mit 60Co als radioaktivem Indikator, indem Kation und Chelat papierelektrophoretisch getrennt werden.
Etudes sur les matières végétales volatiles CXCVIII. Contribution à la connaissance des farnésènes
Authors: Naves Yves‐René 
Published: December 2004

AbstractThe dehydration of farnesols or nerolidols is similar to that of geraniol and nerol or linalool. It yields a mixture of hydrocarbons including trans‐β‐farnesene, two allofarnesenes, α‐curcumene, α‐, β‐ and γ‐bisabolenes, and triterpenes. The triterpenes result from dienisation of β‐farnesenes or α‐farnesenes with β‐farnesenes, or dimerization of allofarnesenes.
Die Reaktion von Isonitrilen und Nitrilen mit Alkali‐ und Erdalkalimetallen
Authors: Büchner W. , Dufaux R. 
Published: December 2004

AbstractIsocyanides RNC and the isomeric nitriles, RCN, reacting with alkali or alkaline earth metals in liquid ammonia undergo reductive fission to metal cyanides and carbanions R−. The latter are ammonolized to the corresponding hydrocarbons.
Die Struktur des Alstonia‐Alkaloides Villalstonin
Authors: Hesse M. , Bodmer F. , Gemenden C. W. , Joshi B. S. , Taylor W. I. , Schmid H. 
Published: December 2004

AbstractEs werden die Experimente beschrieben, die zur Aufstellung der Konstitutionsformel 2 für das «dimere» Indolalkaloid Villalstonin aus Alstonia macrophylla WALL. führten.
Langsame Inversion am pyramidal gebundenen Stickstoff: Isolierung und Epimerisierung diastereomerer N‐Methoxy‐3,3‐di‐methoxycarbonyl‐5‐cyan‐1, 2‐oxazolidine. Vorläufige Mitteilung
Authors: Müller K. , Eschenmoser A. 
Published: December 2004

AbstractTwo crystalline diastereomeric N‐methoxy‐3, 3‐di‐methoxycarbonyl‐5‐cyano‐1, 2‐oxazolidines (II and III) have been isolated. The pyramidal arrangement at the respective nitrogen atoms does not invert at room temperature. The ARRHENIUS activation energy for the epimerization of the thermodynamically less stable isomer to the more stable one in bromoform solution is 29,2 ± 0,5 kcal/Mol (log A = 14,2 ± 0,3).
Kristallstruktur und absolute Konfiguration von (+)‐Meloscin‐Nb‐methobromid
Authors: Oberhänsli W. E. 
Published: December 2004

AbstractThe crystal structure of the Nb‐methobromid of the alcaloid meloscin has been determined by three‐dimensional X‐ray crystallographic methods. The crystals belong to the orthorhombic space group P212121 with four molecules per unit cell. The cell constants are a = 10.01, b = 17.79, c = 11.43 Å. The absolute configuration has been obtained by the use of anomalous dispersion effects.
Revidierte Struktur von Verrucarin E. Eine Synthese des Antibioticums und verwandter β‐Acetyl‐Pyrrol‐Derivate. Verrucarine und Roridine, 18. Mitteilung [1]
Authors: Pfäffli P. , Tamm Ch. 
Published: December 2004

AbstractThe structure of Verrucarin E, an antibiotic isolated from Myrothecium verrucaria, has been corrected (cf. [4]) and shown to be that of 3‐acetyl‐4‐hydroxymethyl‐pyrrole (2) by comparison with a variety of β‐acetylpyrrole‐derivatives, whose NMR. chemical shifts and coupling constants are reported. Verrucarin E (2) has been synthesized in low yield from 3‐acetylpyrrole (12). The following previously unknown β‐acetylpyrrole‐derivatives are described: 3‐acetyl‐5‐methyl‐pyrrole‐2‐carbonic‐acid (11), 4‐acetyl‐2‐methyl‐pyrrole (13), 3‐acetyl‐4‐formyl‐pyrrole (7), 3‐acetyl‐1‐hydroxymethyl‐pyrrole (14), 3‐(3‐hydroxypropionyl)‐pyrrole (15), 3‐(3‐hydroxy‐2‐hydroxymethyl‐propionyl)‐pyrrole (16), and 3‐(3‐acetyl‐pyrr‐1‐yl)‐1‐(pyrr‐3‐yl)‐propan‐1‐one (17).
Gomphogenin‐Teilsynthese und Struktur des Calotropagenins. Glykoside und Aglykone, 319. Mitteilung
Authors: Lardon A. , Stöckel K. , Reichstein T. 
Published: December 2004

