Polymerisation of bicyclohepta-(2,5)-diene with palladium-π-complexes

A pinene-π-allylic complex of palladium was capable of catalysing the polymerisation of bicyclohepta-(2,5)-diene. Polymerisation pattern was the same as in the case of PdCl₂, i.e. only one double bond of the diene was opened by this reaction. The optimum temperature range for the polymerisation was between 130 and 200 °C. Polar solvents retarded the reaction. The Pd-π-allylic complex, for the polymerisation of the same olefin, was a more active catalyst than other palladium compounds (e.g. PdCl₂).     

Zur σ-Akzeptorstärke von starken organischen Elektronenakzeptoren

On the σ-Acceptor Strength of Strong Organic Electron Acceptors Acceptor numbers (AN) according to GUTMANN of various strong organic electron acceptors, such as TCNE, chloranile, C₇H₇^⊕ or triphenylmethylium salts, have been obtained by means of complexation with Fe(phen)₂(CN)₂ in 1,2-dichloro-ethane and nitromethane. The AN of organic electron acceptors reflect the capability of a weak coordinative electrophilic attack upon nucleophilic compounds. Based on these results the influence of solvents upon CT-energy (ṽ_CT) in weak π-electron-donor-acceptor complexes is discussed. The blue shift of ṽ_CT depends on the donicity (D) of the solvent, which leads to linear correlations of ṽ_CT versus parameters of donicity. The sensitivity of solvatochromy depends on the AN of the acceptor. On the variation of the bπ-donor the sensitivity of solvatochromy in relation to the quotient dṽ_CT/dD is influenced. With the help of polarographic results can be demonstrated that the influence of solvents on ṽ_CT remarkably depends on the specific solvation in the ground state of the electron acceptor.     

Synthese von ω-Acetyl-α-methylenpolyencarbonsäureestern

Synthesis of ω-Acetyl-α-methylenpolyene Carboxylic Esters The α-methylenpolyene carboxylic acids 1 and 2 are highly active against Gram-positive bacteria. If this activity arises from an interference with the cell membranes, then an abrupt change in biological properties is to be expected with growing chain length of simple model compounds. To make these tests possible, we describe here the synthesis of a series of homologue esters of type 40 . Their synthesis was achieved by Wittig reactions of polyene αω-dialdehydes 6 with acetyl-methylentriphenylphosphoran 5a and the protected carboxy-methylmethylen triphenylphosphonium salt 8 .     

Bestimmung der Nullfeldparameter optisch angeregter 3(π,π*)-Zustände ausgewählter aromatischer Systeme

Determination of the Zero Field Parameters Optically Excited ³(π,π*)-States in Selected Aromatic Systems Experimental zero field parameters of optically excited naphthalene and quinoxaline derivatives are presented. The (D*), (D) and (E) parameters are determined by the position of the transitions by means of simple approximation formula, magnetophotoselection and simulation of spectra. Possibilities of comparison of the zero field parameters of optically excited ³(π,π*)-states with parameters of ground state for simple aromatic hydrocarbones are presented.     

Kristallinflüssige trans-4-(ω-Cyanalkyl)cyclohexylester und 4-(ω-Cyanalkyl)phenylester

Liquid Crystalline trans-4-(ω-Cyanalkyl)cyclohexylester and 4-(ω-Cyanalkyl)phenylesters The synthesis of the title esters 1 and 2a–e (n = 0 – 3) and their mesomorphic properties are described. When the alkyl-spacer n between the polar CN-group and the cyclohexane ring of cyanalkyl-cyclohexylesters 1 is increased the difference of the clearing points between the phenylesters 2 and the cyclohexylesters 1 decreases to nearly zero. The reason of higher clearing temperatures of 2 is a dynamic conformational effect of ring inversion of cyclohexane in the ester 1 with two polar substituents at the ring.     

