Photoelectron spectra of carbonyls,carbonates, oxalates and esterification effects

Photoelectron spectra are reported for dimethyl carbonate, ethylene carbonate, oxalic acid, dimethyl oxalate and diethyl oxalate. These spectra are discussed on a composite molecule basis using CNDO/s computational data and many of the individual bands are identified. The differential effects of esterification on ionization energies are discussed briefly.     

Electronic transitions in mono-olefinic hydrocarbons

Mulliken-Wolfsberg-Helmholz calculations have been performed on ethylene and methyl-substituted ethylenes. The Mulliken assignment (i.e., that the transition between 5–7 eV isR(3s)N in nature) is validated. Spin-orbit coupling calculations indicate that the weakest olefin band at 2700 Å is too intense to be triplet singlet, as is usually assumed. However, behaviour of a predicted low-energyR ^*(3s, 2s)N transition agrees well with the characteristics of these weak bands in the absorption spectra of liquid olefins. That these trends are believable is supported by the accuracy with which the computations predict the experimental changes of ionization potential andVN transition energy caused by increased methylation. In particular, it is predicted that the excitation energy of theVN transition should be strongly dependent on molecular geometry — in agreement with experiment. It is suggested, on the basis of intensity calculations, that theR(3s)N transition gains part of its intensity, at least,via vibronic stealing from theVN transition. Computations on cyclic olefins predict the possibility of several low-lying ^* transitions; the unusual broadening of theVN transition in these molecules may possibly be associated with this complexity. Computations on methylene cycloalkanes and cycloalkylidene-cycloalkanes reveal that-strain can lead to low-lying ^* (valence-shell) transitions. In general, it is found that the 3s atomic orbital can mix appreciably, in both bonding and antibonding combinations, with valence-shell orbitals.

---

Zusammenfassung Mulliken-Wolfsberg-Helmholz-Rechnungen werden für Äthylen und eine Reihe methylsubstituierter Äthylene durchgeführt. Die Mullikenzuordnung [d. h. der Übergang zwischen 5 –7 eV entsprichtR(3s)N] wird daraufhin für zutreffend erklärt. Spin-Bahn-Kopplungs-Berechnungen deuten darauf hin, daß das schwächste Olefinband bei 2700 Å zu intensiv ist, um — wie gewöhnlich angenommen —in Triplett-Singulett-Übergang zu sein. Andererseits stimmt das Verhalten eines energetisch tief liegendenR ^*(3s, 2s)N-Übergangs gut mit den Charakteristika dieser schwachen Banden im Absorptionsspektrum der flüssigen Olefine überein. Daß diese Interpretation möglich ist, wird auch durch die Genauigkeit unterstützt, mit der eine Berechnung die experimentell gefundene Änderung von Ionisations- undVN-Übergangsenergie bei zunehmender Methylierung ergibt. Insbesondere wird auch vorhergesagt, daß die Anregungsenergie desVN-Übergangs stark von der molekularen Geometrie abhängt — in Übereinstimmung mit dem Experiment. Es wird deshalb auf Grund einer Intensitätsberechnung vorgeschlagen, daß derR(3s)N-Übergang zumindest einen Teil seiner Intensität durch eine Schwingungs-Anleihe vomVN-Übergang gewinnt. Berechnungen für cyclische Olefine weisen auf verschieden niedrig liegende ^*-Übergänge hin; die ungewöhnliche Verbreitung derVN-Bande bei diesen Molekülen kann möglicherweise damit zusammenhängen. Berechnungen der Methyl-cycloalkane und der Cycloalkylidin-cycloalkane zeigen, daß eine Spannung im-Gerüst zu einem tief liegenden ^*-(Valenz-) Übergang führen kann. Im allgemeinen zeigt sich, daß 3s-Zustände merklich an Valenzzuständen beteiligt sein können, und zwar sowohl bei bindenden als auch bei lockernden Molekülzuständen.

---

Résumé Des calculs Mulliken-Wolfsberg-Helmholz ont été effectués sur l'éthylène et sur la série des éthylènes méthyl-substitués. Ces calculs confirment l'assignation de Mulliken: la transition entre 5–7 eV est de natureNR(3s). Des calculs de couplage spin-orbite montrent que la bande oléfinique la plus faible à 2700 Å est trop intense pour être une transition singulet-triplet comme on le suppose généralement. Cependant, le comportement d'une transition théorique de faible énergieNR ^* (3s, 2s) est en accord avec les caractéristiques de ces faibles bandes dans le spectre d'absorption des oléfines liquides. La vraisemblance de ce point de vue est renforcée par la précision avec laquelle les calculs prédisent l'évolution des potentiels d'ionisation, et des énergies des transitionsNV par méthylation croissante. En particulier, il est prévu que l'énergie d'excitationNV dépend fortement de la géométrie moléculaire ce qui est en accord avec l'expérience. On suggère sur la base de calculs d'intensité que la transitionNR (3s) tire une partie de son intensité au moins par transfert vibronique à partir de la transitionNV. Des calculs sur des oléfines cycliques prédisent la possibilité de plusieurs transitions ^* de faible énergie; l'élargissement inhabituel de la transitionN V dans ces molécules pourrait provenir de cette situation. Des calculs sur les méthylène-cycloalkanes et les cycloalkylidène cycloalkanes révèlent la possibilité pour une tension de provoquer l'existence de transitions ^* (couche de valence) de faible énergie. On trouve qu'en général les orbitales atomiques 3s peuvent se mélanger d'une manière appréciable aux orbitales de la couche de valence donnant des combinaisons liantes et antiliantes.

