Etude théorique et possibilités d'application de la méthode de «variations continues» [1] aux complexes très dissociés

A theoretical study of the possibilities of applicability to very unstable complexes of the «continuous variation» principle shows that the general equation of a theoretical Job's curve can be reduced, for limiting values of x and 1 ? x (x being the ligand's mole fraction), to expressions permitting the determination of the number «m» of the central groupes, the number «n» of the ligands, and the stability constants of highly dissociated complexes. Theoretical and practical limitations are discussed.     

Die Komplexe der Hexamine «penten» und «ptetraen» Thermodynamik ihrer Bildung in wässeriger Lösung

The two hexamines (H₂N? CH₂? CH_{2? )2}N? (CH_2)n? N(? CH₂? CH₂? NH₂₎₂, «penten» (n = 2) and «ptetraen» (n=3) have been investigated as chelating agents for COIII (preparative Study) and some of the divalent metal ions (potentiometric and calorimetric studies). Both amines function as sexadentate ligands for Co^III, Co^II and Ni^II, but one of the terminal aminogroups is much easier detached from the metal in case of M (penten)^v+ than in case of M(ptetraen)^v+, thus revealing more strain in the fivemembered chelate rings of the girdle plane of the «penten» complexes. On the other hand, the sixmembered chelate ring in M(ptetraen)^v+ is more strained than the five-membered ring comprising the tertiary nitrogen atoms of M(penten)^v+ Cu^II and Zn^II coordinate with both ligands only 5 of the 6 basic nitrogen atoms present. Both hexaamines function as sexadentates again with Mn^II, but the metal is coordinated with a molecule of water in addition to the 6 nitrogen atoms in the «penten» complex in contrast to the «ptetraen» complex. The thermodynamic functions for the protonation of the hexamines and for the addition of metal ions in aqueous solution are understood in almost every detail. The dielectric shielding of the charges of the reactants exerted by the solvent has to be taken into account; it is reduced by electrostriction as well as by an increase in temperature. It is shown that the approach of charges of equal sign often is an exothermic process.     

‘Non-Koopmans’ States in Stilbene Cations and a Remarkable Example to the «SDT-Equation»: Indeno [2,1-a]indene

The radical cations of indeno [2, 1-a]indene ( 1 ), stilbene ( 2 ) and 3, 5, 3', 5'-tetramethylstilbene ( 3 ) were prepared by γ-irradiation of the neutral precursors in an electron-scavenging matrix at 77 K . Their electronic spectra were recorded and compared to the photoelectron spectra ( PE .) of the neutral precursors. The results show that either the fourth or the fifth excited doublet state of the cations is of «Non-Koopmans» type, with specific doublet energy (D) D (²B_g)=2.74 eV ( 1 ⁺), =2.59 eV ( 2 ⁺), =2.49 eV ( 3 ⁺). Remarkably, 1 ⁺ possesses two electronic states in the 2.7-2.8 eV energy range: ²A_u («Koopmans»-type) and ²B_g («Non -Koopmans»-type). The «SDT»-equation \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm D} = \sqrt {{\rm S} \cdot {\rm T}} $\end{document} approximately connecting excited singlet (S) and triplet (T) states of a neutral alternant system with the excited doublet (D) states of its radical cation - provided e-promotion occurs For all three excited states between the same (paired) orbitals-is satisfyingly exemplified by 1 : S¹ = 3.92 eV and T¹= 2.06 eV for 1 , D^{4 or 5}=2.74 eV for 1 ⁺.     