ω-Alkyl-ω-Nitroacetophenones

Nitroketones of the formula Ar. CO. CHR. NO₂ are best obtained by chromic acid oxidation of the easily accessible corresponding nitroalcohols. The nitroketones form stable salts with secondary amines. A series of ω-nitro-ω-(2-furfurylidene) - acetophenones has been synthesized. The infrared spectra of the new compounds prepared have been determined and are discussed.     

ω-3- und ω-6-Fettsäuren – Biochemische Besonderheiten und biologische Wirkungen

ω-3- and ω-6-Fatty Acids – Biochemical Specialities and Biological Effects ω-6- and ω-3-fatty acids are essential for mammals and human beings. Deficiency symptoms of ω-6- and ω-3-fatty acids are known in infants and adults. In higher doses ω-6-and ω-3-fatty acids produce biological effects, which can have positive or negative consequences. Therefore a well balanced supply of these fatty acids must be considered. By a mixed diet according to the recommendations of the German Nutrition Society a sufficient supply with ω-6- and ω-3-fatty acids will be possible. In the present state of knowledge an uncontrolled medication of fish oil capsules cannot be recommended, but an increase of the present intake of salt water fish with a favourable type of fat and other useful nutrients like iodine, selenium et. is desirable.     

Synthese und π-Elektronenstruktur von 2,5-Bis-alkylamino-terephthalsäurediethylestern

Synthesis and π-Electronic Structure of 2,5-Bis(alkylamino)-terephthalic Acid Diethyl Ester 2,5-Dioxocyclohexane-1,4-dicarboxylic acid diethyl ester 1 reacts with primary alkylamines 2 to 2,5-bis-(alkyl-amino)-cyclohexa-1,4-diene-1,4-dicarboxylic acid diethyl ester 3 . The dehydrogenation of 3 by means of bromine or chloranil leads to 2,5-bis(alkylamino) terephthalic acid diethyl ester 4 . Electronic spectra and quantumchemical calculations according the SCF-LCI method indicated that the absorption proporties of 4 in the visible spectral region follow the general pattern of substituted aromatic compounds. A merocyanine-like electronic structure seems to be less probable.     

Die elektrische leitfähigkeit von α,ω-bis-polyenen

The preparation and isolation of the coloured reaction products of maleic anhydride-methylvinylether-copolymer (Gantrez AN) and aprotic liquids yields α,ω-bis-polyenes of the copolymer each containing double bond sequences of equal length, irrespective of the order of reaction. Prior to the formation of the polyenes in hexamethylphosphoramide (HMPA), a chemical reaction involving this aprotic substance occurs at the anhydride ring of the Gantrez AN. The electrical conductivity is improved by addition of iodine, dichloro-dicyano-p-benzoquinone (DDQ), tetracyanoethylene (TCNE) and tetracyanoquinonedimethane (TCNQ) to the resultant α,ω-bis-polyenes. If the unsubstituted α,ω-bis-polyenes are treated with boiling xylene or pressure sintered, specific resistances as high as that of polyacetylene (PA) are obtained. On the whole, the specific resistance is reduced by ten orders of magnitude, Gantrez AN: 2.8·10¹³ Ω. cm, pressure-sintered α,ω-bis-polyene: 1.1·10⁴ Ω·cm, α,ω-bis-polyene containing iodine: 2·10³ Ω·cm. IR spectroscopy can be used to detect the polyene and complex formation and to demonstrate that the actively conducting reaction product is a 3- or 4-substituted α,ω-(bis-polyene)-1,2-polybutene.     

Funktionell substituierte zinnorganische Verbindungen. I. ω-Triäthylstannylalkylphosphon- und -phosphinsäureester

Functionally Substituted Organotin Compounds. I ω-Triethylstannylalkylphosphonic- and -phosphinic Esters ω-Triethylstannylalkylphosphonic- and -phosphinic esters 1 can be synthesized by radical addition of triethylstannane to alkenylphosphonic- and -phosphinic esters. Their reaction with bromine or hydrochloric acid causes a substitution of an ethyl group forming organotin halides 2 and 3 . On alkaline hydrolysis of stannylsubstituted phosphinic esters, the acids 4 were obtained which can be transformed into the cyclic organotin phosphinates 5 . Lithium aluminium hydride reduces ω-triethylstannylalkylphosphonic- and -phosphinic esters to ω-triethylstannyl-alkylphosphines 6 . The P-phenylsubstituted compounds 6 are oxidized by sulfur via the dithioacids 8 to 1-diethyl-3-phenyl-1,2,3-stannathiaphospholane- and -phosphorinane-P-sulfid 9 , respectively.     