AbstractGomphogenin = 2α, 3β, 14β‐trihydroxy‐5α‐card‐20:22‐enolide (6) was synthetised through hydroxylation of uzarigenone (4), followed by reduction with LiAlH[OC(CH3)3]3. Treatment of its di‐O‐acetylderivative (7) with SOCl2 in pyridine gave di‐O‐acetyl‐β‐anhydro‐gomphogenin (3). 3 was identical with the product obtained by WATSON AND WRIGHT from Gomphocarpus fruticosus; this proves that the formulae suggested by COOMBE AND WATSON are correct.From the mixture of about 7 unidentified cardenolides obtained by MITTAL et al. after WOLFF‐KISHNER reduction of ene‐dihydrocalactin we could now isolate and identify dihydrogomphogenin (6), dihydrocoroglaucigenin (11) and dihydro‐uzarigenin‐19‐acidlactone‐(19→3) (13). These results, together with former evidence and spectra, prove the structure of calotropagenin as 2α, 3β, 14β‐trihydroxy‐19‐oxo‐5α‐card‐20:22‐enolide (15) and give support to the formulation of calactin and calotropin as stereoisomers of formula 8, analogous to the formula of gomphoside established by COOMBE AND WATSON.
Bestimmung scheinbarer Aciditätskonstanten von schwachen Säuren in flüssigem Ammoniak durch Titration mit Hilfe von Glaselektroden
Authors: Baumann W. M. , Simon W. 
Published: December 2004

AbstractA titration method for the determination of apparent acidity constants of weak acids in liquid ammonia (−38°C) using glass electrode cell assemblies is described.
Die Glykoside von Calotropis procera, R. BR.. Glykoside und Aglykone, 320. Mitteilung
Authors: Brüschweiler F. , Stöcklin W. , Stöckel K. , Reichstein T. 
Published: December 2004

AbstractFrom the latex of Calotropis procera, HESSE et al. [2] had isolated free calotropagenin (8) and six of its glycosides. We now obtained three additional compounds: uzarigenin (4), syriogenin [10] (a 3 β, 14α, x‐trihydroxy‐card‐(20:22)‐enolide) and proceroside. The latter is a new glycoside containing a sugar moiety identical or stereoisomeric with those present in gomphoside, calactin and calotropin. Its aglycone, not yet known in free form, contains one (probably secondary) hydroxyl group more than calotropagenin and is most probably a 2α, 3β, 14β, x‐tetrahydroxy‐card‐(20:22)‐enolide.
Strahlungschemie von Kohlenwasserstoffen. 17. Mitteilung. Hexan‐NO
Authors: Menger André , Gäumann Tino 
Published: December 2004

AbstractThe influence of NO on the radiolysis of hexane at −70°C has been studied. The results allow the following interpretations: The bimolecular part of the hydrogen production is in contrary to N2O efficiently quenched by NO. This part involves non‐thermal hydrogen atoms and has a G‐value of about 1.4. All olefins are suppressed, probably in a secondary chain reaction with NO. The radical yield is drastically reduced by very low concentrations of NO, but by higher concentrations this decrease is slowed down. A reaction scheme proposed by BURRELL is able to explain these results.
Cardenolid‐korksäurehalbester und weitere Bufadienolid‐korksäurehalbester in Ch' an Su. Über Krötengifte, 36. Mitteilung
Authors: Höriger Niklaus , Živanov Dobrila , Linde Horst H. A. , Meyer Kuno 
Published: December 2004

