Volume 26, Issue 7

The significance of isosbestic points and absorbance-difference diagrams for testing the “Einheitlichkeit” (“uniformity”) of a reaction is discussed by use of the imidazole catalysed hydrolysis of p-nitrophenyl acetate as an example. The analysis was based on kinetic spectra E(λ)t 1 , t 2 ,..., t n and time dependant absorbance values at various wave lengths E (t) λ1 , λ 2 ,..., λ m measured preferably in the same reaction vessel. The (pseudo-) first-order rate constants were calculated from the absorbance-time curves E(t)) λ by formal integration. The kinetic constants of the various reaction steps were used for digital simulation of the total reaction by an electronic computer. The evaluation methods described need neither extinction coefficients nor experimentally determined E ∞ values but make it possible to compute them.

The 2 J (PH) coupling constant of mixtures of (CH 3 ) 3 SiCH 2 CH 2 P(CH 3 ) 2 and BF 3 depends on the ratio of the two components. During the investigation of the simpler system (CH 3 ) 3 P/BF 3 the following results were obtained: 1. τH[P(CH 3 ) 3 ] and 2 J(PH) vary steadily with the ratio (CH 3 ) 3 P/BF 3 , 2. Only one doublet is observed even for mixtures with excess P(CH 3 ) 3 , 3. 2 J (PH) becomes zero for the given ratio BF 3 : P(CH 3 ) 3 = 0.4. The results can be explained by assuming a fast exchange according to equation (2) and opposite signs for the coupling constants of P(CH 3 ) 3 [ 2 J (PH) = +2.5 Hz] and the adduct (CH 3 ) 3 P →BF 3 [ 2 J(PH) = -11.3 Hz].

During the pyrolysis of gaseous BCl 3 or BBr 3 and H 2 on boron nitride substrate at 1150 - 1600 °C under very clean conditions, boron is formed with the α- or β-rhombohedral lattice and the II-tetragonal lattice. These lattices disappear when molecular nitrogen is added to the gas. Then the I-tetragonal lattice of (B 12 ) 4 B 2 N x appears, in which x depends on the temperature (1< x < 2).

2-Organo-1,3,2-dioxaborolanediones- (4,5) RBC 2 O 4 (R = CH 3 , C 2 H 5 , C 6 H 5 , C 6 F 5 ) are formed from anhydrous oxalic acid and dihalogeno-organo-boranes. The five-membered ring-compounds are strong Lewis acids. The thermal degradation yields CO, CO 2 , and organoboroxines (RBO) 3 .

Equimolar mixtures of a biguanide and a diphenylphosphonite on heating under reduced pressure split off 2 moles of phenol. As products cyclic phosphazanes 3 were to be expected. Instead they undergo a hydrogen shift from N to P to give 2-hydrogen-2-alkyl-4.6-diamino-1.3.5.2-triazaphosphorines (4). This is taken as evidence that a phosphazene π-bond may well become part of a cyclic delocalised system and thus contribute substantially more to stabilize the PH-tautomer than an isolated one. Carbonyl compounds add readily to the PH-bond, CCl 4 substitutes the hydrogen for chlorine, which in turn may be displaced by alkoxy and amino groups. 31 P- and 1 H-NMR data, especially the PH- and PD-coupling patterns sustain the assigned structures.

The tetramethoxyethylene (TME) complexes, Fe (CO) 4 (TME) and C 5 H 5 Mn (CO) 2 (TME), have been prepared in which the olefin is symmetrically coordinated. The IR spectra indicate that TME possesses considerable acceptor properties.

