Field ionization mass spectrometry—I. Nucleosides

The field ionization mass spectra of a series of nucleosides are reported, and compared with spectra obtained by conventional electron-impact ionization. The latter are complex, with structurally significant molecular ion and sugar cleavage peaks often of low intensity or completely absent. In contrast, the field ion spectra are extremely simple, with all except guanosine (highest mass peak [M — 18]) showing intense molecular ion peaks, and the characteristic sugar (S) and base (B + H) cleavage products as the only other important fragments.     

Hydrolytic polymerization of caprolactam. I. Hydrolysis—polycondensation kinetics

In a study aimed at process optimization of caprolactam polymerization, particular reference has been paid to the competing role of water in caprolactam hydrolysis and endgroup polycondensation. The dependence of the apparent equilibrium constant for polycondensation on water concentration indicated that there is a strong effect of the medium on the activities of the reacting species which can not be neglected in a kinetic study of the polycondensation reaction. The effect of a variation of the medium was taken into account by using a polycondensation rate constant which included a function of the water present at any given time. With the aid of analog computer curve-fitting techniques, good agreement with second-order kinetics was found. The validity of a second-order mechanism was confirmed in a kinetic study of the chain amide linkage hydrolysis. The hydrolysis of caprolactam follows substantially different kinetics, where the generation of carboxyl groups reduces the activation energy of the reaction, which follows predominantly a third-order mechanism.     

Ozone interaction with conjugated polymers—I. Polyacetylene

Free-standing films of cis- and trans-rich polyacetylene (PA) obtained on a Rh(I) catalyst, were treated with ozonized oxygen (O₃ 1% by weight on average). The initial superficial charge-transfer complex formed between ozone and the polyene chain and the subsequent ozone accelerated cis-trans isomerization were studied by electronic and FT-IR spectroscopies. A peculiar mechanism of interaction between ozone and polyenic chain was proposed, and cation radicals were observed on the ozone doped surfaces of PA. Ozone treatment of PA films creates a superficial oxidized barrier that prevents subsequent thermo-oxidative destruction of the bulk portion of PA film. This treatment could be a way of protecting PA from degradative oxidation.     

Pyrophthalone and its derivatives as ligands—I. Mode of coordination—formation of isomeric iminopyrophthalone complexes

The complex formation of Co(II), Ni(II), Zn(II) with aminopyrophthalone was studied by means of electronic, IR, EPR and ¹H-NMR spectroscopy. It was established that with Co(II) and Ni(II) two isomeric complexes are formed in contrast to Zn(II) and Cu(II) complex formation. On the basis of the spectral data obtained the coordination mode and structure of the complex species are assumed.     

On Mercury(I) Oxo Compounds — Quasi‐Relativistic Computational and Experimental Studies

About 60 molecular species composed of up to 10 mercury atoms and of oxygen atoms and/or of some other elements or groups (such as halogen, OH₂, OH, H, alkali, NO₃) have been investigated quantum chemically. Different density functional approaches and the ab initio SCF‐MP2 method were applied, comparing different basis sets and different atomic core sizes. It is important not to treat the Hg 5s, p, d as inactive core shells, and to use sufficiently many polarization functions. The shape of the 〉O‐Hg‐Hg‐O〈 units is not favorable concerning the formation of lattices composed of Hg^I, O and OH only. Despite its bulkiness, the OHgHgO units can easily come into contact with each other and then disproportionate. This is prevented in the so‐called ternary M‐Hg^I oxides by the embedded oxometallate (oxoacidic) anions. Furthermore, the Hg^I and Hg^II oxide bond energies are less favorable towards the stability of Hg^I oxo compounds, as compared to Hg halidic or oxoacidic compounds. Both points are not promising concerning the search for Hg^I oxides/hydroxides, although the preparation of such compounds, including spacer groups, by topochemical reactions can still not be excluded. So far, experimental efforts towards the synthesis of such a new class of compounds have only demonstrated that Hg^II is strictly preferred over Hg^I in the formation of solids of binary Hg‐O or ternary A‐Hg‐O composition (A = electropositive metal such as alkali, in contrast to M = transition or semi‐metal). This is so even if compounds containing ‘electron rich Hg^δ— atoms’ (i.e. A‐Hg amalgams) are oxidized under mild conditions.     

Reconciling semiclassical and Bohmian mechanics. I. Stationary states

The semiclassical method is characterized by finite forces and smooth, well-behaved trajectories, but also by multivalued representational functions that are ill behaved at caustics. In contrast, quantum trajectory methods--based on Bohmian mechanics (quantum hydrodynamics)--are characterized by divergent forces and erratic trajectories near nodes, but also well-behaved, single-valued representational functions. In this paper, we unify these two approaches into a single method that captures the best features of both, and in addition, satisfies the correspondence principle. Stationary eigenstates in one degree of freedom are the primary focus, but more general applications are also anticipated.     