AbstractFrom the toad venom Ch'an Su the methyl esters of the cardenolide hydrogen suberates 3 and 6 were isolated, as well as a number of new bufadienolide hydrogensuberates. The partial synthesis of some of these compounds is described.
Photochromism in Bianthrone and Related Compounds. Part VI. The structure of the photocromic isomers of bianthrones
Authors: Korenstein R. , Muszkat K. A. , Fischer E. 
Published: December 2004

AbstractThe cyclic structure III is assigned to the C photochromic isomer of 1, 8′‐dimethylbianthrones on the basis of spectral and chemical evidence. Similar considerations indicate that this does not apply to the B photoisomers of bianthrones.
Mesomeric Vinyl Cations. Part III. Stereochemistry of cations derived from 2‐bromo‐1, 3‐dienes
Authors: Grob C. A. , Pfaendler H. R. 
Published: December 2004

AbstractIn contrast to their acyclic analogues, 2‐bromocyclohexa‐1, 3‐diene (11a) and 3‐bromo‐1, 5‐dimethyl‐cyclohexa‐1, 3‐diene (11b) do not react with silver ion, nor do they undergo solvolysis in 80% ethanol at temperatures up to 180°. The inertness to ionization of these cyclic bromodienes is attributed to steric inhibition of mesomerism involving the π electrons of the second double bond in the planar vinyl cation 12 and to the bent structure of this hypothetical intermediate.
Synthèses dans la série des bis‐indéno‐anthracènes, I Le tétraoxo‐5, 10, 15, 16‐tétrahydro‐5, 10, 15, 16‐bis‐indéno [2.1‐a; 2′.1′‐c] anthracène et le dihydro‐5, 16‐bis‐indéno [2.1‐a; 2′.1′‐c] anthracène
Authors: Chardonnens Louis , Schorderet François , Salamin Luc , Sunder‐Plassmann Paul 
Published: December 2004

AbstractStarting from 5‐carboxy‐6‐methyl‐7, 12‐dioxo‐7, 12‐dihydro‐indeno [1.2‐a] fluorene (phthalacone‐carboxylic acid) the first title compound, XI, has been synthesized in 4 steps (overall yield 28%). By anindependent way the corresponding hydrocarbon (second title compound, IV) has been obtained in 3 steps (overall yield 35%) starting from 2, 3′‐bi‐indenyle and 1, 4‐naphthoquinone.
Synthesen von 2‐Pyronen aus α, β‐ungesättigten Säurechloriden und tertiären Aminen
Authors: Rey M. , Dunkelblum E. , Allain R. , Dreiding André S. 
Published: December 2004

AbstractA new synthesis of 2‐pyrones has been developed. Two molecules of α, β‐unsaturated acid chlorides (8, 12 and 18) condense, with loss of two molecules hydrogen chloride, to pairs of substituted 2‐pyrones (9 and 10, 13 and 14, 19 and 20) when treated with triethyl amine in chloroform or methylene chloride at room temperature. In the case of 18, two additional products were obtained, namely the resorcinol derivative 21 and traces of the 1, 3‐cyclobutanedione derivative 22. Under the same conditions the α, β‐unsaturated acid chlorides 8, 15, 18 and 41 were condensed with trichloroacetyl chloride to give 6‐trichloromethyl‐2‐pyrones (42, 43, 44 and 46). These 2‐pyrones are valuable intermediates for the synthesis of 6‐carboxy‐2‐pyrones and 6‐methyl‐2‐pyrones.A methyl group in β‐position of the α, β‐unsaturated acid chloride appears to be essential for the described condensations, for the acid chlorides 16 and 17 did not yield defined products and the acid chloride 40 reacted with trichloroacetyl chloride in a very low yield. It is considered that the described reactions proceed via the 1, 4‐addition of an acid chloride to a vinyl ketene or through the acylation of an intermediate anion by an acyl derivative as outlined in reaction scheme 1. The structures of the 2‐pyrones were confirmed by their spectroscopic properties, summarized in table 3, and by some of their chemical transformations.
Demethylierung des Lysergsäuregerüstes. 73. Mitteilung über Mutterkornalkaloide [1]
Authors: Fehr T. , Stadler P. A. , Hofmann A. 
Published: December 2004