Desaktivierungsverhalten von Arenen und Heteroarenen. XL. Mechanismus der reversiblen intramolekularen [π4s + π4s]-Photocycloaddition von α, ω-Bis-(9-acridiziniumyl)-alkanen

Deactivation Behaviour of Arenes and Heteroarenes. XL. The Mechanism of the Reversible Intramolecular [_π4_s + _π4_s]-Photocycloaddition Reaction of α,ω-Bis-(9-acridiziniumyl)-alkanes. On electronic excitation the bichromophores deactivate by fluorescence and radiationless photophysical processes from its local excited state. Simultaneously, intramolecular interaction occurs between the excited chromophor and that in the ground state (i.e. by reversible energy migration or intramolecular excimer formation). The excimer rapidly collapses to the cyclomer assuming a common pericyclic transition state for the reversible photocycloaddition. In the pericyclic state the reaction is split into cyclomer formation or backformation of bichromophores in the ground state, respectively. This mechanism of the reversible intramolecular [_π4_s + _π4_s]- photo-cycloaddition reaction is discussed on the basis of a potential correlation diagram.     

Strukturaufklärung cyclischer Fettsäuremethylester I: Massenspektrometrie von ω-(o-Alkylphenyl)alkancarbonsäure-methylestern

Structure Determination of Cyclic Methyl Esters of Fatty Acids II: Mass-Spectrometry of Methyl Esters of ω-(o-Alkylphenyl)-Alkane-Carboxylic Acids Methyl esters of aromatic fatty acids (AFA-Me) of the general structure I with n = 6, 7, 8, 10 and 11 were synthesized and characterized by IR-, UV- and mass spectrometry. The fragmentation due to electron impact is discussed. In the case of AFA-Me with n ? 8 even-numbered ions are formed which enable the exact identification of these compounds.     

Regio- and stereoselectivity of 1-(Pyridazin-3-yl)-3-oxidopyridinium Betaines towards 2π- and 4π-conjugated olefins

1-(6-Phenyl) and 1-(6-(4-tolyl)-3-oxidopyridinium betaines ( 1a , b ) react as 1,3-dipoles with conjugated olefines, namely 4-vinylpyridine, ethyl cinnamate and styrene as 2π-1,3-dipolarophiles to give 2,6-cycloadducts [6-substituted-8-azabicyclo[3,2,1]oct-3-en-2-ones ( 3a , b , 4a , b and 5b )] and with butadiene and furan as 4π-dipolarophiles to give 2,4-cycloadducts [7-substituted-7-azabicyclo[4,3,1]deca-3,8-diene-10-one] and 3-6-phenylpyridazin-3-yl)-3-aza-10-oxatricyclo-[5,2,1,1^2,6]undeca-4,8-diene-11-one ( 9a ). Structural and configurational assignments were based on H.n.m.r. spectral analysis.     

Eigenschaften der CT-Banden einiger EDA-Komplexe vom aπ-bπ-Typ

Properties of the CT-Bands of some aπ-bπ-Type EDA-Complexes CT-bands with two maxima exist in the visible range of the spectra of EDA-complexes between tetracyanoethylene (TCNE) and stilbene derivatives. The CT-bands in the long wave length range of TCNE-complexes are in a linear correlation with the band maxima of the corresponding chloranile (CA) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) complexes. Ionization energies of the donors calculated from band positions of TCNE-, CA- and TCNQ-complexes are in a good accordance. For long wave length maxima of double bands a linear coherence exists between the transition energy and the stability of complexes.