Die gasförmigen Komplexe NiAl2Cl8 und NiAl3Cl11

Gaseous Complexes NiAl₂Cl₈ and NiAl₃Cl₁₁ Spectral photometric measurements of equilibria which are established by reaction of solid NiCl₂ with gaseous Al₂Cl₆ have been made. Results see ?Inhaltsübersicht”?.     

Orientational aspect of transient absorption in solutions

In picosecond spectroscopy transient absorption methods are utilized to measure ground-state repopulation kinetics. Since linearly polarized light pulses from mode-locked lasers are used, the transient absorption characteristics in solutions are governed by the rotational diffusion of the absorbing molecules, too. The theory for isotropic diffusion is given and compared to a measurement on the rhodamine 6G molecule dissolved in solvents of different viscosity using a novel pulse spectrophotometer.     

Borazin—metallkomplexe : VI. Über ligandenaustauschreaktionen an borazin—metallkomplexen: synthese von B-trimethylborazin-tricarbonylchrom

Me₃B₃N₃H₃Cr(CO)₃ has been obtained by ring-ligand exchange starting from Et₃B₃N₃Me₃Cr(CO)₃ and Me₃B₃N₃H₃. The new compound has been characterised by means of their IR, NMR, UV and mass spectroscopic data.     

Open- and closed-shell states in few-particle quantum mechanics. II. Classification of atomic states

The system developed in the first paper of this series for the classification of states as open- or closed-shed type is applied to atomic states. These may be classified in the isoelectronic limit (Z → ∞) from knowledge of the true wave function in this limit. One-matrix occupation numbers are tabulated for a number of states of the first-row atoms in the limit Z → ∞ and the states classified. A classification for finite Z is possible in the framework of the Z-dependent perturbation theory by use of a thoerem for the stability of a closed-shed with respect to small perturbations. Such a stability does not hold in general for open-shel states.     

Totalsynthese von (+)-D-Homoöstron-3-methyläther

Total Synthesis of (+)-D-Homoestrone 3-methyl ether A novel total synthesis of (+)-D-homoestrone 3-methyl ether ( 21 ) is described starting from (S)-8a-methyl-3,4,8,8a-tetrahydro-2H, 7H-naphthalene-1,6-dione ( 1 ) as a chiral synthon for the rings C and D. The key step involves alkylation of the derived 3 with m-methoxyphenacyl bromide ( 4 ) as an AB-building block to give the dioxo-secosteroid 5 . Hydrogenation of 5 affords the trans-decalone 11 . As by-products the epimeric cis-decalones 12 and 13 were characterized. Cyclization of 11 leads under kinetic control predominantly to the Δ⁹⁽¹¹⁾-tetraene 14 . Catalytic hydrogenation of 14 and subsequent modification in ring D give the title compound 21 . It was found that 14 and also the derived Δ⁸-isomer 15a add hydrogen from the α-face of the molecule to an extent of about 80%. The 8α-D-homoestrone derivatives 20a and 23 as well as the 9β-isomers 19a and 22 were characterized.     

Delocalization resonance energy of the allylic radical from the geometrical isomerization of hexa-1,3,5-trienes

Thermal cis, trans geometrical isomerization theoretically involves a 90° twisted, singlet diradical-like transition state which may serve as a base for the examination of structural perturbations. Although thermal rearrangement of hexa-1, trans-3,5-triene (and all-trans octa-2,4,6-triene) to the cis isomer cannot be followed directly owing to subsequent cyclization and 1,5 hydrogen shifts, activation parameters for disappearance have been determined. Experimental complications and mechanistic uncertainties which make interpretation difficult are removed in the bicyclic hexatriene, cyclopentenylidenecyclopentene. These geometrical isomers undergo uncomplicated thermal cis, trans isomerization in vessels of lead-potash glass: log k₁ = 12·03±0·32?41·7±0·8/(0·004575T_abs). Extraction of a value for allylic delocalization energy from the behavior of hexa-1, trans-3,5-triene [log k₁ = 12·91 ± 0·47?44·3±1·2/(0·004575 T_abs)] requires corrections of the Dewar-Schmeising type for changes in hybridization of the σ bonds. Depending on whether ethylene or trans-butene is taken as standard, values of 12·2 and 13·1 kcal/mol are obtained (estimated uncertainty ± 2 kcal/mol).     

Isolierung,Konstitution und Synthese der (R)-(−)-Eucominsäure

From the bulbs of Eucomis punctata L'Hérit. (Liliaceae) and of a hitherto undefined species of Eucomis a new optically active phenolic carboxylic acid, eucomic acid, was isolated. Structure 1 was assigned on the basis of chemical and spectral evidence. The absolute configuration of eucomic acid was determined by its correlation with piscidic acid ((2 R, 3 S)-2-(4′-hydroxybenzyl)-tartaric acid) ( 8 ). Consequently, eucomic acid is (R)-(?)-2-(4′-hydroxybenzyl)-malic acid ( 1 ). For the stereospecific synthesis, methyl cis-p-methoxybenzylidene-succinic acid ( 22 ) was transformed into the γ-lactone 24 which, by catalytic hydrogenolysis, yielded (±)-2-(4′-hydroxybenzyl)-malic acid 1-methyl ester ( 27 ). Resolution with (?)-quinine led to the enantiomeric acids 29 and 30 . The methyl ester of the levorotatory enantiomer 30 was identical with the dimethyl ester 3 of 4′-O-methyl-eucomic acid.     

ON THE LUMINESCENCE OF ESTROGENS

Abstract —The absorption, fluorescence, and phosphorescence of a series of estrogens is reported. The behavior of estrogens without a keto-group is compared with that of the isolated phenylic, phenolic and naphtholic chromophores. In the latter two, attachment to the steroidal frame is inconsequential as regards their luminescent behavior. In all keto-estrogens with the exception of equilenin there is a very strong transfer of excitation energy from the A ring chromophore to the keto group. The fluorescence of 6-keto-estradiol, which has a conjugated aromatic carbonyl chromophore, is apparently due to the rigidity of the steroid frame and exhibits a rather perculiar excitation spectrum.