Die nucleofuge Aktivität von Substituenten am Brückenkopf von Bicyclo[2.2.2]octan und Chinuclidin Das kOTs/kBr-Verhältnis als mechanistisches Kriterium. Fragmentierungsreaktionen, 24. Mitteilung

The rate ratios k_OTs/k_Br of the bridgehead tosylate and bromide of bicyclo [2.2.2]-octane and quinuclidine, respectively, have been determined in 80 vol.-% ethanol. The high ratio for the bicyclo [2.2.2] octane derivatives (3,3 · 10³ at 25°) indicates a highly ionic transition state. Since nucleophilic assistance to ionisation by solvent is precluded in this system a ratio of 10³ or greater is typical for the «limiting» S_N1 mechanism. Lower k_OTs/k_Br ratios therefore reflect increasing nucleophilic participation in the transition state of substitution and elimination reactions. The high k_OTs/k_Br ratio for 4-substituted quinuclidines, namely 1,6 · 10³ at 25°, indicates the absence of anchimeric nitrogen participation in the transition state of this synchronous fragmentation. The rates of the 4-haloquinuclidines follow the normal order of nucleofugal activity for halides in solvolysis reactions.     

Photofragmentierung von Cyclohexa-1,3-dien-5,6-dicarbonsäure-anhydriden [1]

The photochemical elimination of the anhydride function («C₂O₃») from the dihydrobenzenoid anhydrides 6a-6c is described. Some applications and limitations of this double bond producing reaction are given. A formal correlation between ease of «C₂O₃» elimination upon irradiation and upon electron impact respectively is indicated.     

Nachtrag und Berichtigung zur 3. Mitteilung über: Die Glykoside der Blätter von Isoplexis isabelliana (WEBB) MASF.

The name «trichothecane» (I) with a particular numbering is proposed for the basic skeleton of a series of related sesquiterpenes, the corresponding rearranged skeleton (II) (its atoms with the numbers they had in I) is called «apo-trichothecane».     

C-glycosylic derivatives. X. Reversed oxadiazole C-nucleosides

The synthesis of «reversed» 1, 3, 4-oxadiazolyl C-nucleosides by treatment of alduronic chlorides with N-benzoylamino-triphenylphosphinimine or by oxidation of aldehydodialdose benzoylphenylhydrazones is described. One of these compounds is the first example of an «reversed» C-amino-nucleoside having a β-heteroaryl-ethylamino grouping, a structural unit whose introduction into a sugar molecule is interesting from a pharmacological standpoint.     

C1‐Chemie: «Sehen Sie sich die Bäume an»

Chemie‐Nobelpreisträger George A. Olah hat in seiner Heimatstadt Budapest seine Vorstellungen einer Zeit «beyond oil and gas» präsentiert. Seine «Methanol Economy» nutzt den C1‐Alkohol als Stoff, der Öl ersetzen könnte. Die Nachrichten haben nachgefragt.     

Concentration of neptunium from the ground waters of the Karachai Lake contamination area

Neptunium(V) sorption from simulated and natural ground waters, containing ammonium carbonates, acetates, oxalates and citrates, on multi-walled carbon nanotubes (MWCNT) «Taunit»^® was studied. It has been discovered that ammonium acetate and carbonate are not adsorbed on MWCNT «Taunit», but humic acid, oxalates and citrates are adsorbed quite efficiently. Neptunium is extracted from the ammonium carbonate solution by MWCNT «Taunit» with low sorption degrees. While conducting the sorption process from the ammonium carbonate solution with addition of organic substances, it has been revealed that the neptunium extraction degree is not dependent on addition of humic acid and acetate. At the same time, the extraction degree is substantially increased at addition of ammonium oxalate and citrate. It enables modifying MWCNT «Taunit» by means of related organic ligands and using them for the purpose of extraction and concentration of neptunium from contaminated natural waters.     

A Further Synthetic Approach to the Adamantane Isomer 2, 5-Trimethylenenorbornane (Tricyclo [5.3.0.03,9]decane, 4-Homotwistbrendane)

A further synthetic approach to 2, 5-trimethylenenorbornane ( 1 ; tricycle [5.3.0.0^3,9]decane, 4-homotwistbrendane), a member of the «adamantaneland», is described starting from methyl 5-oxo-2endo-norbornanecarboxylate ( 5 ). The required C2-chain was introduced by a Wittig-Horner reaction and the ring closure of the trimethylene bridge achieved by an acyloin condensation.     

