Metal-Ammonia Reduction. Part II. Space-Conjugated Olefins

Whilst metal-alcohol-liquid ammonia conditions do not reduce isolated double bonds², the “space-conjugated”³ norbornadiene has been shown to reduce to norbonene⁴. This result has been interpreted as the consequence of the availability of a low energy antibonding orbital arising from the proximity interaction of the two double bonds. The “nonclassical radical anion” 1 has been proposed⁴ as the intermediate though no nortricyclene could be detected to support this suggestion. However nortricyclene was produced when lithium in ethylamine was used as the reducing agent.⁵     

The i.r. spectrum of berkelium-249

The spectrum of ²⁴⁹Bk, excited in an electrodeless lamp, has been recorded between 3700 and 12,000 cm^?1 on a Fourier-transform spectrometer. The strongest 90 lines are listed along with the classification for 77 of them. The lowest levels of the 5f⁹6d7s, 5f⁹7s7p, 5f⁹7s8s, 5f⁸6d7s² , 5f⁸7s²7p and 5f⁸6d7s7p configurations of Bk I and of the 5f⁹6d and 5f⁹7p configurations of Bk II have been identified. Lists of the energies and hfs data of the Bk I levels involved in the i.r. transitions are also included.     

Benzothiazolium derivatives. III. Nucleophilic substitution reactions of benzothiazolium salts

The reactions of 2,3-dihydrothiazolo[2,3-b]benzothiazolium bromide 1 (A^? ?Br^?) with certain nucleophilic reagents have been performed for the purpose of ascertaining the reaction pathways and identifying the group that is displaced from the central carbon atom of the dithiocarbamate system. The nature of complex salt-like intermediates formed initially from 1 (A^? ?Br^?) has been studied and confirmed. For comparison, a number of nucleophilic substitution reactions of 2-methylthio-3-methylbenzothiazolium iodide 17 and 2-dimethylamino-3-methylbenzothiazolium perchlorate 18 have been examined.     

Macrocyclische Spermidinalkaloide aus Pleurostylia africana LOES. 9. Mitteilung über Celastraceen-Inhaltsstoffe

Macrocyclic Spermidine Alcaloids from Pleurostylia africana LOES . The structure of pleurostyline, a new macrocyclic spermidine alkaloid from Pleurostylia africana (Celastraceae), has been elucidated mainly by ¹H- and ¹³C-NMR.-spectroscopy. Pleurostyline represents a new structure type in which spermidine is incorporated in a 13-membered lactam ring to which an additional cinnamoyl residue is fused to yield a 7-membered ring. The same plant contains also the spermidine alkaloids celacinnine and cellallocinnine of which ¹³C- and high field ¹H-NMR.-measurements have been carried out for the first time. Both alkaloids are interconvertible by UV.-irradiation. In addition the existence of rotational isomerism of one amide group of these alkaloids has been demonstrated by NMR.-spectroscopy.     

Laser induced fluorescence of Sb2. I. Visible B–X system

Diatomic antimony molecules have been produced in a heat-pipe oven at pressures from 10^?2 to 10 Torr. Laser induced fluorescence of Sb₂ has been studied in the spectral range 420–730 nm with various laser sources. In order to investigate different isotopic molecules and to enhance fluorescence intensity, intracavity measurements have been performed. For the isotopic molecules rotational and vibrational constants of the ground state X(¹Σ_g⁺) and for the excited state B(O_u⁺) have been determined. RKR potential curves have been calculated and used to comput Franck—Condon factors.     

Studies with inorganic precipitate membranes. III. Consideration of energetics of electrolyte permeation through membranes

The permeability of various electrolytes through parchment-supported ferrocyanide membranes of manganese, cobalt, silver, and cadmium has been measured at 10, 15, 20, 25, and 30°C. The order of permeability at a given temperature was Cl^- > NO₃^- > CNS^- > CH₃COO^- > SO₄^2- for both monovalent and divalent cations. For any given anion, the cations followed the sequence NH₄⁺ > Li⁺ > Ba²⁺ > Ca²⁺ > Mg²⁺ > Al³⁺. This sequence has been correlated with the size of the hydrated ion. Further, the data have been considered from the standpoint of the theory of rate processes and the values for the entropy of activation (ΔS′) have been derived assuming an equilibrium distance of 3 Å in the membrane. The values of ΔS′ were all negative and decreased with increasing valence of the ions. This was interpreted to mean electrolyte permeation with partial immobilization in the membrane.     