A reaction mechanism for the formation of the paratungstate A ion “HW 6 O 21 5⊖ ” is developed. Because of geometric reasons and in consideration of the formerly ί 1 stated criterion for stable polytungstates the stepwise aggregation to a hexatungstate ion can proceed only via the tetratungstate ion and - in conformity with the lower rate of formation of the ion - only under condensation of water. Decisive to the way of the aggregation according to this mechanism are therefore the number and the positions of the Η-atoms in the growing polytungstate ion as well as the degree of protonation of the monomer tungstate ion. The rules which are obeyed are deduced. The end of the aggregation with a 7,6-tungstate ion results from a consideration of the free energies of reaction for the formation of the polytungstate ions as they are possible according to these rules. For this it is supposed, that ΔG r r is composed of increments for the characteristic reaction and structure parameters. The correct formula for the paratungstate A ion is [W 6 O 19 (OH) 3 ] 5⊖ . One of the two structures discussed for this ion is in close relation to that of the heptamolybdate ion Μο 7 O 24 6⊖ which is formed under similar conditions.

P 3 N 3 F 5 NCO was prepared by reaction of P 3 N 3 F 5 NSO with (COCl) 2 . Substituted amides were obtained from the reaction of P 3 N 3 F 5 NSO with carbonic acids e. g. P 3 N 3 F 5 NHCOCH 3 , P 3 N 3 F 5 NHCOC 2 H 5 , and P 3 N 3 F 5 NHCOC 3 H 7 . If these substances were treated with PCl 5 the following compounds P 3 N 3 F 5 N = CClCH 3 , P 3 N 3 F 5 N = CClCH 5 , and P 3 N 3 F 5 TN = CClC 3 H 7 were formed. They reacted with nucleophiles to give P 3 N 3 F 5 N = CNH 2 CH 3 , P 3 N 3 F 5 N = TN (CH 3 ) 2 C 2 H 5 , and P 3 N 3 F 5 N = CN (CH 3 ) 2 CH 7 . The properties of these compounds are described. They were characterized by elemental analysis and IR-spectra. 19 F-, 1 H-NMR, and mass spectra are reported.

Preparation, IR- and EPR-spectra of paramagnetic dichloro-porphyrexid-palladium(II) from porphyrexid and sodium-tetrachloropalladate are reported. The reaction of organic radicals with tetrakis (triphenylphosphine) platinum (O) provides a new type of oxydative addition. Treatment of Pt (PPh 3 ) 4 with 1,2-diphenyl-2-picrylhydrazyl yielded diphenylamido-2,4,6-trinitrophenyl-bis (triphenylphosphine) platinum (II). Dibenzoylperoxide yielded cis-dibenzoato-bis (triphenylphosphine) platinum (II), whereas with diaryl- and dialkylnitrogenoxide and tetraarylhydrazine no reaction was observed.

Infrared spectroscopic investigations have shown that on the basis of changes in the ν 3 , SO 4 band which occur when calcium sulphate is heated from 400° to 1400 °C, there are two forms of insoluble anhydrite, designated as β′- and β-CaSO 4 . β′-CaSO 4 is metastable and is completely converted into β-CaSO 4 by heating above 1000 °C. With longer heating periods this conversion can even take place at lower temperatures. β-CaSO 4 is stable and is of the same type as the naturally occurring form of anhydrite.

Reaction rates of the ethanolysis and hydrolysis of the phenyl- and methylpolyphosphate-esters and of tetraphenylpyrophosphate were measured by potentiometric titration methods. Exceptionally high rate constants were obtained for the solvolysis of these compounds, some reactions occurring with half-times of less than 10 seconds. The phosphorylating activity of the phenylpolyphosphateester on polyfunctional nucleophilic compounds (SN 2P -reaction) was tested and shown to exceed the activity of the conventional agent diphenylphosphoro-chloridate considerably. The catalytic effects of dimethylformamide were measured under several conditions and were shown to be complex solvent phenomena rather than conventional catalysis. The reactivity of the polyphosphate-esters is discussed with respect to their structure as well as the reactivity of P -O -P-bonds as a function of their ligands.

2-Hydroxy-6,7-dimethyl-naphtalene is sulfonated to 2-Hydroxy-6,7-dimethyl-naphtalene 3-sulfonic acid at 100°. On fusion of this sulfonic acid with potassium hydroxide 2,3-Dihydroxy-6,7-dimethylnaphtalene is obtained. The structure of this compound was proved by nuclear magnetic resonance spectroscopy. The latter compound is a good starting material for the synthesis of 6′,7′-Dimethylnaphto- (2′,3′) -imidazole-4,5 the base of a new vitamin B 12 -analogue, which was biosynthetically prepared recently.