Über die Konstitution zweier neuartiger «dimerer» Indolalkaloide Pycnanthin und Pleiomutinin 132. Mitteilung über Alkaloide

The «dimeric» indole alkaloid (+)-pycnanthine ( 2 ) has been isolated, along with (+)-pleiocarpamine, (+)-quebrachamine, (+)-macusine B and an unknown alkaloid D from Pleiocarpa pycnantha (K. SCHUM .) STAPF , var. pycnantha M. PICHON. An investigation of its chemical and spectroscopic properties has led to the determination of structure 2 for this base. Its 6′,7′-dihydro derivative has been shown to be identical with the alkaloid pleiomutinine, previously isolated from Pleiocarpa mutica BENTH .     

[18O]-Studien zur Carboxylbeteiligung bei der sauren Hydrolyse von γ-substituierten Carbonsäuren. 1. Mitteilung: Zum Sauerstoffaustausch von γ-Lactonen in saurer Lösung

Specifically [¹⁸O]-labelled γ-valerolactone and 4-methyl-γ-valerolactone were submitted to tracer equilibration in dilute mineral acid at reflux temperature. Though under these conditions the two lactones are known to be hydrolyzed to the extent of about 25% to the corresponding γ-hydroxy acids only the «tertiary» 4-methyl derivative lost its alkoxyl label whereas the unsubstituted «secondary» one retained it. – This may be understood on the base of two alternative mecanisms possible for lactone reformation. The results permit a quantitative evaluation of the amount of carboxyl-participation during acid hydrolysis of 4-substituted carboxylic acids to 4-monoalkylated γ-butyrolactones.     

Supramolecular nanoscale systems based on amphiphilic tetramethylensulfonatocalix[4]resorcinarenes and cationic polyelectrolyte with controlled guest molecule binding

The water-soluble tetramethylensulfonatocalix[4]resorcinarene with methyl (C1) and pentyl (C5) substitutes on the lower rim forms colloid nanoscale aggregates with poly(diallyldimethylammonium chloride) (PDDA) in aqueous solutions. The size and stability of nanoparticles depend on concentrations of the components and their ratio in the ‘calixarene-polymer’ system. Ternary supramolecular complexes «polymer–macrocycle–guest molecule L-tryptophan (Trp) in conditions of spontaneous pH (3.80 and 4.78 for C1-PDDA and C5-PDDA systems, respectively) in an aqueous solution and in phosphate buffer (pH 7) were investigated by fluorescence method. The addition of the third component – PDDA – to the «non-aggregated C1–Trp» associates leads to the release of Trp in all studied conditions. The possibility of the «binding–release» process of L-tryptophan in «C5–Trp» associates after PDDA addition in the ternary complex is achieved and controlled by the structure of the macrocyclic self-associates and pH conditions.     

Spektroskopische Eigenschaften alkylsubstituierter Diazulyle (Die photochemische Darstellung des 3,3′ und des 2,2′ -Di-guaj-azulyls)

Irradiation with light of 366 nm wave-length of guay-azulene-2-sulfonic acid (IV) or of guay-azulene-3-sulfonic acid (I) dissolved in concentrated sulfuric acid yields 2,2′-di-guayazulyl (VI) or 3,3′-di-guay-azulyl (III) respectively. The nmr and electronic spectra of III and VI and of their conjugate acids are recorded. The essential features of the electronic spectra of III and VI can be understood in terms of a model based on SIMPSON'S «independent system approach».     