The use of the selective population inversion technique in the assignment of carbon-13 n.m.r. resonances in 3,6-epoxy-pentacyclo[6.2.1.02,7.04,10.05,9]undecane

Different applications of the selective population inversion technique in an n.m.r. study of 3,6-epoxypentacyclo-[6.2.1.0^2,7.0^4,10.0^5,9] undecane have been demonstrated. The intensity gain accompanying heteronuclear ¹³C—{¹H} experiments allowed the detection of fine structure due to long range C? H couplings otherwise hidden in normal proton coupled ¹³C spectra. Definite assignments of two very similar, directly bonded, C? H couplings within a methylene group have been made.     

Carbon-13 n.m.r. investigation on the nitrogen methylation of the mono- and diazanaphthalenes

The ¹³C n.m.r. spectra of the N-methylated mono- and diazanaphthalenes have been recorded and analysed. It has been shown that N-methylation as well as N-protonation in cinnoline occur predominantly at the β-nitrogen atom. N-methylation and N-protonation show a similar effect on the ¹³C chemical shifts.     

Front Cover: A Dibismuthane with Olefin Functional Groups: Towards Tridentate Hybrid Chalcogen/Olefin Ligands (Eur. J. Inorg. Chem. 32/2023)

Bis[dibenzobismepine], a dibismuthane composed of two bismepine units (R₂Bi−BiR₂), was synthesized and fully characterized (R₂=(C₆H₄CH)₂). Reactions of this dibismuthane with diphenyl dichalcogenides, dibenzoylperoxide, and elemental chalcogens have been investigated. All products of these reactions have been isolated and fully characterized, including a series of compounds R₂Bi−E−BiR₂ (E=O−Te). These species contain two olefin units of the bismepine moieties and a chalcogen atom as potential coordination sites. The potential of these species to act as hybrid tridentate chalcogen/olefin ligands with bismuth atoms as structure-determining elements in the backbone has been investigated by theoretical approaches, aiming at the complexation of Co^I, Rh^I, Ir^I and Ni⁰, Pd⁰, Pt⁰. The analytical techniques applied in this work include heteronuclear and 2D NMR spectroscopy, elemental analysis, single-crystal X-ray diffraction analysis, and DFT calculations.     

Five ingol esters and a 17-hydroxyingenol ester from the latex of Euphorbia Kamerunica. Assignment of esters using 13C.N.M.R. methods.

The structures of five ingol esters and a 17-hydroxyingenol ester from the latex of $\text{Euphorbia kamerunica}$ have been determined. The ¹³C n.m.r. spectra of these compounds have been assigned using 2D δ_C/δ_H correlations. The specific positions of attachment of esters have been assigned unambiguously using ¹³C n.m.r. methods including 2D long range δ_C/δ_H correlation.     

Studies related to cephalosporins. Part 2 . Displacement reactions on 3-bromomethylcephems with salts of carboxylic acids

The reactivity of Δ³- and Δ²-3-bromomethylcephems toward carboxylate nucleophiles has been studied. The Δ³-bromomethylcephem 1 , less reactive than the Δ²-analogue 4 , is converted in high yields into 3-acyl-oxymethyl-3-cephems 2a-d , generally with no isomerization of the double bond, only within a narrow range of conditions. In particular, the Δ³-7-aminocephalosporanic acid (7-ACA) derivative 2a has been obtained as the only product in 91% yield by treatment of 1 with triethylammonium acetate in acetic acid. The Δ²-bromomethyl-cephem 4 is easily converted into the Δ²-acyloxymethyl-cepheras 5a-d without double bond isomerization, in very high yields.     

Vinyl Polymerization. 282. Vinyl Polymerization Initiated by Dimethylhydroxylamine-Titanous(lll) Chloride Redox System

Abstract

The polymerization of vinyl monomers initiated by dimethylhydroxylamine hydrochloride (DHA)-titanous(III) chloride redox system has been studied in water under a nitrogen atmosphere. In the polymerization of methyl methyacrylate (MMA) initiated by the above system, the rate of polymerization has been found to be proportional to [DHA]^0.5 for DHA concentrations of less than 2.06 × 10^?3 mole/liter, whereas at higher concentrations the rate tends to fall rapidly. The rate has also been found to be proportional to [Ti(m)] ^0.58 and to [MMA] ^1.0. The maximum rate of polymerization has been observed at a 1:1 molar ratio of DHA to Ti(III). The polymerization proceeded via a radical mechanism. The overall activation energy was estimated as 5.5 kcal/mole. It has been suggested that the reduction of dimethylhydroxylamine by titanous(III) chloride yields the dimethylamino radical, which initiates vinyl polymerization. An examination of the initiating capacity of the initiator system for the polymerization of some vinyl monomers has also been made.     