Kinetics of catalyzed acyl group exchange between acetic-1- 14 C anhydride and alkyl thiolacetates was investigated. The exchange is not accompanied by chemical reaction and demonstrates the full equivalency of anhydride acyl groups in the process. The rate of exchange is lowered by increasing branching rather than lengthening in S-alkyl substituents. The role of catalyst and structures of possible intermediates are interpreted. Upon existing linear structure-reactivity relationship a common mechanism involving sulfur atom as the reaction site seems to be operative.

Cyclophane, Konformationsanalyse, Nitril-Gruppe, Protonenresonanz, Sterische Wechselwirkungen The bridged aromatic compounds 1-3 with internally projecting nitrile groups have been prepared. The cyclophanes 1 and 3 are conformationally rigid due to steric hindrance of the inner cyano groups; 2 shows partial conf ormational mobility.

The microsomal fraction of rat placenta contains a 17β-hydroxysteroid-oxidoreductase which transfers hydrogen from position 17 of estradiol to androstenedione. This hydrogen transfer is dependent on NAD, NADP as cofactor is without effect. The optimum pH is at 6,9. In the presence of NAD the Michaelis constant for estradiol is 4,17 · 10 -5 м at pH 7,4. In the presence of androstenedione in the incubation medium the K m -value for estradiol is decreased, which indicates an increased affinity for the enzyme. The temperature optimum of the enzyme is 38 °C. Addition of SH-blocking agents inhibited the enzyme activity. Zinc and magnesium ions had an inhibitory effect on the “transhydrogenase” and B-NADPT specifically labelled from [1-T]-glucose showed that the non-effect of NADP on transhydrogenation from estradiol to androstenedione resulting in reduction of position 17 is not due to different stereospecifity. The results show a close relation between the oxidative metabolism of estradiol and the reduction of androstenedione, indicating that estradiol-17β, as the preferred hydrogen-donating substrate, is an essential component of the androstenedione-hydrogenating system in the microsomal fraction of rat placenta.

Systematic alterations of the central amino acid in the peptidic juvenile hormone analogues consisting of three parts connected by amidic bonds tert.-butyloxycarbonyl group - amino acid - p-aminobenzoic acid ethylester) have revealed that the hormonal activity is dependent on the L-configuration of the central amino acids. The compounds exhibit specific activity on insects of the family Pyrrhocoridae, being inactive on several other insects tested.

The phases of the cell cycle of Potorous tridactylus (PtK 2 ) cells were determined in vitro by analysis of labeled mitoses for 37-½ hours after a tritiated thymidine pulse. The mean duration of DNA synthesis (t S ) was 8 h. The mean duration of the gap phase before appearance of labeled mitoses was 5 h. Whereas the duration of the cell cycle (t C ) based on analysis of labeled mitoses was 30 h, the doubling time (t D ) derived from cell counts in the same cultures was only about 23 h. The analysis of the indices of labeled nuclei and mitoses suggests a stimulation of cells at the time of pulse labeling, which was maximal after beginning of the gap phase before DNA-synthesis, and possibly caused the observed difference between t C and t D .

The stromata of etioplasts, greening etioplasts, and chloroplasts contain proteins which crossreact with proteins of the lamellar system of chloroplasts. It is shown that at least one cross-reacting protein is a water-soluble precursor of the lamellar system. The water-insoluble fractions of the plastids were dissolved in buffer containing Na-benzene-dodecylsulfonate and analyzed by gel electrophoresis. The disc electrophoresis patterns of the prolamellar bodies of etioplasts showed 8 protein-containing bands of which 7 were also present in the preparations from greening etioplasts. The latter also yielded 5 new protein-containing bands. The lamellar system of chloroplasts showed only 8 bands which were identical with those of greening etioplasts, but it had only 3 bands in common with the prolamellar bodies of the etioplasts. Two of these proteins may be identical with antigens cross-reacting with stroma proteins.