Synthese und Eigenschaften von 2-(α-Hydroxyalkyl)-und 2-(α-alkoxycarbonyl)-substituierten 4-Methyl-5-(β-hydroxyäthyl)-thiazolen und -thiazoliumsalzen

Condensation of the tetrahydropyranyl ether of the α-hydroxyalkyl-thioamides with 3-bromo-4-hydroxy-2-pentanones yields DL -2-(α-hydroxyalkyl)-4-methyl-5-(β-hydroxyethyl)-thiazoles. By oxidation with chromic anhydride 2-hydroxymethyl-4-methyl-5-(β-acetoxyethyl)-thiazole yields the corresponding 2-formyl derivative. The latter compound reacted with GRIGNARD complexes gives the homologous DL -2-(α-hydroxyalkyl)-4-methyl-5-(β-hydroxyethyl)-thiazoles. This is a general method for the synthesis of the thiazole part of the «active aldehydes». 2-Acetyl-4-methyl-5-(β-hydroxyethyl)-thiazole is also obtained by chromic oxidation of the suitable methylthiazol-2-yl-carbinol. The condensation of the thioamides obtained from the α-ethoxycarbonyl-nitriles with 3-bromo-5-acetoxy-2-pentanone results in the DL -2-(α-ethoxycarbonyl-alkyl)-4-methyl-5-(β-acetoxyethyl)-thiazoles. The α-hydroxyl function is introduced into the 2-(α-ethoxycarbonyl-alkyl) group by chlorination with sulfuryl chloride and replacement of the introduced chlorine by acetate. The latter compounds are the esters of the thiazole part of the «active α-oxo-carboxylic acids» (e.g. active pyruvate, etc.). The reaction of 2-(α-hydroxyalkyl)-4-methyl-5-(β-hydroxyethyl)-thiazoles and 2-(α-ethoxycarbonyl-α-acetoxy-alkyl)-4-methyl-5-(β-acetoxyethyl)-thiazoles, respectively, with alkyl, alkenyl and aralkyl haloids, or with 2-methyl-4-amino-5-bromomethyl-pyrimidine hydrobromide results in the quaternary thiazolium compounds belonging to the group of the active aldehydes, active α-oxo-carboxylic acids, etc. According to this method 2-hydroxymethyl-thiamine bromide hydro-bromide has been synthesized, which can be considered as the pyrophosphate-free «active formal-dehyde». The 2-α-hydrogen atom in 2-(α-hydroxyalkyl)-thiazolium compounds cannot be replaced by deuterium under conditions similar to those used for the H → D exchange in thiamine. The main peaks in the mass spectra of 2-(α-hydroxyalkyl) substituted thiazoles and thiazolium quaternary salts are listed.     

Die Chemie des Wieland-Gumlich-Aldehyds und seiner Derivate [1] 136. Mitteilung über Alkaloide [2]

The course of the reactions involved in the process of degradation of strychnine ( 1 ) to Wieland-Gumlich aldehyde (WGA) ( 2 ), first performed by Wieland, Kaziro & Gumlich , has been elucidated. 23-Isonitrosostrychnine hydrochloride ( 9a ) upon treatment with thionyl chloride undergoes a fragmentation (2nd order Beckmann rearrangement), thus furnishing N(a)-cyanoformyl-WGA hydrochloride ( 14a ). On heating in an acidic medium, the latter compound is transformed — at least partially via the cyclic urethane 15 — into WGA ( 2 ), which is an important keyintermediate in the syntheses of strychnine and curare alkaloids. The compound 2 can now be obtained in high purity and good yield. A corresponding degradation has been realized with quaternary analogues ( 27 → 3 ) as well as with 10-chlorostrychnine ( 58 → 62 ). 10-Chlorostrychnine ( 58 ) was prepared by chlorination of strychnine with chlorine in conc. hydrochloric acid according to Leuchs & Steinborn. As by-products of the reaction, 10, 15-dichlorostrychnine ( 59 ) and 10, 15, 19-trichlorostrychnine ( 60 ) could be identified. Starting from WGA a series of derivatives have been prepared. Special mention is made of the two epimeric methyl ethers 18 and 19 . The absolute configuration at the centre 17 of WGA and of these two substances has been established by optical comparisons of 3 epimeric pairs. The methyl ether 18 , by-product « B », is obtained if methanol is used in working up the Beckmann rearrangement products of 23-isonitrosostrychnine hydrochloride ( 9a ). A second by-product, « A », results by working up under alkaline conditions. This compound has the structure 44 with inverted configuration at centre 16. Degradation of 44 under controlled conditions leads either to WG-diol ( 42 ) or to 16-epi-WG-diol ( 51 ). Besides « A z.rdang; and « B » a series of by-products and intermediates ( 16, 17, 11a, 22. 23, 24 and 25 ) could be detected in the course of the process of strychnine degradation.     