---

---

Supported by The United States Air Force and The United States Atomic Energy Commission-Biology Branchvia Grants to the Louisiana State University.     

Monomers,dimers, and tetramers of 1- and 2-naphthoic acids

The absorption and emission spectra of 1- and 2-naphthoic acids and a number of their derivatives have been investigated. The S₁, T₁, and S₀ energy levels of solvent H-bonded monomers and internally H-bonded dimers are affected by the type of H-bonding, by periinteractions, by steric factors provided by substituent groups, and by solvent effects. The excimer fluorescence of 1-naphthoic acid has been detected and is the sole fluorescece of the crystal; it is attributed to a tetrameric sandwich complex of two dimers. The 1-naphthoic acid crystal also exhibits delayed excimer flurescence of a triplet-triplet annihilative type.     

Environmental noise – ‘Forgotten’ or ‘Ignored’ pollutant?

It has been 20 years since the European Commission adopted the Green Paper on Future Noise Policy in 1996, taking the first comprehensive step towards the development of an EU-wide noise policy. This document envisioned a directive that would harmonise methods for the assessment of environmental noise and the dissemination of information to the public. This led to the establishment of Directive 2002/49/EC in 2002 also known as the Environmental Noise Directive (END). The END called for the development of strategic noise maps and action plans across every EU Member State in five year intervals. Two phases of noise mapping and action planning have now been completed and Member States are about to embark on the third phase of noise mapping, due in 2017. Focussing on results reported to the European Commission, this study summarises the current state of noise mapping, 20 years after the publication of the Green Paper, and identifies critical needs for future noise mapping phases.     

Positional and conformational dependence of long-range interactions in 3,16- and 3,17-androstanediones

The 5- and 5-conformations of androstane, androstan-3-one, androstan-16-one, androstan-17-one, androstane-3,16-dione and androstane-3,17-dione have been calculated by the SCF MNDO method, using full geometry optimization, in order to assess the dependence of long-range electronic interactions of the carbonyl groups on their location and on the conformation of the steroid ring system.     

The niobium and tantalum riddle: gas-phase monocation reactions with pyrene and pyrene-D10

Metal monocation gas-phase reactions with pyrene (Py) have been investigated. Of those cations which bind Py by abstraction of two hydrogen atoms, there are two subgroups of which Nb⁺ and Ta⁺ are the most striking and puzzling representatives. The Ta⁺-like group binds three Py units consecutively, each by expulsion of two hydrogen atoms, whereas the Nb⁺ group binds four Py units; however, in this latter case, the second Py attachment occurs without the expulsion of any hydrogen. When perdeuterated Py-D₁₀ is used, the Ta⁺ group behavior is unaffected, but the Nb⁺ group now exhibits a considerable degree of Py attachment in which no deuterium atoms are lost in the first reaction step. We will attempt to explain this behavior by using the results of reactions of Nb⁺ and Ta⁺ with Py in a Fourier transform mass spectrometer (FTMS).     

Synthesis of vinylsilanes by palladium-catalyzed reaction of trimethylsilylallyl acetates with nucleophiles

Treatment of 1-trimethylsilylallyl and 3-trimethylsilylallyl acetates with nucleophiles (active methylene compounds and enamines) in the presence of a catalytic amount of Pd(PPh₃)₄ affords vinylsilane derivatives selectively.     

Delayed luminescence of organic mixed crystals. IX. Amino acids and proteins

Abstract— This paper discusses the possibility of triplet exciton motion and triplet-triplet annihilation in mixed crystal systems in which the hosts are phenylalanine, tyrosine and trypto-phan and in four protein systems. Triplet-triplet annihilation and triplet transfer are observed in certain phenylalanine- and tryptophan-host systems. No evidence of either triplet transfer or energy multiplication is found in tyrosine-host crystal systems or in any protein system.     

Photoelectron Spectra of Carbonyls. Oxalyl Chloride,Ethyl Oxalyl Choride,Ethyl Oxamate and N,N-Dimethyl Ethyl Oxamate

Photoelectron spectra are reported for oxalyl chloride, ethyl oxalyl chloride, ethyl oxamate and N,N-dimethyl ethyl oxamate. The spectra are assigned using a composite molecule approach.