AbstractThe N‐demethylation of the lysergic acid skeleton could be achieved by a new modification of the von Braun reaction. The formed cyanamide was reduced either with zinc in acetic acid or with hydrogen and Raney nickel.
Photochemische Umwandlungen, XXXVII [1]. Synthese von Methylen‐tetracyclo[3.2.0.02,7.04,6]heptan‐Derivaten
Authors: Prinzbach H. , Rivier J. 
Published: December 2004

AbstractSeveral isopropylidene‐, benzylidene‐ and benzhydrylidene‐norbornadiene derivatives (11, 16) have been synthesized. The [2π+2π] cycloadditions leading to the tetracyclic isomers 12 and 17 resp. upon direct photoexcitation proceed practically quantitatively in the case of the trienes 11, much less specifically, however, with 16. Sensitization by acetone or fluorenone allows the isolation of the quadricyclanes 17 in 20–90% yields.
Recherches dans la série des cyclitols, XLI. Synthèses de deux cyclopentane‐pentols
Authors: Wolczunowicz G. , Bors L. , Cocu F. , Posternak Th. 
Published: December 2004

AbstractTwo new cyclopentane‐pentols, namely the 1, 2, 3, 4/5‐ and 1, 2, 3/4, 5‐isomers have been prepared by hydroxylation of the three 3, 4, 5‐trihydroxy‐1‐cyclopentenes. The stereoselectivity of some hydroxylating agents is discussed.
The Interaction of Nonbonding Orbitals in Carbonyls
Authors: Swenson Jerrald R. , Hoffmann Roald 
Published: December 2004

AbstractIn dicarbonylen wie Glyoxal oder Benzochinon bilden die nichtbindenden Sauerstofforbitale delokalisierte Molekelorbitale mit verschiedenen Energien. Wir berichten über EHT‐ und CNDO/2‐Berechnungen einiger Dione und Trione. Die berechnete Aufspaltung zwischen den «nichtbindenden» Kombinationen wird auf der Grundlage der «through‐space» und «through‐bond» Wechselwirkung analysiert. Bei den tiefliegenden nichtbindenden Orbitalen der Carbonylgruppen scheint der zweite Faktor zu dominieren. Gerüst‐σ‐Orbitale und nichtbindende Sauerstofforbitale sind stark miteinander gemischt.
Vibrations de valence CH/CD fondamentales et harmoniques de dérivés halogénés du méthane et du deutériométhane
Authors: Avanessoff M. , Thang Ho Dac , Gäumann T. 
Published: December 2004

AbstractThe fundamentals and overtones of the CH stretching vibrations of a number of halogenated methanes and deuteriomethanes are compared with a hypothetical model consisting of isolated groups. The anharmonicity constants are evaluated and lie between −20 cm−1 and −130 cm−1 for the CH and CD stretching vibrations. The value of the anharmonicity constant for a coupling between two different modes of vibration is always greater (in absolute numbers) than its value for an overtone of one frequency. The constant is larger for a symmetric mode than for an asymmetric mode in the case of a CH vibration; the contrary is true for a CD bond. Complex interactions between different vibrations often strongly modify the spectra of the overtones. It is shown, however, that the conception of an isolated group is helpful for evaluating the spectra of these substances.
The Structure of 2,5‐Semiquinones derived from 1,6‐Bridged [10] Annulenes
Authors: Gerson F. , Müllen K. , Vogel E. 
Published: December 2004

AbstractESR. spectra are reported for the radical anions of the diketones I and II (see below), recently prepared from 1, 6‐methano[10]annulene and its 11, 11‐difluoro‐derivative, respectively [1]. The π‐spin populations of I⊖ and II⊖ are shown to be incompatible with the structure A an enedione‐norcaradiene. Although the alternative structure B of a [10]annulenequinone is acceptable for both I⊖ and II⊖, the ESR. data is more satisfactorily rationalized in terms of a structure ‘intermediate’ to A and B. This is particularly true for the radical anion I⊖, for which the π‐spin populations suggest a structural ‘shift’ B → A relative to II⊖. Structures A and B were postulated [1] for the neutral diketones I and II, respectively.