N.m.r. studies in the heterocyclic series: XVI—determination of the structure of 3-azidoindazole by 1H and 13C n.m.r. spectroscopy

The 1-NH structure for 3-azidoindazole has been demonstrated by the observation of ¹H? ¹H and ¹³C? ¹H couplings involving the hydrogen atom attached to nitrogen. A comparison between 3-azidoindazole and indazole shows that both compounds have the same tautomeric structure.     

A spatial study of electron density and analyte emission in a d.c. argon plasma

Spatially resolved electron density measurements have been performed on a three-electrode d.c. plasma using a linear photodiode array based spectrometer. The electron density values measured are between 1× 10¹⁵ and 1 × 10¹⁶ cm^?3 depending on spatial position. The spatial distribution of Ca I (422.7 nm) and Ca II (393.4 nm) emission has also been measured and the Ca II-Ca I emission intensity ratio evaluated. Using the n_e values measured, an analagous LTE ratio has been calculated and this has been compared to the experimental values. Measured ratios are found to be from 28 to 100 times less than LTE ratios. Some possible sources leading to these infrathermal ratios are discussed.     

Excluded-volume effect for various chain models. I. Application to optical anisotropy and end-to-end distance of linear polymers

A study of the effect of excluded volume on the mean-square optical anisotropy 〈γ²〉 and the mean-square end-to-end distance 〈R²〉 has been carried out for polymer chains of up to 2000 bonds. The calculations have been made for models assuming (a) equiprobability of internal rotations and (b) interdependence of short-range intramolecular interactions. All the results indicate that 〈γ²〉 is practically insensitive to the excluded-volume effect. Concomitantly the behavior of 〈R²〉 has been analyzed.     

Fulvene,VII. Analyse der 13C- und 1H-NMR.-Spektren

Carbon-13 and proton NMR. spectra of pentafulvene and of a series of 6-substituted fulvenes have been analysed and assigned by homo- and heteronuclear double resonance and with the aid of iterative computation. ¹³C and ¹H chemical shifts are interpreted in terms of substituent effects and compared with π-electron charges calculated for the unsubstituted fulvene. From ¹³C shifts a 10 percent contribution of dipolar structures to the electronic configuration of fulvene may be estimated. All long-range proton-proton coupling constants including relative signs and some proton-carbon couplings in the fulvene spin system have been determined and assigned.     

STUDIES OF PHOSPHAZENES. PART VI.1 THE PREPARATION OF THE ISOMERIC TETRACHLOROBIS-ISOPROPYLAMINOCYCLOTRIPHOSPHAZATRIENES

Abstract

The three isomers of N₃P₃Cl₄(NHPr¹)₂ have been prepared and separated by gas-liquid chromatography. Their structures have been assigned on the basis of ¹H and ³¹P nmr data.     

Some observations on the radionuclidic and radiochemical control of radiopharmaceuticals at the N.R.C. Democritos

In the production of¹³¹I, the presence of a contamination extractable with organic solvents has been detected and its source discovered. The influence of overheating was established in the preparation of^99m Tc by the extraction method. Finally, details are given of the procedure used for the estimation of¹⁹⁹Au present in¹⁹⁸Au.     

Low-molecular-mass metabolites of fungi. III. Stachybotrolide fromStachybotrys alternans

The new nitrogen-free compound stachybotrolide has been detected among the products of the vital activity ofStachybotrys alternans. The structure of stachybotrolide has been determined on the basis of IR, mass, and¹H and¹³C NMR spectra. To interpret the latter we have made use of DEPT, 2M NMR¹H−¹H chemical shift correlation (¹H−¹H COSY or HMQC) and 2M NMR correlations of¹H−¹³C long-range interactions (HMBC). Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (371) 120 64 75. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 679–683, September–October, 1998.