Die Bildungsenthalpie 1,6-überbrückter [10] Annulene

The enthalpies of formation of 1.6-methano-[10] annulene (IV) (ΔHf₂₉₈ (IV, g) = 75.2 ± 0.6 kcal mol^?1), 1.6-imino-[10] annulene (V) (ΔHf₂₉₈(V, g) = 87.8 ± 0.7 kcal mol^?1) and of 1.6-oxido-[10] annulene (VI) (ΔHf₂₉₈(VI, g) = 47.8 ± 1.2 kcal mol^?1) have been determined by combustion calorimetry. The difficulties connected with an attempt to derive meaningfull «resonance energies» are discussed.     

An analysis of the integrand occurring in correlation energy functionals

An analysis of the integrand occurring in current density functional calculations is presented, concentrating attention on correlation energy functionals and the atomic regions, i.e., the regions of space surrounding atomic centers. The analysis follows the structure of a previously proposed numerical integration scheme for three-dimensional integrals occurring in electronic structure calculations. The scheme is based on the choice of density-based weight functions that naturally partition the space into «atomic» volumes (in which the integration is performed in terms of spherical coordinates) and «diatomic» volumes (in which the integration is performed in terms of confocal elliptical coordinates). From this analysis, a simplified procedure for the atomic «internal» integrations is developed, whereas preliminary results are discussed for the atomic and diatomic «external» integrations. The numerical tests are performed on the C₆₀ molecule in the symmetrical configuration. © John Wiley & Sons, Inc.     

The synthesis of 4'-azido-3',5'-ditritio-l-phenylalanine peptides as "photo-affinity probes" for ligand-receptor interaction (author's transl)]

The Synthesis of 4′-Azido-3′,5′-ditrito-L -phenylalanine Peptides as « Photoaffinity Probes » for Ligand-Receptor Interaction The synthesis of L -p-azido-phenylalanine and peptides thereof containing tritium atoms in the m,m′-positions of the phenyl ring is described. Starting materials are L -p-amino-phenylalanine and L -p-amino-m,m′-diiodo-phenylalanine. Such peptides are being used for specific photoaffinity labelling of receptor and enzyme molecules.     

Stereoselektivität diastereogener CC-Verknüpfungen II Eine Carben/Carbenoid-Kaskade und «Hypermechanismen»

Stereoselectivity of Diastereogenic CC-Linking Reactions II. A Carbene/Carbenoid-Cascade and «Hypermechanisms» In a systematic study four pairs of dihalocarbene precursors were treated with methyllithium in the presence of 2-methyl-2-pentene. Each pair was made up of a tetrahalomethane and a trihalomethane, namely CCl₄ vs. CHCl₃, CCl₃F vs. CHCl₂F, CCl₂F₂ vs. CHClF₂ and CClF₃ vs. CHF₃. Since all the tetrahalomethanes reacted exclusively by chlorine/lithium exchange and all the trihalomethanes by hydrogen/lithium exchange, each pair gave rise (at least formally) to an identical ‘carbenoid’. Two different carbenoids may always undergo elimination of LiCl or LiF and thus collapse generating the same carbene. A comparison of the product composition (ratios of straight-forward cycloaddition vs. consecutive substitution reactions, ratios of diastereoisomers) reveals more or less marked, but always significant discrepancies in the outcome of ‘carbene-convergent’ as well as ‘carbenoid-convergent’ reactions.