Massenspektrometrie isomerer Diazaphenanthrene—I

The mass spectra of five diazaphenanthrenes formed by photochemical cyclodehydrogenation of styryl diazines are investigated. It is shown that fragmentation of these compounds starts almost exclusively at the heterocyclic part of the molecule and proceeds by competitive α-cleavage. From the intensity ratios of the ions [M ? H˙]⁺, [M ? HCN]⁺˙, [M ? N₂]⁺˙ and [M ? 2 HCN]⁺˙ generated in this way, each isomer can unequivocally be identified.     

Restricted rotation in amides. VII—methods of resonance assignment in tertiary amides—an evaluation

Examination and evaluation of various methods for resonance assignments in amides reveals that only three of these are reliable: (a) the nuclear Overhauser effect, which leads to unequivocal results in tertiary amides; (b) the aromatic solvent induced shift, which is rapid and accurate for tertiary amides without polar substituents; (c) the lanthanide-induced shift, which although easy, can be applied only to tertiary amides with substituents that do not complex lanthanides.     

Investigations into the formation and characterization of microemulsions. I. Phase diagrams of the ternary system water—sodium alkyl benzene sulfonate—hexanol and the quaternary system water—xylene—sodium alkyl benzene sulfonate—hexanol

The phase diagrams of the ternary system water—sodium alkylbenzene sulfonate (NaDBS)-hexanol and the quaternary system water—xylene—NADBS—hexanol have been established at three different temperatures, namely 25, 37, and 50°C. The different phases formed have been qualitatively examined using optical (phase contrast and polarizing) microscopy. The textures of the various liquid crystalline phases in the ternary system have been identified, by comparison with previous studies in the literature. Some of the liquid crystalline phases have been quantitatively assessed using low angle X-ray diffraction. The latter measurements were also used to determine the unit cell dimensions in the various phases studied. With the quaternary system, particular attention was paid to the transparent region which consisted of an L₂ (inverse micellar) phase extending into another transparent region which has a blue “tinge” in some cases, namely the microemulsion (M) region. The amount of water solubilized in the L₂ (reverse micelle) or M + L₂ phase was calculated from the phase diagrams. With the ternary system the results showed a maximum in moles of water solubilized per mole total surfactant (NaDBS + hexanol) at a concentration of 0.3 mole surfactant, at an optimum molar ratio of n-hexanol to NaDBS of 4.5:1. This maximum was about twice with the quaternary system, when compared with that of the ternary system, indicating the importance of the role of xylene in solubilization of water by the surfactants. The present investigation has also shown that the extent of the microemulsion region is significantly reduced by increases of temperature when the NaDBS is lower than 15 wt%.     

Stereoisomeric effects on mass spectra—I. A Review

The unimolecular reactions that give rise to mass spectra are controlled by spatial relationships and energy considerations. In molecules that contain a heteroatom, elimination reactions, involving bond-making as well as breaking, are often prominent, e.g. loss of water from alcohols. The ease of such reactions depends on spatial relationships in the molecule, and the resultant ion intensities in the spectra of geometric isomers can consequently be correlated with differences in geometry and hence furnish a basis for assigning structures. Processes that do not involve bond-making do not have such rigorous geometric requirements, but depend rather on attainment of a transition state defined in terms of a minimum energy content. Common product ions from stereoisomeric hydrocarbons seem often to arise via a common transition state. When this condition holds, the difference between the enthalpies of the isomers is reflected in the relative appearance potentials and–though the cause-and-effect relationship here is less direct and more readily obscured by other factors–relative intensities of the common product derived from the isomers. In both classes of processes, the spectra of stereoisomers can be simplified and made more distinctive by lowering source temperature and ionizing voltage.     

Diquinones—I The oosporein-tomichaedin degradation

It is established, by synthesis, that tomichaedin, the degradation product obtained from the dibenzoquinone, oosporein, by fusion with potash, has the structure 3-hydroxy-2-methyl-1,4-naphthaquinone-6-carboxylic acid. A mechanism for the reaction is proposed which accounts for all the products which have been isolated.

Iso-oosporein is identical with oosporein.     

Conformational studies—I Conformational transmission

A semi-qualitative approach to the interpretation of the factors effecting conformational transmission is described.     

Hashish—I The structure of Cannabidiol

Cannabidiol, one of the major components of hashish, has been shown to possess structure IIIa.     

Elektronenstoss-Induzierte Molekülumlagerungen—I. Massenspektrometrische Fragmentierungen von Azinen und Phosphazinen

The mass spectra of 15 azines and 5 phosphazines are investigated by deuterium labelling and high resolution mass measurements. Azines of aldehydes undergo a skeletal rearrangement in which HCN and (HCN + H) are eliminated from the molecular ion. Azines of ketones first eliminate an aryl or alkyl radical and then rearrange with the expulsion of CN. or (CN. + H). Analogies to the photolytic or thermal elimination of nitrogen in azines could not be detected. o,o′-Dinitrobenzaldazin undergoes a double oxygen rearrangement in which carbon dioxide is eliminated. Phosphazines show a similar behaviour under electron-impact as under pyrolytic conditions.